feat: do not derive path for veneer (#3237)

Do not derive googleapis path and service config for veneer library
because these two parameters live in modules, not in channels

For #3193

Author: JoeWang1127

internal/librarian/generate.go

@@ -244,12 +244,17 @@ func prepareLibrary(language string, lib *config.Library, defaults *config.Defau
 		// If no channels are specified, create an empty channel first
 		lib.Channels = append(lib.Channels, &config.Channel{})
 	}
-	for _, ch := range lib.Channels {
-		if ch.Path == "" {
-			ch.Path = deriveChannelPath(language, lib)
-		}
-		if ch.ServiceConfig == "" {
-			ch.ServiceConfig = deriveServiceConfig(ch.Path)
+
+	// The googleapis path of a veneer library lives in language-specific configurations,
+	// so we only need to derive the path and service config for non-veneer libraries.
+	if !lib.Veneer {
+		for _, ch := range lib.Channels {
+			if ch.Path == "" {
+				ch.Path = deriveChannelPath(language, lib)
+			}
+			if ch.ServiceConfig == "" {
+				ch.ServiceConfig = deriveServiceConfig(ch.Path)
+			}
 		}
 	}
 

internal/librarian/generate_test.go

@@ -254,11 +254,20 @@ func TestPrepareLibrary(t *testing.T) {
 			name:              "rust with no channels creates default and derives path",
 			language:          "rust",
 			channels:          nil,
-			wantErr:           false,
 			wantOutput:        "src/generated/cloud/test/v1",
 			wantChannelPath:   "google/cloud/test/v1",
 			wantServiceConfig: "google/cloud/test/v1/test_v1.yaml",
 		},
+		{
+			name:              "veneer rust with no channels does not derive path and service config",
+			language:          "rust",
+			output:            "src/storage/test/v1",
+			veneer:            true,
+			channels:          nil,
+			wantOutput:        "src/storage/test/v1",
+			wantChannelPath:   "",
+			wantServiceConfig: "",
+		},
 		{
 			name:    "veneer without output returns error",
 			veneer:  true,