Handle .srcjar inputs in Bazel aspect

[antonsviridov-src]

The aspect will add a new entry to sourceFiles:

  "sourceFiles": [
    "Foo.java",
    "bazel-out/darwin_arm64-fastbuild/bin/extracted_srcjar/sources.srcjar"
  ]

and ScipBuildTool will be able to traverse folders and lookup all source files in them.

Together this allows us to avoid unpacking jars in scip-java (which would entail tracking their location and caching, which would be annoying), instead delegating all that to Bazel.

Test plan

• New example that is used as part of the CI

[olafurpg]

LGTM 👍🏻 Very nice to see more interest in the Bazel aspects, a lot of work went into making those

[JohnnyMorganz]

Thank you very much for taking a look at this, very excited! I decided to build from source and seems to work for most cases.

However, it seems to fail when there are 2 java libraries in the same BUILD.bazel that use the same srcjar.
I was curious if this might be due to the fact scip-java doesn't use sandboxing (--spawn_strategy=local), but bazel build --spawn_strategy=local //test/... works for me.

Here's an extended example:

genrule(
    name = "generated-srcjar",
    outs = ["sources.srcjar"],
    cmd = "echo 'package com.testing; public class Bar {};' > Bar.java && jar cf $(@) Bar.java",
)

java_library(
    name = "other_library",
    srcs = [
        "Baz.java", # create a new file in source at test/Baz.java, alongside test/Foo.java
        ":generated-srcjar",
    ],
)

java_library(
    name = "testing",
    srcs = [
        "Foo.java",
        ":generated-srcjar",
    ],
)

$ /home/code/scip-java/out/bin/scip-java index --build-tool=bazel --bazel-scip-java-binary="/home/code/scip-java/out/bin/scip-java" --output=index-java.scip -- -- //test/...
...
ERROR: file 'test/extracted_srcjar/test/sources.srcjar' is generated by these conflicting actions:
Label: //test:testing, //test:other_library
Aspects: [//aspects:scip_java.bzl%scip_java_aspect]
RuleClass: java_library rule
JavaActionClass: class com.google.devtools.build.lib.analysis.actions.StarlarkAction
Configuration: 3ba97bf385bd693a2d11797e9a10970d8a18bd9a3c65cca1cc949fcdaf192b6a
Mnemonic: ExtractSourceJars
Action key: 4d908d0c4683f4e763487790dac25b2e8b0deb9f1d629ba30b7749749bdb03c0
Progress message: Extracting source jar bazel-out/k8-dbg--cd/bin/test/sources.srcjar
Action describeKey: Extracting source jar bazel-out/k8-dbg--cd/bin/test/sources.srcjar
  Argument: /bin/bash
  Argument: -c
  Argument: '
                unzip bazel-out/k8-dbg--cd/bin/test/sources.srcjar -d bazel-out/k8-dbg--cd/bin/test/extracted_srcjar/test/sources.srcjar
            '
  Output paths mode: OFF

PrimaryInput: File:[[source]]bin/jar
PrimaryOutput: File:[[<execution_root>]bazel-out/k8-dbg--cd/bin]test/extracted_srcjar/test/sources.srcjar
Owner information: //test:testing#//aspects:scip_java.bzl%scip_java_aspect ConfiguredTargetKey{label=//test:testing, config=BuildConfigurationKey[3ba97bf385bd693a2d11797e9a10970d8a18bd9a3c65cca1cc949fcdaf192b6a]} {}, //test:other_library#//aspects:scip_java.bzl%scip_java_aspect ConfiguredTargetKey{label=//test:other_library, config=BuildConfigurationKey[3ba97bf385bd693a2d11797e9a10970d8a18bd9a3c65cca1cc949fcdaf192b6a]} {}
MandatoryInputs: Attempted action contains artifacts not in previous action (first 5): 
        test/Foo.java
Previous action contains artifacts not in attempted action (first 5): 
        test/Bar.java
Outputs: are equal
ERROR: com.google.devtools.build.lib.actions.MutableActionGraph$ActionConflictException: for test/extracted_srcjar/test/sources.srcjar, previous action: action 'Extracting source jar bazel-out/k8-dbg--cd/bin/test/sources.srcjar', attempted action: action 'Extracting source jar bazel-out/k8-dbg--cd/bin/test/sources.srcjar'

[JohnnyMorganz]

Also, somewhat of an edge case, but we have some srcjars that end up becoming empty due to Reasons, causing the following error:

genrule(
    name = "empty-srcjar",
    outs = ["sources.srcjar"],
    cmd = "touch test.txt && zip $(@) test.txt && zip -d $(@) test.txt",
)

java_library(
    name = "testing",
    srcs = [
        "Foo.java",
        ":empty-srcjar",
    ],
)

ERROR: /home/code/repository/test/BUILD.bazel:7:13: Extracting source jar bazel-out/k8-dbg--cd/bin/test/sources.srcjar failed: (Exit 1): bash failed: error executing ExtractSourceJars command (from target //test:testing) 
  (cd /home/.cache/bazel/.../execroot/_main && \
  exec env - \
  /bin/bash -c '
                unzip bazel-out/k8-dbg--cd/bin/test/sources.srcjar -d bazel-out/k8-dbg--cd/bin/test/extracted_srcjar/test/sources.srcjar
            ')
# Configuration: 3ba97bf385bd693a2d11797e9a10970d8a18bd9a3c65cca1cc949fcdaf192b6a
warning [bazel-out/k8-dbg--cd/bin/test/sources.srcjar]:  zipfile is empty
Aspect //aspects:scip_java.bzl%scip_java_aspect of //test:testing failed to build

But other than these 2 things, it is looking very promising. Thank you!!