Fix incorrect viewed files counter if reverted change was viewed

services/gitdiff/gitdiff.go

@@ -1481,21 +1481,25 @@ func SyncUserSpecificDiff(ctx context.Context, userID int64, pull *issues_model.
 	filesChangedSinceLastDiff := make(map[string]pull_model.ViewedState)
 outer:
 	for _, diffFile := range diff.Files {
-		fileViewedState := review.UpdatedFiles[diffFile.GetDiffFileName()]
+		filename := diffFile.GetDiffFileName()
+		fileViewedState := review.UpdatedFiles[filename]
 
 		// Check whether it was previously detected that the file has changed since the last review
 		if fileViewedState == pull_model.HasChanged {
 			diffFile.HasChangedSinceLastReview = true
 			continue
 		}
 
-		filename := diffFile.GetDiffFileName()
-
 		// Check explicitly whether the file has changed since the last review
-		for _, changedFile := range changedFiles {
+		for i, changedFile := range changedFiles {
 			diffFile.HasChangedSinceLastReview = filename == changedFile
 			if diffFile.HasChangedSinceLastReview {
 				filesChangedSinceLastDiff[filename] = pull_model.HasChanged
+
+				// File changes are processed, no need to check them again
+				changedFiles[i] = changedFiles[len(changedFiles)-1]
+				changedFiles = changedFiles[:len(changedFiles)-1]
+
 				continue outer // We don't want to check if the file is viewed here as that would fold the file, which is in this case unwanted
 			}
 		}
@@ -1505,6 +1509,15 @@ outer:
 		}
 	}
 
+	// All changed files still present at this point aren't part of the diff anymore, this occurs
+	// when a file was modified in a previous commit of the diff and the modification got reverted afterwards.
+	// Marking the files as unviewed to prevent errors where a non-existing file has a view state
+	for _, changedFile := range changedFiles {
+		if _, ok := review.UpdatedFiles[changedFile]; ok {
+			filesChangedSinceLastDiff[changedFile] = pull_model.Unviewed
+		}
+	}
+
 	if len(filesChangedSinceLastDiff) > 0 {
 		// Explicitly store files that have changed in the database, if any is present at all.
 		// This has the benefit that the "Has Changed" attribute will be present as long as the user does not explicitly mark this file as viewed, so it will even survive a page reload after marking another file as viewed.

services/gitdiff/gitdiff_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 
 	issues_model "code.gitea.io/gitea/models/issues"
+	pull_model "code.gitea.io/gitea/models/pull"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
@@ -1143,3 +1144,57 @@ func TestHighlightCodeLines(t *testing.T) {
 		}, ret)
 	})
 }
+
+func TestSyncUserSpecificDiff_UpdatedFiles(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	pull := unittest.AssertExistsAndLoadBean(t, &issues_model.PullRequest{ID: 7})
+	assert.NoError(t, pull.LoadBaseRepo(t.Context()))
+
+	stdin := `commit refs/heads/branch1
+committer test <test@example.com> 1772749114 +0000
+data 7
+revert
+from 1978192d98bb1b65e11c2cf37da854fbf94bffd6
+D test10.txt`
+	require.NoError(t, gitcmd.NewCommand("fast-import").WithDir(pull.BaseRepo.RepoPath()).WithStdinBytes([]byte(stdin)).Run(t.Context()))
+
+	gitRepo, err := git.OpenRepository(t.Context(), pull.BaseRepo.RepoPath())
+	assert.NoError(t, err)
+	defer gitRepo.Close()
+
+	firstReviewCommit := "1978192d98bb1b65e11c2cf37da854fbf94bffd6"
+	firstReviewUpdatedFiles := map[string]pull_model.ViewedState{
+		"test1.txt":  pull_model.Viewed,
+		"test10.txt": pull_model.Viewed,
+	}
+
+	_, err = pull_model.UpdateReviewState(t.Context(), user.ID, pull.ID, firstReviewCommit, firstReviewUpdatedFiles)
+	assert.NoError(t, err)
+	firstReview, err := pull_model.GetNewestReviewState(t.Context(), user.ID, pull.ID)
+	assert.NoError(t, err)
+	assert.NotNil(t, firstReview)
+	assert.Equal(t, firstReviewUpdatedFiles, firstReview.UpdatedFiles)
+	assert.Equal(t, 2, firstReview.GetViewedFileCount())
+
+	secondReviewCommit := "ec334573ae49726c78c6ff793138fd5334f31695"
+	secondReviewUpdatedFiles := map[string]pull_model.ViewedState{
+		"test1.txt":  pull_model.Viewed,
+		"test10.txt": pull_model.Unviewed,
+	}
+
+	opts := &DiffOptions{
+		AfterCommitID:     secondReviewCommit,
+		BeforeCommitID:    pull.MergeBase,
+		MaxLines:          setting.Git.MaxGitDiffLines,
+		MaxLineCharacters: setting.Git.MaxGitDiffLineCharacters,
+	}
+	diff, err := GetDiffForAPI(t.Context(), gitRepo, opts)
+	assert.NoError(t, err)
+	secondReview, err := SyncUserSpecificDiff(t.Context(), user.ID, pull, gitRepo, diff, opts)
+	assert.NoError(t, err)
+	assert.NotNil(t, secondReview)
+	assert.Equal(t, secondReviewUpdatedFiles, secondReview.UpdatedFiles)
+	assert.Equal(t, 1, secondReview.GetViewedFileCount())
+}