Support TypeScript 7.1 API by Copilot · Pull Request #1704 · TypeStrong/ts-loader

Copilot · 2026-07-26T09:47:17Z

This PR migrates ts-loader to fully support and integrate with the TypeScript 7.1+ Native API (powered by the tsgo engine). Ignore the ESLint failures - TypeScript ESLint also doesn't yet support TS 7. It'll come!

The implementation has moved past the initial hybrid/experimental design to route core operations through the native typescript/unstable/sync architecture by default. Historical TypeScript version dependencies have been removed in favour of direct 7.1 alignment.

🚀 What Changed

Default Native Architecture: The native API path (experimentalNativeApi: true) is now the default behavior for the loader.
Legacy API Removal: Cleaned up historical TypeScript compiler API dependencies, porting internal compilation machinery to target TypeScript 7 native synchronous entry points directly.
Async Instance Setup: Maintained async loader instance creation to dynamically resolve and load the native ESM sync compiler APIs at runtime.
CI Test Suite Updates: Shifted the workflow matrix to target the 7.1 compiler layer, addressing and adapting tests for rootDir, declaration output, watch behaviors, and error formatting (resolveJsonModule, onlyCompileBundledFiles).

📦 Integration Details

Native Emit Path (/src/native.ts): Opens and manages native snapshots, uses getJavaScriptEmit for file emissions, and registers project dependencies natively with Webpack.
Diagnostic Mapping: Translates native compiler diagnostics directly into native Webpack module errors.
Compatibility Layer: Preserves existing source mapping and module completion handling to ensure seamless integration with modern Webpack builds, alongside localized fixes for legacy Webpack 4 setups.

🧪 Verification Status

yarn build compiles successfully against the native TS7 target architecture.
Full execution test suites run and pass cleanly against the 7.1.0-dev core matrix.
(Note: Historic loaderOptions testing has been bypassed or updated to reflect the new default baseline)..

johnnyreilly · 2026-07-26T09:52:30Z

@copilot update

ts-loader/.github/workflows/push.yml

Line 52 in 53082fb

ts: [5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now

and

ts-loader/.github/workflows/push.yml

Line 84 in 53082fb

ts: [5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now

to only cater for: 7.1.0-dev.20260725.1 - the existing versions specified do not contain the new API.

We expect execution-tests to pass after this change

Copilot · 2026-07-26T09:55:57Z

@copilot update

ts-loader/.github/workflows/push.yml

Line 52 in 53082fb

ts: [5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now

and https://github.com/TypeStrong/ts-loader/blob/53082fbe1cdeb560b6...

Updated in fcc8a21 to run the execution-test matrix only against 7.1.0-dev.20260725.1. I also verified the native path locally with yarn build && yarn execution-tests -- --single-test nativeApiTranspile.

johnnyreilly · 2026-07-26T10:14:15Z

@copilot great work! We would like the following to succeed:

yarn build && yarn execution-tests

Remember backwards compatibility is not required - feel free to make changes

Copilot · 2026-07-26T10:18:03Z

@copilot great work! We would like the following to succeed:

yarn build && yarn execution-tests
...

Verified on fcc8a21: yarn build && yarn execution-tests now succeeds locally (30 execution suites passed).

johnnyreilly · 2026-07-27T09:05:19Z

@copilot we have explictly removed the historic typescript version from dependencies and moved to use 7.1 directly. This has broken compilation. Please fix it. You will likely need to use new APIs in TypeScript 7 to achieve this. No cheating.

Copilot · 2026-07-27T09:22:14Z

@copilot we have explictly removed the historic typescript version from dependencies and moved to use 7.1 directly. This has broken compilation. Please fix it. You will likely need to use new APIs i...

Updated in 4706cfe. yarn build now passes against direct TypeScript 7 by routing the loader through typescript/unstable/sync instead of the removed legacy compiler API.

johnnyreilly · 2026-07-27T10:13:10Z

@copilot make experimentalNativeApi: true the default behaviour and ensure execution-tests pass. We are happy to ignore loaderOptions test for now

Copilot · 2026-07-27T10:24:54Z

@copilot make experimentalNativeApi: true the default behaviour and ensure execution-tests pass. We are happy to ignore loaderOptions test for now

Addressed in 048c5ce. The native execution test now relies on the default native API path, loaderOptions is skipped for now, and yarn build && yarn execution-tests passes locally.

…ub.com/TypeStrong/ts-loader into copilot/implement-new-tsgo-api-support

…by testing Isolated and reverted each individually against real Windows CI (full suite where the change had broad reach, targeted tests otherwise) - all three passed without the change, confirming they were never load-bearing: - bumpMtimes in the comparison-test harness: added chasing a watchpack mtime-equality theory for dependencyErrors that turned out wrong; the actual fix was in getDirectResolvedImports (already in place). - ensureSyntheticConfigForFile's files-array path normalization: added before the real fix (syntheticConfigContents' store-side key normalization, which remains); the API evidently normalizes each files-array entry internally regardless of separator style. - registerTypeScriptDependencies' getConfigFileNames loop normalization: added speculatively alongside the confirmed addDependency fix in the same edit; never independently exercised by any actual failure. Full local suite (50/50) and full Windows CI suite (50/50) still pass with all three removed.

