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Add protoc-gen-go-fieldpath
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This command will replace protobuf/plugin/fieldpath when we migrate
off from gogo/protobuf.

See containerd#6564 for the detail.

Signed-off-by: Kazuyoshi Kato <[email protected]>
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kzys committed Feb 21, 2022
1 parent d128c37 commit 3febabf
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155 changes: 155 additions & 0 deletions cmd/protoc-gen-go-fieldpath/generator.go
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/*
Copyright The containerd Authors.
Licensed 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.
*/

package main

import (
"google.golang.org/protobuf/compiler/protogen"
"google.golang.org/protobuf/reflect/protoreflect"
)

type generator struct {
out *protogen.GeneratedFile
}

func newGenerator(out *protogen.GeneratedFile) *generator {
gen := generator{out: out}
return &gen
}

func (gen *generator) genFieldMethod(m *protogen.Message) {
p := gen.out

p.P("// Field returns the value for the given fieldpath as a string, if defined.")
p.P("// If the value is not defined, the second value will be false.")
p.P("func (m *", m.GoIdent, ") Field(fieldpath []string) (string, bool) {")

var (
fields []*protogen.Field
unhandled []*protogen.Field
)

for _, f := range m.Fields {
if f.Desc.Kind() == protoreflect.BoolKind ||
f.Desc.Kind() == protoreflect.StringKind ||
isLabelsField(f) || isAnyField(f) || isMessageField(f) {
fields = append(fields, f)
} else {
unhandled = append(unhandled, f)
}

}

if len(fields) > 0 {
p.P("if len(fieldpath) == 0 {")
p.P(`return "", false`)
p.P("}")

p.P("switch fieldpath[0] {")

for _, f := range unhandled {
p.P("// unhandled: ", f.Desc.Name())
}

for _, f := range fields {
p.P(`case "`, f.Desc.Name(), `":`)
switch {
case isLabelsField(f):
stringsJoin := gen.out.QualifiedGoIdent(protogen.GoIdent{
GoImportPath: "strings",
GoName: "Join",
})

p.P(`// Labels fields have been special-cased by name. If this breaks,`)
p.P(`// add better special casing to fieldpath plugin.`)
p.P("if len(m.", f.GoName, ") == 0 {")
p.P(`return "", false`)
p.P("}")
p.P("value, ok := m.", f.GoName, "[", stringsJoin, `(fieldpath[1:], ".")]`)
p.P("return value, ok")
case isAnyField(f):
typeurlUnmarshalAny := gen.out.QualifiedGoIdent(protogen.GoIdent{
GoImportPath: "github.com/containerd/typeurl",
GoName: "UnmarshalAny",
})

p.P("decoded, err := ", typeurlUnmarshalAny, "(m.", f.GoName, ")")
p.P("if err != nil {")
p.P(`return "", false`)
p.P("}")
p.P("adaptor, ok := decoded.(interface{ Field([]string) (string, bool) })")
p.P("if !ok {")
p.P(`return "", false`)
p.P("}")
p.P("return adaptor.Field(fieldpath[1:])")
case isMessageField(f):
p.P(`// NOTE(stevvooe): This is probably not correct in many cases.`)
p.P(`// We assume that the target message also implements the Field`)
p.P(`// method, which isn't likely true in a lot of cases.`)
p.P(`//`)
p.P(`// If you have a broken build and have found this comment,`)
p.P(`// you may be closer to a solution.`)
p.P("if m.", f.GoName, " == nil {")
p.P(`return "", false`)
p.P("}")
p.P("return m.", f.GoName, ".Field(fieldpath[1:])")
case f.Desc.Kind() == protoreflect.StringKind:
p.P("return string(m.", f.GoName, "), len(m.", f.GoName, ") > 0")
case f.Desc.Kind() == protoreflect.BoolKind:
fmtSprint := gen.out.QualifiedGoIdent(protogen.GoIdent{
GoImportPath: "fmt",
GoName: "Sprint",
})

p.P("return ", fmtSprint, "(m.", f.GoName, "), true")
}
}

p.P("}")
} else {
for _, f := range unhandled {
p.P("// unhandled: ", f.Desc.Name())
}
}

p.P(`return "", false`)
p.P("}")
}

func isMessageField(f *protogen.Field) bool {
return f.Desc.Kind() == protoreflect.MessageKind && f.GoIdent.GoName != "Timestamp"
}

func isLabelsField(f *protogen.Field) bool {
return f.Desc.Kind() == protoreflect.MessageKind && f.Desc.Name() == "labels"
}

func isAnyField(f *protogen.Field) bool {
return f.Desc.Kind() == protoreflect.MessageKind && f.GoIdent.GoName == "Any"
}

func generate(plugin *protogen.Plugin, input *protogen.File) error {
file := plugin.NewGeneratedFile(input.GeneratedFilenamePrefix+"_fieldpath.pb.go", input.GoImportPath)
file.P("// Code generated by protoc-gen-go-fieldpath. DO NOT EDIT.")
file.P("// source: ", input.Desc.Path())
file.P("package ", input.GoPackageName)

gen := newGenerator(file)
for _, m := range input.Messages {
gen.genFieldMethod(m)
}
return nil
}
35 changes: 35 additions & 0 deletions cmd/protoc-gen-go-fieldpath/main.go
Original file line number Diff line number Diff line change
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/*
Copyright The containerd Authors.
Licensed 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.
*/

package main

import (
"google.golang.org/protobuf/compiler/protogen"
)

func main() {
protogen.Options{}.Run(func(gen *protogen.Plugin) error {
for _, f := range gen.Files {
if !f.Generate {
continue
}
if err := generate(gen, f); err != nil {
return err
}
}
return nil
})
}
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