feat(sidekick): split model.rs into modules (#2213)

In Rust, the documentation browser shows the code, and this code was
getting too large to render effectively. For some crates, the module is
also too large for some IDE defaults.

Author: coryan

internal/sidekick/internal/api/model.go

@@ -154,6 +154,14 @@ type API struct {
 	State *APIState
 }
 
+// HasMessages returns true if the API contains messages (most do).
+//
+// This is useful in the mustache templates to skip code that only makes sense
+// when per-message code follows.
+func (api *API) HasMessages() bool {
+	return len(api.Messages) != 0
+}
+
 // APIState contains helpful information that can be used when generating
 // clients.
 type APIState struct {

internal/sidekick/internal/api/mustache_helpers_test.go

@@ -0,0 +1,40 @@
+// 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 api
+
+import "testing"
+
+func TestHasMessages(t *testing.T) {
+	m := &Message{
+		Name:    "Message",
+		Package: "test",
+		ID:      ".test.Message",
+	}
+	model := NewTestAPI([]*Message{m}, []*Enum{}, []*Service{})
+
+	if !model.HasMessages() {
+		t.Errorf("expected HasMessages() == true for: %v", model)
+	}
+
+	e := &Enum{
+		Name:    "Enum",
+		Package: "test",
+		ID:      ".test.Enum",
+	}
+	model = NewTestAPI([]*Message{}, []*Enum{e}, []*Service{})
+	if model.HasMessages() {
+		t.Errorf("expected HasMessages() == false for: %v", model)
+	}
+}

internal/sidekick/internal/rust/generate_test.go

@@ -19,14 +19,57 @@ import (
 	"os/exec"
 	"path"
 	"path/filepath"
+	"slices"
+	"strings"
 	"testing"
 
 	"github.com/googleapis/librarian/internal/sidekick/internal/config"
 	"github.com/googleapis/librarian/internal/sidekick/internal/parser"
 )
 
 var (
-	testdataDir, _ = filepath.Abs("../../testdata")
+	testdataDir, _  = filepath.Abs("../../testdata")
+	expectedInNosvc = []string{
+		"README.md",
+		"Cargo.toml",
+		path.Join("src", "lib.rs"),
+		path.Join("src", "model.rs"),
+		path.Join("src", "model", "debug.rs"),
+		path.Join("src", "model", "deserialize.rs"),
+		path.Join("src", "model", "serialize.rs"),
+	}
+	expectedInCrate = append(expectedInNosvc,
+		path.Join("src", "builder.rs"),
+		path.Join("src", "client.rs"),
+		path.Join("src", "tracing.rs"),
+		path.Join("src", "transport.rs"),
+		path.Join("src", "stub.rs"),
+		path.Join("src", "stub", "dynamic.rs"),
+	)
+	expectedInClient = []string{
+		path.Join("mod.rs"),
+		path.Join("model.rs"),
+		path.Join("model", "debug.rs"),
+		path.Join("model", "deserialize.rs"),
+		path.Join("model", "serialize.rs"),
+		path.Join("builder.rs"),
+		path.Join("client.rs"),
+		path.Join("tracing.rs"),
+		path.Join("transport.rs"),
+		path.Join("stub.rs"),
+		path.Join("stub", "dynamic.rs"),
+	}
+	unexpectedInClient = []string{
+		"README.md",
+		"Cargo.toml",
+		path.Join("src", "lib.rs"),
+	}
+	expectedInModule = []string{
+		path.Join("mod.rs"),
+		path.Join("debug.rs"),
+		path.Join("deserialize.rs"),
+		path.Join("serialize.rs"),
+	}
 )
 
 func TestRustFromOpenAPI(t *testing.T) {
@@ -47,7 +90,7 @@ func TestRustFromOpenAPI(t *testing.T) {
 	if err := Generate(model, outDir, cfg); err != nil {
 		t.Fatal(err)
 	}
-	for _, expected := range []string{"README.md", "Cargo.toml", "src/lib.rs"} {
+	for _, expected := range expectedInCrate {
 		filename := path.Join(outDir, expected)
 		stat, err := os.Stat(filename)
 		if os.IsNotExist(err) {
@@ -57,6 +100,7 @@ func TestRustFromOpenAPI(t *testing.T) {
 			t.Errorf("generated files should not be executable %s: %o", filename, stat.Mode())
 		}
 	}
+	importsModelModules(t, path.Join(outDir, "src", "model.rs"))
 }
 
