codeBehindMe commented on a change in pull request #11976:
URL: https://github.com/apache/beam/pull/11976#discussion_r440723127
##########
File path: sdks/go/pkg/beam/pardo.go
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@@ -414,7 +412,36 @@ 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(formatParDoError(dofn, len(ret), 7))
}
return ret[0], ret[1], ret[2], ret[3], ret[4], ret[5], ret[6]
}
+
+//formatParDoError is a helper function to provide a more concise error
+// message to the users when a DoFn and its ParDo pairing is incorrect.
+//
+// We construct a new graph.Fn using the doFn which is passed. We explicitly
+// ignore the error since we already know that its already a DoFn type as
+// TryParDo would have panicked otherwise.
+func formatParDoError(doFn interface{}, emitSize int, parDoSize int) string {
+ doFun, _ := graph.NewFn(doFn)
+ doFnName := doFun.Name()
+
+ thisParDo := recommendParDo(parDoSize) // Conveniently keeps the API
slim.
Review comment:
b31ab3a885
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