fix(devtools/cmd/migrate-sidekick): generate config for google-cloud-wkt (#3269)

To generate google-cloud-wkt using the librarian config created by
migrate-sidekick tool, we need to
- Add source roots at the module level
- Add disabled rustdoc warnings at the module level

Add a type alias for `[]string` because we need a way to marshal empty
slice to `[]` but omit `nil`.

To generate google-cloud-wkt:
```
migrate-sidekick .
// wkt/src/generated
librarian generate google-cloud-wkt
// wkt/tests/common/src/generated
librarian generate common
```

Result:
```
deleted:    src/wkt/src/generated/.sidekick.toml
deleted:    src/wkt/tests/common/src/generated/.sidekick.toml
```

Note that the common package needs a 2nd command to generate as its
package name is not `google-cloud-wkt`.

Fixes #3200

Author: JoeWang1127

devtools/cmd/migrate-sidekick/main.go

@@ -213,7 +213,7 @@ func readRootSidekick(repoPath string) (*config.Config, error) {
 			ReleaseLevel: releaseLevel,
 			Rust: &config.RustDefault{
 				PackageDependencies:     packageDependencies,
-				DisabledRustdocWarnings: strToSlice(warnings),
+				DisabledRustdocWarnings: strToSlice(warnings, false),
 				GenerateSetterSamples:   generateSetterSamples,
 			},
 		},
@@ -358,7 +358,7 @@ func buildGAPIC(files []string, repoPath string) (map[string]*config.Library, er
 		}
 
 		if extraModules, ok := sidekick.Codec["extra-modules"].(string); ok {
-			for _, module := range strToSlice(extraModules) {
+			for _, module := range strToSlice(extraModules, false) {
 				if module == "" {
 					continue
 				}
@@ -421,7 +421,7 @@ func buildGAPIC(files []string, repoPath string) (map[string]*config.Library, er
 		rustCrate := &config.RustCrate{
 			RustDefault: config.RustDefault{
 				PackageDependencies:     packageDeps,
-				DisabledRustdocWarnings: strToSlice(disabledRustdocWarnings),
+				DisabledRustdocWarnings: strToSlice(disabledRustdocWarnings, false),
 				GenerateSetterSamples:   generateSetterSamples,
 			},
 			PerServiceFeatures:        strToBool(perServiceFeatures),
@@ -430,12 +430,12 @@ func buildGAPIC(files []string, repoPath string) (map[string]*config.Library, er
 			TitleOverride:             titleOverride,
 			PackageNameOverride:       packageNameOverride,
 			RootName:                  rootName,
-			Roots:                     strToSlice(roots),
-			DefaultFeatures:           strToSlice(defaultFeatures),
-			IncludeList:               strToSlice(includeList),
-			IncludedIds:               strToSlice(includeIds),
-			SkippedIds:                strToSlice(skippedIds),
-			DisabledClippyWarnings:    strToSlice(disabledClippyWarnings),
+			Roots:                     strToSlice(roots, false),
+			DefaultFeatures:           strToSlice(defaultFeatures, false),
+			IncludeList:               strToSlice(includeList, false),
+			IncludedIds:               strToSlice(includeIds, false),
+			SkippedIds:                strToSlice(skippedIds, false),
+			DisabledClippyWarnings:    strToSlice(disabledClippyWarnings, false),
 			HasVeneer:                 strToBool(hasVeneer),
 			RoutingRequired:           strToBool(routingRequired),
 			IncludeGrpcOnlyMethods:    strToBool(includeGrpcOnlyMethods),
@@ -522,9 +522,9 @@ func buildVeneer(files []string) (map[string]*config.Library, error) {
 	return veneers, nil
 }
 
