feat(diff): Enable commenting on expanded lines in PR diffs

routers/web/repo/commit.go

@@ -276,20 +276,24 @@ func Diff(ctx *context.Context) {
 	userName := ctx.Repo.Owner.Name
 	repoName := ctx.Repo.Repository.Name
 	commitID := ctx.PathParam("sha")
-	var (
-		gitRepo *git.Repository
-		err     error
-	)
+
+	diffBlobExcerptData := &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ctx.Repo.RepoLink + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: commitID,
+	}
+	gitRepo := ctx.Repo.GitRepo
+	var gitRepoStore gitrepo.Repository = ctx.Repo.Repository
 
 	if ctx.Data["PageIsWiki"] != nil {
-		gitRepo, err = gitrepo.OpenRepository(ctx, ctx.Repo.Repository.WikiStorageRepo())
+		var err error
+		gitRepoStore = ctx.Repo.Repository.WikiStorageRepo()
+		gitRepo, err = gitrepo.RepositoryFromRequestContextOrOpen(ctx, gitRepoStore)
 		if err != nil {
 			ctx.ServerError("Repo.GitRepo.GetCommit", err)
 			return
 		}
-		defer gitRepo.Close()
-	} else {
-		gitRepo = ctx.Repo.GitRepo
+		diffBlobExcerptData.BaseLink = ctx.Repo.RepoLink + "/wiki/blob_excerpt"
 	}
 
 	commit, err := gitRepo.GetCommit(commitID)
@@ -324,7 +328,7 @@ func Diff(ctx *context.Context) {
 		ctx.NotFound(err)
 		return
 	}
-	diffShortStat, err := gitdiff.GetDiffShortStat(ctx, ctx.Repo.Repository, gitRepo, "", commitID)
+	diffShortStat, err := gitdiff.GetDiffShortStat(ctx, gitRepoStore, gitRepo, "", commitID)
 	if err != nil {
 		ctx.ServerError("GetDiffShortStat", err)
 		return
@@ -360,6 +364,7 @@ func Diff(ctx *context.Context) {
 	ctx.Data["Title"] = commit.Summary() + " · " + base.ShortSha(commitID)
 	ctx.Data["Commit"] = commit
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = diffBlobExcerptData
 
 	if !fileOnly {
 		diffTree, err := gitdiff.GetDiffTree(ctx, gitRepo, false, parentCommitID, commitID)

routers/web/repo/compare.go

@@ -14,6 +14,7 @@ import (
 	"net/http"
 	"net/url"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
@@ -43,6 +44,7 @@ import (
 	"code.gitea.io/gitea/services/context/upload"
 	"code.gitea.io/gitea/services/gitdiff"
 	pull_service "code.gitea.io/gitea/services/pull"
+	user_service "code.gitea.io/gitea/services/user"
 )
 
 const (
@@ -638,6 +640,11 @@ func PrepareCompareDiff(
 	}
 	ctx.Data["DiffShortStat"] = diffShortStat
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ci.HeadRepo.Link() + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: headCommitID,
+	}
 	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	if !fileOnly {
@@ -865,6 +872,28 @@ func CompareDiff(ctx *context.Context) {
 	ctx.HTML(http.StatusOK, tplCompare)
 }
 
