lostluck commented on a change in pull request #10991: [BEAM-3301] Refactor
DoFn validation & allow specifying main inputs.
URL: https://github.com/apache/beam/pull/10991#discussion_r385893620
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File path: sdks/go/pkg/beam/core/graph/fn.go
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@@ -209,21 +209,58 @@ func (f *DoFn) RestrictionT() *reflect.Type {
// a KV or not based on the other signatures (unless we're more loose about
which
// sideinputs are present). Bind should respect that.
+// Constants so we can avoid magic numbers in validation. Represent number of
+// DoFn main inputs based on what kind of input the DoFn has.
+const (
+ unknownInNum = -1 // Used when we don't know the number of main inputs.
+ singleInNum = 1
+ kvInNum = 2
+)
+
// NewDoFn constructs a DoFn from the given value, if possible.
func NewDoFn(fn interface{}) (*DoFn, error) {
ret, err := NewFn(fn)
if err != nil {
return nil, errors.WithContext(errors.Wrapf(err, "invalid
DoFn"), "constructing DoFn")
}
- return AsDoFn(ret)
+ return AsDoFn(ret, unknownInNum)
}
-// AsDoFn converts a Fn to a DoFn, if possible.
-func AsDoFn(fn *Fn) (*DoFn, error) {
+// NewDoFnKv constructs a DoFn from the given value, if possible, with
+// improved validation from knowing whether the DoFn's main input is a KV or
+// single element.
+func NewDoFnKv(fn interface{}, mainKv bool) (*DoFn, error) {
+ ret, err := NewFn(fn)
+ if err != nil {
+ return nil, errors.WithContext(errors.Wrapf(err, "invalid
DoFn"), "constructing DoFn")
+ }
+
+ if mainKv {
+ return AsDoFn(ret, kvInNum)
+ } else {
+ return AsDoFn(ret, singleInNum)
+ }
+}
+
+// AsDoFn converts a Fn to a DoFn, if possible. numMainIn specifies how many
+// main inputs are expected in the DoFn's method signatures. Valid values are
+// -1 (unknown), 1 (single elements), or 2 (KVs). If the value is unknown then
+// validation is done by best effort and may miss some edge cases.
+func AsDoFn(fn *Fn, numMainIn int) (*DoFn, error) {
addContext := func(err error, fn *Fn) error {
return errors.WithContextf(err, "graph.AsDoFn: for Fn named
%v", fn.Name())
}
+ // Validate numMainIn. This check should match this method's comment.
+ if numMainIn != unknownInNum &&
+ numMainIn != singleInNum &&
+ numMainIn != kvInNum {
+ err := errors.Errorf("invalid number of main inputs given. "+
+ "Got: %v, Want: One of the following: %v",
+ processElementName, []int{unknownInNum, singleInNum,
kvInNum})
+ return nil, addContext(err, fn)
+ }
Review comment:
Consider a switch instead.
```suggestion
switch numMainIn {
case unknownInNum, singleInNum, kvInNum: // Valid
default: // Invalid
err := errors.Errorf("invalid number of main inputs given. "+
"Got: %v, Want: One of the following: %v",
processElementName, []int{unknownInNum, singleInNum,
kvInNum})
return nil, addContext(err, fn)
}
```
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