feat(generator/rust): support wkt bootstrapping

generator/internal/language/rusttemplate.go

@@ -44,6 +44,9 @@ type RustTemplateData struct {
 	NotForPublication bool
 	HasFeatures       bool
 	Features          []string
+	// When bootstrapping the well-known types crate the templates add some
+	// ad-hoc code.
+	IsWktCrate bool
 }
 
 type RustService struct {
@@ -201,6 +204,7 @@ func newRustTemplateData(model *api.API, c *rustCodec, outdir string) (*RustTemp
 		}),
 		NameToLower:       strings.ToLower(model.Name),
 		NotForPublication: c.doNotPublish,
+		IsWktCrate:        c.sourceSpecificationPackageName == "google.protobuf",
 	}
 	// Determine if any service has an LRO.
 	for _, s := range data.Services {

generator/internal/language/templates/rust/mod/mod.rs.mustache

@@ -22,6 +22,12 @@ limitations under the License.
 #![allow(rustdoc::invalid_html_tags)]
 {{! We use explicit links because it is easier to generate the code with them. }}
 #![allow(rustdoc::redundant_explicit_links)]
+{{#IsWktCrate}}
+{{!
+This file is used to bootstrap the `gcp-sdk-wkt` crate. In all other crates
+`wkt` is well-defined and refers to said crate.}}
+use crate as wkt;
+{{/IsWktCrate}}
 {{#Messages}}
 {{> message}}
 {{/Messages}}

generator/internal/sidekick/sidekick_test.go

@@ -198,6 +198,49 @@ func TestRustModuleFromProtobuf(t *testing.T) {
 	}
 }
 
+func TestRustBootstrapWkt(t *testing.T) {
+	type TestConfig struct {
+		Source        string
+		ServiceConfig string
+		Name          string
+		ExtraOptions  map[string]string
+	}
+	configs := []TestConfig{
+		{
+			Source: "google/protobuf/source_context.proto",
+			Name:   "wkt",
+			ExtraOptions: map[string]string{
+				"module-path": "crate",
+			},
+		},
+	}
+
+	for _, config := range configs {
+		cmdLine := &CommandLine{
+			Command:             []string{},
+			ProjectRoot:         projectRoot,
+			SpecificationFormat: "protobuf",
+			SpecificationSource: config.Source,
+			Source: map[string]string{
+				"googleapis-root": testdataDir,
+			},
+			Language: "rust",
+			Output:   path.Join(testdataDir, "rust/protobuf/golden/wkt/generated", config.Name),
+			Codec: map[string]string{
+				"copyright-year":  "2025",
+				"generate-module": "true",
+			},
+		}
+		for k, v := range config.ExtraOptions {
+			cmdLine.Codec[k] = v
+		}
+		cmdGenerate, _, _ := cmdSidekick.lookup([]string{"generate"})
+		if err := runCommand(cmdGenerate, cmdLine); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
 func TestGoFromProtobuf(t *testing.T) {
 	var outDir = fmt.Sprintf("%s/go/protobuf/golden", testdataDir)
 	type TestConfig struct {

generator/testdata/google/protobuf/source_context.proto

@@ -0,0 +1,48 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf;
+
+option java_package = "com.google.protobuf";
+option java_outer_classname = "SourceContextProto";
+option java_multiple_files = true;
+option objc_class_prefix = "GPB";
+option csharp_namespace = "Google.Protobuf.WellKnownTypes";
+option go_package = "google.golang.org/protobuf/types/known/sourcecontextpb";
+
+// `SourceContext` represents information about the source of a
+// protobuf element, like the file in which it is defined.
+message SourceContext {
+  // The path-qualified name of the .proto file that contained the associated
+  // protobuf element.  For example: `"google/protobuf/source_context.proto"`.
+  string file_name = 1;
+}

generator/testdata/rust/protobuf/golden/wkt/generated/wkt/.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]
+language = 'rust'
+specification-format = 'protobuf'
+specification-source = 'google/protobuf/source_context.proto'
+
+[source]
+googleapis-root = 'testdata'
+
+[codec]
+copyright-year = '2025'
+generate-module = 'true'
+module-path = 'crate'

generator/testdata/rust/protobuf/golden/wkt/generated/wkt/mod.rs

@@ -0,0 +1,48 @@
+// 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.
+//
+// Code generated by sidekick. DO NOT EDIT.
+
+#![allow(rustdoc::invalid_html_tags)]
+#![allow(rustdoc::redundant_explicit_links)]
+use crate as wkt;
+
+/// `SourceContext` represents information about the source of a
+/// protobuf element, like the file in which it is defined.
+#[serde_with::serde_as]
+#[derive(Clone, Debug, Default, PartialEq, serde::Deserialize, serde::Serialize)]
+#[serde(default, rename_all = "camelCase")]
+#[non_exhaustive]
+pub struct SourceContext {
+
+    /// The path-qualified name of the .proto file that contained the associated
+    /// protobuf element.  For example: `"google/protobuf/source_context.proto"`.
+    #[serde(skip_serializing_if = "std::string::String::is_empty")]
+    pub file_name: std::string::String,
+}
+
+impl SourceContext {
+
+    /// Sets the value of `file_name`.
+    pub fn set_file_name<T: std::convert::Into<std::string::String>>(mut self, v: T) -> Self {
+        self.file_name = v.into();
+        self
+    }
+}
+
+impl wkt::message::Message for SourceContext {
+    fn typename() -> &'static str {
+        "type.googleapis.com/google.protobuf.SourceContext"
+    }
+}