 func TestRustFromProtobuf(t *testing.T) {
@@ -80,7 +124,91 @@ func TestRustFromProtobuf(t *testing.T) {
 	if err := Generate(model, outDir, cfg); err != nil {
 		t.Fatal(err)
 	}
-	for _, expected := range []string{"README.md", "Cargo.toml", "src/lib.rs"} {
+	for _, expected := range expectedInCrate {
+		filename := path.Join(outDir, expected)
+		stat, err := os.Stat(filename)
+		if os.IsNotExist(err) {
+			t.Errorf("missing %s: %s", filename, err)
+		}
+		if stat.Mode().Perm()|0666 != 0666 {
+			t.Errorf("generated files should not be executable %s: %o", filename, stat.Mode())
+		}
+	}
+	importsModelModules(t, path.Join(outDir, "src", "model.rs"))
+}
+
+func TestRustClient(t *testing.T) {
+	requireProtoc(t)
+	for _, override := range []string{"http-client", "grpc-client"} {
+		outDir := t.TempDir()
+
+		cfg := &config.Config{
+			General: config.GeneralConfig{
+				SpecificationFormat: "protobuf",
+				ServiceConfig:       "google/cloud/secretmanager/v1/secretmanager_v1.yaml",
+				SpecificationSource: "google/cloud/secretmanager/v1",
+			},
+			Source: map[string]string{
+				"googleapis-root": path.Join(testdataDir, "googleapis"),
+			},
+			Codec: map[string]string{
+				"copyright-year":    "2025",
+				"template-override": path.Join("templates", override),
+			},
+		}
+		model, err := parser.CreateModel(cfg)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := Generate(model, outDir, cfg); err != nil {
+			t.Fatal(err)
+		}
+		for _, expected := range expectedInClient {
+			filename := path.Join(outDir, expected)
+			stat, err := os.Stat(filename)
+			if os.IsNotExist(err) {
+				t.Errorf("missing %s: %s", filename, err)
+			}
+			if stat.Mode().Perm()|0666 != 0666 {
+				t.Errorf("generated files should not be executable %s: %o", filename, stat.Mode())
+			}
+		}
+		for _, unexpected := range unexpectedInClient {
+			filename := path.Join(outDir, unexpected)
+			if stat, err := os.Stat(filename); err == nil {
+				t.Errorf("did not expect file %s, got=%v", unexpected, stat)
+			}
+		}
+		importsModelModules(t, path.Join(outDir, "model.rs"))
+	}
+}
+
+func TestRustNosvc(t *testing.T) {
+	requireProtoc(t)
+	outDir := t.TempDir()
+
+	cfg := &config.Config{
+		General: config.GeneralConfig{
+			SpecificationFormat: "protobuf",
+			ServiceConfig:       "google/cloud/secretmanager/v1/secretmanager_v1.yaml",
+			SpecificationSource: "google/cloud/secretmanager/v1",
+		},
+		Source: map[string]string{
+			"googleapis-root": path.Join(testdataDir, "googleapis"),
+		},
+		Codec: map[string]string{
+			"copyright-year":    "2025",
+			"template-override": path.Join("templates", "nosvc"),
+		},
+	}
+	model, err := parser.CreateModel(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := Generate(model, outDir, cfg); err != nil {
+		t.Fatal(err)
+	}
+	for _, expected := range expectedInNosvc {
 		filename := path.Join(outDir, expected)
 		stat, err := os.Stat(filename)
 		if os.IsNotExist(err) {
@@ -90,6 +218,7 @@ func TestRustFromProtobuf(t *testing.T) {
 			t.Errorf("generated files should not be executable %s: %o", filename, stat.Mode())
 		}
 	}
+	importsModelModules(t, path.Join(outDir, "src", "model.rs"))
 }
 
 func TestRustModuleRpc(t *testing.T) {
@@ -118,7 +247,7 @@ func TestRustModuleRpc(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	for _, expected := range []string{"mod.rs"} {
+	for _, expected := range expectedInModule {
 		filename := path.Join(outDir, "rpc", expected)
 		stat, err := os.Stat(filename)
 		if os.IsNotExist(err) {
@@ -128,6 +257,7 @@ func TestRustModuleRpc(t *testing.T) {
 			t.Errorf("generated files should not be executable %s: %o", filename, stat.Mode())
 		}
 	}
+	importsModelModules(t, path.Join(outDir, "rpc", "mod.rs"))
 }
 
 func TestRustBootstrapWkt(t *testing.T) {
@@ -157,7 +287,7 @@ func TestRustBootstrapWkt(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	for _, expected := range []string{"mod.rs"} {
+	for _, expected := range expectedInModule {
 		filename := path.Join(outDir, "wkt", expected)
 		stat, err := os.Stat(filename)
 		if os.IsNotExist(err) {
@@ -169,6 +299,20 @@ func TestRustBootstrapWkt(t *testing.T) {
 	}
 }
 
+func importsModelModules(t *testing.T, filename string) {
+	t.Helper()
+	contents, err := os.ReadFile(filename)
+	if err != nil {
+		t.Fatal(err)
+	}
+	lines := strings.Split(string(contents), "\n")
+	for _, want := range []string{"mod debug;", "mod serialize;", "mod deserialize;"} {
+		if !slices.Contains(lines, want) {
+			t.Errorf("expected file %s to have a line matching %q, got:\n%s", filename, want, contents)
+		}
+	}
+}
+
 func requireProtoc(t *testing.T) {
 	t.Helper()
 	if _, err := exec.LookPath("protoc"); err != nil {