rule() API is not documented at all

[Timmmm]

Adding custom rules is quite a fundamental part of a build system, but as far as I can tell the API for rule() is not documented at all. The best you get is a single example in this page:

pascal_binary = rule(
    impl = pascal_binary_impl,
    attrs = {
        "deps": attrs.list(attrs.dep()),
        "src": attrs.source(),
    }
)

I tracked the source to here which lists all the parameters:

• impl
• attrs
• cfg
• doc
• is_configuration_rule
• is_toolchain_rule
• uses_plugins
• eval

[IanChilds]

I think the API is documented here: https://buck2.build/docs/api/build/#rule

[Timmmm]

Ah you're right. That has a really confusing structure - it's not listed at all in the tree on the left and it's not obvious that the heading (Starlark APIs, Build APIs, etc.) actually has a load of the documentation.

Also unfortunately the documentation you linked doesn't actually document anything (except the types). E.g. what does is_toolchain_rule do?

[cbarrete]

I agree with Tim, this is really not very discoverable for such a fundamental API, and a function signature without more than a trivial example in its docstring hardly counts as documentation :/