chore(internal/gapicgen): add more tooling for generating aliases

internal/gapicgen/cmd/genbot/README.md

@@ -103,6 +103,33 @@ This will speed up the build a bit:
 -v `go env GOMODCACHE`:/root/go/pkg/mod
 ```
 
+### Generating new stubs
+
+Flip status in aliasfix for gapics being migrated to in progress.
+
+```shell
+cd /path/to/internal/gapicgen
+go run cloud.google.com/go/internal/gapicgen/cmd/genbot \
+   -local \
+   -only-gapics
+   -gocloud-dir=/path/to/google-cloud-go \
+   -gapic=cloud.google.com/go/foo/apiv1
+```
+
+### Generating type aliases
+
+Flip status in aliasfix for gapics being migrated to migrated.
+
+```shell
+cd /path/to/internal/gapicgen
+go run cloud.google.com/go/internal/gapicgen/cmd/genbot \
+   -local \
+   -generate-alias
+   -gocloud-dir=/path/to/google-cloud-go \
+   -genproto-dir=/path/to/go-genproto \
+   -gapic=cloud.google.com/go/foo/apiv1
+```
+
 ## FAQ
 
 ### How to bump to a later version of the microgenerator

internal/gapicgen/cmd/genbot/local.go

@@ -39,6 +39,7 @@ type localConfig struct {
 	regenOnly       bool
 	forceAll        bool
 	genModule       bool
+	genAlias        bool
 }
 
 func genLocal(ctx context.Context, c localConfig) error {
@@ -75,6 +76,7 @@ func genLocal(ctx context.Context, c localConfig) error {
 		RegenOnly:         c.regenOnly,
 		ForceAll:          c.forceAll,
 		GenModule:         c.genModule,
+		GenAlias:          c.genAlias,
 	}
 	if _, err := generator.Generate(ctx, conf); err != nil {
 		log.Printf("Generator ran (and failed) in %s\n", tmpDir)

internal/gapicgen/cmd/genbot/main.go

@@ -53,6 +53,7 @@ func main() {
 	onlyGapics := flag.Bool("only-gapics", strToBool(os.Getenv("ONLY_GAPICS")), "Enabling stops regenerating genproto.")
 	regenOnly := flag.Bool("regen-only", strToBool(os.Getenv("REGEN_ONLY")), "Enabling means no vetting, manifest updates, or compilation.")
 	genModule := flag.Bool("generate-module", strToBool(os.Getenv("GENERATE_MODULE")), "Enabling means a new module will be generated for API being generated.")
+	genAlias := flag.Bool("generate-alias", strToBool(os.Getenv("GENERATE_ALIAS")), "Enabling means alias files will be generated.")
 
 	flag.Parse()
 
@@ -67,6 +68,7 @@ func main() {
 			regenOnly:       *regenOnly,
 			forceAll:        *forceAll,
 			genModule:       *genModule,
+			genAlias:        *genAlias,
 		}); err != nil {
 			log.Fatal(err)
 		}

internal/gapicgen/generator/gapics.go

@@ -53,6 +53,7 @@ type GapicGenerator struct {
 	genModule         bool
 	modifiedPkgs      []string
 	forceAll          bool
+	genAlias          bool
 }
 
 // NewGapicGenerator creates a GapicGenerator.
@@ -68,6 +69,7 @@ func NewGapicGenerator(c *Config, modifiedPkgs []string) *GapicGenerator {
 		genModule:         c.GenModule,
 		modifiedPkgs:      modifiedPkgs,
 		forceAll:          c.ForceAll,
+		genAlias:          c.GenAlias,
 	}
 }
 
@@ -104,6 +106,11 @@ func (g *GapicGenerator) Regen(ctx context.Context) error {
 		if err := g.genVersionFile(c); err != nil {
 			return err
 		}
+		if g.genAlias {
+			if err := g.genAliasShim(modPath); err != nil {
+				return err
+			}
+		}
 		if g.genModule {
 			if err := gocmd.ModTidy(modPath); err != nil {
 				return nil
@@ -620,6 +627,40 @@ func (g *GapicGenerator) copyMicrogenFiles() error {
 	return c.Run()
 }
 
+func (g *GapicGenerator) genAliasShim(modPath string) error {
+	aliasshimBody := `// Copyright 2022 Google LLC
+//
+// 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.
+
+// Code generated by gapicgen. DO NOT EDIT.
+
+//go:build aliasshim
+// +build aliasshim
+
+// Package aliasshim is used to keep the dependency on go-genproto during our
+// go-genproto to google-cloud-go stubs migration window.
+package aliasshim
+`
+	os.MkdirAll(filepath.Join(modPath, "aliasshim"), os.ModePerm)
+	f, err := os.Create(filepath.Join(modPath, "aliasshim", "aliasshim.go"))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = fmt.Fprint(f, aliasshimBody)
+	return err
+}
+
 func ParseAPIShortnames(googleapisDir string, confs []*MicrogenConfig, manualEntries []ManifestEntry) (map[string]string, error) {
 	shortnames := map[string]string{}
 	for _, conf := range confs {

internal/gapicgen/generator/generator.go

@@ -40,6 +40,7 @@ type Config struct {
 	RegenOnly         bool
 	ForceAll          bool
 	GenModule         bool
+	GenAlias          bool
 }
 
 // Generate generates genproto and gapics.

