fix: associate bulk change to individual libraries (#2626)

Fixes #2609

Author: JoeWang1127

internal/librarian/release_notes_test.go

@@ -551,8 +551,8 @@ func TestLanguageRepoChangedFiles(t *testing.T) {
 				IsCleanValue:  true,
 				HeadHashValue: "1234",
 				ChangedFilesInCommitValueByHash: map[string][]string{
-					"abcd": []string{"a/b/c", "d/e/f"},
-					"1234": []string{"g/h/i", "j/k/l"},
+					"abcd": {"a/b/c", "d/e/f"},
+					"1234": {"g/h/i", "j/k/l"},
 				},
 			},
 			want: []string{"g/h/i", "j/k/l"},

internal/librarian/tag_and_release.go

@@ -15,14 +15,17 @@
 package librarian
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
+	"html/template"
 	"log/slog"
 	"net/url"
 	"path/filepath"
 	"regexp"
 	"slices"
+	"sort"
 	"strconv"
 	"strings"
 	"time"
@@ -40,15 +43,40 @@ const (
 )
 
 var (
-	detailsRegex = regexp.MustCompile(`(?s)<details><summary>(.*?)</summary>(.*?)</details>`)
-	summaryRegex = regexp.MustCompile(`(.*?): (v?\d+\.\d+\.\d+)`)
+	bulkChangeSectionRegex = regexp.MustCompile(`(feat|fix|perf|revert|docs): (.*)\nLibraries: (.*)`)
+	contentRegex           = regexp.MustCompile(`### (Features|Bug Fixes|Performance Improvements|Reverts|Documentation)\n`)
+	detailsRegex           = regexp.MustCompile(`(?s)<details><summary>(.*?)</summary>(.*?)</details>`)
+	summaryRegex           = regexp.MustCompile(`(.*?): (v?\d+\.\d+\.\d+)`)
+
+	libraryReleaseTemplate = template.Must(template.New("libraryRelease").Parse(`### {{.Type}}
+{{ range .Messages }}
+{{.}}
+{{ end }}
+
+`))
 )
 
 type tagAndReleaseRunner struct {
 	ghClient    GitHubClient
 	pullRequest string
 }
 
+// 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
+}
+
+type libraryReleaseBuilder struct {
+	typeToMessages map[string][]string
+	title          string
+	version        string
+}
+
 func newTagAndReleaseRunner(cfg *config.Config) (*tagAndReleaseRunner, error) {
 	if cfg.GitHubToken == "" {
 		return nil, fmt.Errorf("`%s` must be set", config.LibrarianGithubToken)
@@ -203,43 +231,86 @@ func (r *tagAndReleaseRunner) processPullRequest(ctx context.Context, p *github.
 	return r.replacePendingLabel(ctx, p)
 }
 
-// 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
+	idToBuilder := make(map[string]*libraryReleaseBuilder)
 	matches := detailsRegex.FindAllStringSubmatch(body, -1)
 	for _, match := range matches {
 		summary := match[1]
+		content := strings.TrimSpace(match[2])
 		if summary == "Bulk Changes" {
+			// Associated bulk changes to individual libraries.
+			sections := bulkChangeSectionRegex.FindAllStringSubmatch(content, -1)
+			for _, section := range sections {
+				if len(section) != 4 {
+					slog.Warn("bulk change does not associated with a library id", "content", section)
+					continue
+				}
+
+				commitType, ok := commitTypeToHeading[strings.TrimSpace(section[1])]
+				if !ok {
+					slog.Warn("unrecognized commit type, skipping", "commit", section[1])
+					continue
+				}
+				message := fmt.Sprintf("* %s", strings.TrimSpace(section[2]))
+				libraries := section[3]
+				for _, library := range strings.Split(libraries, ",") {
+					// Bulk change doesn't have title and version, put an empty string so that
+					// title and version are not overwritten, if exists.
+					updateLibraryReleaseBuilder(idToBuilder, library, commitType, "", message, "")
+				}
+			}
+
 			continue
 		}
-		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,
-			})
-		} else {
+		summaryMatch := summaryRegex.FindStringSubmatch(summary)
+		if len(summaryMatch) != 3 {
 			slog.Warn("failed to parse pull request body", "match", strings.Join(match, "\n"))
+			continue
+		}
+
+		slog.Info("parsed pull request body", "library", summaryMatch[1], "version", summaryMatch[2])
+		library := strings.TrimSpace(summaryMatch[1])
+		version := strings.TrimSpace(summaryMatch[2])
+		// Split the content using commit types, e.g., Features, Bug Fixes, etc.
+		// For non-bulk changes, the first match (i = 0) is the release title, the i-th match is
+		// the commit messages of typeMatches[i-1].
+		contentMatches := contentRegex.Split(content, -1)
+		title := contentMatches[0]
+		typeMatches := contentRegex.FindAllStringSubmatch(content, -1)
+		if len(typeMatches) == 0 {
+			// No commit message in a library.
+			updateLibraryReleaseBuilder(idToBuilder, library, "", title, "", version)
+		}
+		for i, typeMatch := range typeMatches {
+			commitType := typeMatch[1]
+			contentMatch := contentMatches[i+1]
+			messages := strings.Split(contentMatch, "\n\n")
+			for _, message := range messages {
+				message = strings.TrimSpace(message)
+				if message != "" {
+					updateLibraryReleaseBuilder(idToBuilder, library, commitType, title, message, version)
+				}
+			}
 		}
+
+	}
+
+	var parsedBodies []libraryRelease
+	for libraryID, builder := range idToBuilder {
+		parsedBodies = append(parsedBodies, libraryRelease{
+			Body:    buildReleaseBody(builder.typeToMessages, builder.title),
+			Library: libraryID,
+			Version: builder.version,
+		})
 	}
 
