perf: speed up lint and check-types (cache, incremental, staged-only hook) #2090

Problem

pnpm lint and pnpm check-types are slow. The src package causes most of the wait in both.
The pre-commit hook runs pnpm lint on the whole repo. The pre-push hook runs pnpm check-types.

Measurements

All runs are warm, with the turbo cache bypassed (--force). Machine: WSL2, 20 cores.

Lint

Turbo runs the packages in parallel. The total is about 2 s more than src alone.

TIMING=15 on src:

no-floating-promises is the only type-aware rule. It needs a TypeScript program (parserOptions.project: true in src/eslint.config.mjs).

Check types

tsc --noEmit --extendedDiagnostics on src:

• 3,428 files. 1.7 GB of memory.
• Check time is 16.4 s of 20.3 s total. Parse time is 1.7 s. Bind time is 0.9 s.
• skipLibCheck is already on. File loading is not the cost.

Experiments

Run on src with CLI flags and a scratch cache. No repo files changed.

TypeScript incremental mode

Command: tsc --noEmit --incremental --tsBuildInfoFile <path>.
Today packages/config-typescript/base.json sets "incremental": false, and src/tsconfig.json does not extend it.

Without the declaration option, tsc cannot tell if a change affects other files. Any edit invalidates every file that depends on the edited file.
So incremental mode helps for edits to leaf files. It does not help for edits to shared files.
tsc --noEmit --incremental --declaration exits with TS errors in src. Do not use it until we fix them.

ESLint cache

Command: eslint . --ext=ts --max-warnings=0 --cache --cache-strategy content --cache-location <path>.

The edited file was outside the typed-lint globs. An edit to a file inside those globs may cost more. We did not test that.

Proposed changes

1. Add --cache --cache-strategy content to the lint scripts in src and webview-ui. Put the cache under node_modules/.cache/ so git ignores it.
2. Add "incremental": true and a tsBuildInfoFile under node_modules/.cache/ to src/tsconfig.json and webview-ui/tsconfig.json.
3. Change the pre-commit hook to lint only staged files through lint-staged. Keep the full lint in CI.
4. Check that webview-ui check-types needs to emit. Its script is tsc without --noEmit.

Not yet measured

• Cold-start time on CI or on other machines.
• webview-ui with the proposed changes.
• ESLint after an edit to a file inside the typed-lint globs.
• parserOptions.projectService against project: true. The typescript-eslint performance repo reports that projectService no longer beats project.
• A claim that --prune-suppressions slows ESLint. We found no evidence for it.

Sources

• typescript-eslint: Typed linting performance
• typescript-eslint/performance repo
• typescript-eslint: Typed linting
• ESLint v9 CLI reference (--cache, --cache-strategy, --cache-location)
• ESLint v9 stats docs
• OpenReplay: Slow ESLint rules (TIMING)

🤖 Generated with Claude Code