TypeScript/src/compiler/builder.ts

/*@internal*/
namespace ts {
    export interface ReusableDiagnostic extends ReusableDiagnosticRelatedInformation {
        /** May store more in future. For now, this will simply be `true` to indicate when a diagnostic is an unused-identifier diagnostic. */
        reportsUnnecessary?: {};
        source?: string;
        relatedInformation?: ReusableDiagnosticRelatedInformation[];
    }

    export interface ReusableDiagnosticRelatedInformation {
        category: DiagnosticCategory;
        code: number;
        file: string | undefined;
        start: number | undefined;
        length: number | undefined;
        messageText: string | ReusableDiagnosticMessageChain;
    }

    export type ReusableDiagnosticMessageChain = DiagnosticMessageChain;

    export interface ReusableBuilderProgramState extends ReusableBuilderState {
        /**
         * Cache of bind and check diagnostics for files with their Path being the key
         */
        semanticDiagnosticsPerFile?: ReadonlyMap<readonly ReusableDiagnostic[] | readonly Diagnostic[]> | undefined;
        /**
         * The map has key by source file's path that has been changed
         */
        changedFilesSet?: ReadonlyMap<true>;
        /**
         * Set of affected files being iterated
         */
        affectedFiles?: readonly SourceFile[] | undefined;
        /**
         * Current changed file for iterating over affected files
         */
        currentChangedFilePath?: Path | undefined;
        /**
         * Map of file signatures, with key being file path, calculated while getting current changed file's affected files
         * These will be committed whenever the iteration through affected files of current changed file is complete
         */
        currentAffectedFilesSignatures?: ReadonlyMap<string> | undefined;
        /**
         * Newly computed visible to outside referencedSet
         */
        currentAffectedFilesExportedModulesMap?: Readonly<BuilderState.ComputingExportedModulesMap> | undefined;
        /**
         * True if the semantic diagnostics were copied from the old state
         */
        semanticDiagnosticsFromOldState?: Map<true>;
        /**
         * program corresponding to this state
         */
        program?: Program | undefined;
        /**
         * compilerOptions for the program
         */
        compilerOptions: CompilerOptions;
        /**
         * Files pending to be emitted
         */
        affectedFilesPendingEmit?: readonly Path[] | undefined;
        /**
         * Files pending to be emitted kind.
         */
        affectedFilesPendingEmitKind?: ReadonlyMap<BuilderFileEmit> | undefined;
        /**
         * Current index to retrieve pending affected file
         */
        affectedFilesPendingEmitIndex?: number | undefined;
        /*
         * true if semantic diagnostics are ReusableDiagnostic instead of Diagnostic
         */
        hasReusableDiagnostic?: true;
    }

    export const enum BuilderFileEmit {
        DtsOnly,
        Full
    }

    /**
     * State to store the changed files, affected files and cache semantic diagnostics
     */
    // TODO: GH#18217 Properties of this interface are frequently asserted to be defined.
    export interface BuilderProgramState extends BuilderState {
        /**
         * Cache of bind and check diagnostics for files with their Path being the key
         */
        semanticDiagnosticsPerFile: Map<readonly Diagnostic[]> | undefined;
        /**
         * The map has key by source file's path that has been changed
         */
        changedFilesSet: Map<true>;
        /**
         * Set of affected files being iterated
         */
        affectedFiles: readonly SourceFile[] | undefined;
        /**
         * Current index to retrieve affected file from
         */
        affectedFilesIndex: number | undefined;
        /**
         * Current changed file for iterating over affected files
         */
        currentChangedFilePath: Path | undefined;
        /**
         * Map of file signatures, with key being file path, calculated while getting current changed file's affected files
         * These will be committed whenever the iteration through affected files of current changed file is complete
         */
        currentAffectedFilesSignatures: Map<string> | undefined;
        /**
         * Newly computed visible to outside referencedSet
         */
        currentAffectedFilesExportedModulesMap: BuilderState.ComputingExportedModulesMap | undefined;
        /**
         * Already seen affected files
         */
        seenAffectedFiles: Map<true> | undefined;
        /**
         * whether this program has cleaned semantic diagnostics cache for lib files
         */
        cleanedDiagnosticsOfLibFiles?: boolean;
        /**
         * True if the semantic diagnostics were copied from the old state
         */
        semanticDiagnosticsFromOldState?: Map<true>;
        /**
         * program corresponding to this state
         */
        program: Program | undefined;
        /**
         * compilerOptions for the program
         */
        compilerOptions: CompilerOptions;
        /**
         * Files pending to be emitted
         */
        affectedFilesPendingEmit: Path[] | undefined;
        /**
         * Files pending to be emitted kind.
         */
        affectedFilesPendingEmitKind: Map<BuilderFileEmit> | undefined;
        /**
         * Current index to retrieve pending affected file
         */
        affectedFilesPendingEmitIndex: number | undefined;
        /**
         * true if build info is emitted
         */
        emittedBuildInfo?: boolean;
        /**
         * Already seen emitted files
         */
        seenEmittedFiles: Map<BuilderFileEmit> | undefined;
        /**
         * true if program has been emitted
         */
        programEmitComplete?: true;
    }

    function hasSameKeys<T, U>(map1: ReadonlyMap<T> | undefined, map2: ReadonlyMap<U> | undefined): boolean {
        // Has same size and every key is present in both maps
        return map1 as ReadonlyMap<T | U> === map2 || map1 !== undefined && map2 !== undefined && map1.size === map2.size && !forEachKey(map1, key => !map2.has(key));
    }

    /**
     * Create the state so that we can iterate on changedFiles/affected files
     */
    function createBuilderProgramState(newProgram: Program, getCanonicalFileName: GetCanonicalFileName, oldState?: Readonly<ReusableBuilderProgramState>): BuilderProgramState {
        const state = BuilderState.create(newProgram, getCanonicalFileName, oldState) as BuilderProgramState;
        state.program = newProgram;
        const compilerOptions = newProgram.getCompilerOptions();
        state.compilerOptions = compilerOptions;
        // With --out or --outFile, any change affects all semantic diagnostics so no need to cache them
        if (!compilerOptions.outFile && !compilerOptions.out) {
            state.semanticDiagnosticsPerFile = createMap<readonly Diagnostic[]>();
        }
        state.changedFilesSet = createMap<true>();

        const useOldState = BuilderState.canReuseOldState(state.referencedMap, oldState);
        const oldCompilerOptions = useOldState ? oldState!.compilerOptions : undefined;
        const canCopySemanticDiagnostics = useOldState && oldState!.semanticDiagnosticsPerFile && !!state.semanticDiagnosticsPerFile &&
            !compilerOptionsAffectSemanticDiagnostics(compilerOptions, oldCompilerOptions!);
        if (useOldState) {
            // Verify the sanity of old state
            if (!oldState!.currentChangedFilePath) {
                const affectedSignatures = oldState!.currentAffectedFilesSignatures;
                Debug.assert(!oldState!.affectedFiles && (!affectedSignatures || !affectedSignatures.size), "Cannot reuse if only few affected files of currentChangedFile were iterated");
            }
            const changedFilesSet = oldState!.changedFilesSet;
            if (canCopySemanticDiagnostics) {
                Debug.assert(!changedFilesSet || !forEachKey(changedFilesSet, path => oldState!.semanticDiagnosticsPerFile!.has(path)), "Semantic diagnostics shouldnt be available for changed files");
            }

