gazelle -proto=default mysteriously removing go srcs and rules

[ixdy]

In kubernetes/test-infra, I updated our rules_go and gazelle dependencies to 0cd983e, and then updated all of our BUILD files, first with -proto=legacy, then without (separating this into two commits).

When I ran gazelle -mode=fix without -proto=legacy, it did weird things to testgrid/config/BUILD (see commit), removing all of the go sources and go_binary rule, but leaving an invalid go_test rule.

I have no idea why it did this, and whether it's something weird we're doing or a bug in gazelle.

[jayconrod]

This is confusing behavior, but it's actually working as intended.

When Gazelle finds source files in a directory that declare different packages, it normally prints an error and skips processing that directory. As a special case, if one of the packages matches the base name of the directory, that Gazelle will generate rules for that package and ignore source files belonging to other packages. This is common with libraries that also have helper tools in package main. Generally, people want the library and not the tool, so we avoid emitting an error and ignore the tool.

With the new support for proto rules, .proto files are treated as sources that are part of a package. If the proto has option go_package or package statements, the package name is derived from those. If not, the package name is derived from the filename. This is intended to match what protoc does.

This directory, test-infra/config, contains .go files in package main. It also has config.proto, which doesn't specify its package. So Gazelle determines that config.proto belongs to package config. Since that matches the directory name, it will ignore files belonging to the main package. It will generate proto_library, go_proto_library, and go_library rules for config and will delete empty rules (go_binary). It would delete the go_test as well, but that contains a manually written data attribute, so it doesn't completely remove it.

---

I'm not sure how the proto is used in this directory. It wasn't mentioned in the BUILD file before, so if you don't need it, perhaps it's best to add # gazelle:exclude config.proto before running gazelle fix. # gazelle:proto disable would also do the trick. If you want to generate code from it, you could add something like option go_package = "k8s.io/test-infra/testgrid/config;main"; to force it to be in the main package.

---

I'm not sure there's an immediate fix for this. This is the confusing result of several behaviors overlapping in an unsual way. Eventually, Gazelle will support multiple packages in each directory, and then we won't have to choose between them like this.

[jayconrod]

Closing old Gazelle issues. Support for multiple packages is bazelbuild/bazel-gazelle#7. Please open a new issue at bazelbuild/bazel-gazelle if something isn't covered though.