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ArtifactValue

A reference to an artifact whose contents can be accessed in starlark.

Artifacts normally only provide access to path information and do not allow starlark code to read the contents; this type represents access to an artifact in those cases where reading the contents is supported.

Where ArtifactValue is Used

1. Dynamic Dependencies​

Dynamic attributes declared with dynattrs.artifact_value() in dynamic_actions() provide access to artifact contents in the implementation function.

2. Action Error Handlers​

The output_artifacts field in ActionErrorContext provides access to output artifacts that can be read to extract structured error information.

Examples

Example 1: Dynamic Dependencies​

def _dynamic_impl(actions: AnalysisActions, config: ArtifactValue, metadata: ArtifactValue, out: OutputArtifact):
    # Read configuration as string
    config_content = config.read_string()

    # Parse JSON metadata
    data = metadata.read_json()
    version = data["version"]

    # Make build decisions based on content
    if "feature_enabled" in config_content:
        actions.write(out, "Feature enabled for version {}".format(version))
    else:
        actions.write(out, "Feature disabled")

    return [DefaultInfo()]

Example 2: Error Handler with ArtifactValue​

def _error_handler(ctx: ActionErrorContext) -> list[ActionSubError]:
    # Access output artifacts from failed action
    errors = []
    for artifact_value in ctx.output_artifacts:
        # Read error logs to extract structured information
        error_json = artifact_value.read_json()
        errors.append(
            ctx.new_sub_error(
                category="category",
                message=error_json["message"],
                file=error_json["path"],
                lnum=error_json["line"],
                col=error_json["col"],
            ),
        )

    return errors

ArtifactValue.read_json​

def ArtifactValue.read_json()

Reads and parses the artifact as JSON

ArtifactValue.read_string​

def ArtifactValue.read_string() -> str

Reads the entire contents of the artifact as a string.