internal/gapicgen/generator/genproto.go

@@ -26,6 +26,8 @@ import (
 	"strconv"
 	"strings"
 
+	"cloud.google.com/go/internal/aliasfix"
+	"cloud.google.com/go/internal/aliasgen"
 	"cloud.google.com/go/internal/gapicgen/execv"
 	"cloud.google.com/go/internal/gapicgen/execv/gocmd"
 	"cloud.google.com/go/internal/gapicgen/git"
@@ -52,19 +54,25 @@ var noGRPC = map[string]bool{
 
 // GenprotoGenerator is used to generate code for googleapis/go-genproto.
 type GenprotoGenerator struct {
-	genprotoDir   string
-	googleapisDir string
-	protoSrcDir   string
-	forceAll      bool
+	genprotoDir     string
+	googleapisDir   string
+	protoSrcDir     string
+	googleCloudDir  string
+	gapicToGenerate string
+	forceAll        bool
+	genAlias        bool
 }
 
 // NewGenprotoGenerator creates a new GenprotoGenerator.
 func NewGenprotoGenerator(c *Config) *GenprotoGenerator {
 	return &GenprotoGenerator{
-		genprotoDir:   c.GenprotoDir,
-		googleapisDir: c.GoogleapisDir,
-		protoSrcDir:   filepath.Join(c.ProtoDir, "/src"),
-		forceAll:      c.ForceAll,
+		genprotoDir:     c.GenprotoDir,
+		googleapisDir:   c.GoogleapisDir,
+		protoSrcDir:     filepath.Join(c.ProtoDir, "/src"),
+		googleCloudDir:  c.GapicDir,
+		gapicToGenerate: c.GapicToGenerate,
+		forceAll:        c.ForceAll,
+		genAlias:        c.GenAlias,
 	}
 }
 
@@ -99,6 +107,10 @@ func hasPrefix(s string, prefixes []string) bool {
 func (g *GenprotoGenerator) Regen(ctx context.Context) error {
 	log.Println("regenerating genproto")
 
+	if g.genAlias {
+		return g.generateAliases()
+	}
+
 	// Create space to put generated .pb.go's.
 	c := execv.Command("mkdir", "-p", "generated")
 	c.Dir = g.genprotoDir
@@ -279,3 +291,22 @@ func (g *GenprotoGenerator) moveAndCleanupGeneratedSrc() error {
 
 	return nil
 }
+
+func (g *GenprotoGenerator) generateAliases() error {
+	for genprotoImport, newPkg := range aliasfix.GenprotoPkgMigration {
+		if !isMigrated(genprotoImport) || g.gapicToGenerate == "" {
+			continue
+		}
+		// remove the stubs dir segment from path
+		gapicImport := newPkg.ImportPath[:strings.LastIndex(newPkg.ImportPath, "/")]
+		if !strings.Contains(g.gapicToGenerate, gapicImport) {
+			continue
+		}
+		srdDir := filepath.Join(g.googleCloudDir, strings.TrimPrefix(newPkg.ImportPath, "cloud.google.com/go/"))
+		destDir := filepath.Join(g.genprotoDir, "googleapis", strings.TrimPrefix(genprotoImport, "google.golang.org/genproto/googleapis/"))
+		if err := aliasgen.Run(srdDir, destDir); err != nil {
+			return err
+		}
+	}
+	return nil
+}

internal/gapicgen/go.mod

@@ -5,6 +5,7 @@ go 1.19
 require (
 	cloud.google.com/go v0.102.1
 	cloud.google.com/go/internal/aliasfix v0.0.0
+	cloud.google.com/go/internal/aliasgen v0.0.0-20220902151655-a6004e762f78
 	cloud.google.com/go/internal/godocfx v0.0.0-20220625055333-3f8d1627b9c2
 	github.com/google/go-github/v35 v35.3.0
 	github.com/shurcooL/githubv4 v0.0.0-20220520033151-0b4e3294ff00
@@ -39,3 +40,5 @@ require (
 )
 
 replace cloud.google.com/go/internal/aliasfix => ../aliasfix
+
+replace cloud.google.com/go/internal/aliasgen => ../aliasgen

internal/gapicgen/go.sum

@@ -678,6 +678,7 @@ google.golang.org/grpc v1.45.0/go.mod h1:lN7owxKUQEqMfSyQikvvk5tf/6zMPsrK+ONuO11
 google.golang.org/grpc v1.46.0/go.mod h1:vN9eftEi1UMyUsIF80+uQXhHjbXYbm0uXoFCACuMGWk=
 google.golang.org/grpc v1.46.2/go.mod h1:vN9eftEi1UMyUsIF80+uQXhHjbXYbm0uXoFCACuMGWk=
 google.golang.org/grpc v1.47.0/go.mod h1:vN9eftEi1UMyUsIF80+uQXhHjbXYbm0uXoFCACuMGWk=
+google.golang.org/grpc v1.48.0 h1:rQOsyJ/8+ufEDJd/Gdsz7HG220Mh9HAhFHRGnIjda0w=
 google.golang.org/grpc/cmd/protoc-gen-go-grpc v1.1.0/go.mod h1:6Kw0yEErY5E/yWrBtf03jp27GLLJujG4z/JK95pnjjw=
 google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
 google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=