TypeScript/src/server/moduleSpecifierCache.ts

import {
    Debug,
    FileWatcher,
    ModulePath,
    ModuleSpecifierCache,
    ModuleSpecifierOptions,
    nodeModulesPathPart,
    Path,
    ResolvedModuleSpecifierInfo,
    UserPreferences,
} from "./_namespaces/ts";

/** @internal */
export interface ModuleSpecifierResolutionCacheHost {
    watchNodeModulesForPackageJsonChanges(directoryPath: string): FileWatcher;
}

/** @internal */
export function createModuleSpecifierCache(host: ModuleSpecifierResolutionCacheHost): ModuleSpecifierCache {
    let containedNodeModulesWatchers: Map<string, FileWatcher> | undefined;
    let cache: Map<Path, ResolvedModuleSpecifierInfo> | undefined;
    let currentKey: string | undefined;
    const result: ModuleSpecifierCache = {
        get(fromFileName, toFileName, preferences, options) {
            if (!cache || currentKey !== key(fromFileName, preferences, options)) return undefined;
            return cache.get(toFileName);
        },
        set(fromFileName, toFileName, preferences, options, modulePaths, moduleSpecifiers) {
            ensureCache(fromFileName, preferences, options).set(toFileName, createInfo(modulePaths, moduleSpecifiers, /*isBlockedByPackageJsonDependencies*/ false));

            // If any module specifiers were generated based off paths in node_modules,
            // a package.json file in that package was read and is an input to the cached.
            // Instead of watching each individual package.json file, set up a wildcard
            // directory watcher for any node_modules referenced and clear the cache when
            // it sees any changes.
            if (moduleSpecifiers) {
                for (const p of modulePaths) {
                    if (p.isInNodeModules) {
                        // No trailing slash
                        const nodeModulesPath = p.path.substring(0, p.path.indexOf(nodeModulesPathPart) + nodeModulesPathPart.length - 1);
                        if (!containedNodeModulesWatchers?.has(nodeModulesPath)) {
                            (containedNodeModulesWatchers ||= new Map()).set(
                                nodeModulesPath,
                                host.watchNodeModulesForPackageJsonChanges(nodeModulesPath),
                            );
                        }
                    }
                }
            }
        },
        setModulePaths(fromFileName, toFileName, preferences, options, modulePaths) {
            const cache = ensureCache(fromFileName, preferences, options);
            const info = cache.get(toFileName);
            if (info) {
                info.modulePaths = modulePaths;
            }
            else {
                cache.set(toFileName, createInfo(modulePaths, /*moduleSpecifiers*/ undefined, /*isBlockedByPackageJsonDependencies*/ undefined));
            }
        },
        setBlockedByPackageJsonDependencies(fromFileName, toFileName, preferences, options, isBlockedByPackageJsonDependencies) {
            const cache = ensureCache(fromFileName, preferences, options);
            const info = cache.get(toFileName);
            if (info) {
                info.isBlockedByPackageJsonDependencies = isBlockedByPackageJsonDependencies;
            }
            else {
                cache.set(toFileName, createInfo(/*modulePaths*/ undefined, /*moduleSpecifiers*/ undefined, isBlockedByPackageJsonDependencies));
            }
        },
        clear() {
            containedNodeModulesWatchers?.forEach(watcher => watcher.close());
            cache?.clear();
            containedNodeModulesWatchers?.clear();
            currentKey = undefined;
        },
        count() {
            return cache ? cache.size : 0;
        },
    };
    if (Debug.isDebugging) {
        Object.defineProperty(result, "__cache", { get: () => cache });
    }
    return result;

    function ensureCache(fromFileName: Path, preferences: UserPreferences, options: ModuleSpecifierOptions) {
        const newKey = key(fromFileName, preferences, options);
        if (cache && (currentKey !== newKey)) {
            result.clear();
        }
        currentKey = newKey;
        return cache ||= new Map();
    }

    function key(fromFileName: Path, preferences: UserPreferences, options: ModuleSpecifierOptions) {
        return `${fromFileName},${preferences.importModuleSpecifierEnding},${preferences.importModuleSpecifierPreference},${options.overrideImportMode}`;
    }

    function createInfo(
        modulePaths: readonly ModulePath[] | undefined,
        moduleSpecifiers: readonly string[] | undefined,
        isBlockedByPackageJsonDependencies: boolean | undefined,
    ): ResolvedModuleSpecifierInfo {
        return { modulePaths, moduleSpecifiers, isBlockedByPackageJsonDependencies };
    }
}