Use full-file highlighting for diff sections (#36561)

* Fix #35252
* Fix #35999
* Improve diff rendering, don't add unnecessary "added"/"removed" tags for a full-line change
* Also fix a "space trimming" bug in #36539 and add tests
* Use chroma "SQL" lexer instead of "MySQL" to workaround a bug (35999)

routers/web/repo/compare.go

@@ -4,7 +4,6 @@
 package repo
 
 import (
-	"bufio"
 	gocontext "context"
 	"encoding/csv"
 	"errors"
@@ -744,13 +743,16 @@ func attachHiddenCommentIDs(section *gitdiff.DiffSection, lineComments map[int64
 // ExcerptBlob render blob excerpt contents
 func ExcerptBlob(ctx *context.Context) {
 	commitID := ctx.PathParam("sha")
-	lastLeft := ctx.FormInt("last_left")
-	lastRight := ctx.FormInt("last_right")
-	idxLeft := ctx.FormInt("left")
-	idxRight := ctx.FormInt("right")
-	leftHunkSize := ctx.FormInt("left_hunk_size")
-	rightHunkSize := ctx.FormInt("right_hunk_size")
-	direction := ctx.FormString("direction")
+	opts := gitdiff.BlobExcerptOptions{
+		LastLeft:      ctx.FormInt("last_left"),
+		LastRight:     ctx.FormInt("last_right"),
+		LeftIndex:     ctx.FormInt("left"),
+		RightIndex:    ctx.FormInt("right"),
+		LeftHunkSize:  ctx.FormInt("left_hunk_size"),
+		RightHunkSize: ctx.FormInt("right_hunk_size"),
+		Direction:     ctx.FormString("direction"),
+		Language:      ctx.FormString("filelang"),
+	}
 	filePath := ctx.FormString("path")
 	gitRepo := ctx.Repo.GitRepo
 
@@ -770,61 +772,27 @@ func ExcerptBlob(ctx *context.Context) {
 		diffBlobExcerptData.BaseLink = ctx.Repo.RepoLink + "/wiki/blob_excerpt"
 	}
 
-	chunkSize := gitdiff.BlobExcerptChunkSize
 	commit, err := gitRepo.GetCommit(commitID)
 	if err != nil {
-		ctx.HTTPError(http.StatusInternalServerError, "GetCommit")
+		ctx.ServerError("GetCommit", err)
 		return
 	}
-	section := &gitdiff.DiffSection{
-		FileName: filePath,
-	}
-	if direction == "up" && (idxLeft-lastLeft) > chunkSize {
-		idxLeft -= chunkSize
-		idxRight -= chunkSize
-		leftHunkSize += chunkSize
-		rightHunkSize += chunkSize
-		section.Lines, err = getExcerptLines(commit, filePath, idxLeft-1, idxRight-1, chunkSize)
-	} else if direction == "down" && (idxLeft-lastLeft) > chunkSize {
-		section.Lines, err = getExcerptLines(commit, filePath, lastLeft, lastRight, chunkSize)
-		lastLeft += chunkSize
-		lastRight += chunkSize
-	} else {
-		offset := -1
-		if direction == "down" {
-			offset = 0
-		}
-		section.Lines, err = getExcerptLines(commit, filePath, lastLeft, lastRight, idxRight-lastRight+offset)
-		leftHunkSize = 0
-		rightHunkSize = 0
-		idxLeft = lastLeft
-		idxRight = lastRight
-	}
+	blob, err := commit.Tree.GetBlobByPath(filePath)
 	if err != nil {
-		ctx.HTTPError(http.StatusInternalServerError, "getExcerptLines")
+		ctx.ServerError("GetBlobByPath", err)
 		return
 	}
-
-	newLineSection := &gitdiff.DiffLine{
-		Type: gitdiff.DiffLineSection,
-		SectionInfo: &gitdiff.DiffLineSectionInfo{
-			Path:          filePath,
-			LastLeftIdx:   lastLeft,
-			LastRightIdx:  lastRight,
-			LeftIdx:       idxLeft,
-			RightIdx:      idxRight,
-			LeftHunkSize:  leftHunkSize,
-			RightHunkSize: rightHunkSize,
-		},
+	reader, err := blob.DataAsync()
+	if err != nil {
+		ctx.ServerError("DataAsync", err)
+		return
 	}
-	if newLineSection.GetExpandDirection() != "" {
-		newLineSection.Content = fmt.Sprintf("@@ -%d,%d +%d,%d @@\n", idxLeft, leftHunkSize, idxRight, rightHunkSize)
-		switch direction {
-		case "up":
-			section.Lines = append([]*gitdiff.DiffLine{newLineSection}, section.Lines...)
-		case "down":
-			section.Lines = append(section.Lines, newLineSection)
-		}
+	defer reader.Close()
+
+	section, err := gitdiff.BuildBlobExcerptDiffSection(filePath, reader, opts)
+	if err != nil {
+		ctx.ServerError("BuildBlobExcerptDiffSection", err)
+		return
 	}
 
 	diffBlobExcerptData.PullIssueIndex = ctx.FormInt64("pull_issue_index")
@@ -865,37 +833,3 @@ func ExcerptBlob(ctx *context.Context) {
 
 	ctx.HTML(http.StatusOK, tplBlobExcerpt)
 }
-
-func getExcerptLines(commit *git.Commit, filePath string, idxLeft, idxRight, chunkSize int) ([]*gitdiff.DiffLine, error) {
-	blob, err := commit.Tree.GetBlobByPath(filePath)
-	if err != nil {
-		return nil, err
-	}
-	reader, err := blob.DataAsync()
-	if err != nil {
-		return nil, err
-	}
-	defer reader.Close()
-	scanner := bufio.NewScanner(reader)
-	var diffLines []*gitdiff.DiffLine
-	for line := 0; line < idxRight+chunkSize; line++ {
-		if ok := scanner.Scan(); !ok {
-			break
-		}
-		if line < idxRight {
-			continue
-		}
-		lineText := scanner.Text()
-		diffLine := &gitdiff.DiffLine{
-			LeftIdx:  idxLeft + (line - idxRight) + 1,
-			RightIdx: line + 1,
-			Type:     gitdiff.DiffLinePlain,
-			Content:  " " + lineText,
-		}
-		diffLines = append(diffLines, diffLine)
-	}
-	if err = scanner.Err(); err != nil {
-		return nil, fmt.Errorf("getExcerptLines scan: %w", err)
-	}
-	return diffLines, nil
-}