feat: add --incremental and --tsgo flags to @sveltejs/package#15467
feat: add --incremental and --tsgo flags to @sveltejs/package#15467datstarkey wants to merge 2 commits intosveltejs:mainfrom
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Add write-to-disk + shell-out pipeline for declaration emit, adapted from the approach used in svelte-check's incremental mode (PR sveltejs#2932). When `--incremental` or `--tsgo` is passed, svelte-package: 1. Pre-transpiles .svelte files to .ts via svelte2tsx() with manifest caching 2. Generates an overlay tsconfig with declaration emit settings 3. Spawns tsc (or tsgo from @typescript/native-preview) as a child process 4. Post-processes emitted .d.ts files (alias resolution, sourcemap fixup) The default path (no flags) is completely unchanged. Benchmarks on a 264-component Svelte library: - Baseline (emitDts): ~7.2s every run - --incremental warm: ~3.1s (2.3x faster) - --tsgo cold: ~3.7s (2x faster) - --incremental --tsgo: ~1.6s (4.5x faster) Also bumps svelte2tsx to ~0.7.51 for rewriteExternalImports and emitJsDoc support, and adds @typescript/native-preview as an optional peer dependency.
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The optional peer dependency caused lockfile sync issues in CI. The --tsgo flag already handles the missing package gracefully with a clear error message directing users to install it.
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Stale declaration files from deleted source files persist in the output when using incremental declaration emit.
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| emitted.push(file.name); | ||
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| console.error(`Error transpiling ${file.name}: ${/** @type {Error} */ (e).message}`); |
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When a Svelte file fails to transpile via svelte2tsx, stale generated files from previous successful runs are not cleaned up, causing tsc to produce outdated type declarations.
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Summary
Adds
--incrementaland--tsgoCLI flags tosvelte-packagefor faster declaration emit. This adapts the write-to-disk + shell-out architecture from svelte-check's incremental mode (language-tools PR #2932) for declaration emit in@sveltejs/package.When either flag is set, the new pipeline replaces the
emitDts()call with:.sveltefiles to.tson disk viasvelte2tsx()with manifest-based caching (mtime+size)declaration: true,emitDeclarationOnly: truetscortsgoas a child process to emit.d.tsfiles.d.tsfiles: resolve$libaliases, fix sourcemap paths, handle hand-written.d.tsprecedenceThe default path (no flags) is completely unchanged — all existing tests pass unmodified.
How the flags interact
emitDts()--incremental.tsbuildinfo--tsgo--incremental --tsgo.tsbuildinfoBenchmarks
Tested on a 264-component Svelte library (420 total files):
svelte-package(baseline)--incremental--tsgo--incremental --tsgoChanges
packages/package/src/emit-dts-incremental.js— core pipeline (~500 lines)cli.js(flags),types.d.ts(types),index.js(routing),typescript.js(extracted sharedresolve_svelte_shimshelper)svelte2tsxto~0.7.51forrewriteExternalImportsandemitJsDocsupport@typescript/native-previewas optional peer dependencyKnown limitations
.d.tsoutput from the incremental path may have minor differences from the default path (whitespace from tsc formatting, slightly less precise types for edge cases in dts mode). Functionally equivalent.Test plan
@sveltejs/packagetests pass (default path unchanged)pnpm run lintpassespnpm run checkpasses (0 errors)pnpm -F @sveltejs/kit test:unitpassespnpm test:otherspasses--incrementalproduces equivalent output ontypescript-esnextfixture--tsgofails gracefully when@typescript/native-previewnot installed