Miguel's fix (f999b40d) added the require/__filename/__dirname shims to the
Lambda handler bundle after #1932 crashed every render at import with
"__dirname is not defined in ES module scope" (wawoff2's emscripten build
reads __dirname at module scope; it's inlined via producer -> fontCompression).
The accompanying test only grepped build-zip.ts for the banner literals, so it
passes even if the shim is renamed, reordered into a broken form, or if a new
inlined CJS dep needs a global the banner doesn't provide.
Replace it with a behavioral test: extract the banner to _handlerBanner.ts
(build-zip.ts self-executes on import, so it can't be imported directly),
bundle a fixture that touches __dirname/__filename/require with the real
banner, and import the output under real Node -- not the bun test runtime,
which defines __dirname in ESM and would mask a missing shim. The import
faithfully reproduces Lambda's Node ESM environment and fails with the exact
#1932 error when any shim is dropped.
Handler bundle output is unchanged (identical banner string).
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
James Russo
2b1109db4c