            // Copy old state's changed files set
            if (changedFilesSet) {
                copyEntries(changedFilesSet, state.changedFilesSet);
            }
            if (!compilerOptions.outFile && !compilerOptions.out && oldState!.affectedFilesPendingEmit) {
                state.affectedFilesPendingEmit = oldState!.affectedFilesPendingEmit.slice();
                state.affectedFilesPendingEmitKind = cloneMapOrUndefined(oldState!.affectedFilesPendingEmitKind);
                state.affectedFilesPendingEmitIndex = oldState!.affectedFilesPendingEmitIndex;
            }
        }

        // Update changed files and copy semantic diagnostics if we can
        const referencedMap = state.referencedMap;
        const oldReferencedMap = useOldState ? oldState!.referencedMap : undefined;
        const copyDeclarationFileDiagnostics = canCopySemanticDiagnostics && !compilerOptions.skipLibCheck === !oldCompilerOptions!.skipLibCheck;
        const copyLibFileDiagnostics = copyDeclarationFileDiagnostics && !compilerOptions.skipDefaultLibCheck === !oldCompilerOptions!.skipDefaultLibCheck;
        state.fileInfos.forEach((info, sourceFilePath) => {
            let oldInfo: Readonly<BuilderState.FileInfo> | undefined;
            let newReferences: BuilderState.ReferencedSet | undefined;

            // if not using old state, every file is changed
            if (!useOldState ||
                // File wasnt present in old state
                !(oldInfo = oldState!.fileInfos.get(sourceFilePath)) ||
                // versions dont match
                oldInfo.version !== info.version ||
                // Referenced files changed
                !hasSameKeys(newReferences = referencedMap && referencedMap.get(sourceFilePath), oldReferencedMap && oldReferencedMap.get(sourceFilePath)) ||
                // Referenced file was deleted in the new program
                newReferences && forEachKey(newReferences, path => !state.fileInfos.has(path) && oldState!.fileInfos.has(path))) {
                // Register file as changed file and do not copy semantic diagnostics, since all changed files need to be re-evaluated
                state.changedFilesSet.set(sourceFilePath, true);
            }
            else if (canCopySemanticDiagnostics) {
                const sourceFile = newProgram.getSourceFileByPath(sourceFilePath as Path)!;

                if (sourceFile.isDeclarationFile && !copyDeclarationFileDiagnostics) { return; }
                if (sourceFile.hasNoDefaultLib && !copyLibFileDiagnostics) { return; }

                // Unchanged file copy diagnostics
                const diagnostics = oldState!.semanticDiagnosticsPerFile!.get(sourceFilePath);
                if (diagnostics) {
                    state.semanticDiagnosticsPerFile!.set(sourceFilePath, oldState!.hasReusableDiagnostic ? convertToDiagnostics(diagnostics as readonly ReusableDiagnostic[], newProgram, getCanonicalFileName) : diagnostics as readonly Diagnostic[]);
                    if (!state.semanticDiagnosticsFromOldState) {
                        state.semanticDiagnosticsFromOldState = createMap<true>();
                    }
                    state.semanticDiagnosticsFromOldState.set(sourceFilePath, true);
                }
            }
        });

        if (oldCompilerOptions && compilerOptionsAffectEmit(compilerOptions, oldCompilerOptions)) {
            // Add all files to affectedFilesPendingEmit since emit changed
            newProgram.getSourceFiles().forEach(f => addToAffectedFilesPendingEmit(state, f.resolvedPath, BuilderFileEmit.Full));
            Debug.assert(state.seenAffectedFiles === undefined);
            state.seenAffectedFiles = createMap<true>();
        }

        state.emittedBuildInfo = !state.changedFilesSet.size && !state.affectedFilesPendingEmit;
        return state;
    }

    function convertToDiagnostics(diagnostics: readonly ReusableDiagnostic[], newProgram: Program, getCanonicalFileName: GetCanonicalFileName): readonly Diagnostic[] {
        if (!diagnostics.length) return emptyArray;
        const buildInfoDirectory = getDirectoryPath(getNormalizedAbsolutePath(getTsBuildInfoEmitOutputFilePath(newProgram.getCompilerOptions())!, newProgram.getCurrentDirectory()));
        return diagnostics.map(diagnostic => {
            const result: Diagnostic = convertToDiagnosticRelatedInformation(diagnostic, newProgram, toPath);
            result.reportsUnnecessary = diagnostic.reportsUnnecessary;
            result.source = diagnostic.source;
            const { relatedInformation } = diagnostic;
            result.relatedInformation = relatedInformation ?
                relatedInformation.length ?
                    relatedInformation.map(r => convertToDiagnosticRelatedInformation(r, newProgram, toPath)) :
                    emptyArray :
                undefined;
            return result;
        });

        function toPath(path: string) {
            return ts.toPath(path, buildInfoDirectory, getCanonicalFileName);
        }
    }

    function convertToDiagnosticRelatedInformation(diagnostic: ReusableDiagnosticRelatedInformation, newProgram: Program, toPath: (path: string) => Path): DiagnosticRelatedInformation {
        const { file } = diagnostic;
        return {
            ...diagnostic,
            file: file ? newProgram.getSourceFileByPath(toPath(file)) : undefined
        };
    }

    /**
     * Releases program and other related not needed properties
     */
    function releaseCache(state: BuilderProgramState) {
        BuilderState.releaseCache(state);
        state.program = undefined;
    }

    /**
     * Creates a clone of the state
     */
    function cloneBuilderProgramState(state: Readonly<BuilderProgramState>): BuilderProgramState {
        const newState = BuilderState.clone(state) as BuilderProgramState;
        newState.semanticDiagnosticsPerFile = cloneMapOrUndefined(state.semanticDiagnosticsPerFile);
        newState.changedFilesSet = cloneMap(state.changedFilesSet);
        newState.affectedFiles = state.affectedFiles;
        newState.affectedFilesIndex = state.affectedFilesIndex;
        newState.currentChangedFilePath = state.currentChangedFilePath;
        newState.currentAffectedFilesSignatures = cloneMapOrUndefined(state.currentAffectedFilesSignatures);
        newState.currentAffectedFilesExportedModulesMap = cloneMapOrUndefined(state.currentAffectedFilesExportedModulesMap);
        newState.seenAffectedFiles = cloneMapOrUndefined(state.seenAffectedFiles);
        newState.cleanedDiagnosticsOfLibFiles = state.cleanedDiagnosticsOfLibFiles;
        newState.semanticDiagnosticsFromOldState = cloneMapOrUndefined(state.semanticDiagnosticsFromOldState);
        newState.program = state.program;
        newState.compilerOptions = state.compilerOptions;
        newState.affectedFilesPendingEmit = state.affectedFilesPendingEmit && state.affectedFilesPendingEmit.slice();
        newState.affectedFilesPendingEmitKind = cloneMapOrUndefined(state.affectedFilesPendingEmitKind);
        newState.affectedFilesPendingEmitIndex = state.affectedFilesPendingEmitIndex;
        newState.seenEmittedFiles = cloneMapOrUndefined(state.seenEmittedFiles);
        newState.programEmitComplete = state.programEmitComplete;
        return newState;
    }

