feat(internal/librarian): add logic to parse pr bodies (#1767)

Updates: #1009

Author: codyoss

internal/librarian/tag_and_release.go

@@ -17,11 +17,19 @@ package librarian
 import (
 	"context"
 	"fmt"
+	"log/slog"
+	"regexp"
+	"strings"
 
 	"github.com/googleapis/librarian/internal/cli"
 	"github.com/googleapis/librarian/internal/config"
 )
 
+var (
+	detailsRegex = regexp.MustCompile(`(?s)<details><summary>(.*?)</summary>(.*?)</details>`)
+	summaryRegex = regexp.MustCompile(`(.*?): (v?\d+\.\d+\.\d+)`)
+)
+
 // cmdTagAndRelease is the command for the `release tag-and-release` subcommand.
 var cmdTagAndRelease = &cli.Command{
 	Short:     "release tag-and-release tags and creates a GitHub release for a merged pull request.",
@@ -61,3 +69,39 @@ func newTagAndReleaseRunner(cfg *config.Config) (*tagAndReleaseRunner, error) {
 func (r *tagAndReleaseRunner) run(ctx context.Context) error {
 	return nil
 }
+
+// libraryRelease holds the parsed information from a pull request body.
+type libraryRelease struct {
+	// Body contains the release notes.
+	Body string
+	// Library is the library id of the library being released
+	Library string
+	// Version is the version that is being released
+	Version string
+}
+
+// parsePullRequestBody parses a string containing release notes and returns a slice of ParsedPullRequestBody.
+func parsePullRequestBody(body string) []libraryRelease {
+	slog.Info("parsing pull request body")
+	var parsedBodies []libraryRelease
+	matches := detailsRegex.FindAllStringSubmatch(body, -1)
+	for _, match := range matches {
+		summary := match[1]
+		content := strings.TrimSpace(match[2])
+
+		summaryMatches := summaryRegex.FindStringSubmatch(summary)
+		if len(summaryMatches) == 3 {
+			slog.Info("parsed pull request body", "library", summaryMatches[1], "version", summaryMatches[2])
+			library := strings.TrimSpace(summaryMatches[1])
+			version := strings.TrimSpace(summaryMatches[2])
+			parsedBodies = append(parsedBodies, libraryRelease{
+				Version: version,
+				Library: library,
+				Body:    content,
+			})
+		}
+		slog.Warn("failed to parse pull request body", "match", strings.Join(match, "\n"))
+	}
+
+	return parsedBodies
+}

internal/librarian/tag_and_release_test.go

@@ -17,6 +17,7 @@ package librarian
 import (
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/googleapis/librarian/internal/config"
 )
 
@@ -52,3 +53,128 @@ func TestNewTagAndReleaseRunner(t *testing.T) {
 		})
 	}
 }
+
+func TestParsePullRequestBody(t *testing.T) {
+	tests := []struct {
+		name string
+		body string
+		want []libraryRelease
+	}{
+		{
+			name: "single library",
+			body: `
+Librarian Version: v0.2.0
+Language Image: image
+
+<details><summary>google-cloud-storage: 1.2.3</summary>
+
+[1.2.3](https://github.com/googleapis/google-cloud-go/compare/google-cloud-storage-v1.2.2...google-cloud-storage-v1.2.3) (2025-08-15)
+
+### Features
+
+* Add new feature ([abcdef1](https://github.com/googleapis/google-cloud-go/commit/abcdef1))
+
+</details>`,
+			want: []libraryRelease{
+				{
+					Version: "1.2.3",
+					Library: "google-cloud-storage",
+					Body: `[1.2.3](https://github.com/googleapis/google-cloud-go/compare/google-cloud-storage-v1.2.2...google-cloud-storage-v1.2.3) (2025-08-15)
+
+### Features
+
+* Add new feature ([abcdef1](https://github.com/googleapis/google-cloud-go/commit/abcdef1))`,
+				},
+			},
+		},
+		{
+			name: "multiple libraries",
+			body: `
+Librarian Version: 1.2.3
+Language Image: gcr.io/test/image:latest
+
+<details><summary>library-one: 1.0.0</summary>
+
+[1.0.0](https://github.com/googleapis/repo/compare/library-one-v0.9.0...library-one-v1.0.0) (2025-08-15)
+
+### Features
+
+* some feature ([1234567](https://github.com/googleapis/repo/commit/1234567))
+
+</details>
+
+<details><summary>another-library-name: 2.3.4</summary>
+
+[2.3.4](https://github.com/googleapis/repo/compare/another-library-name-v2.3.3...another-library-name-v2.3.4) (2025-08-15)
+
+### Bug Fixes
+
+* some bug fix ([abcdefg](https://github.com/googleapis/repo/commit/abcdefg))
+
+</details>`,
+			want: []libraryRelease{
+				{
+					Version: "1.0.0",
+					Library: "library-one",
+					Body: `[1.0.0](https://github.com/googleapis/repo/compare/library-one-v0.9.0...library-one-v1.0.0) (2025-08-15)
+
+### Features
+
+* some feature ([1234567](https://github.com/googleapis/repo/commit/1234567))`,
+				},
+				{
+					Version: "2.3.4",
+					Library: "another-library-name",
+					Body: `[2.3.4](https://github.com/googleapis/repo/compare/another-library-name-v2.3.3...another-library-name-v2.3.4) (2025-08-15)
+
+### Bug Fixes
+
+* some bug fix ([abcdefg](https://github.com/googleapis/repo/commit/abcdefg))`,
+				},
+			},
+		},
+		{
+			name: "empty body",
+			body: "",
+			want: nil,
+		},
+		{
+			name: "malformed summary",
+			body: `
+Librarian Version: 1.2.3
+Language Image: gcr.io/test/image:latest
+
+<details><summary>no-version-here</summary>
+
+some content
+
+</details>`,
+			want: nil,
+		},
+		{
+			name: "v prefix in version",
+			body: `
+<details><summary>google-cloud-storage: v1.2.3</summary>
+
+[v1.2.3](https://github.com/googleapis/google-cloud-go/compare/google-cloud-storage-v1.2.2...google-cloud-storage-v1.2.3) (2025-08-15)
+
+</details>`,
+			want: []libraryRelease{
+				{
+					Version: "v1.2.3",
+					Library: "google-cloud-storage",
+					Body:    "[v1.2.3](https://github.com/googleapis/google-cloud-go/compare/google-cloud-storage-v1.2.2...google-cloud-storage-v1.2.3) (2025-08-15)",
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := parsePullRequestBody(tt.body)
+			if diff := cmp.Diff(tt.want, got); diff != "" {
+				t.Errorf("ParsePullRequestBody() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}