private void processArg()

in src/java/io/bazel/rulesscala/coverage/instrumenter/JacocoInstrumenter.java [36:89]
36 lines of code
3 McCabe index (conditional complexity)

  private void processArg(Instrumenter jacoco, String[] args) throws Exception {
    if (args.length < 3) {
      throw new Exception(
          "expected format `in_path out_path src1 src2 ... srcN`  for arguments: "
              + Arrays.asList(args));
    }

    Path inPath = Paths.get(args[0]);
    Path outPath = Paths.get(args[1]);
    String[] srcs = Arrays.copyOfRange(args, 2, args.length);

    // Use a directory for coverage metadata that is unique to each built jar. Avoids
    // multiple threads performing read/write/delete actions on the instrumented classes directory.
    Path instrumentedClassesDirectory = getMetadataDirRelativeToJar(outPath);
    Files.createDirectories(instrumentedClassesDirectory);

    JarCreator jarCreator = new JarCreator(outPath);

    try (FileSystem inFS = FileSystems.newFileSystem(inPath, null)) {
      FileVisitor fileVisitor =
          createInstrumenterVisitor(jacoco, instrumentedClassesDirectory, jarCreator);
      inFS.getRootDirectories()
          .forEach(
              root -> {
                try {
                  Files.walkFileTree(root, fileVisitor);
                } catch (final Exception e) {
                  throw new RuntimeException(e);
                }
              });

      /*
       * https://github.com/bazelbuild/bazel/blob/567ca633d016572f5760bfd027c10616f2b8c2e4/src/java_tools/junitrunner/java/com/google/testing/coverage/JacocoCoverageRunner.java#L411
       *
       * Bazel / JacocoCoverageRunner will look for any file that ends with '-paths-for-coverage.txt' within the JAR to be later used for reconstructing the path for source files.
       * This is a fairly undocumented feature within bazel at this time, but in essence, it opens all the jars, searches for all files matching '-paths-for-coverage.txt'
       * and then adds them to a single in memory set.
       *
       * https://github.com/bazelbuild/bazel/blob/567ca633d016572f5760bfd027c10616f2b8c2e4/src/java_tools/junitrunner/java/com/google/testing/coverage/JacocoLCOVFormatter.java#L70
       * Which is then used in the formatter to find the corresponding source file from the set of sources we wrote in all the JARs.
       */
      Path pathsForCoverage = instrumentedClassesDirectory.resolve("-paths-for-coverage.txt");
      Files.write(
          pathsForCoverage,
          String.join("\n", srcs).getBytes(java.nio.charset.StandardCharsets.UTF_8));

      jarCreator.addEntry(
          instrumentedClassesDirectory.relativize(pathsForCoverage).toString(), pathsForCoverage);
      jarCreator.setCompression(true);
      jarCreator.execute();
    } finally {
      DeleteRecursively.run(instrumentedClassesDirectory);
    }
  }