    /**
     * Verifies that source file is ok to be used in calls that arent handled by next
     */
    function assertSourceFileOkWithoutNextAffectedCall(state: BuilderProgramState, sourceFile: SourceFile | undefined) {
        Debug.assert(!sourceFile || !state.affectedFiles || state.affectedFiles[state.affectedFilesIndex! - 1] !== sourceFile || !state.semanticDiagnosticsPerFile!.has(sourceFile.resolvedPath));
    }

    /**
     * This function returns the next affected file to be processed.
     * Note that until doneAffected is called it would keep reporting same result
     * This is to allow the callers to be able to actually remove affected file only when the operation is complete
     * eg. if during diagnostics check cancellation token ends up cancelling the request, the affected file should be retained
     */
    function getNextAffectedFile(state: BuilderProgramState, cancellationToken: CancellationToken | undefined, computeHash: BuilderState.ComputeHash): SourceFile | Program | undefined {
        while (true) {
            const { affectedFiles } = state;
            if (affectedFiles) {
                const seenAffectedFiles = state.seenAffectedFiles!;
                let affectedFilesIndex = state.affectedFilesIndex!; // TODO: GH#18217
                while (affectedFilesIndex < affectedFiles.length) {
                    const affectedFile = affectedFiles[affectedFilesIndex];
                    if (!seenAffectedFiles.has(affectedFile.resolvedPath)) {
                        // Set the next affected file as seen and remove the cached semantic diagnostics
                        state.affectedFilesIndex = affectedFilesIndex;
                        handleDtsMayChangeOfAffectedFile(state, affectedFile, cancellationToken, computeHash);
                        return affectedFile;
                    }
                    affectedFilesIndex++;
                }

                // Remove the changed file from the change set
                state.changedFilesSet.delete(state.currentChangedFilePath!);
                state.currentChangedFilePath = undefined;
                // Commit the changes in file signature
                BuilderState.updateSignaturesFromCache(state, state.currentAffectedFilesSignatures!);
                state.currentAffectedFilesSignatures!.clear();
                BuilderState.updateExportedFilesMapFromCache(state, state.currentAffectedFilesExportedModulesMap);
                state.affectedFiles = undefined;
            }

            // Get next changed file
            const nextKey = state.changedFilesSet.keys().next();
            if (nextKey.done) {
                // Done
                return undefined;
            }

            // With --out or --outFile all outputs go into single file
            // so operations are performed directly on program, return program
            const program = Debug.assertDefined(state.program);
            const compilerOptions = program.getCompilerOptions();
            if (compilerOptions.outFile || compilerOptions.out) {
                Debug.assert(!state.semanticDiagnosticsPerFile);
                return program;
            }

            // Get next batch of affected files
            state.currentAffectedFilesSignatures = state.currentAffectedFilesSignatures || createMap();
            if (state.exportedModulesMap) {
                state.currentAffectedFilesExportedModulesMap = state.currentAffectedFilesExportedModulesMap || createMap<BuilderState.ReferencedSet | false>();
            }
            state.affectedFiles = BuilderState.getFilesAffectedBy(state, program, nextKey.value as Path, cancellationToken, computeHash, state.currentAffectedFilesSignatures, state.currentAffectedFilesExportedModulesMap);
            state.currentChangedFilePath = nextKey.value as Path;
            state.affectedFilesIndex = 0;
            state.seenAffectedFiles = state.seenAffectedFiles || createMap<true>();
        }
    }

    /**
     * Returns next file to be emitted from files that retrieved semantic diagnostics but did not emit yet
     */
    function getNextAffectedFilePendingEmit(state: BuilderProgramState) {
        const { affectedFilesPendingEmit } = state;
        if (affectedFilesPendingEmit) {
            const seenEmittedFiles = state.seenEmittedFiles || (state.seenEmittedFiles = createMap());
            for (let i = state.affectedFilesPendingEmitIndex!; i < affectedFilesPendingEmit.length; i++) {
                const affectedFile = Debug.assertDefined(state.program).getSourceFileByPath(affectedFilesPendingEmit[i]);
                if (affectedFile) {
                    const seenKind = seenEmittedFiles.get(affectedFile.resolvedPath);
                    const emitKind = Debug.assertDefined(Debug.assertDefined(state.affectedFilesPendingEmitKind).get(affectedFile.resolvedPath));
                    if (seenKind === undefined || seenKind < emitKind) {
                        // emit this file
                        state.affectedFilesPendingEmitIndex = i;
                        return { affectedFile, emitKind };
                    }
                }
            }
            state.affectedFilesPendingEmit = undefined;
            state.affectedFilesPendingEmitKind = undefined;
            state.affectedFilesPendingEmitIndex = undefined;
        }
        return undefined;
    }

    /**
     *  Handles semantic diagnostics and dts emit for affectedFile and files, that are referencing modules that export entities from affected file
     *  This is because even though js emit doesnt change, dts emit / type used can change resulting in need for dts emit and js change
     */
    function handleDtsMayChangeOfAffectedFile(state: BuilderProgramState, affectedFile: SourceFile, cancellationToken: CancellationToken | undefined, computeHash: BuilderState.ComputeHash) {
        removeSemanticDiagnosticsOf(state, affectedFile.resolvedPath);

        // If affected files is everything except default library, then nothing more to do
        if (state.allFilesExcludingDefaultLibraryFile === state.affectedFiles) {
            if (!state.cleanedDiagnosticsOfLibFiles) {
                state.cleanedDiagnosticsOfLibFiles = true;
                const program = Debug.assertDefined(state.program);
                const options = program.getCompilerOptions();
                forEach(program.getSourceFiles(), f =>
                    program.isSourceFileDefaultLibrary(f) &&
                    !skipTypeChecking(f, options, program) &&
                    removeSemanticDiagnosticsOf(state, f.resolvedPath)
                );
            }
            return;
        }

        forEachReferencingModulesOfExportOfAffectedFile(state, affectedFile, (state, path) => handleDtsMayChangeOf(state, path, cancellationToken, computeHash));
    }