-func buildModules(path string) ([]*config.RustModule, error) {
+func buildModules(rootDir string) ([]*config.RustModule, error) {
 	var modules []*config.RustModule
-	err := filepath.WalkDir(path, func(path string, d os.DirEntry, err error) error {
+	err := filepath.WalkDir(rootDir, func(path string, d os.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
@@ -533,6 +533,22 @@ func buildModules(path string) ([]*config.RustModule, error) {
 			return nil
 		}
 
+		if strings.Contains(path, "tests") {
+			// Only use a .sidekick.toml in tests directory to represent a rust module if the following directory
+			// exists:
+			//
+			// |-src
+			// |  |-generated
+			// |     |-.sidekick.toml
+			// |-Cargo.toml
+			// Only one pair of Cargo.toml and .sidekick.toml (within tests directory) is not comply this structure in
+			// google-cloud-rust, which is wkt/Cargo.toml and src/wkt/tests/common/src/generated/.sidekick.toml.
+			srcDir := strings.TrimSuffix(path, fmt.Sprintf("/src/generated/%s", sidekickFile))
+			if rootDir != srcDir {
+				return nil
+			}
+		}
+
 		sidekick, err := readTOML[SidekickConfig](path)
 		if err != nil {
 			return err
@@ -542,6 +558,17 @@ func buildModules(path string) ([]*config.RustModule, error) {
 		includeList, _ := sidekick.Source["include-list"].(string)
 		skippedIds, _ := sidekick.Source["skipped-ids"].(string)
 		titleOverride, _ := sidekick.Source["title-override"].(string)
+		moduleRoots := make(map[string]string)
+		roots, ok := sidekick.Source["roots"].(string)
+		if ok {
+			for _, root := range strings.Split(roots, ",") {
+				root = fmt.Sprintf("%s-root", root)
+				modPath, ok := sidekick.Source[root].(string)
+				if ok {
+					moduleRoots[root] = modPath
+				}
+			}
+		}
 
 		hasVeneer, _ := sidekick.Codec["has-veneer"].(string)
 		includeGrpcOnlyMethods, _ := sidekick.Codec["include-grpc-only-methods"].(string)
@@ -551,15 +578,16 @@ func buildModules(path string) ([]*config.RustModule, error) {
 		nameOverrides, _ := sidekick.Codec["name-overrides"].(string)
 		postProcessProtos, _ := sidekick.Codec["post-process-protos"].(string)
 		templateOverride, _ := sidekick.Codec["template-override"].(string)
+
 		generateSetterSamples, ok := sidekick.Codec["generate-setter-samples"].(string)
 		if !ok {
 			generateSetterSamples = "true"
 		}
 
-		modules = append(modules, &config.RustModule{
+		module := &config.RustModule{
 			GenerateSetterSamples:  strToBool(generateSetterSamples),
 			HasVeneer:              strToBool(hasVeneer),
-			IncludedIds:            strToSlice(includedIds),
+			IncludedIds:            strToSlice(includedIds, false),
 			IncludeGrpcOnlyMethods: strToBool(includeGrpcOnlyMethods),
 			IncludeList:            includeList,
 			ModulePath:             modulePath,
@@ -569,11 +597,22 @@ func buildModules(path string) ([]*config.RustModule, error) {
 			RoutingRequired:        strToBool(routingRequired),
 			ExtendGrpcTransport:    strToBool(extendGrpcTransport),
 			ServiceConfig:          sidekick.General.ServiceConfig,
-			SkippedIds:             strToSlice(skippedIds),
+			SkippedIds:             strToSlice(skippedIds, false),
 			Source:                 sidekick.General.SpecificationSource,
 			Template:               strings.TrimPrefix(templateOverride, "templates/"),
 			TitleOverride:          titleOverride,
-		})
+		}
+
+		if len(moduleRoots) > 0 {
+			module.ModuleRoots = moduleRoots
+		}
+
+		disabledRustdocWarnings, ok := sidekick.Codec["disabled-rustdoc-warnings"].(string)
+		if ok {
+			module.DisabledRustdocWarnings = strToSlice(disabledRustdocWarnings, true)
+		}
+
+		modules = append(modules, module)
 
 		return nil
 	})
@@ -657,8 +696,17 @@ func strToBool(s string) bool {
 	return s == "true"
 }
 
