lib: ensure TextDecoder only removes utf8 BOM on utf8 encoding

[phated]

While working on gulpjs/remove-bom-stream#8, I noticed that our test case to ensure a UTF-8 BOM at the beginning of a UTF-16 file wouldn't be removed; however, it was.

I dug into the PR at #30132 and noticed that it lost the utf-8 and utf-16-le checks in the refactor.

This should limit the BOM removal to just the UTF-8 encoding. There should also be a follow-up PR that adds the utf-16-le BOM removal back to the code.

[Trott]

I'm guessing lib: would be the generic choice for the start of the commit message.

[phated]

Updated! I also attempted to add a test, let me know if it is wrong.

[Trott]

I also attempted to add a test, let me know if it is wrong.

Looks right to me. Anyone more encoding-knowledgable want to review?

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/43557/

[phated]

@Trott can you help me with these failures so I don't need to approve the Jenkins CI to my entire GH account?

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/43558/

[Trott]

@Trott can you help me with these failures so I don't need to approve the Jenkins CI to my entire GH account?

AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:
+ actual - expected

+ 'utf-16le'
- 'utf-16-le'
         ^
    at /home/iojs/build/workspace/node-test-commit-linuxone/test/parallel/test-whatwg-encoding-custom-textdecoder.js:46:12
    at Array.forEach (<anonymous>)
    at Object.<anonymous> (/home/iojs/build/workspace/node-test-commit-linuxone/test/parallel/test-whatwg-encoding-custom-textdecoder.js:39:26)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Module._load (node:internal/modules/cjs/loader:827:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
    at node:internal/main/run_main_module:17:47 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: 'utf-16le',
  expected: 'utf-16-le',
  operator: 'strictEqual'
}

[phated]

🤦 I totally looked at those conversions too. Thanks!

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/43559/

[Trott]

@phated It appears that the change here causes a failure in test/parallel/test-whatwg-encoding-custom-textdecoder.js. Is the bug in the test or in the change here?

AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:
+ actual - expected

+ '믯璿攀猀琀가�'
- 'test€'
    at /home/iojs/build/workspace/node-test-commit-linux/test/parallel/test-whatwg-encoding-custom-textdecoder.js:48:12
    at Array.forEach (<anonymous>)
    at Object.<anonymous> (/home/iojs/build/workspace/node-test-commit-linux/test/parallel/test-whatwg-encoding-custom-textdecoder.js:39:26)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Module._load (node:internal/modules/cjs/loader:827:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
    at node:internal/main/run_main_module:17:47 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: '믯璿攀猀琀가�',
  expected: 'test€',
  operator: 'strictEqual'
}

[phated]

@Trott thanks. It looks like a bug in my test specifically.

[phated]

When I tried decoding this on current node 16, the bug shows itself in an invalid character at the end: '믯璿攀猀琀가�'

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/43572/

[phated]

If my last commit doesn't work. I might need to copy the gulp test case into here (even though it is a larger buffer)

[Trott]

node:assert:123
  throw new AssertionError(obj);
  ^

AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:
+ actual - expected

+ '믯璿攀猀琀가�'
- '믯璿攀猀琀가'
         ^
    at /Users/iojs/build/workspace/node-test-commit-osx/nodes/osx1015/test/parallel/test-whatwg-encoding-custom-textdecoder.js:48:12
    at Array.forEach (<anonymous>)
    at Object.<anonymous> (/Users/iojs/build/workspace/node-test-commit-osx/nodes/osx1015/test/parallel/test-whatwg-encoding-custom-textdecoder.js:39:26)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Module._load (node:internal/modules/cjs/loader:827:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
    at node:internal/main/run_main_module:17:47 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: '믯璿攀猀琀가�',
  expected: '믯璿攀猀琀가',
  operator: 'strictEqual'
}

Node.js v19.0.0-pre

[phated]

I don't know how to test this. In the gulp tests, we save files with different encodings and I have no idea how to craft those buffers inside a Buffer.

[Trott]

Did you mean to close this? I'd like to keep chipping away at it unless you're opening a new PR or something?

[Trott]

You can create a file and save it in the test temp directory. (I can write that code or point you to a sample, so you don't have to learn that API unless you think you're going to be writing more Node.js tests.)

We could also put a file permanently in the test/fixtures directory.

[phated]

Did you mean to close this?

Yeah, I meant to close it. At this point, I can't determine if I'm crazy or not because reading the file into the repl seems to give me the expected results, but my tests fail. The furthest I got before giving up was possibly a re-encoding issue (back into a buffer).

One thing that I noticed is that \ufeff is actually the <Buffer ff fe> buffer, which is actually the utf16 BOM (not the utf8 BOM), so I'm not sure.