MachineLearningScorer: metric list is double-encoded into one string

[kz930]

What happened?

MachineLearningScorerOpDesc.getSelectedMetrics() returns the chosen metric names as one comma-separated, already-quoted fragment, and its return type is EncodableString:

common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/machineLearning/Scorer/MachineLearningScorerOpDesc.scala

private def getSelectedMetrics(): EncodableString = {
  val metric = if (isRegression) regressionMetrics else classificationMetrics
  metric.map(metric => getMetricName(metric)).mkString("'", "','", "'")   // -> 'Accuracy','F1 Score'
}

It is spliced into the generated Python as a list:

metric_list = [${getSelectedMetrics()}]

Because the value is an EncodableString, the Python template builder re-encodes the whole fragment as one Python string value (rendered via self.decode_python_template(...)) instead of splicing it verbatim. The generated code becomes:

metric_list = ["'Accuracy','F1 Score'"]   # ONE element: the literal string, incl. inner quotes

instead of the intended:

metric_list = ['Accuracy', 'F1 Score']

So every downstream if 'X' in metric_list and for metric in metric_list / metrics_func[metric] operates on that single malformed element — the selected metrics are never matched, and the classification path hits a KeyError on the bogus key. The Scorer produces wrong/empty output for both the classification and regression paths.

Expected: metric_list is a proper list of metric names and each selected metric is computed.

How to reproduce?

A — user-facing: Add a Machine Learning Scorer operator, select one or more metrics (e.g. Accuracy, F1 Score), give it prediction/label columns, and run. The selected metrics are not computed correctly (empty result / KeyError).

B — confirmed against main's operator directly: construct MachineLearningScorerOpDesc with isRegression = false and classificationMetrics = List(accuracy, f1Score), then call generatePythonCode(). The emitted line is:

metric_list = [self.decode_python_template('J0FjY3VyYWN5JywnRjEgU2NvcmUn')]

The base64 J0FjY3VyYWN5JywnRjEgU2NvcmUn decodes to 'Accuracy','F1 Score' — i.e. the entire quoted list collapses into a single decoded string element, so metric_list has one malformed entry rather than two metric names.

Proposed fix: change getSelectedMetrics()'s return type from EncodableString to plain String, so the builder splices it verbatim into metric_list = ['Accuracy','F1 Score']. The method body is unchanged.

Version/Branch

1.3.0-incubating-SNAPSHOT (main)

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