Details
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Improvement
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Status: Resolved
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P3
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Resolution: Fixed
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None
Description
User report noted the confusion in the error if you use a DoFn with 0 outputs with beam.ParDo instead of beam.ParDo0.
In that case, a panic stack trace is followed by the cryptic: "expected 1 output. Found: []"
We can do better.
While we can't change the return signature dynamically (that's for ParDoN only), we can instead clearly indicate:
- the DoFn in question.
- the number of outputs the DoFn has
- and recommend using ParDo0, ParDo, ParDo2,...ParDo7, or ParDoN, as appropriate.
https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/pardo.go#L361 would need to change as well as any of the specific cases that follow.
