Bazel classpath_collision_test

Overview

Test and report tool to validate classpath collision cases

Getting started

1. Add to your WORKSPACE file the following:

   # WORKSPACE file
   load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
   
   jvm_classpath_validator_version="ea3ebc47cf1d3ebe0759d3319f31a928df7f24a5" # update this as needed
   jvm_classpath_validator_sha256="fee14b69faaefce808cf86aa627bc727c7be91b40bdeda04052b1d980a45df8d" # update this as needed
   http_archive(
       name = "jvm_classpath_validator",
       url = "https://github.com/or-shachar/jvm-classpath-validator/archive/%s.tar.gz" % jvm_classpath_validator_version,
       strip_prefix = "jvm-classpath-validator-%s" % jvm_classpath_validator_version,
       sha256 = jvm_classpath_validator_sha256
   )

2. Add a test in one of the build files:

   # BUILD.bazel file
   load("@jvm_classpath_validator//:classpath_validator.bzl", "classpath_collision_test")
   java_binary(
       name = "foo",
       runtime_deps = [...]
   )
   classpath_collision_test(
       name = "test_classpath",
       target = "foo",
       ignore_prefixes = ["example_prefix"], #optional
       ignore_suffixes = ["example_suffix"], #optional
       include_prefixes = ["example_prefix"], #optional
       include_suffixes = ["example_suffix"], #optional
   )

3. Run bazel test //path/to/package:test_classpath

How does the test work?

• The test would inspect the different jar entries of any jar in runtime closure of given target
• The test would ignore entries with given prefixes or suffix and look only at entries that match the provided prefixes or suffixes (or all entries if the include_prefix and include_suffixes are not provided)
• If same entry was found in two places with different content (digest based) the test would fail and a report would be emitted.

Example for failure report

Classpath Collision Finder
====================
[INFO]	Looking for collisions in 3 jar files
=======
Found 1 collisions

[//example/a/com/example/duppy:duppy <> //example/b/com/example/duppy:duppy]:
	 com/example/duppy/Duppy.class

##ignore_ vs include_ parameters The test will perform the filtering out of all entries from JARs before looking at what to include, i.e. if an entry from a JAR matches both ignore_ and include_ pattern, then ignore_ will take precedence.

Default ignore list

I allowed myself to add few default prefixes / suffixes to ignore. You can find them here. If you feel like the defaults should change - please kindly open an issue.