feat(librariangen): add request package (#3933)

This will be used for parsing Librarian CLI requests. Copied from https://github.com/googleapis/google-cloud-go/tree/main/internal/librariangen/request.

Author: meltsufin

internal/librariangen/go.mod

@@ -1,3 +1,5 @@
 module cloud.google.com/java/internal/librariangen
 
 go 1.24.4
+
+require github.com/google/go-cmp v0.7.0 // indirect

internal/librariangen/go.sum

@@ -0,0 +1,2 @@
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=

internal/librariangen/request/request.go

@@ -0,0 +1,78 @@
+// 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
+//
+// 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.
+
+package request
+
+import (
+"encoding/json"
+"fmt"
+"os"
+)
+
+// Library is the combination of all the fields used by CLI requests and responses.
+// Each CLI command has its own request/response type, but they all use Library.
+type Library struct {
+ID string `json:"id,omitempty"`
+Version string `json:"version,omitempty"`
+APIs []API `json:"apis,omitempty"`
+// SourcePaths are the directories to which librarian contributes code.
+// For Go, this is typically the Go module directory.
+SourcePaths []string `json:"source_roots,omitempty"`
+// PreserveRegex are files/directories to leave untouched during generation.
+// This is useful for preserving handwritten helper files or customizations.
+PreserveRegex []string `json:"preserve_regex,omitempty"`
+// RemoveRegex are files/directories to remove during generation.
+RemoveRegex []string `json:"remove_regex,omitempty"`
+// Changes are the changes being released (in a release request)
+Changes []*Change `json:"changes,omitempty"`
+// Specifying a tag format allows librarian to honor this format when creating
+// a tag for the release of the library. The replacement values of {id} and {version}
+// permitted to reference the values configured in the library. If not specified
+// the assumed format is {id}-{version}. e.g., {id}/v{version}.
+TagFormat string `yaml:"tag_format,omitempty" json:"tag_format,omitempty"`
+// ReleaseTriggered indicates whether this library is being released (in a release request)
+ReleaseTriggered bool `json:"release_triggered,omitempty"`
+}
+
+// API corresponds to a single API definition within a librarian request/response.
+type API struct {
+Path string `json:"path,omitempty"`
+ServiceConfig string `json:"service_config,omitempty"`
+}
+
+// Change represents a single commit change for a library.
+type Change struct {
+Type string `json:"type"`
+Subject string `json:"subject"`
+Body string `json:"body"`
+PiperCLNumber string `json:"piper_cl_number"`
+SourceCommitHash string `json:"source_commit_hash"`
+}
+
+// ParseLibrary reads a file from the given path and unmarshals
+// it into a Library struct. This is used for build and generate, where the requests
+// are simply the library, with no wrapping.
+func ParseLibrary(path string) (*Library, error) {
+data, err := os.ReadFile(path)
+if err != nil {
+return nil, fmt.Errorf("librariangen: failed to read request file from %s: %w", path, err)
+}
+
+var req Library
+if err := json.Unmarshal(data, &req); err != nil {
+return nil, fmt.Errorf("librariangen: failed to unmarshal request file %s: %w", path, err)
+}
+
+return &req, nil
+}

internal/librariangen/request/request_test.go

@@ -0,0 +1,98 @@
+// 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
+//
+// 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.
+
+package request
+
+import (
+"os"
+"path/filepath"
+"testing"
+
+"github.com/google/go-cmp/cmp"
+)
+
+func TestParseLibrary(t *testing.T) {
+testCases := []struct {
+name string
+content string
+want *Library
+wantErr bool
+}{
+{
+name: "valid request",
+content: `{
+"id": "asset",
+"version": "1.15.0",
+"apis": [
+{
+"path": "google/cloud/asset/v1",
+"service_config": "cloudasset_v1.yaml"
+}
+],
+"source_roots": ["asset/apiv1"],
+"preserve_regex": ["asset/apiv1/foo.go"],
+"remove_regex": ["asset/apiv1/bar.go"]
+}`,
+want: &Library{
+ID: "asset",
+Version: "1.15.0",
+APIs: []API{
+{
+Path: "google/cloud/asset/v1",
+ServiceConfig: "cloudasset_v1.yaml",
+},
+},
+SourcePaths: []string{"asset/apiv1"},
+PreserveRegex: []string{"asset/apiv1/foo.go"},
+RemoveRegex: []string{"asset/apiv1/bar.go"},
+},
+wantErr: false,
+},
+{
+name: "malformed json",
+content: `{"id": "foo",`,
+wantErr: true,
+},
+}
+
+for _, tc := range testCases {
+t.Run(tc.name, func(t *testing.T) {
+tmpDir := t.TempDir()
+reqPath := filepath.Join(tmpDir, "generate-request.json")
+if err := os.WriteFile(reqPath, []byte(tc.content), 0644); err != nil {
+t.Fatalf("failed to write test file: %v", err)
+}
+
+got, err := ParseLibrary(reqPath)
+
+if (err != nil) != tc.wantErr {
+t.Errorf("Parse() error = %v, wantErr %v", err, tc.wantErr)
+return
+}
+
+if !tc.wantErr {
+if diff := cmp.Diff(tc.want, got); diff != "" {
+t.Errorf("Parse() mismatch (-want +got):\n%s", diff)
+}
+}
+})
+}
+}
+
+func TestParseLibrary_FileNotFound(t *testing.T) {
+_, err := ParseLibrary("non-existent-file.json")
+if err == nil {
+t.Error("Parse() expected error for non-existent file, got nil")
+}
+}