    /**
     * Handle the dts may change, so they need to be added to pending emit if dts emit is enabled,
     * Also we need to make sure signature is updated for these files
     */
    function handleDtsMayChangeOf(state: BuilderProgramState, path: Path, cancellationToken: CancellationToken | undefined, computeHash: BuilderState.ComputeHash) {
        removeSemanticDiagnosticsOf(state, path);

        if (!state.changedFilesSet.has(path)) {
            const program = Debug.assertDefined(state.program);
            const sourceFile = program.getSourceFileByPath(path);
            if (sourceFile) {
                // Even though the js emit doesnt change and we are already handling dts emit and semantic diagnostics
                // we need to update the signature to reflect correctness of the signature(which is output d.ts emit) of this file
                // This ensures that we dont later during incremental builds considering wrong signature.
                // Eg where this also is needed to ensure that .tsbuildinfo generated by incremental build should be same as if it was first fresh build
                BuilderState.updateShapeSignature(
                    state,
                    program,
                    sourceFile,
                    Debug.assertDefined(state.currentAffectedFilesSignatures),
                    cancellationToken,
                    computeHash,
                    state.currentAffectedFilesExportedModulesMap
                );
                // If not dts emit, nothing more to do
                if (getEmitDeclarations(state.compilerOptions)) {
                    addToAffectedFilesPendingEmit(state, path, BuilderFileEmit.DtsOnly);
                }
            }
        }

        return false;
    }

    /**
     * Removes semantic diagnostics for path and
     * returns true if there are no more semantic diagnostics from the old state
     */
    function removeSemanticDiagnosticsOf(state: BuilderProgramState, path: Path) {
        if (!state.semanticDiagnosticsFromOldState) {
            return true;
        }
        state.semanticDiagnosticsFromOldState.delete(path);
        state.semanticDiagnosticsPerFile!.delete(path);
        return !state.semanticDiagnosticsFromOldState.size;
    }

    function isChangedSignagure(state: BuilderProgramState, path: Path) {
        const newSignature = Debug.assertDefined(state.currentAffectedFilesSignatures).get(path);
        const oldSignagure = Debug.assertDefined(state.fileInfos.get(path)).signature;
        return newSignature !== oldSignagure;
    }

    /**
     * Iterate on referencing modules that export entities from affected file
     */
    function forEachReferencingModulesOfExportOfAffectedFile(state: BuilderProgramState, affectedFile: SourceFile, fn: (state: BuilderProgramState, filePath: Path) => boolean) {
        // If there was change in signature (dts output) for the changed file,
        // then only we need to handle pending file emit
        if (!state.exportedModulesMap || !state.changedFilesSet.has(affectedFile.resolvedPath)) {
            return;
        }

        if (!isChangedSignagure(state, affectedFile.resolvedPath)) return;

        // Since isolated modules dont change js files, files affected by change in signature is itself
        // But we need to cleanup semantic diagnostics and queue dts emit for affected files
        if (state.compilerOptions.isolatedModules) {
            const seenFileNamesMap = createMap<true>();
            seenFileNamesMap.set(affectedFile.resolvedPath, true);
            const queue = BuilderState.getReferencedByPaths(state, affectedFile.resolvedPath);
            while (queue.length > 0) {
                const currentPath = queue.pop()!;
                if (!seenFileNamesMap.has(currentPath)) {
                    seenFileNamesMap.set(currentPath, true);
                    const result = fn(state, currentPath);
                    if (result && isChangedSignagure(state, currentPath)) {
                        const currentSourceFile = Debug.assertDefined(state.program).getSourceFileByPath(currentPath)!;
                        queue.push(...BuilderState.getReferencedByPaths(state, currentSourceFile.resolvedPath));
                    }
                }
            }
        }

        Debug.assert(!!state.currentAffectedFilesExportedModulesMap);
        const seenFileAndExportsOfFile = createMap<true>();
        // Go through exported modules from cache first
        // If exported modules has path, all files referencing file exported from are affected
        if (forEachEntry(state.currentAffectedFilesExportedModulesMap!, (exportedModules, exportedFromPath) =>
            exportedModules &&
            exportedModules.has(affectedFile.resolvedPath) &&
            forEachFilesReferencingPath(state, exportedFromPath as Path, seenFileAndExportsOfFile, fn)
        )) {
            return;
        }

        // If exported from path is not from cache and exported modules has path, all files referencing file exported from are affected
        forEachEntry(state.exportedModulesMap, (exportedModules, exportedFromPath) =>
            !state.currentAffectedFilesExportedModulesMap!.has(exportedFromPath) && // If we already iterated this through cache, ignore it
            exportedModules.has(affectedFile.resolvedPath) &&
            forEachFilesReferencingPath(state, exportedFromPath as Path, seenFileAndExportsOfFile, fn)
        );
    }

    /**
     * Iterate on files referencing referencedPath
     */
    function forEachFilesReferencingPath(state: BuilderProgramState, referencedPath: Path, seenFileAndExportsOfFile: Map<true>, fn: (state: BuilderProgramState, filePath: Path) => boolean) {
        return forEachEntry(state.referencedMap!, (referencesInFile, filePath) =>
            referencesInFile.has(referencedPath) && forEachFileAndExportsOfFile(state, filePath as Path, seenFileAndExportsOfFile, fn)
        );
    }

    /**
     * fn on file and iterate on anything that exports this file
     */
    function forEachFileAndExportsOfFile(state: BuilderProgramState, filePath: Path, seenFileAndExportsOfFile: Map<true>, fn: (state: BuilderProgramState, filePath: Path) => boolean): boolean {
        if (!addToSeen(seenFileAndExportsOfFile, filePath)) {
            return false;
        }

        if (fn(state, filePath)) {
            // If there are no more diagnostics from old cache, done
            return true;
        }

        Debug.assert(!!state.currentAffectedFilesExportedModulesMap);
        // Go through exported modules from cache first
        // If exported modules has path, all files referencing file exported from are affected
        if (forEachEntry(state.currentAffectedFilesExportedModulesMap!, (exportedModules, exportedFromPath) =>
            exportedModules &&
            exportedModules.has(filePath) &&
            forEachFileAndExportsOfFile(state, exportedFromPath as Path, seenFileAndExportsOfFile, fn)
        )) {
            return true;
        }

        // If exported from path is not from cache and exported modules has path, all files referencing file exported from are affected
        if (forEachEntry(state.exportedModulesMap!, (exportedModules, exportedFromPath) =>
            !state.currentAffectedFilesExportedModulesMap!.has(exportedFromPath) && // If we already iterated this through cache, ignore it
            exportedModules.has(filePath) &&
            forEachFileAndExportsOfFile(state, exportedFromPath as Path, seenFileAndExportsOfFile, fn)
        )) {
            return true;
        }

        // Remove diagnostics of files that import this file (without going to exports of referencing files)
        return !!forEachEntry(state.referencedMap!, (referencesInFile, referencingFilePath) =>
            referencesInFile.has(filePath) &&
            !seenFileAndExportsOfFile.has(referencingFilePath) && // Not already removed diagnostic file
            fn(state, referencingFilePath as Path) // Dont add to seen since this is not yet done with the export removal
        );
    }


