Clarification required to make use of --labels

[JoKrefting]

Right now i don't get the documentation about how to use the option flag --labels.
It states:

Additional flags. Can be accessed in feedback and mirror context objects via the cli_labels field. In core.workflow, they are accessible as labels, but with names uppercased and prefixed with FLAG_ to avoid name clashes with existing labels. I.e. --labels=label1:value1 will define a label FLAG_LABEL1Format: --labels=flag1:value1,flag2:value2 Or: --labels flag1:value1,flag2:value2

But if i try to access labels within the workflow i only get:
name 'labels' is not defined.

I tried using it within the workflow and outside, but now luck. Probably i get something wrong.

An example would look like:

url = "https://github.com/google/copybara.git"

core.workflow(
    name = "default",
    origin = git.origin(
        url = url,
        ref = "master",
    ),
    destination = git.destination(
        url = "file:///tmp/foo",
        fetch = labels.get("FLAG_DESTINATION_FETCH", "main"),
        push = "master",
    ),
    # Copy everything but don't remove a README_INTERNAL.txt file if it exists.
    destination_files = glob(["third_party/copybara/**"], exclude = ["README_INTERNAL.txt"]),

    authoring = authoring.pass_thru("Default email <default@default.com>"),
    transformations = [
	    core.move("", "third_party/copybara"),
	],
)

Which i invoked like:
java -jar copybara.jar copy.bara.sky --labels destination_fetch:develop in hopes to be able to dynamically change the actual fetch source. Same idea would apply for push and ref.

[JoKrefting]

@hsudhof @chris-campos maybe u can already tell based on your experience? I wasn't able to quickly spin up locally copybara to debug myself.

[macrael]

It's not well documented, but you can access labels in templated strings like destination.tag_name.

git.destination(
  tag_name = "${FLAG_NEWTAG}"
)

Will read from the cli flag --flags=newtag:v0.0.3

it's not clear which all fields will accept this flag

[JoKrefting]

@macrael thx for your first feedback.
I at least can access now one flag but multiple i'm failing with.
I tried the following syntax similar to documented --labels

1. java -jar copybara.jar copy.bara.sky default --git-credential-helper-store-file=.git-credentials --git-committer-name="Open Source My Repo" --flags=ORIGIN_REF:dev,DESTINATION_FETCH:dev,DESTINATION_PUSH:dev
   1. this results into error: ERROR: Fetching refspecs that contain local ref path locations or wildcards is not supported. Invalid ref: --flags=ORIGIN_REF:dev,DESTINATION_FETCH:dev,DESTINATION_PUSH:dev ... so i think the variables are actually not split up?
2. java -jar copybara.jar copy.bara.sky default --git-credential-helper-store-file=.git-credentials --git-committer-name="Open Source My Repo" --flags=ORIGIN_REF:dev --flags=DESTINATION_FETCH:dev --flags=DESTINATION_PUSH:dev
   1. this results into error: ERROR: Workflow does not support multiple source_ref arguments yet: [--flags=ORIGIN_REF:dev, --flags=DESTINATION_FETCH:dev, --flags=DESTINATION_PUSH:dev] ... so i think the variables are actually not split up either?
3. java -jar copybara.jar copy.bara.sky default --git-credential-helper-store-file=.git-credentials --git-committer-name="Open Source Civora" --flags=BRANCH:dev basically a simplification for just one flag
4. this results as well into error ERROR: Fetching refspecs that contain local ref path locations or wildcards is not supported. Invalid ref: --flags=BRANCH:dev

My configuration looks like:

core.workflow(
    name = "default",
    origin = git.origin(
        url = "https://gitlab.com/my-repo.git",
        ref = "${FLAG_ORIGIN_REF}" if "${FLAG_ORIGIN_REF}" else "main",
    ),
    destination = git.destination(
        url = "https://gitlab.opencode.de/my-repo.git",
        fetch = "${FLAG_DESTINATION_FETCH}" if "${FLAG_DESTINATION_FETCH}" else "main",
        push = "${FLAG_DESTINATION_PUSH}" if "${FLAG_DESTINATION_PUSH}" else "main",
    ),
    authoring = authoring.pass_thru("Open Source My Repo <myRepo@email.de>"),
    origin_files = glob(files_and_dir_to_open_source),
    destination_files = glob(files_and_dir_to_open_source),
    transformations = [
        #        core.move("tests", "ospo/copybara"),
    ],
)

I tested with: Copybara source mover (Version: v20250922)

[macrael]

I was able to have it dry run fine with two different flags, I feel like this error is about how you're using the flags as refs? I'm not sure, I'm a user of the library not an author and am still trying to figure out how things work

[JoKrefting]

@macrael thx for taking the time. Can you maybe share how you are using the flags so far? So how your copybara snippet looks like and how you invoke it successfully?

[chris-campos]

If your goal is to get the git destination's fetch and push refs dynamically, I highly recommending using the --git-destination-fetch and --git-destination-push flags for this.

More information on these flags can be found in the Command line flags section here: https://github.com/google/copybara/blob/master/docs/reference.md#gitdestination