Command line length limit in GenerateProtoTask causes overwriting of proto descriptors

[SlavikN14]

Description

When compiling a large number of .proto files, the generated command exceeds the Default CMD character limit.

// Most OSs impose some kind of command length limit.
// Rather than account for all cases, pick a reasonable default of 64K.
  static final int DEFAULT_CMD_LENGTH_LIMIT = 65536

To circumvent this, the generateCmds function splits the command into multiple smaller commands. However, each of these commands writes to the same output descriptor file via --descriptor_set_out, causing the last command to overwrite the previous ones.

Affected Code

GenerateProtoTask.groovy (Lines 187-211)

static List<List<String>> generateCmds(List<String> baseCmd, List<File> protoFiles, int cmdLengthLimit) {
  List<List<String>> cmds = []
  if (!protoFiles.isEmpty()) {
    int baseCmdLength = baseCmd.sum { it.length() + CMD_ARGUMENT_EXTRA_LENGTH } as int
    List<String> currentArgs = []
    int currentArgsLength = 0
    for (File proto: protoFiles) {
      String protoFileName = proto
      int currentFileLength = protoFileName.length() + CMD_ARGUMENT_EXTRA_LENGTH
      if (baseCmdLength + currentArgsLength + currentFileLength > cmdLengthLimit) {
        cmds.add(baseCmd + currentArgs) // Adds a command before overflow
        currentArgs.clear()
        currentArgsLength = 0
      }
      currentArgs.add(protoFileName)
      currentArgsLength += currentFileLength
    }
    cmds.add(baseCmd + currentArgs)
  }
  return cmds
}

Expected Behavior

Each split command should write to a unique descriptor file and then merge them, preventing data loss.

Actual Behavior

Each generated command uses the same --descriptor_set_out parameter, leading to overwriting instead of appending.

Steps to Reproduce

1. Compile a large number of .proto files that exceed the CMD character limit.
2. Observe that multiple commands are executed.
3. Check the final descriptor file – it contains only the last batch of .proto files.

Proposed Fix

• Modify the --descriptor_set_out path for each split command.
• Merge the descriptor files after all commands are executed.

Would appreciate feedback or any alternative suggestions! 🚀