damccorm commented on code in PR #17429:
URL: https://github.com/apache/beam/pull/17429#discussion_r864441783
##########
sdks/go/pkg/beam/registration/registration.tmpl:
##########
@@ -0,0 +1,263 @@
+{{define "BuildWrapper_StartFinishBundle"}}
+{{$lowerName := "unknown"}}{{$upperName := "unknown"}}{{if (eq .func
"startBundle")}}{{$lowerName = "startBundle"}}{{$upperName =
"StartBundle"}}{{end}}{{if (eq .func "finishBundle")}}{{$lowerName =
"finishBundle"}}{{$upperName = "FinishBundle"}}{{end}}{{$startFinishBundleMaxIn
:= .startFinishBundleMaxIn}}{{$processElementMaxIn := .processElementMaxIn}}
+{{range $funcIn := upto $startFinishBundleMaxIn}}{{range $funcOut := upto 2}}
+func
register{{$upperName}}{{$funcIn}}x{{$funcOut}}FuncAndMakeStructWrapper{{(genericTypingRepresentation
$funcIn $funcOut true)}}() func(interface{}) reflectx.Func {
+ reflectx.RegisterFunc(reflect.TypeOf((*func({{range $in := upto
$funcIn}}{{if $in}}, {{end}}I{{$in}}{{end}}){{if $funcOut}}
R0{{end}})(nil)).Elem(), func(fn interface{}) reflectx.Func {
+ return &caller{{$funcIn}}x{{$funcOut}}{{(genericTypingRepresentation
$funcIn $funcOut false)}}{fn: fn.(func({{range $in := upto $funcIn}}{{if $in}},
{{end}}I{{$in}}{{end}}){{if $funcOut}} R0{{end}})}
+ })
+
+ return func(fn interface{}) reflectx.Func {
+ return reflectx.MakeFunc(func({{range $in := upto $funcIn}}{{if $in}},
{{end}}a{{$in}} I{{$in}}{{end}}){{if $funcOut}} R0{{end}} {
+ {{if $funcOut}}return
{{end}}fn.({{$lowerName}}{{$funcIn}}x{{$funcOut}}{{(genericTypingRepresentation
$funcIn $funcOut false)}}).{{$upperName}}({{range $in := upto $funcIn}}{{if
$in}}, {{end}}a{{$in}}{{end}})
+ })
+ }
+}
+{{end}}{{end}}
+{{$numParams := $processElementMaxIn}}
+func build{{$upperName}}Wrapper{{(genericTypingRepresentation $numParams 0
true)}}(doFn interface{}) func(interface{}) reflectx.Func {
+ {{$lowerName}}In := -1
+ {{$lowerName}}Out := -1
+ {{$lowerName}}Method :=
reflect.ValueOf(doFn).MethodByName("{{$upperName}}")
+ if {{$lowerName}}Method.IsValid() {
+ {{$lowerName}}In = {{$lowerName}}Method.Type().NumIn()
+ {{$lowerName}}Out = {{$lowerName}}Method.Type().NumOut()
+ switch {
+{{range $funcIn := upto $startFinishBundleMaxIn}}
+ case {{$lowerName}}In == {{$funcIn}}:
+ switch { {{range $funcOut := upto 2}}{{$possibleCombos :=
(possibleBundleLifecycleParameterCombos $funcIn $numParams)}}{{if
$possibleCombos}}
+ case {{$lowerName}}Out == {{$funcOut}}:
+{{$first := true}}{{range $funcCombo := $possibleCombos}}{{if $first}}{{$first
= false}} {{else}} else {{end}}if _, ok :=
doFn.({{$lowerName}}{{$funcIn}}x{{$funcOut}}{{if (or $funcIn
$funcOut)}}[{{(join $funcCombo ", ")}}{{if $funcOut}}{{if $funcIn}},
{{end}}error{{end}}]{{end}}); ok {
+ return
register{{$upperName}}{{$funcIn}}x{{$funcOut}}FuncAndMakeStructWrapper{{if (or
$funcIn $funcOut)}}[{{(join $funcCombo ", ")}}{{if $funcOut}}{{if $funcIn}},
{{end}}error{{end}}]{{end}}()
+ } {{end}}{{end}}{{end}}
+ default:
+ panic("Invalid signature for {{$upperName}}")
+ }
+{{end}}
+ default:
+ panic("Invalid signature for {{$upperName}}")
+ }
+ }
+ return nil
Review Comment:
We could get there if either the function doesn't have a StartBundle
function (or whatever function we're dealing with here), or if we were unable
to infer the types of the StartBundle function.
Returning nil in the first case is definitely the right thing, I updated to
panic in the second case. The second should never happen, but I agree its
better to be explicit
##########
sdks/go/pkg/beam/registration/doc.go:
##########
@@ -0,0 +1,31 @@
+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with
+// the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:generate go install github.com/apache/beam/sdks/v2/go/cmd/specialize
+//go:generate specialize --package=registration --input=registration.tmpl
--x=data,universals --imports=typex
+//go:generate go fmt
+
+/*
+Package registration contains functions for registering and optimizing your
DoFn.
+
+This package contains generic registration/optimization function for each
possible combination of input and output arities in a DoFn's ProcessElement
function.
+For example, given a DoFn with a ProcessElement function that takes 4 inputs
and returns 3 outputs, you can call
+register.DoFn4x3[input1 type, input2 type, input3 type, input4 type, output1
type, output2 type, output3 type](&doFn{}) during pipeline construction. This
will
+register your DoFn and perform some reflection based optimization to
significantly speed up execution at runtime.
+
+See DoFn2x1 for a full example.
+*/
+
Review Comment:
Neat - I did not understand this before
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