    /**
     * This is called after completing operation on the next affected file.
     * The operations here are postponed to ensure that cancellation during the iteration is handled correctly
     */
    function doneWithAffectedFile(
        state: BuilderProgramState,
        affected: SourceFile | Program,
        emitKind?: BuilderFileEmit,
        isPendingEmit?: boolean,
        isBuildInfoEmit?: boolean
    ) {
        if (isBuildInfoEmit) {
            state.emittedBuildInfo = true;
        }
        else if (affected === state.program) {
            state.changedFilesSet.clear();
            state.programEmitComplete = true;
        }
        else {
            state.seenAffectedFiles!.set((affected as SourceFile).resolvedPath, true);
            if (emitKind !== undefined) {
                (state.seenEmittedFiles || (state.seenEmittedFiles = createMap())).set((affected as SourceFile).resolvedPath, emitKind);
            }
            if (isPendingEmit) {
                state.affectedFilesPendingEmitIndex!++;
            }
            else {
                state.affectedFilesIndex!++;
            }
        }
    }

    /**
     * Returns the result with affected file
     */
    function toAffectedFileResult<T>(state: BuilderProgramState, result: T, affected: SourceFile | Program): AffectedFileResult<T> {
        doneWithAffectedFile(state, affected);
        return { result, affected };
    }

    /**
     * Returns the result with affected file
     */
    function toAffectedFileEmitResult(
        state: BuilderProgramState,
        result: EmitResult,
        affected: SourceFile | Program,
        emitKind: BuilderFileEmit,
        isPendingEmit?: boolean,
        isBuildInfoEmit?: boolean
    ): AffectedFileResult<EmitResult> {
        doneWithAffectedFile(state, affected, emitKind, isPendingEmit, isBuildInfoEmit);
        return { result, affected };
    }

    /**
     * Gets semantic diagnostics for the file which are
     * bindAndCheckDiagnostics (from cache) and program diagnostics
     */
    function getSemanticDiagnosticsOfFile(state: BuilderProgramState, sourceFile: SourceFile, cancellationToken?: CancellationToken): readonly Diagnostic[] {
        return concatenate(
            getBinderAndCheckerDiagnosticsOfFile(state, sourceFile, cancellationToken),
            Debug.assertDefined(state.program).getProgramDiagnostics(sourceFile)
        );
    }

    /**
     * Gets the binder and checker diagnostics either from cache if present, or otherwise from program and caches it
     * Note that it is assumed that when asked about binder and checker diagnostics, the file has been taken out of affected files/changed file set
     */
    function getBinderAndCheckerDiagnosticsOfFile(state: BuilderProgramState, sourceFile: SourceFile, cancellationToken?: CancellationToken): readonly Diagnostic[] {
        const path = sourceFile.resolvedPath;
        if (state.semanticDiagnosticsPerFile) {
            const cachedDiagnostics = state.semanticDiagnosticsPerFile.get(path);
            // Report the bind and check diagnostics from the cache if we already have those diagnostics present
            if (cachedDiagnostics) {
                return cachedDiagnostics;
            }
        }

        // Diagnostics werent cached, get them from program, and cache the result
        const diagnostics = Debug.assertDefined(state.program).getBindAndCheckDiagnostics(sourceFile, cancellationToken);
        if (state.semanticDiagnosticsPerFile) {
            state.semanticDiagnosticsPerFile.set(path, diagnostics);
        }
        return diagnostics;
    }

    export type ProgramBuildInfoDiagnostic = string | [string, readonly ReusableDiagnostic[]];
    export interface ProgramBuildInfo {
        fileInfos: MapLike<BuilderState.FileInfo>;
        options: CompilerOptions;
        referencedMap?: MapLike<string[]>;
        exportedModulesMap?: MapLike<string[]>;
        semanticDiagnosticsPerFile?: ProgramBuildInfoDiagnostic[];
    }

    /**
     * Gets the program information to be emitted in buildInfo so that we can use it to create new program
     */
    function getProgramBuildInfo(state: Readonly<ReusableBuilderProgramState>, getCanonicalFileName: GetCanonicalFileName): ProgramBuildInfo | undefined {
        if (state.compilerOptions.outFile || state.compilerOptions.out) return undefined;
        const currentDirectory = Debug.assertDefined(state.program).getCurrentDirectory();
        const buildInfoDirectory = getDirectoryPath(getNormalizedAbsolutePath(getTsBuildInfoEmitOutputFilePath(state.compilerOptions)!, currentDirectory));
        const fileInfos: MapLike<BuilderState.FileInfo> = {};
        state.fileInfos.forEach((value, key) => {
            const signature = state.currentAffectedFilesSignatures && state.currentAffectedFilesSignatures.get(key);
            fileInfos[relativeToBuildInfo(key)] = signature === undefined ? value : { version: value.version, signature };
        });

        const result: ProgramBuildInfo = {
            fileInfos,
            options: convertToReusableCompilerOptions(state.compilerOptions, relativeToBuildInfoEnsuringAbsolutePath)
        };
        if (state.referencedMap) {
            const referencedMap: MapLike<string[]> = {};
            state.referencedMap.forEach((value, key) => {
                referencedMap[relativeToBuildInfo(key)] = arrayFrom(value.keys(), relativeToBuildInfo);
            });
            result.referencedMap = referencedMap;
        }

        if (state.exportedModulesMap) {
            const exportedModulesMap: MapLike<string[]> = {};
            state.exportedModulesMap.forEach((value, key) => {
                const newValue = state.currentAffectedFilesExportedModulesMap && state.currentAffectedFilesExportedModulesMap.get(key);
                // Not in temporary cache, use existing value
                if (newValue === undefined) exportedModulesMap[relativeToBuildInfo(key)] = arrayFrom(value.keys(), relativeToBuildInfo);
                // Value in cache and has updated value map, use that
                else if (newValue) exportedModulesMap[relativeToBuildInfo(key)] = arrayFrom(newValue.keys(), relativeToBuildInfo);
            });
            result.exportedModulesMap = exportedModulesMap;
        }

        if (state.semanticDiagnosticsPerFile) {
            const semanticDiagnosticsPerFile: ProgramBuildInfoDiagnostic[] = [];
            // Currently not recording actual errors since those mean no emit for tsc --build
            state.semanticDiagnosticsPerFile.forEach((value, key) => semanticDiagnosticsPerFile.push(
                value.length ?
                    [
                        relativeToBuildInfo(key),
                        state.hasReusableDiagnostic ?
                            value as readonly ReusableDiagnostic[] :
                            convertToReusableDiagnostics(value as readonly Diagnostic[], relativeToBuildInfo)
                    ] :
                    relativeToBuildInfo(key)
            ));
            result.semanticDiagnosticsPerFile = semanticDiagnosticsPerFile;
        }

        return result;

        function relativeToBuildInfoEnsuringAbsolutePath(path: string) {
            return relativeToBuildInfo(getNormalizedAbsolutePath(path, currentDirectory));
        }

        function relativeToBuildInfo(path: string) {
            return ensurePathIsNonModuleName(getRelativePathFromDirectory(buildInfoDirectory, path, getCanonicalFileName));
        }
    }

    function convertToReusableCompilerOptions(options: CompilerOptions, relativeToBuildInfo: (path: string) => string) {
        const result: CompilerOptions = {};
        const { optionsNameMap } = getOptionsNameMap();

