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fix(vite): scan top-level imports with Vite's native parser - #11634
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aleclarson wants to merge 1 commit into
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Babel's skipBlockComment rescans to the next line break for every block comment, so a module whose code sits on a few very long lines parses quadratically. A large served dependency (about 2,000 block comments on a 1.9 MB line) took ~1.5 s per Babel parse, and the /ns/m pipeline parsed it about six times per request while blocking the dev server event loop. iOS loader requests then timed out during cold boot. Top-level import record collection and the dev default-import link check now use Vite's parseAst (Oxc) and fall back to the previous Babel parse when Oxc rejects the input.
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What
The
/ns/mdev route parses each served module with Babel several times just to find its top-level imports (collectTopLevelImportRecordsin two places, plus the dev default-import link check). On modules whose code sits on a few very long lines, Babel'sskipBlockCommentbecomes quadratic: for every block comment it runslineBreakG.test(this.input)from the comment start to the next line break anywhere in the input, not just to the comment's end.Real case: a 3.9 MB dependency chunk (
shaders/dist/core/std-*.js) is transformed by Vite's dev pipeline into 225 lines, the longest 1.9 MB with about 2,000 block comments. One Babel parse of that output takes ~1.5 s (0.26 s on the original multi-line file), and a single cold request did about six of them. CPU profiles showed@babel/parserat 8.7 s of an 11.25 s request, 7.2 s of it inskipBlockComment. Because this runs synchronously, the dev server's event loop is blocked for the whole request, and the iOS runtime's module loader timed out during cold boot (NSURLErrorDomain -1001) before the app could start.How
parseTopLevelStatements(code)inwebsocket-served-module-helpers.tsreturns top-level statements from Vite'sparseAst(code, { lang: 'tsx' })(Oxc), ornullif Oxc rejects the code.collectTopLevelImportRecordsimplementations use it first and fall back to the unchanged Babel parse. If both fail, they still return[]. Node checks are plaintypecomparisons that work on either AST. Output fields are unchanged.collectStaticImportDefaultIntents(code)replaces the link check's inline parse and traverse. Static imports can only appear at top level, so scanning top-levelImportDeclarations is equivalent. It falls back to the previous Babel parse and traverse, and still throws on a double failure, so the caller'stry/catchbehaves as before.astExtractImportsAndStripTypes,collectReExportAndDynamicImportSources, the normalizer) are untouched.viteis already a dependency of@nativescript/vite(^8.0.0), so no new dependency.Test plan
npx vitest run hmr/server/websocket-served-module-helpers.spec.ts hmr/server/websocket-import-records-fallback.spec.ts: 26 pass. Covers default, named and string-named specifiers, exacttextslices after non-ASCII text,import type, TS+JSX input, no imports, a forced Oxc failure falling back to Babel,ensureNativeScriptModuleBindingson both paths, and default-import intents.npx nx run vite:build. Touched files are lint-clean;vite:lintstill reports 3 existing errors in untouched files (configuration/base.ts,css-device-module.ts).@babel/parsershare dropped from 8.7 s to 1.2 s. A serial cold crawl of the app's 1,443-module boot graph went from 241.6 s to 108.9 s, with the slowest module dropping from 4.9 s to 1.4 s.