📝 Biome doesn't format .jsonc file with trailing commas

[Sec-ant]

Environment information

❯ npx biome rage
CLI:
  Version:                      1.5.3
  Color support:                true

Platform:
  CPU Architecture:             x86_64
  OS:                           linux

Environment:
  BIOME_LOG_DIR:                unset
  NO_COLOR:                     unset
  TERM:                         "xterm-256color"
  JS_RUNTIME_VERSION:           "v21.6.0"
  JS_RUNTIME_NAME:              "node"
  NODE_PACKAGE_MANAGER:         "npm/10.2.4"

Biome Configuration:
  Status:                       Loaded successfully
  Formatter disabled:           false
  Linter disabled:              false
  Organize imports disabled:    false
  VCS disabled:                 true

Workspace:
  Open Documents:               0

Configuration

{
  "$schema": "./node_modules/@biomejs/biome/configuration_schema.json",
  "formatter": {
    "enabled": true
  },
  "overrides": [
    {
      "include": ["*.jsonc"],
      "json": {
        "parser": {
          "allowComments": true,
          "allowTrailingCommas": true
        }
      }
    }
  ]
}

Playground link

https://github.com/Sec-ant/biome-jsonc-formatting-bug-repro

Code of Conduct

• I agree to follow Biome's Code of Conduct

[Sec-ant]

emmm, I seem to mess up the CSB link. You can test it with a .jsonc file like this:

{"foo":          "bar",
}

A GitHub repo to repro is provided.

[Sec-ant]

Also, FWIW, there's a discussion around the trailing comma formatting behavior of jsonc files in Prettier recently: prettier/prettier#15956

I'm curious about what position will Biome take in this question?

[ematipico]

Personally, I would like to not deviate too much from the specs. Fortunately, we offer the option to allow trailing commas. That should help. Unless there's a bug when you enable parser.json.allowTrailingCommas

[Sec-ant]

Unless there's a bug when you enable parser.json.allowTrailingCommas

Yes that's what this issue is about. But I have trouble sharing the link to my repro in the CSB devbox (the link always jumps to a new template, I don't know why), so I created a github repo here: https://github.com/Sec-ant/biome-jsonc-formatting-bug-repro Thanks for checking this.

[Sec-ant]

Personally, I would like to not deviate too much from the specs. Fortunately, we offer the option to allow trailing commas. That should help.

Ok, let me rephrase my question in a more specific way: If I configure biome in a way that trailing commas are allowed for all the .jsonc files, and I have a .jsonc file that do not have trailing commas (or only has some trailing commas over the place, but not everywhere) that need to be formatted, will trailing commas be added to (or deleted from, or kept untouched in) the file after formatting?

[Sec-ant]

I not very confident with the codebase but I think the switch to support it is here, is this planned to be fixed @ematipico ?

biome/crates/biome_json_formatter/src/separated.rs

Line 55 in f490b15

.with_trailing_separator(TrailingSeparator::Disallowed)

#926 seems also related.

[ematipico]

Working on this issue. It seems that our tests weren't optimal, and I can see that this isn't working at all.

Sorry for neglecting the issue