[gazelle] Support lazy indexing in the java gazelle plugin

[shs96c]

No description provided.

[jeffmace]

I took a look at this today and hit issues in our repository which uses gazelle:java_module_granularity module. The current lazy-indexing logic will only index directories that include BUILD.bazel files. This condition fails in our repository so the additional paths are not indexed.

https://github.com/bazel-contrib/bazel-gazelle/blob/master/cmd/gazelle/fix-update.go#L338

Am I understanding the logic correctly? Do you think there is a way to handle this in the extension or do we need to suggest a reorganization of the upstream logic?

[jeffmace]

The disconnect appears to be coming from the Resolver.Imports function. It is reading the cached package information from the rule. But that package information is populated by GenerateRules which hasn't been called.

https://github.com/shs96c/rules_jvm/blob/gazelle-lazy-index/java/gazelle/resolve.go#L61

If my understanding is right; I'm unsure how to proceed:

• Update Imports to return a set of ImportSpec based on the pathnames for the files in the Rule if it matches the Maven layout
• Breakout the java parsing logic from GenerateRules so it can be called from Imports if the package data isn't available
• Work with the Gazelle maintainers to reorder the logic so GenerateRules is called before Imports