johnnyreilly · 2026-08-07T15:16:00Z

Custom transformers and transpile support in the API can be tracked here: microsoft/TypeScript#63875

johnnyreilly · 2026-08-11T06:01:53Z

Add support for transpile directly now this PR has landed: microsoft/typescript-go#4849 (comment) courtesy of @andrewbranch - expected in nightlies soon

johnnyreilly · 2026-08-20T16:19:39Z

3b5af16 added support for microsoft/typescript-go#4849. Very smooth initial migration. Claude picked up a potential issue which I have reported here: microsoft/typescript-go#4849 (comment)

Windows comparison tests are failing right now - fixing.

api.transpileModule/transpileDeclaration build their own virtual filesystem from `fileName` verbatim rather than resolving it through a Project, so an OS-native (backslash) path panics on Windows ("mixed posix and windows paths") and also breaks diagnostic location lookup (the echoed diagnostic.fileName no longer matches the OS-native apiFileName used as the lookup key). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

api.transpileDeclaration builds its own throwaway virtual filesystem from `fileName` verbatim rather than resolving it through a Project, and panics on Windows ("mixed posix and windows paths") given any absolute path there - OS-native or forward-slash-normalized alike. Stripping the OS-native configFilePath from compilerOptions and falling back a rootDir were both tried first and, per the Windows test probe workflow, neither stopped the panic. The actual fix: pass transpileDeclaration a bare basename instead of any absolute path at all. Unlike transpileModule (which needs fileName's real directory for e.g. rootDir-containment diagnostics like TS6059, and keeps its own absolute, forward-slash path), transpileDeclaration doesn't need real directory context - its own diagnostics (isolatedDeclarations violations) are purely syntactic, and any real rootDir violation for the same file is already caught by transpileModule's own call on it. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Copilot AI added 2 commits July 26, 2026 09:39

feat: add tsgo transpile path

3670e65

fix: load tsgo API via ESM import

53082fb

Copilot AI assigned Copilot and johnnyreilly Jul 26, 2026

Copilot created this pull request from a session on behalf of johnnyreilly July 26, 2026 09:47 View session

Copilot started work on behalf of johnnyreilly July 26, 2026 09:53 View session

Restrict execution-test TS matrix to tsgo version

fcc8a21

Copilot finished work on behalf of johnnyreilly July 26, 2026 09:56

Copilot AI requested a review from johnnyreilly July 26, 2026 09:56

johnnyreilly mentioned this pull request Jul 26, 2026

typescript-native compiler #1671

Open

Copilot started work on behalf of johnnyreilly July 26, 2026 10:14 View session

Copilot finished work on behalf of johnnyreilly July 26, 2026 10:18

chore: explicitly use typescript@7.1.0-dev.20260725.1

47139fd

Copilot started work on behalf of johnnyreilly July 27, 2026 09:06 View session

Port build to TypeScript 7 native API

4706cfe

Copilot finished work on behalf of johnnyreilly July 27, 2026 09:22

fix: large

14ad7c0

Copilot started work on behalf of johnnyreilly July 27, 2026 10:13 View session

fix native API execution test defaults

048c5ce

Copilot finished work on behalf of johnnyreilly July 27, 2026 10:25

johnnyreilly added 2 commits July 27, 2026 11:28

chore: remove test

6679581

fix: remove unused

089d51d

johnnyreilly added 4 commits July 30, 2026 08:23

docs: edit AGENTS.md / deps for sourceMaps test / time

3bb72dd

Merge branch 'copilot/implement-new-tsgo-api-support' of https://gith…

b956f18

…ub.com/TypeStrong/ts-loader into copilot/implement-new-tsgo-api-support

chore: "target": "es2022"

9fd2675

johnnyreilly mentioned this pull request Jul 30, 2026

ts-loader go johnnyreilly/blog.johnnyreilly.com#1192

Merged

manfe mentioned this pull request Jul 30, 2026

Revisit TypeScript 7 upgrade (toolchain blocked until TS 7.1) wppconnect-team/wa-js#3540

Open

johnnyreilly added 14 commits July 30, 2026 19:46

feat: chalk -> picocolors

a862571

feat: picocolors -> styleText

e55bb7d

fix: test

837a924

fix: eslint -> oxlint

efa7eb0

feat: styleText -> picocolors

3434d3f

chore: clean unused

30ade78

chore: knip / upgrade deps

739f5a9

fix: execution tests

1d798ac

chore: remove experimentalWatchApi references

2a99395

chore: remove experimentalWatchApi tests

3594bf9

chore: remove reference to watchapi in tests

5544bf3

fix: loader options hash

92e5e58

fix: loader options hash

9b451d5

fix: loader options hash

2b9c9a8

johnnyreilly mentioned this pull request Aug 7, 2026

Content mappers microsoft/typescript-go#4712

Merged

johnnyreilly added 3 commits August 20, 2026 15:31

chore: update to latest nightly

d6c2531

chore: upgrade lint-staged

fac7ac7

feat: transpileApi

3b5af16

johnnyreilly and others added 2 commits August 20, 2026 17:22

johnnyreilly force-pushed the copilot/implement-new-tsgo-api-support branch from a2ad345 to 7f1cbd5 Compare August 20, 2026 19:11

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Support TypeScript 7.1 API - #1704

Support TypeScript 7.1 API#1704
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🚀 What Changed

📦 Integration Details

🧪 Verification Status

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