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Put a cache in front of matchFromAbsolutePaths #227

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Put a cache in front of matchFromAbsolutePaths #227

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23 changes: 17 additions & 6 deletions src/match-path-sync.ts
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Expand Up @@ -52,6 +52,7 @@ export function createMatchPath(
);
}

const matchFromAbsolutePathsCache = new Map(); // This is a very hot path for most apps, so we want to cache calls into it
/**
* Finds a path from tsconfig that matches a module load request.
*
Expand All @@ -69,19 +70,29 @@ export function matchFromAbsolutePaths(
readJson: Filesystem.ReadJsonSync = Filesystem.readJsonFromDiskSync,
fileExists: Filesystem.FileExistsSync = Filesystem.fileExistsSync,
extensions: Array<string> = Object.keys(require.extensions),
mainFields: (string | string[])[] = ["main"]
mainFields: (string | string[])[] = ['main'],
): string | undefined {
const tryPaths = TryPath.getPathsToTry(
// Create stable cache keys for future invocations
const cacheKey = [
absolutePathMappings.map(mapping => `${mapping.pattern}:${mapping.paths.join('')}`),
extensions,
absolutePathMappings,
requestedModule
);
requestedModule,
].join('|');

if (matchFromAbsolutePathsCache.has(cacheKey)) {
return matchFromAbsolutePathsCache.get(cacheKey);
}

const tryPaths = TryPath.getPathsToTry(extensions, absolutePathMappings, requestedModule);

if (!tryPaths) {
matchFromAbsolutePathsCache.set(cacheKey, undefined);
return undefined;
}

return findFirstExistingPath(tryPaths, readJson, fileExists, mainFields);
const path = findFirstExistingPath(tryPaths, readJson, fileExists, mainFields);
matchFromAbsolutePathsCache.set(cacheKey, path);
return path;
}

function findFirstExistingMainFieldMappedFile(
Expand Down