codeBehindMe commented on a change in pull request #11976:
URL: https://github.com/apache/beam/pull/11976#discussion_r439726617
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File path: sdks/go/pkg/beam/pardo.go
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@@ -414,7 +414,45 @@ func ParDo6(s Scope, dofn interface{}, col PCollection,
opts ...Option) (PCollec
func ParDo7(s Scope, dofn interface{}, col PCollection, opts ...Option)
(PCollection, PCollection, PCollection, PCollection, PCollection, PCollection,
PCollection) {
ret := MustN(TryParDo(s, dofn, col, opts...))
if len(ret) != 7 {
- panic(fmt.Sprintf("expected 7 output. Found: %v", ret))
+ panic(ParDoErrorFormatter(dofn, ParDo7))
}
return ret[0], ret[1], ret[2], ret[3], ret[4], ret[5], ret[6]
}
+
+//ParDoErrorFormatter is a helper function to provide a more concise error
+// message to the users when a DoFn and its ParDo pairing is incorrect.
+func ParDoErrorFormatter(doFn interface{}, parDo interface{}) string {
+ doFnName := reflectx.FunctionName(doFn)
+ doFnOutSize := reflectx.FunctionOutputSize(doFn)
+
+ parDoName := reflectx.FunctionName(parDo)
+ parDoOutSize := reflectx.FunctionOutputSize(parDo)
+
+ useParDo := reflectx.FunctionName(RecommendParDo(doFnOutSize))
+ return fmt.Sprintf("DoFn %v has %v outptus, but %v requires %v outputs,
Use %v instead.", doFnName, doFnOutSize, parDoName, parDoOutSize, useParDo)
+
+}
+
+// recommendParDo takes a in a DoFns emit dimension and recommends the correct
+// ParDo to use.
+func RecommendParDo(emitDim int) interface{} {
Review comment:
db99bf446a
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