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astgen: opt-in timing diagnostics for TypeScript type generation - #24
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…ING) Per-file stderr line with wall ms, node count, checker call counts (getTypeAtLocation/writeType with own ms), node-kind histogram, same-node repeat-query count, and with ASTGEN_TYPE_TIMING_SLOW_MS=n the n slowest individual queries. Off by default; verified byte-identical output. Signed-off-by: Team AppThreat <cloud@appthreat.com>
One wrapper per checker method instead of three stacked ones on getTypeAtLocation, node kinds reported by name, and counters reset by the report. Output stays byte-identical to main (npm test, five repos and twelve synthetic projects). Signed-off-by: Team AppThreat <cloud@appthreat.com>
prabhu
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enhancement
prabhu
enabled auto-merge
October 24, 2026 17:07
The PR build runs npm publish --dry-run, which fails while package.json still names the already-published 1.10.3. The AST format version stays 4.5.1: the timing diagnostics do not change what astgen emits. Signed-off-by: Team AppThreat <cloud@appthreat.com>
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Typed astgen runs on cdxgen take about 75 minutes, and almost all of that is one file,
lib/cli/index.js. This adds opt-in diagnostics that show where type generation spends its time. It doesn't make anything faster, because we didn't find a speedup that keeps the output the same.With
ASTGEN_TYPE_TIMING=1, astgen prints one stderr line per file with:ASTGEN_TYPE_TIMING_SLOW_MS=nalso lists the queries that took longer than n ms, with the file and line of each. With the variable unset, nothing changes.npm testpasses, and typemaps and ASTs are byte-identical to main on juice-shop, bulletproof-react, nestjs-realworld, node-express-boilerplate, node-express-realworld, twelve synthetic projects and a full cdxgen run.What the diagnostics found:
lib/cli/index.jsreassigns the same variable from itself about ninety times in one function (components = components.concat(...)). For each reference, TypeScript's control-flow analysis walks back over every earlier assignment, and working out each assignment's type starts another walk of the same kind. The cost per reference roughly doubles each time. The first 700 lines of that function take 15 seconds; the first 800 take 228 seconds. In the end, a singlegetTypeAtLocationcall runs for more than ten minutes. TypeScript 5.9 behaves the same as 6.0. Branch labels are only memoised within one walk, so nothing astgen can do by reordering or caching its own queries helps. Its repeat queries are already TypeScript cache hits.The ways to make it faster all change the output or live outside astgen: query declared types instead of narrowed ones at such sites, or fix it in TypeScript by memoising branch-label types across walks. They aren't in this PR.