Fix ESM resolution by adding file extensions to imports#5656
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iclanton wants to merge 4 commits intomicrosoft:mainfrom
Open
Fix ESM resolution by adding file extensions to imports#5656iclanton wants to merge 4 commits intomicrosoft:mainfrom
iclanton wants to merge 4 commits intomicrosoft:mainfrom
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…es (microsoft#5650)" This reverts commit 7e14cda.
…ce import/extensions ESLint rule
…mportExtensions Migrates all relative import/export specifiers across the repo to include explicit .ts/.tsx file extensions. This enables TypeScript's rewriteRelativeImportExtensions compiler option to produce correct .js extensions in compiled output, fixing ESM resolution under Node.js. Also includes: - heft-typescript-plugin: inject rewriteRelativeImportExtensions and allowImportingTsExtensions in tsconfigLoader; enhance wrapWriteFile to rewrite .js specifiers when jsExtensionOverride is set; remove the old addJsExtensionToImports approach - ESLint import/extensions rule added to local-eslint-config - ESLint rule disabled for ts-loader and composite-test projects - require() calls use .js extensions (not rewritten by TS) - esm-node-import-test: new build-test validating ESM imports work - rush.json: register esm-node-import-test project Fixes microsoft#5644
TheLarkInn
approved these changes
Feb 21, 2026
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Summary
This PR migrates all relative import/export specifiers across the repo to include explicit
.ts/.tsxfile extensions, enabling TypeScript'srewriteRelativeImportExtensionscompiler option. This ensures that compiled.jsoutput includes proper file extensions in import specifiers, fixing Node.js ESM resolution when consuming Rush Stack packages via their ESM entry points.Further work toward resolving #5644
Details
Approach:
Reverted the earlier addition of
"node"entries fromexportsinpackage.jsonfiles (Temporarily add "node" entries to exports in package.json files #5650), restoring ESM entry points for packages that had them.Enabled
rewriteRelativeImportExtensionsin the local rigtsconfig.jsonconfigurations and added theimport/extensionsESLint rule tolocal-eslint-configto enforce.tsextensions in source imports going forward.Added
.tsextensions to all relative imports (~1,251 files changed) across the repo so TypeScript can rewrite them to.jsin compiled output.Updated
@rushstack/heft-typescript-pluginto:rewriteRelativeImportExtensionsandallowImportingTsExtensionsintsconfigLoaderwrapWriteFileto rewrite.jsspecifiers whenjsExtensionOverrideis setaddJsExtensionToImportsapproach (now handled natively by the TypeScript compiler)require()calls use.jsextensions directly (TypeScript does not rewrite these).ESLint rule disabled for
ts-loaderand composite-test projects where it doesn't apply.New
esm-node-import-testbuild-test added to validate that ESM imports resolve correctly at runtime under Node.js.Backwards compatibility: The
addJsExtensionToImportsoption in@rushstack/heft-typescript-pluginis removed (breaking for anyone using it), replaced by the standard TypeScriptrewriteRelativeImportExtensionsmechanism. This is reflected as aminorversion bump.How it was tested
rush buildcompletes successfully across the repo with the new import extensions andrewriteRelativeImportExtensionsenabled.esm-node-import-testbuild-test validates that ESM imports with.jsextensions resolve correctly at runtime under Node.js (uses--no-warningsto suppress expectedMODULE_TYPELESS_PACKAGE_JSONwarnings on Node 22+).import/extensionsrule catches missing.tsextensions in new code.Impacted documentation
None.