Color *_test.go files the same way *.test.ts are colored

[jakebailey]

For JS/TS, test files are shown in another color:

I'd love to have this for Go, where it's hard to visually find test files:

But, this didn't end up working out of the box as the highlighting system only looks for dot separated strings.

Adding _ separation enables this:

There are other languages that use a *_test.<ext> convention or similar, including:

• Elixir: https://hexdocs.pm/ex_unit/ExUnit.html, https://github.com/elixir-lang/elixir/tree/main/lib/elixir/test/elixir
• Ruby: https://rspec.info/features/3-12/rspec-core/command-line/pattern-option/
• Python: https://docs.pytest.org/en/stable/explanation/goodpractices.html#conventions-for-python-test-discovery (though test_*.py is also listed, which I have not handled)

Which could benefit from a change like this, though I don't know what color to give those (TS vs Go is easy because they're both blue, so orange seems fine!)

[jakebailey]

This only handles suffixes; this whole suffixing method does not work for something like test_*.py where I don't even know what would go into the icon theme.

[Copilot]

Pull request overview

This PR extends the file-icon class generation so icon themes can target underscore-suffixed filename conventions (e.g. Go’s *_test.go) similarly to existing dot-based compound extensions (e.g. *.test.ts).

Changes:

• Extend getIconClasses to emit an additional “underscore-suffix + extension” class (e.g. _test.go-ext-file-icon) when applicable.
• Add a focused unit test suite validating dot-based and underscore-suffix class generation behavior.
• Update the Seti icon theme to color Go _test.go files distinctly, and clarify the JSON schema description.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/vs/workbench/services/themes/common/fileIconThemeSchema.ts	Updates schema description to document dot-compound and underscore-suffix extension support.
src/vs/editor/common/services/getIconClasses.ts	Adds underscore-suffix compound extension class generation alongside existing dot-compound extension classes.
src/vs/editor/test/common/services/getIconClasses.test.ts	Adds new unit tests covering the new underscore-suffix behavior and related edge cases.
extensions/theme-seti/icons/vs-seti-icon-theme.json	Introduces Seti mappings/definitions to apply a distinct color to _test.go files in dark/light themes.

[benvillalobos]

LGTM but I think this has implications for other languages as well. Assigning @aeschli (area owner) to review

What an agent brought up for me:

Every file with underscores gets additional CSS classes on its DOM element. In a large repo with thousands of snake_case files, that's non-trivial class list bloat. It's probably negligible in practice, but worth the team being aware of.

It's a new public contract for icon theme authors. Any third-party theme could start defining _spec.rb, _test.py, etc. This is presumably the intent, but it's a feature surface area expansion that should be a deliberate decision.

[jakebailey]

Yeah, probably worth asking some designers or Go people; I can understand why some might be surprised by this. It turned out that only TS/JS do this in VS Code today.