[daniel-stoian-lgp]

Checklist

• I have read and understand the contribution guide
• A CHANGELOG entry is included
• I have run automated testing and it is passed
• Documentation was added or is not needed
• This is an API breaking change

Issue Resolved / Feature Added

Follow-up to the TypeScript 6/7 support change (#404 ). That change lets TypeScript 7 apps build, but skips type checking for them entirely. fork-ts-checker-webpack-plugin needs the JS compiler API (createProgram), and TypeScript 7 doesn't ship it. As a result, type errors in TS 7 apps don't show up in enact pack / enact serve.

This PR adds type checking for TypeScript 7 apps by running the tsc binary that TS 7 ships.

Resolution

• New config/TypeScriptCheckPlugin.js: a webpack plugin that runs tsc --project tsconfig.json --noEmit --skipLibCheck --incremental --pretty false with Node. Build info goes to node_modules/.cache/tsconfig.tsbuildinfo, the same file fork-ts-checker used.

  • tsc starts each time webpack starts compiling (run / watchRun) and runs while webpack bundles.
  • When webpack finishes compiling (afterCompile), the plugin waits for tsc and adds each diagnostic to the compilation as an error. Existing error output, exit code 1 on failure and the dev-server overlay all work without other changes.
  • With TSC_COMPILE_ON_ERROR=true, diagnostics are added as warnings instead, as with the existing checker plugin.
  • Diagnostics in test and setup files (__tests__, *.spec.* / *.test.*, src/setupProxy.*, src/setupTests.*) are skipped, matching fork-ts-checker's filters.
  • Child compilations (e.g. html-webpack-plugin's) are ignored.
  • If tsc can't run, the build gets a warning instead of failing.
  • A tsc run still in progress is stopped when a watch or serve session ends.

• config/webpack.config.js: resolveLegacyTypeScript() becomes resolveTypeScript(). It returns {typescriptPath} when the app's typescript package has createProgram (TS 5/6, still handled by fork-ts-checker). Otherwise it returns {tscPath} from the package's bin field (TS 7, handled by the new plugin). The skip warning now only appears when typescript can't be resolved at all.

Additional Considerations

Test scenario

Setup:

1. Check out this branch of cli and link it globally (npm link inside cli), so enact runs this branch.
2. cd samples/tutorial-typescript && npm install (installs typescript@^7.0.2).
3. Add a deliberate type error at the end of src/views/MainPanel.tsx:
   const typeErrorProbe: number = 'not a number';
   export {typeErrorProbe};

TypeScript 7 (new TypeScriptCheckPlugin)

1. Run enact pack.
   • Expected: Failed to compile. with src/views/MainPanel.tsx(20,7) and TS2322: Type 'string' is not assignable to type 'number'.; exit code 1.
2. Run enact pack -p.
   • Expected: same error; exit code 1.
3. Run TSC_COMPILE_ON_ERROR=true enact pack (PowerShell: $env:TSC_COMPILE_ON_ERROR='true'; enact pack).
   • Expected: build succeeds; TS2322 is shown as a warning; exit code 0.
4. Run enact serve and open the app in the browser.
   • Expected: TS2322 in the terminal and in the browser error overlay.
5. While serving, change the line to const typeErrorProbe: number = 42; and save.
   • Expected: rebuild shows Compiled successfully! and the overlay disappears.
6. Stop serve and run enact pack -p.
   • Expected: build succeeds; exit code 0.

TypeScript 6 regression (still uses fork-ts-checker-webpack-plugin)

1. Put the type error back, run npm install --no-save typescript@6, then run enact pack.
   • Expected: error reported with a code frame (> 20 | const typeErrorProbe ...); exit code 1.
2. Remove the type error and run enact pack.
   • Expected: build succeeds.

Links

NXT-20954

Comments

Enact-DCO-1.0-Signed-off-by: Daniel Stoian (daniel.stoian@lgepartner.com)

[dan-ichim-lgp]

src/setupTests.ts and src/setupProxy.* are not excluded when tsc prints a relative path.

[dan-ichim-lgp]

A tsc process stopped on Windows is not treated as cancelled. (optional)

[dan-ichim-lgp]

TypeScriptCheckPlugin is registered before ESLintPlugin and pushes its diagnostic during afterCompile. In enact serve, createCompiler keeps only errors[0], so an ESLint error from the same compilation is dropped from the terminal and the overlay when a type error is also present. enact pack still prints every error. Worth confirming this is acceptable, since on TypeScript 5/6 fork-ts-checker reports asynchronously and does not take that first slot.