        for (const name in options) {
            if (hasProperty(options, name)) {
                result[name] = convertToReusableCompilerOptionValue(
                    optionsNameMap.get(name.toLowerCase()),
                    options[name] as CompilerOptionsValue,
                    relativeToBuildInfo
                );
            }
        }
        if (result.configFilePath) {
            result.configFilePath = relativeToBuildInfo(result.configFilePath);
        }
        return result;
    }

    function convertToReusableCompilerOptionValue(option: CommandLineOption | undefined, value: CompilerOptionsValue, relativeToBuildInfo: (path: string) => string) {
        if (option) {
            if (option.type === "list") {
                const values = value as readonly (string | number)[];
                if (option.element.isFilePath && values.length) {
                    return values.map(relativeToBuildInfo);
                }
            }
            else if (option.isFilePath) {
                return relativeToBuildInfo(value as string);
            }
        }
        return value;
    }

    function convertToReusableDiagnostics(diagnostics: readonly Diagnostic[], relativeToBuildInfo: (path: string) => string): readonly ReusableDiagnostic[] {
        Debug.assert(!!diagnostics.length);
        return diagnostics.map(diagnostic => {
            const result: ReusableDiagnostic = convertToReusableDiagnosticRelatedInformation(diagnostic, relativeToBuildInfo);
            result.reportsUnnecessary = diagnostic.reportsUnnecessary;
            result.source = diagnostic.source;
            const { relatedInformation } = diagnostic;
            result.relatedInformation = relatedInformation ?
                relatedInformation.length ?
                    relatedInformation.map(r => convertToReusableDiagnosticRelatedInformation(r, relativeToBuildInfo)) :
                    emptyArray :
                undefined;
            return result;
        });
    }

    function convertToReusableDiagnosticRelatedInformation(diagnostic: DiagnosticRelatedInformation, relativeToBuildInfo: (path: string) => string): ReusableDiagnosticRelatedInformation {
        const { file } = diagnostic;
        return {
            ...diagnostic,
            file: file ? relativeToBuildInfo(file.resolvedPath) : undefined
        };
    }

    export enum BuilderProgramKind {
        SemanticDiagnosticsBuilderProgram,
        EmitAndSemanticDiagnosticsBuilderProgram
    }

    export interface BuilderCreationParameters {
        newProgram: Program;
        host: BuilderProgramHost;
        oldProgram: BuilderProgram | undefined;
        configFileParsingDiagnostics: readonly Diagnostic[];
    }

    export function getBuilderCreationParameters(newProgramOrRootNames: Program | readonly string[] | undefined, hostOrOptions: BuilderProgramHost | CompilerOptions | undefined, oldProgramOrHost?: BuilderProgram | CompilerHost, configFileParsingDiagnosticsOrOldProgram?: readonly Diagnostic[] | BuilderProgram, configFileParsingDiagnostics?: readonly Diagnostic[], projectReferences?: readonly ProjectReference[]): BuilderCreationParameters {
        let host: BuilderProgramHost;
        let newProgram: Program;
        let oldProgram: BuilderProgram;
        if (newProgramOrRootNames === undefined) {
            Debug.assert(hostOrOptions === undefined);
            host = oldProgramOrHost as CompilerHost;
            oldProgram = configFileParsingDiagnosticsOrOldProgram as BuilderProgram;
            Debug.assert(!!oldProgram);
            newProgram = oldProgram.getProgram();
        }
        else if (isArray(newProgramOrRootNames)) {
            oldProgram = configFileParsingDiagnosticsOrOldProgram as BuilderProgram;
            newProgram = createProgram({
                rootNames: newProgramOrRootNames,
                options: hostOrOptions as CompilerOptions,
                host: oldProgramOrHost as CompilerHost,
                oldProgram: oldProgram && oldProgram.getProgramOrUndefined(),
                configFileParsingDiagnostics,
                projectReferences
            });
            host = oldProgramOrHost as CompilerHost;
        }
        else {
            newProgram = newProgramOrRootNames;
            host = hostOrOptions as BuilderProgramHost;
            oldProgram = oldProgramOrHost as BuilderProgram;
            configFileParsingDiagnostics = configFileParsingDiagnosticsOrOldProgram as readonly Diagnostic[];
        }
        return { host, newProgram, oldProgram, configFileParsingDiagnostics: configFileParsingDiagnostics || emptyArray };
    }

    export function createBuilderProgram(kind: BuilderProgramKind.SemanticDiagnosticsBuilderProgram, builderCreationParameters: BuilderCreationParameters): SemanticDiagnosticsBuilderProgram;
    export function createBuilderProgram(kind: BuilderProgramKind.EmitAndSemanticDiagnosticsBuilderProgram, builderCreationParameters: BuilderCreationParameters): EmitAndSemanticDiagnosticsBuilderProgram;
    export function createBuilderProgram(kind: BuilderProgramKind, { newProgram, host, oldProgram, configFileParsingDiagnostics }: BuilderCreationParameters) {
        // Return same program if underlying program doesnt change
        let oldState = oldProgram && oldProgram.getState();
        if (oldState && newProgram === oldState.program && configFileParsingDiagnostics === newProgram.getConfigFileParsingDiagnostics()) {
            newProgram = undefined!; // TODO: GH#18217
            oldState = undefined;
            return oldProgram;
        }

        /**
         * Create the canonical file name for identity
         */
        const getCanonicalFileName = createGetCanonicalFileName(host.useCaseSensitiveFileNames());
        /**
         * Computing hash to for signature verification
         */
        const computeHash = host.createHash || generateDjb2Hash;
        let state = createBuilderProgramState(newProgram, getCanonicalFileName, oldState);
        let backupState: BuilderProgramState | undefined;
        newProgram.getProgramBuildInfo = () => getProgramBuildInfo(state, getCanonicalFileName);

        // To ensure that we arent storing any references to old program or new program without state
        newProgram = undefined!; // TODO: GH#18217
        oldProgram = undefined;
        oldState = undefined;

        const builderProgram = createRedirectedBuilderProgram(state, configFileParsingDiagnostics);
        builderProgram.getState = () => state;
        builderProgram.backupState = () => {
            Debug.assert(backupState === undefined);
            backupState = cloneBuilderProgramState(state);
        };
        builderProgram.restoreState = () => {
            state = Debug.assertDefined(backupState);
            backupState = undefined;
        };
        builderProgram.getAllDependencies = sourceFile => BuilderState.getAllDependencies(state, Debug.assertDefined(state.program), sourceFile);
        builderProgram.getSemanticDiagnostics = getSemanticDiagnostics;
        builderProgram.emit = emit;
        builderProgram.releaseProgram = () => {
            releaseCache(state);
            backupState = undefined;
        };

        if (kind === BuilderProgramKind.SemanticDiagnosticsBuilderProgram) {
            (builderProgram as SemanticDiagnosticsBuilderProgram).getSemanticDiagnosticsOfNextAffectedFile = getSemanticDiagnosticsOfNextAffectedFile;
        }
        else if (kind === BuilderProgramKind.EmitAndSemanticDiagnosticsBuilderProgram) {
            (builderProgram as EmitAndSemanticDiagnosticsBuilderProgram).getSemanticDiagnosticsOfNextAffectedFile = getSemanticDiagnosticsOfNextAffectedFile;
            (builderProgram as EmitAndSemanticDiagnosticsBuilderProgram).emitNextAffectedFile = emitNextAffectedFile;
        }
        else {
            notImplemented();
        }

        return builderProgram;

