jeremydaly / lambda-api / #234

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Build Type

push

github

Committed by web-flow

Commit Message

fix: keep the CommonJS interop shim out of the ESM build (#346) (#347)

* fix: keep the CommonJS interop shim out of the ESM build (#346)

The dual CJS/ESM build (#326, shipped in 1.5.0) compiles a single `src/` tree
twice. Seven source files ended with an interop shim:

    if (typeof module !== 'undefined') {
      module.exports = createAPI;
      module.exports.default = createAPI;
    }

which restores the historical CommonJS shape — but it was emitted into
`dist/esm` as well. Bundlers that inline the ESM artifact into a generated
CommonJS wrapper (esbuild `--format=cjs`, AWS CDK `NodejsFunction`, SST,
Serverless Framework) leave exactly one `module` in scope: the consumer's. The
shim then replaced the consumer's `module.exports`, deleting their `handler`.

On Lambda this deployed cleanly and failed on every invocation with
`Runtime.HandlerNotFound: index.handler is undefined or not exported`, with
nothing in the error naming lambda-api.

`src/` is now pure ESM. The interop footers are appended to `dist/cjs` only, by
`scripts/cjs-interop.js`, which also loads each patched file back and fails the
build if the CommonJS shape is wrong. Footers are per-file on purpose: the
`.default` self-reference is correct on the package root but would make
`mimemap['default']` resolve to the whole MIME map.

`src/lib/s3-service.js` now exports its `service` object so the footer can
reach it; that object must stay the module value so `response.js` and the unit
suites (`sinon.stub`) share one set of mutable properties.

Nothing about `dist/cjs` changes: `require('lambda-api')` is still callable,
`.default` still self-references, and `require('lambda-api/lib/*')` still
returns the value itself.

Regression coverage:
- `module-compat` fails if any `dist/esm` file references `module.exports`,
  `typeof module`, or `exports.` — it named all 7 files before the fix.
- `module-compat` pins the `dist/cjs` interop shape the footers must preserve.
- New e2e Layer 1 fixture b... (continued)

Coverage Stats

813 of 994 branches covered (81.79%)

Branch coverage included in aggregate %.

20 of 36 new or added lines in 1 file covered. (55.56%)

26 existing lines in 1 file now uncovered.

793 of 952 relevant lines covered (83.3%)

120.11 hits per line