Extending existing languages

In practice, very few people actually need to write an extension for a new language. Many extension implementations in Go already exist, and more are likely to be written.

However, it’s not possible to customize Go extensions, other than by forking them, or via the limited directives they expose. You can use Starlark extensions to do smaller jobs that augment what you get from the standard Gazelle binary.

• Put a go_image OCI target next to each Go file that has a main:

• Create a py3_image OCI target next to __main__.py but only when it contains a # oci: build pragma:

• Create a js_binary target for each entry in package.json#scriptsthat matches a simple pattern:

• Add a linting test next to every library, for example generate ruff_test for every package with Python code
• Look for a specific config file for a tool, and generate a rule that calls the tool. Examples:
• look for webpack.config.js and generate a webpack_bundle rule
• look for jest.config.mjs and generate a jest_test target
• If a pattern exists in a source file, then generate a custom extraction target. Example: i18n
• https://github.com/nicksnyder/go-i18n
• Take a naming convention like locales/**/*.json
• generate message translation targets
• Scan for sources that match a pattern and generate copy_to_bin

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