+// attachCommentsToLines attaches comments to their corresponding diff lines
+func attachCommentsToLines(section *gitdiff.DiffSection, lineComments map[int64][]*issues_model.Comment) {
+	for _, line := range section.Lines {
+		if comments, ok := lineComments[int64(line.LeftIdx*-1)]; ok {
+			line.Comments = append(line.Comments, comments...)
+		}
+		if comments, ok := lineComments[int64(line.RightIdx)]; ok {
+			line.Comments = append(line.Comments, comments...)
+		}
+		sort.SliceStable(line.Comments, func(i, j int) bool {
+			return line.Comments[i].CreatedUnix < line.Comments[j].CreatedUnix
+		})
+	}
+}
+
+// attachHiddenCommentIDs calculates and attaches hidden comment IDs to expand buttons
+func attachHiddenCommentIDs(section *gitdiff.DiffSection, lineComments map[int64][]*issues_model.Comment) {
+	for _, line := range section.Lines {
+		gitdiff.FillHiddenCommentIDsForDiffLine(line, lineComments)
+	}
+}
+
 // ExcerptBlob render blob excerpt contents
 func ExcerptBlob(ctx *context.Context) {
 	commitID := ctx.PathParam("sha")
@@ -874,19 +903,26 @@ func ExcerptBlob(ctx *context.Context) {
 	idxRight := ctx.FormInt("right")
 	leftHunkSize := ctx.FormInt("left_hunk_size")
 	rightHunkSize := ctx.FormInt("right_hunk_size")
-	anchor := ctx.FormString("anchor")
 	direction := ctx.FormString("direction")
 	filePath := ctx.FormString("path")
 	gitRepo := ctx.Repo.GitRepo
+
+	diffBlobExcerptData := &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ctx.Repo.RepoLink + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: commitID,
+	}
+
 	if ctx.Data["PageIsWiki"] == true {
 		var err error
-		gitRepo, err = gitrepo.OpenRepository(ctx, ctx.Repo.Repository.WikiStorageRepo())
+		gitRepo, err = gitrepo.RepositoryFromRequestContextOrOpen(ctx, ctx.Repo.Repository.WikiStorageRepo())
 		if err != nil {
 			ctx.ServerError("OpenRepository", err)
 			return
 		}
-		defer gitRepo.Close()
+		diffBlobExcerptData.BaseLink = ctx.Repo.RepoLink + "/wiki/blob_excerpt"
 	}
+
 	chunkSize := gitdiff.BlobExcerptChunkSize
 	commit, err := gitRepo.GetCommit(commitID)
 	if err != nil {
@@ -947,10 +983,43 @@ func ExcerptBlob(ctx *context.Context) {
 			section.Lines = append(section.Lines, lineSection)
 		}
 	}
+
+	diffBlobExcerptData.PullIssueIndex = ctx.FormInt64("pull_issue_index")
+	if diffBlobExcerptData.PullIssueIndex > 0 {
+		if !ctx.Repo.CanRead(unit.TypePullRequests) {
+			ctx.NotFound(nil)
+			return
+		}
+
+		issue, err := issues_model.GetIssueByIndex(ctx, ctx.Repo.Repository.ID, diffBlobExcerptData.PullIssueIndex)
+		if err != nil {
+			log.Error("GetIssueByIndex error: %v", err)
+		} else if issue.IsPull {
+			// FIXME: DIFF-CONVERSATION-DATA: the following data assignment is fragile
+			ctx.Data["Issue"] = issue
+			ctx.Data["CanBlockUser"] = func(blocker, blockee *user_model.User) bool {
+				return user_service.CanBlockUser(ctx, ctx.Doer, blocker, blockee)
+			}
+			// and "diff/comment_form.tmpl" (reply comment) needs them
+			ctx.Data["PageIsPullFiles"] = true
+			ctx.Data["AfterCommitID"] = diffBlobExcerptData.AfterCommitID
+
+			allComments, err := issues_model.FetchCodeComments(ctx, issue, ctx.Doer, ctx.FormBool("show_outdated"))
+			if err != nil {
+				log.Error("FetchCodeComments error: %v", err)
+			} else {
+				if lineComments, ok := allComments[filePath]; ok {
+					attachCommentsToLines(section, lineComments)
+					attachHiddenCommentIDs(section, lineComments)
+				}
+			}
+		}
+	}
+
 	ctx.Data["section"] = section
 	ctx.Data["FileNameHash"] = git.HashFilePathForWebUI(filePath)
-	ctx.Data["AfterCommitID"] = commitID
-	ctx.Data["Anchor"] = anchor
+	ctx.Data["DiffBlobExcerptData"] = diffBlobExcerptData
+
 	ctx.HTML(http.StatusOK, tplBlobExcerpt)
 }
 

routers/web/repo/compare_test.go

@@ -0,0 +1,40 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package repo
+
+import (
+	"testing"
+
+	issues_model "code.gitea.io/gitea/models/issues"
+	"code.gitea.io/gitea/services/gitdiff"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAttachCommentsToLines(t *testing.T) {
+	section := &gitdiff.DiffSection{
+		Lines: []*gitdiff.DiffLine{
+			{LeftIdx: 5, RightIdx: 10},
+			{LeftIdx: 6, RightIdx: 11},
+		},
+	}
+
+	lineComments := map[int64][]*issues_model.Comment{
+		-5: {{ID: 100, CreatedUnix: 1000}},                               // left side comment
+		10: {{ID: 200, CreatedUnix: 2000}},                               // right side comment
+		11: {{ID: 300, CreatedUnix: 1500}, {ID: 301, CreatedUnix: 2500}}, // multiple comments
+	}
+
+	attachCommentsToLines(section, lineComments)
+
+	// First line should have left and right comments
+	assert.Len(t, section.Lines[0].Comments, 2)
+	assert.Equal(t, int64(100), section.Lines[0].Comments[0].ID)
+	assert.Equal(t, int64(200), section.Lines[0].Comments[1].ID)
+
+	// Second line should have two comments, sorted by creation time
+	assert.Len(t, section.Lines[1].Comments, 2)
+	assert.Equal(t, int64(300), section.Lines[1].Comments[0].ID)
+	assert.Equal(t, int64(301), section.Lines[1].Comments[1].ID)
+}

routers/web/repo/pull.go

@@ -827,6 +827,12 @@ func viewPullFiles(ctx *context.Context, beforeCommitID, afterCommitID string) {
 	}
 
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = &gitdiff.DiffBlobExcerptData{
+		BaseLink:       ctx.Repo.RepoLink + "/blob_excerpt",
+		PullIssueIndex: pull.Index,
+		DiffStyle:      ctx.FormString("style"),
+		AfterCommitID:  afterCommitID,
+	}
 	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	if ctx.IsSigned && ctx.Doer != nil {