enhance: truncate but show long lines in diffs (#39279)

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/pull_diff_test.go

@@ -5,12 +5,19 @@ package integration
 
 import (
 	"net/http"
+	"strings"
 	"testing"
 
+	repo_model "gitea.dev/models/repo"
+	"gitea.dev/models/unittest"
+	"gitea.dev/modules/git"
+	"gitea.dev/modules/setting"
+	"gitea.dev/modules/test"
 	"gitea.dev/tests"
 
 	"github.com/PuerkitoBio/goquery"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestPullDiff(t *testing.T) {
@@ -65,3 +72,61 @@ func testPullDiffAssertPage(t *testing.T, prDiffURL string, reviewBtnDisabled bo
 	// Ensure the review button is enabled for full PR reviews
 	assert.Equal(t, reviewBtnDisabled, doc.Find(".js-btn-review").HasClass("disabled"))
 }
+
+func TestLongLineDiffRendering(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+	defer test.MockVariableValue(&setting.Git.MaxGitDiffLineCharacters, 32)()
+
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+	const suffix = "DISCARDED_SUFFIX"
+	const short = "following short line"
+	contextLine := strings.Repeat("context ", 8) + suffix + "\n"
+	before := git.FastImportCommit{Ref: "refs/heads/long-line-before"}
+	after := git.FastImportCommit{Ref: "refs/heads/long-line-after"}
+	for _, name := range []string{"long.txt", "long.csv"} {
+		before.Files = append(before.Files, git.FastImportFile{Path: name, Content: strings.Repeat("old ", 16) + suffix + "\n" + contextLine + short + "\n"})
+		after.Files = append(after.Files, git.FastImportFile{Path: name, Content: strings.Repeat("new ", 16) + suffix + "\n" + contextLine + short + "\n"})
+	}
+	outsideHunk := "header\n" + contextLine + strings.Repeat("unchanged\n", 6)
+	before.Files = append(before.Files, git.FastImportFile{Path: "outside.csv", Content: outsideHunk + "old\n"})
+	after.Files = append(after.Files, git.FastImportFile{Path: "outside.csv", Content: outsideHunk + "new\n"})
+	require.NoError(t, git.ForceFastImport(t.Context(), repo.CodeStorageRepo(), []git.FastImportCommit{before, after}))
+
+	oldPrefix := strings.Repeat("old ", 8)[:31]
+	newPrefix := strings.Repeat("new ", 8)[:31]
+	contextPrefix := contextLine[:31]
+	for style, want := range map[string][]string{
+		"unified": {oldPrefix, newPrefix, contextPrefix, short},
+		"split":   {oldPrefix, newPrefix, contextPrefix, contextPrefix, short, short},
+	} {
+		t.Run(style, func(t *testing.T) {
+			req := NewRequest(t, "GET", "/user2/repo1/compare/long-line-before..long-line-after?style="+style)
+			resp := MakeRequest(t, req, http.StatusOK)
+			doc := NewHTMLParser(t, resp.Body)
+			for _, filename := range []string{"long.txt", "long.csv"} {
+				t.Run(filename, func(t *testing.T) {
+					diffFileBox := doc.Find(`.diff-file-box[data-new-filename="` + filename + `"]`)
+					diffBody := diffFileBox.Find(".code-diff-" + style)
+					require.Equal(t, 1, diffBody.Length())
+					assert.False(t, diffBody.HasClass("tw-hidden"))
+					assert.Empty(t, diffFileBox.Find(".file-view-toggle, .data-table").Nodes)
+					assert.NotContains(t, diffFileBox.Text(), suffix)
+					got := diffBody.Find("tr:not(.tag-code) code.code-inner").Map(func(_ int, s *goquery.Selection) string {
+						markerText := s.Find(".diff-line-truncated").Text()
+						textContent := strings.TrimSpace(strings.TrimSuffix(strings.TrimSpace(s.Text()), markerText))
+						if textContent == short {
+							assert.Empty(t, markerText)
+						} else {
+							assert.Equal(t, "Line truncated", markerText)
+						}
+						return textContent
+					})
+					assert.Equal(t, want, got)
+				})
+			}
+			outside := doc.Find(`.diff-file-box[data-new-filename="outside.csv"]`)
+			assert.Equal(t, 2, outside.Find(".file-view-toggle").Length())
+			assert.Equal(t, 1, outside.Find(".data-table").Length())
+		})
+	}
+}