TypeScript/src/services/codeFixProvider.ts

import {
    arrayFrom,
    cast,
    CodeActionCommand,
    CodeFixAction,
    CodeFixAllContext,
    CodeFixContext,
    CodeFixContextBase,
    CodeFixRegistration,
    CombinedCodeActions,
    computeSuggestionDiagnostics,
    contains,
    createMultiMap,
    Debug,
    Diagnostic,
    DiagnosticAndArguments,
    diagnosticToString,
    DiagnosticWithLocation,
    FileTextChanges,
    flatMap,
    isString,
    map,
    TextChange,
    textChanges,
} from "./_namespaces/ts";

const errorCodeToFixes = createMultiMap<string, CodeFixRegistration>();
const fixIdToRegistration = new Map<string, CodeFixRegistration>();

/** @internal */
export function createCodeFixActionWithoutFixAll(fixName: string, changes: FileTextChanges[], description: DiagnosticAndArguments) {
    return createCodeFixActionWorker(fixName, diagnosticToString(description), changes, /*fixId*/ undefined, /*fixAllDescription*/ undefined);
}

/** @internal */
export function createCodeFixAction(fixName: string, changes: FileTextChanges[], description: DiagnosticAndArguments, fixId: {}, fixAllDescription: DiagnosticAndArguments, command?: CodeActionCommand): CodeFixAction {
    return createCodeFixActionWorker(fixName, diagnosticToString(description), changes, fixId, diagnosticToString(fixAllDescription), command);
}

/** @internal */
export function createCodeFixActionMaybeFixAll(fixName: string, changes: FileTextChanges[], description: DiagnosticAndArguments, fixId?: {}, fixAllDescription?: DiagnosticAndArguments, command?: CodeActionCommand) {
    return createCodeFixActionWorker(fixName, diagnosticToString(description), changes, fixId, fixAllDescription && diagnosticToString(fixAllDescription), command);
}

function createCodeFixActionWorker(fixName: string, description: string, changes: FileTextChanges[], fixId?: {}, fixAllDescription?: string, command?: CodeActionCommand): CodeFixAction {
    return { fixName, description, changes, fixId, fixAllDescription, commands: command ? [command] : undefined };
}

/** @internal */
export function registerCodeFix(reg: CodeFixRegistration) {
    for (const error of reg.errorCodes) {
        errorCodeToFixesArray = undefined;
        errorCodeToFixes.add(String(error), reg);
    }
    if (reg.fixIds) {
        for (const fixId of reg.fixIds) {
            Debug.assert(!fixIdToRegistration.has(fixId));
            fixIdToRegistration.set(fixId, reg);
        }
    }
}

let errorCodeToFixesArray: readonly string[] | undefined;
/** @internal */
export function getSupportedErrorCodes(): readonly string[] {
    return errorCodeToFixesArray ??= arrayFrom(errorCodeToFixes.keys());
}

function removeFixIdIfFixAllUnavailable(registration: CodeFixRegistration, diagnostics: Diagnostic[]) {
    const { errorCodes } = registration;
    let maybeFixableDiagnostics = 0;
    for (const diag of diagnostics) {
        if (contains(errorCodes, diag.code)) maybeFixableDiagnostics++;
        if (maybeFixableDiagnostics > 1) break;
    }

    const fixAllUnavailable = maybeFixableDiagnostics < 2;
    return ({ fixId, fixAllDescription, ...action }: CodeFixAction): CodeFixAction => {
        return fixAllUnavailable ? action : { ...action, fixId, fixAllDescription };
    };
}

/** @internal */
export function getFixes(context: CodeFixContext): readonly CodeFixAction[] {
    const diagnostics = getDiagnostics(context);
    const registrations = errorCodeToFixes.get(String(context.errorCode));
    return flatMap(registrations, f => map(f.getCodeActions(context), removeFixIdIfFixAllUnavailable(f, diagnostics)));
}

/** @internal */
export function getAllFixes(context: CodeFixAllContext): CombinedCodeActions {
    // Currently fixId is always a string.
    return fixIdToRegistration.get(cast(context.fixId, isString))!.getAllCodeActions!(context);
}

/** @internal */
export function createCombinedCodeActions(changes: FileTextChanges[], commands?: CodeActionCommand[]): CombinedCodeActions {
    return { changes, commands };
}

/** @internal */
export function createFileTextChanges(fileName: string, textChanges: TextChange[]): FileTextChanges {
    return { fileName, textChanges };
}

/** @internal */
export function codeFixAll(
    context: CodeFixAllContext,
    errorCodes: number[],
    use: (changes: textChanges.ChangeTracker, error: DiagnosticWithLocation, commands: CodeActionCommand[]) => void,
): CombinedCodeActions {
    const commands: CodeActionCommand[] = [];
    const changes = textChanges.ChangeTracker.with(context, t => eachDiagnostic(context, errorCodes, diag => use(t, diag, commands)));
    return createCombinedCodeActions(changes, commands.length === 0 ? undefined : commands);
}

/** @internal */
export function eachDiagnostic(context: CodeFixAllContext, errorCodes: readonly number[], cb: (diag: DiagnosticWithLocation) => void): void {
    for (const diag of getDiagnostics(context)) {
        if (contains(errorCodes, diag.code)) {
            cb(diag as DiagnosticWithLocation);
        }
    }
}

function getDiagnostics({ program, sourceFile, cancellationToken }: CodeFixContextBase) {
    return [
        ...program.getSemanticDiagnostics(sourceFile, cancellationToken),
        ...program.getSyntacticDiagnostics(sourceFile, cancellationToken),
        ...computeSuggestionDiagnostics(sourceFile, program, cancellationToken)
    ];
}