+	sort.Slice(parsedBodies, func(i, j int) bool {
+		return parsedBodies[i].Library < parsedBodies[j].Library
+	})
+
 	return parsedBodies
 }
 
@@ -258,3 +329,64 @@ func (r *tagAndReleaseRunner) replacePendingLabel(ctx context.Context, p *github
 	}
 	return nil
 }
+
+// updateLibraryReleaseBuilder finds or creates a libraryReleaseBuilder for a given library
+// and updates it with new information.
+func updateLibraryReleaseBuilder(idToVersionAndBody map[string]*libraryReleaseBuilder, library, commitType, title, message, version string) {
+	vab, ok := idToVersionAndBody[library]
+	if !ok {
+		idToVersionAndBody[library] = &libraryReleaseBuilder{
+			typeToMessages: map[string][]string{
+				commitType: {message},
+			},
+			version: version,
+			title:   title,
+		}
+
+		return
+	}
+
+	vab.typeToMessages[commitType] = append(vab.typeToMessages[commitType], message)
+	if version == "" {
+		version = vab.version
+	}
+	vab.version = version
+	if title == "" {
+		title = vab.title
+	}
+	vab.title = title
+}
+
+// buildReleaseBody formats the release notes for a single library.
+//
+// It takes a map of commit types (e.g., "Features", "Bug Fixes") to their corresponding messages and a title string.
+// It returns a formatted string containing the title and all commit messages organized by type, following the order
+// defined in commitTypeOrder.
+func buildReleaseBody(body map[string][]string, title string) string {
+	var builder strings.Builder
+	builder.WriteString(title)
+	for _, commitType := range commitTypeOrder {
+		heading := commitTypeToHeading[commitType]
+		messages, ok := body[heading]
+		if !ok {
+			continue
+		}
+		var out bytes.Buffer
+		data := &struct {
+			Type     string
+			Messages []string
+		}{
+			Type:     heading,
+			Messages: messages,
+		}
+		if err := libraryReleaseTemplate.Execute(&out, data); err != nil {
+			slog.Error("error executing template", "error", err)
+			continue
+		}
+
+		builder.WriteString(strings.TrimSpace(out.String()))
+		builder.WriteString("\n\n")
+	}
+
+	return strings.TrimSpace(builder.String())
+}

internal/librarian/tag_and_release_test.go

@@ -263,9 +263,9 @@ Language Image: gcr.io/test/image:latest
 
 </details>
 
-<details><summary>another-library-name: 2.3.4</summary>
+<details><summary>library-two: 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)
+[2.3.4](https://github.com/googleapis/repo/compare/library-two-v2.3.3...library-two-v2.3.4) (2025-08-15)
 
 ### Bug Fixes
 
@@ -284,8 +284,8 @@ Language Image: gcr.io/test/image:latest
 				},
 				{
 					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)
+					Library: "library-two",
+					Body: `[2.3.4](https://github.com/googleapis/repo/compare/library-two-v2.3.3...library-two-v2.3.4) (2025-08-15)
 
 ### Bug Fixes
 
@@ -350,6 +350,84 @@ some content
 				},
 			},
 		},
+		{
+			name: "bulk_changes_appears_in_github_release",
+			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)
+
+### Features
+
+* add SaveToGcsFindingsOutput ([1234567](https://github.com/googleapis/google-cloud-go/commit/1234567))
+
+* another feature ([9876543](https://github.com/googleapis/google-cloud-go/commit/9876543))
+
+### Documentation
+
+* minor doc revision ([abcdefgh](https://github.com/googleapis/google-cloud-go/commit/abcdefgh))
+
+</details>
+
+
+<details><summary>Bulk Changes</summary>
+
+* feat: this is a bulk change ([abcdefgh](https://github.com/googleapis/google-cloud-go/commit/abcdefgh))
+Libraries: a,b,google-cloud-storage
+
+* fix: this is another bulk change
+Libraries: a,b,c
+
+</details>`,
+			want: []libraryRelease{
+				{
+					Version: "",
+					Library: "a",
+					Body: `### Features
+
+* this is a bulk change ([abcdefgh](https://github.com/googleapis/google-cloud-go/commit/abcdefgh))
+
+### Bug Fixes
+
+* this is another bulk change`,
+				},
+				{
+					Version: "",
+					Library: "b",
+					Body: `### Features
+
+* this is a bulk change ([abcdefgh](https://github.com/googleapis/google-cloud-go/commit/abcdefgh))
+
+### Bug Fixes
+
+* this is another bulk change`,
+				},
+				{
+					Version: "",
+					Library: "c",
+					Body: `### Bug Fixes
+
+* this is another bulk change`,
+				},
+				{
+					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)
+
+### Features
+
+* add SaveToGcsFindingsOutput ([1234567](https://github.com/googleapis/google-cloud-go/commit/1234567))
+
+* another feature ([9876543](https://github.com/googleapis/google-cloud-go/commit/9876543))
+
+* this is a bulk change ([abcdefgh](https://github.com/googleapis/google-cloud-go/commit/abcdefgh))
+
+### Documentation
+
+* minor doc revision ([abcdefgh](https://github.com/googleapis/google-cloud-go/commit/abcdefgh))`,
+				},
+			},
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			got := parsePullRequestBody(test.body)