-func strToSlice(s string) []string {
+// strToSlice converts a comma-separated string into a slice of strings.
+//
+// The wantEmpty parameter controls the behavior when the input string is empty:
+//   - If true: Returns an empty initialized slice (make([]string, 0)).
+//   - If false: Returns nil.
+func strToSlice(s string, wantEmpty bool) []string {
 	if s == "" {
+		if wantEmpty {
+			return make([]string, 0)
+		}
+
 		return nil
 	}
 

devtools/cmd/migrate-sidekick/main_test.go

@@ -414,8 +414,10 @@ func TestBuildVeneer(t *testing.T) {
 					Rust: &config.RustCrate{
 						Modules: []*config.RustModule{
 							{
-								GenerateSetterSamples: true,
-								HasVeneer:             true,
+								DisabledRustdocWarnings: []string{},
+								GenerateSetterSamples:   true,
+								ModuleRoots:             nil,
+								HasVeneer:               true,
 								IncludedIds: []string{
 									".google.storage.v2.Storage.DeleteBucket",
 									".google.storage.v2.Storage.GetBucket",
@@ -435,10 +437,13 @@ func TestBuildVeneer(t *testing.T) {
 							{
 								GenerateSetterSamples: false,
 								ModulePath:            "crate::generated::gapic_control::model",
-								NameOverrides:         ".google.storage.control.v2.IntelligenceConfig.Filter.cloud_storage_buckets=CloudStorageBucketsOneOf",
-								Output:                "testdata/build-veneer/success/lib-1/dir-2/dirdir-2",
-								Source:                "google/storage/control/v2",
-								Template:              "convert-prost",
+								ModuleRoots: map[string]string{
+									"project-root": ".",
+								},
+								NameOverrides: ".google.storage.control.v2.IntelligenceConfig.Filter.cloud_storage_buckets=CloudStorageBucketsOneOf",
+								Output:        "testdata/build-veneer/success/lib-1/dir-2/dirdir-2",
+								Source:        "google/storage/control/v2",
+								Template:      "convert-prost",
 							},
 						},
 					},
@@ -452,6 +457,55 @@ func TestBuildVeneer(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "google_cloud-wkt",
+			files: []string{
+				"testdata/build-veneer/wkt/Cargo.toml",
+				"testdata/build-veneer/wkt/tests/common/Cargo.toml",
+			},
+			want: map[string]*config.Library{
+				"common": {
+					Name:          "common",
+					Veneer:        true,
+					Output:        "testdata/build-veneer/wkt/tests/common",
+					Version:       "0.0.0",
+					CopyrightYear: "2025",
+					Rust: &config.RustCrate{
+						Modules: []*config.RustModule{
+							{
+								DisabledRustdocWarnings: []string{},
+								ModulePath:              "crate::generated",
+								ModuleRoots: map[string]string{
+									"project-root": ".",
+								},
+								Output:   "testdata/build-veneer/wkt/tests/common/src/generated",
+								Source:   "src/wkt/tests/protos",
+								Template: "mod",
+							},
+						},
+					},
+				},
+				"google-cloud-wkt": {
+					Name:          "google-cloud-wkt",
+					Veneer:        true,
+					Output:        "testdata/build-veneer/wkt",
+					Version:       "1.2.0",
+					CopyrightYear: "2025",
+					Rust: &config.RustCrate{
+						Modules: []*config.RustModule{
+							{
+								GenerateSetterSamples: true,
+								IncludeList:           "api.proto,source_context.proto,type.proto,descriptor.proto",
+								ModulePath:            "crate",
+								Output:                "testdata/build-veneer/wkt/src/generated",
+								Source:                "google/protobuf",
+								Template:              "mod",
+							},
+						},
+					},
+				},
+			},
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			got, err := buildVeneer(test.files)

devtools/cmd/migrate-sidekick/testdata/build-veneer/success/lib-1/dir-1/.sidekick.toml