        /**
         * Emits the next affected file's emit result (EmitResult and sourceFiles emitted) or returns undefined if iteration is complete
         * The first of writeFile if provided, writeFile of BuilderProgramHost if provided, writeFile of compiler host
         * in that order would be used to write the files
         */
        function emitNextAffectedFile(writeFile?: WriteFileCallback, cancellationToken?: CancellationToken, emitOnlyDtsFiles?: boolean, customTransformers?: CustomTransformers): AffectedFileResult<EmitResult> {
            let affected = getNextAffectedFile(state, cancellationToken, computeHash);
            let emitKind = BuilderFileEmit.Full;
            let isPendingEmitFile = false;
            if (!affected) {
                if (!state.compilerOptions.out && !state.compilerOptions.outFile) {
                    const pendingAffectedFile = getNextAffectedFilePendingEmit(state);
                    if (!pendingAffectedFile) {
                        if (state.emittedBuildInfo) {
                            return undefined;
                        }

                        const affected = Debug.assertDefined(state.program);
                        return toAffectedFileEmitResult(
                            state,
                            // When whole program is affected, do emit only once (eg when --out or --outFile is specified)
                            // Otherwise just affected file
                            affected.emitBuildInfo(writeFile || maybeBind(host, host.writeFile), cancellationToken),
                            affected,
                            /*emitKind*/ BuilderFileEmit.Full,
                            /*isPendingEmitFile*/ false,
                            /*isBuildInfoEmit*/ true
                        );
                    }
                    ({ affectedFile: affected, emitKind } = pendingAffectedFile);
                    isPendingEmitFile = true;
                }
                else {
                    const program = Debug.assertDefined(state.program);
                    if (state.programEmitComplete) return undefined;
                    affected = program;
                }
            }

            return toAffectedFileEmitResult(
                state,
                // When whole program is affected, do emit only once (eg when --out or --outFile is specified)
                // Otherwise just affected file
                Debug.assertDefined(state.program).emit(
                    affected === state.program ? undefined : affected as SourceFile,
                    writeFile || maybeBind(host, host.writeFile),
                    cancellationToken,
                    emitOnlyDtsFiles || emitKind === BuilderFileEmit.DtsOnly,
                    customTransformers
                ),
                affected,
                emitKind,
                isPendingEmitFile,
            );
        }

        /**
         * Emits the JavaScript and declaration files.
         * When targetSource file is specified, emits the files corresponding to that source file,
         * otherwise for the whole program.
         * In case of EmitAndSemanticDiagnosticsBuilderProgram, when targetSourceFile is specified,
         * it is assumed that that file is handled from affected file list. If targetSourceFile is not specified,
         * it will only emit all the affected files instead of whole program
         *
         * The first of writeFile if provided, writeFile of BuilderProgramHost if provided, writeFile of compiler host
         * in that order would be used to write the files
         */
        function emit(targetSourceFile?: SourceFile, writeFile?: WriteFileCallback, cancellationToken?: CancellationToken, emitOnlyDtsFiles?: boolean, customTransformers?: CustomTransformers): EmitResult {
            if (kind === BuilderProgramKind.EmitAndSemanticDiagnosticsBuilderProgram) {
                assertSourceFileOkWithoutNextAffectedCall(state, targetSourceFile);
                const result = handleNoEmitOptions(builderProgram, targetSourceFile, cancellationToken);
                if (result) return result;
                if (!targetSourceFile) {
                    // Emit and report any errors we ran into.
                    let sourceMaps: SourceMapEmitResult[] = [];
                    let emitSkipped = false;
                    let diagnostics: Diagnostic[] | undefined;
                    let emittedFiles: string[] = [];

                    let affectedEmitResult: AffectedFileResult<EmitResult>;
                    while (affectedEmitResult = emitNextAffectedFile(writeFile, cancellationToken, emitOnlyDtsFiles, customTransformers)) {
                        emitSkipped = emitSkipped || affectedEmitResult.result.emitSkipped;
                        diagnostics = addRange(diagnostics, affectedEmitResult.result.diagnostics);
                        emittedFiles = addRange(emittedFiles, affectedEmitResult.result.emittedFiles);
                        sourceMaps = addRange(sourceMaps, affectedEmitResult.result.sourceMaps);
                    }
                    return {
                        emitSkipped,
                        diagnostics: diagnostics || emptyArray,
                        emittedFiles,
                        sourceMaps
                    };
                }
            }
            return Debug.assertDefined(state.program).emit(targetSourceFile, writeFile || maybeBind(host, host.writeFile), cancellationToken, emitOnlyDtsFiles, customTransformers);
        }

        /**
         * Return the semantic diagnostics for the next affected file or undefined if iteration is complete
         * If provided ignoreSourceFile would be called before getting the diagnostics and would ignore the sourceFile if the returned value was true
         */
        function getSemanticDiagnosticsOfNextAffectedFile(cancellationToken?: CancellationToken, ignoreSourceFile?: (sourceFile: SourceFile) => boolean): AffectedFileResult<readonly Diagnostic[]> {
            while (true) {
                const affected = getNextAffectedFile(state, cancellationToken, computeHash);
                if (!affected) {
                    // Done
                    return undefined;
                }
                else if (affected === state.program) {
                    // When whole program is affected, get all semantic diagnostics (eg when --out or --outFile is specified)
                    return toAffectedFileResult(
                        state,
                        state.program.getSemanticDiagnostics(/*targetSourceFile*/ undefined, cancellationToken),
                        affected
                    );
                }

                // Add file to affected file pending emit to handle for later emit time
                if (kind === BuilderProgramKind.EmitAndSemanticDiagnosticsBuilderProgram) {
                    addToAffectedFilesPendingEmit(state, (affected as SourceFile).resolvedPath, BuilderFileEmit.Full);
                }

                // Get diagnostics for the affected file if its not ignored
                if (ignoreSourceFile && ignoreSourceFile(affected as SourceFile)) {
                    // Get next affected file
                    doneWithAffectedFile(state, affected);
                    continue;
                }

                return toAffectedFileResult(
                    state,
                    getSemanticDiagnosticsOfFile(state, affected as SourceFile, cancellationToken),
                    affected
                );
            }
        }

