fix(report-file): surface write stream errors instead of a TypeError - #2058

testem ci dies with TypeError: Cannot read properties of undefined (reading 'end') when it cannot open the report file, and the real filesystem error never reaches the user. I hit it with a testem.json whose report_file points at an existing directory, so opening it for writing fails with EISDIR.

The cause is in lib/utils/report-file.js. Line 26 registers finish as an error listener on the write stream, but finish is a plain function, so this inside it is the stream that emitted the event, not the ReportFile instance. this.outputStream is undefined there and line 21 throws. That throw happens inside the error emit, before the second error listener on line 30 can reject closePromise, so it escapes as an uncaught exception and the open error is lost. Line 25 registers the same handler for end, which a writable stream never emits. Both are leftovers from when ReportFile wrapped two separate streams, an output stream and the file stream.

This removes both listeners. close() already ends the stream, and closePromise already resolves on finish and rejects on error, so the fs error now reaches the caller and testem shuts down through its normal path with exit code 1, the same as it already does when the report file's directory cannot be created. closePromise also gets a no-op catch, because an open failure rejects on the next tick, long before close() attaches its handler, and node would otherwise kill the process for an unhandled rejection.

Verification on macOS, node 22.23.2:

# the new test against unmodified master
$ npx mocha tests/utils/report-file_tests.js
  1 passing
  1 failing
  1) ReportFile close rejects with the write stream error when the file cannot be opened:
     Uncaught TypeError: Cannot read properties of undefined (reading 'end')
      at WriteStream.finish (lib/utils/report-file.js:21:27)

# with this change
$ npx mocha tests/utils/report-file_tests.js
  2 passing

$ npm run lint
  no output, exit 0

$ npm test
  832 passing (12m)
  2 pending
  8 failing

All 8 failures are 90 second timeouts in tests/ci/ci_tests.js and tests/ci/dev_tests.js, which launch Headless Firefox, and Firefox is not installed on the machine I ran this on. npx mocha tests/ci/ci_tests.js tests/ci/dev_tests.js -g "handles todos correctly|keeps runner association" fails identically on unmodified master. Every report file test passes with the change: the four in tests/ci/report_file_tests.js and the two in tests/utils/report-file_tests.js.