jsonc: Setting to allow trailing commas in jsonc

[andrewbaxter]

Re: #102061

Formatting jsonc with prettier adds trailing commas which vs code then flags as being invalid: prettier/prettier#15553

The proposed solution there is to define a jsonschema and use a vscode-specific extension to json-schema property to allow it. I'm already using an externally defined jsonschema that I can't edit, so this isn't a solution for me.

I'd like to request this be a standard vs code setting (in addition to the existing jsonschema setting). All my tooling supports trailing commas so I do not need to customize the behavior for specific files. I'd be happy for this to be off by default.

FWIW, even if I could disable trailing commas I wouldn't want to. They make editing easier and more robust to reordering fields, adding and deleting the final field, etc.

[aeschli]

If you already have an existing jsonschema setting, just add another one that matches your file. Matching schemas are all combined.
You can even do it for all jsonc files:

{
	"fileMatch": ["*.jsonc"],
	"schema": {
		"allowTrailingCommas": true
	}
}

[andrewbaxter]

Ah thanks, works for me!

[flying-sheep]

It doesn’t for me.

biome.jsonc:

{
	"$schema": "https://biomejs.dev/schemas/1.9.4/schema.json",
}

user settings.json:

{
	...,
	"json.schemas": [{
		"fileMatch": ["*.jsonc"],
		"schema": {
			"allowTrailingCommas": true,
		},
	}],
}

[shian15810]

It doesn’t for me.

Philipp A. (@flying-sheep) Because if getSchemaForResource sees a $schema property in your JSON file, it returns immediately and set the value of $schema as the schema of that JSON file.

The alternative that works is to remove the $schema property from your JSON file, and set the schema only in .vscode/settings.json. This way the schema of a JSON file will be merged for all matching fileMatch.

{
    "json.schemas": [
        {
            "fileMatch": [
                "**/*.jsonc",
            ],
            "schema": {
                "allowComments": true,
                "allowTrailingCommas": true,
            },
        },
        {
            "fileMatch": [
                "**/biome.jsonc",
            ],
            "url": "https://biomejs.dev/schemas/latest/schema.json",
        },
    ],
}

Reference: https://github.com/microsoft/vscode-json-languageservice/blob/a78b2ff4f8903edddb51788698bdf149f64f1650/src/services/jsonSchemaService.ts#L697-L713

[flying-sheep]

That workaround doesn’t work for me and I’m sure in many other cases.

So if there’s no way to make VS Code shut up without touching my data, please reopen this issue Martin Aeschlimann (@aeschli)

[shian15810]

Philipp A. (@flying-sheep) Based on the source code, it should and must work.

I faced the same problem as yours, digging into the source code under frustration, then found the solution I shared, tried it and it really works! Which means the behavior matches exactly what the source code says it does.

So I think maybe you are facing more than this issue, and I suggest you dig deeper into it.

I'm very confident this solution works. Some of my colleagues also tried it and it works as well.

[flying-sheep]

I think I wasn’t clear: I meant that “remove the $schema property from [my] JSON file” isn’t possible, so I can’t use your workaround and need a real solution.

[shian15810]

I meant that “remove the $schema property from [my] JSON file” isn’t possible

Philipp A. (@flying-sheep) Could you explain more on the why?

Note that both allowComments and allowTrailingCommas are vscode-only semantics, so adding them to .vscode/settings.json is appropriate.