        /**
         * Gets the semantic diagnostics from the program corresponding to this state of file (if provided) or whole program
         * The semantic diagnostics are cached and managed here
         * Note that it is assumed that when asked about semantic diagnostics through this API,
         * the file has been taken out of affected files so it is safe to use cache or get from program and cache the diagnostics
         * In case of SemanticDiagnosticsBuilderProgram if the source file is not provided,
         * it will iterate through all the affected files, to ensure that cache stays valid and yet provide a way to get all semantic diagnostics
         */
        function getSemanticDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): readonly Diagnostic[] {
            assertSourceFileOkWithoutNextAffectedCall(state, sourceFile);
            const compilerOptions = Debug.assertDefined(state.program).getCompilerOptions();
            if (compilerOptions.outFile || compilerOptions.out) {
                Debug.assert(!state.semanticDiagnosticsPerFile);
                // We dont need to cache the diagnostics just return them from program
                return Debug.assertDefined(state.program).getSemanticDiagnostics(sourceFile, cancellationToken);
            }

            if (sourceFile) {
                return getSemanticDiagnosticsOfFile(state, sourceFile, cancellationToken);
            }

            // When semantic builder asks for diagnostics of the whole program,
            // ensure that all the affected files are handled
            // eslint-disable-next-line no-empty
            while (getSemanticDiagnosticsOfNextAffectedFile(cancellationToken)) {
            }

            let diagnostics: Diagnostic[] | undefined;
            for (const sourceFile of Debug.assertDefined(state.program).getSourceFiles()) {
                diagnostics = addRange(diagnostics, getSemanticDiagnosticsOfFile(state, sourceFile, cancellationToken));
            }
            return diagnostics || emptyArray;
        }
    }

    function addToAffectedFilesPendingEmit(state: BuilderProgramState, affectedFilePendingEmit: Path, kind: BuilderFileEmit) {
        if (!state.affectedFilesPendingEmit) state.affectedFilesPendingEmit = [];
        if (!state.affectedFilesPendingEmitKind) state.affectedFilesPendingEmitKind = createMap();

        const existingKind = state.affectedFilesPendingEmitKind.get(affectedFilePendingEmit);
        state.affectedFilesPendingEmit.push(affectedFilePendingEmit);
        state.affectedFilesPendingEmitKind.set(affectedFilePendingEmit, existingKind || kind);

        // affectedFilesPendingEmitIndex === undefined
        // - means the emit state.affectedFilesPendingEmit was undefined before adding current affected files
        //   so start from 0 as array would be affectedFilesPendingEmit
        // else, continue to iterate from existing index, the current set is appended to existing files
        if (state.affectedFilesPendingEmitIndex === undefined) {
            state.affectedFilesPendingEmitIndex = 0;
        }
    }

    function getMapOfReferencedSet(mapLike: MapLike<readonly string[]> | undefined, toPath: (path: string) => Path): ReadonlyMap<BuilderState.ReferencedSet> | undefined {
        if (!mapLike) return undefined;
        const map = createMap<BuilderState.ReferencedSet>();
        // Copies keys/values from template. Note that for..in will not throw if
        // template is undefined, and instead will just exit the loop.
        for (const key in mapLike) {
            if (hasProperty(mapLike, key)) {
                map.set(toPath(key), arrayToSet(mapLike[key], toPath));
            }
        }
        return map;
    }

    export function createBuildProgramUsingProgramBuildInfo(program: ProgramBuildInfo, buildInfoPath: string, host: ReadBuildProgramHost): EmitAndSemanticDiagnosticsBuilderProgram {
        const buildInfoDirectory = getDirectoryPath(getNormalizedAbsolutePath(buildInfoPath, host.getCurrentDirectory()));
        const getCanonicalFileName = createGetCanonicalFileName(host.useCaseSensitiveFileNames());

        const fileInfos = createMap<BuilderState.FileInfo>();
        for (const key in program.fileInfos) {
            if (hasProperty(program.fileInfos, key)) {
                fileInfos.set(toPath(key), program.fileInfos[key]);
            }
        }

        const state: ReusableBuilderProgramState = {
            fileInfos,
            compilerOptions: convertToOptionsWithAbsolutePaths(program.options, toAbsolutePath),
            referencedMap: getMapOfReferencedSet(program.referencedMap, toPath),
            exportedModulesMap: getMapOfReferencedSet(program.exportedModulesMap, toPath),
            semanticDiagnosticsPerFile: program.semanticDiagnosticsPerFile && arrayToMap(program.semanticDiagnosticsPerFile, value => toPath(isString(value) ? value : value[0]), value => isString(value) ? emptyArray : value[1]),
            hasReusableDiagnostic: true
        };
        return {
            getState: () => state,
            backupState: noop,
            restoreState: noop,
            getProgram: notImplemented,
            getProgramOrUndefined: returnUndefined,
            releaseProgram: noop,
            getCompilerOptions: () => state.compilerOptions,
            getSourceFile: notImplemented,
            getSourceFiles: notImplemented,
            getOptionsDiagnostics: notImplemented,
            getGlobalDiagnostics: notImplemented,
            getConfigFileParsingDiagnostics: notImplemented,
            getSyntacticDiagnostics: notImplemented,
            getDeclarationDiagnostics: notImplemented,
            getSemanticDiagnostics: notImplemented,
            emit: notImplemented,
            getAllDependencies: notImplemented,
            getCurrentDirectory: notImplemented,
            emitNextAffectedFile: notImplemented,
            getSemanticDiagnosticsOfNextAffectedFile: notImplemented,
            close: noop,
        };

        function toPath(path: string) {
            return ts.toPath(path, buildInfoDirectory, getCanonicalFileName);
        }

        function toAbsolutePath(path: string) {
            return getNormalizedAbsolutePath(path, buildInfoDirectory);
        }
    }

    export function createRedirectedBuilderProgram(state: { program: Program | undefined; compilerOptions: CompilerOptions; }, configFileParsingDiagnostics: readonly Diagnostic[]): BuilderProgram {
        return {
            getState: notImplemented,
            backupState: noop,
            restoreState: noop,
            getProgram,
            getProgramOrUndefined: () => state.program,
            releaseProgram: () => state.program = undefined,
            getCompilerOptions: () => state.compilerOptions,
            getSourceFile: fileName => getProgram().getSourceFile(fileName),
            getSourceFiles: () => getProgram().getSourceFiles(),
            getOptionsDiagnostics: cancellationToken => getProgram().getOptionsDiagnostics(cancellationToken),
            getGlobalDiagnostics: cancellationToken => getProgram().getGlobalDiagnostics(cancellationToken),
            getConfigFileParsingDiagnostics: () => configFileParsingDiagnostics,
            getSyntacticDiagnostics: (sourceFile, cancellationToken) => getProgram().getSyntacticDiagnostics(sourceFile, cancellationToken),
            getDeclarationDiagnostics: (sourceFile, cancellationToken) => getProgram().getDeclarationDiagnostics(sourceFile, cancellationToken),
            getSemanticDiagnostics: (sourceFile, cancellationToken) => getProgram().getSemanticDiagnostics(sourceFile, cancellationToken),
            emit: (sourceFile, writeFile, cancellationToken, emitOnlyDts, customTransformers) => getProgram().emit(sourceFile, writeFile, cancellationToken, emitOnlyDts, customTransformers),
            getAllDependencies: notImplemented,
            getCurrentDirectory: () => getProgram().getCurrentDirectory(),
            close: noop,
        };

        function getProgram() {
            return Debug.assertDefined(state.program);
        }
    }
}