@@ -21,3 +21,4 @@ name-overrides            = '.google.storage.v2.Storage=StorageControl'
 include-grpc-only-methods = 'true'
 has-veneer                = 'true'
 routing-required          = 'true'
+disabled-rustdoc-warnings = ''

devtools/cmd/migrate-sidekick/testdata/build-veneer/success/lib-1/dir-2/dirdir-2/.sidekick.toml

@@ -2,6 +2,10 @@
 language             = 'rust'
 specification-source = 'google/storage/control/v2'
 
+[source]
+roots        = 'project'
+project-root = '.'
+
 [codec]
 copyright-year    = '2025'
 template-override = 'templates/convert-prost'

devtools/cmd/migrate-sidekick/testdata/build-veneer/wkt/Cargo.toml

@@ -0,0 +1,62 @@
+# Copyright 2024 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
+#
+#     https://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]
+description = "Google Cloud Client Libraries for Rust - Well Known Types"
+name        = "google-cloud-wkt"
+# ATTENTION: if you change the major version, remember to change the major
+#     version of all downstream dependencies. For details see:
+#         https://github.com/googleapis/google-cloud-rust/issues/3237
+#         https://github.com/googleapis/google-cloud-rust/issues/3265
+version = "1.2.0"
+# Inherit other attributes from the workspace.
+authors.workspace      = true
+categories.workspace   = true
+edition.workspace      = true
+keywords.workspace     = true
+license.workspace      = true
+repository.workspace   = true
+rust-version.workspace = true
+
+[package.metadata.docs.rs]
+# Generate documentation for some of the optional conversions. It is too early
+# for `prost`.
+features = ["chrono", "time"]
+
+[features]
+chrono = ["dep:chrono"]
+time   = []
+# DO NOT USE: this allows us to detect semver changes in types used in the
+# implementation of client libraries. None of the types or functions gated
+# by this feature are intended for general use. We do not plan to document these
+# features and offer no guarantees on their stability.
+_internal-semver = []
+
+[dependencies]
+base64.workspace     = true
+bytes.workspace      = true
+chrono               = { workspace = true, optional = true }
+serde.workspace      = true
+serde_json.workspace = true
+serde_with.workspace = true
+thiserror.workspace  = true
+time                 = { workspace = true, features = ["formatting", "parsing"] }
+url.workspace        = true
+
+[dev-dependencies]
+anyhow.workspace    = true
+test-case.workspace = true
+time                = { workspace = true, features = ["formatting", "macros", "parsing"] }
+wkt                 = { path = ".", package = "google-cloud-wkt", features = ["chrono", "time"] }
+common              = { path = "tests/common" }

devtools/cmd/migrate-sidekick/testdata/build-veneer/wkt/src/generated/.sidekick.toml

@@ -0,0 +1,26 @@
+# Copyright 2025 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
+#
+#     https://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.
+
+[general]
+specification-source = 'google/protobuf'
+
+[source]
+roots        = 'protobuf-src'
+include-list = "api.proto,source_context.proto,type.proto,descriptor.proto"
+
+[codec]
+copyright-year        = '2025'
+template-override     = 'templates/mod'
+module-path           = 'crate'
+package-name-override = 'google-cloud-wkt'

devtools/cmd/migrate-sidekick/testdata/build-veneer/wkt/tests/common/Cargo.toml

@@ -0,0 +1,28 @@
+# Copyright 2025 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
+#
+#     https://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]
+name              = "common"
+description       = "Generated types for tests."
+version           = "0.0.0"
+edition.workspace = true
+publish           = false
+
+[dependencies]
+bytes.workspace      = true
+serde.workspace      = true
+serde_json.workspace = true
+serde_with.workspace = true
+# Local dependencies
+wkt.workspace = true