feat(js): add JavaScript function tracer with Babel instrumentation#2105
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feat(js): add JavaScript function tracer with Babel instrumentation#2105
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Replaces source-level JavaScript function tracing with Babel AST transformation via babel-tracer-plugin.js and trace-runner.js. Adds replay test generation, Python-side tracer runner, and --language flag to the tracer CLI for explicit JS/TS routing.
KRRT7
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Saga4,
misrasaurabh1 and
mohammedahmed18
as code owners
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Linked issue or discussion
Supersedes #1377 — reimplemented against current main after the original branch diverged too far to rebase (78 days, conflicts in 4+ files).
What changed
Adds function tracing for JavaScript/TypeScript projects, matching the existing Python tracer architecture.
How it works:
babel-tracer-plugin.js) instruments JS/TS functions at runtime by wrapping them with__codeflash_tracer__.wrap()calls — no source modification neededtracer.js) records function calls with nanosecond timing and serialized arguments to a SQLite databasereplay.js) reads the trace DB and generates Jest/Vitest test files that replay the captured callstracer_runner.py,replay_test.py) spawns the Node.js tracer subprocess and converts trace data into codeflash's test formatCLI integration:
codeflash trace --language javascriptroutes to the JS tracerDeferred:
parse.py→parse_test_output.pyconsolidation refactor from feat(js): add JavaScript function tracer with Babel instrumentation #1377 will be done in codeflash-agent (codeflash-ai/codeflash-agent#31)Test plan
test_javascript_tracer.pycovering trace parsing, replay test generation, and E2E tracingjs-tests.ymlCI workflowtest_javascript_instrumentation.pyto reflect that Babel handles instrumentation at runtime (no more source-levelinstrument_source())