Package golang provides support for Go and Go proto rules. It generates
go_library, go_binary, go_test, and go_proto_library rules.
Configuration
Go rules support the flags -build_tags, -go_prefix, and -external.
They also support the directives # gazelle:build_tags, # gazelle:prefix,
and # gazelle:importmap_prefix. See
https://github.com/bazelbuild/bazel-gazelle/blob/master/README.rst#directives
for information on these.
Rule generation
Currently, Gazelle generates rules for one Go package per directory. In
general, we aim to support Go code which is compatible with "go build". If
there are no buildable packages, Gazelle will delete existing rules with
default names. If there are multiple packages, Gazelle will pick one that
matches the directory name or will print an error if no such package is
found.
Gazelle names library and test rules somewhat oddly: go_default_library, and
go_default_test. This is for historic reasons: before the importpath
attribute was mandatory, import paths were inferred from label names. Even if
we never support multiple packages in the future (we should), we should
migrate away from this because it's surprising. Libraries should generally
be named after their directories.
Dependency resolution
Go libraries are indexed by their importpath attribute. Gazelle attempts to
resolve libraries by import path using the index, filtered using the
vendoring algorithm. If an import doesn't match any known library, Gazelle
guesses a name for it, locally (if the import path is under the current
prefix), or in an external repository or vendor directory (depending
on external mode).
Gazelle has special cases for import paths associated with proto Well
Known Types and Google APIs. rules_go declares canonical rules for these.