Bazel: Protobuf classes must be built and used as a dependency to be included in the classpath

[theothertomelliott]

Observed Behavior

When a Bazel workspace includes java_proto_library macros, the proto must be added as a dependency of at least one java_library rule to appear in the classpath for autocompletion, etc.

Expected Behavior

Based on how the rest of the classpath is built, I believe the intention is that proto classes would be included regardless of whether or not they were already used.

Reproduction Steps

See: https://github.com/theothertomelliott/bazel-issues/tree/vscode_java_protos

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It looks like the cause is a combination of Java protos being created as aspects rather than rules, so they don't show up with aquery by default (https://stackoverflow.com/questions/63430530/bazel-aquery-returns-no-action-information-for-java-proto-library/63455560#63455560), and the list of types included in the classpath aquery not including proto_library.

I'd be happy to submit a PR to include all protos up-front, as I've got pretty close to a solution while investigating.

[georgewfraser]

A PR would be welcome!!

[georgewfraser]

The basic strategy for dealing with bazel is to compute a global classpath, that contains the union of the classpaths of every java library and binary in the project. The idea is that the language server doesn't try to deeply understand your build. Instead, it is basically permissive about errors in your dependency structure, and assumes that bazel itself will reveal those to you when you build at the command line.