Fix test coverage

Author: prymitive

go.mod

@@ -3,7 +3,6 @@ module github.com/cloudflare/pint
 go 1.26.0
 
 require (
-	github.com/akedrou/textdiff v0.1.0
 	github.com/cespare/xxhash/v2 v2.3.0
 	github.com/gkampitakis/go-snaps v0.5.21
 	github.com/go-json-experiment/json v0.0.0-20260214004413-d219187c3433

go.sum

@@ -14,8 +14,6 @@ github.com/AzureAD/microsoft-authentication-library-for-go v1.6.0 h1:XRzhVemXdgv
 github.com/AzureAD/microsoft-authentication-library-for-go v1.6.0/go.mod h1:HKpQxkWaGLJ+D/5H8QRpyQXA1eKjxkFlOMwck5+33Jk=
 github.com/agext/levenshtein v1.2.1 h1:QmvMAjj2aEICytGiWzmxoE0x2KZvE0fvmqMOfy2tjT8=
 github.com/agext/levenshtein v1.2.1/go.mod h1:JEDfjyjHDjOF/1e4FlBE/PkbqA9OfWu2ki2W0IB5558=
-github.com/akedrou/textdiff v0.1.0 h1:K7nbOVQju7/coCXnJRJ2fsltTwbSvC+M4hKBUJRBRGY=
-github.com/akedrou/textdiff v0.1.0/go.mod h1:a9CCC49AKtFTmVDNFHDlCg7V/M7C7QExDAhb2SkL6DQ=
 github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b h1:mimo19zliBX/vSQ6PWWSL9lK8qwHozUj03+zLoEB8O0=
 github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b/go.mod h1:fvzegU4vN3H1qMT+8wDmzjAcDONcgo2/SZ/TyfdUOFs=
 github.com/apparentlymart/go-textseg/v15 v15.0.0 h1:uYvfpb3DyLSCGWnctWKGj857c6ew1u1fNQOlOtuGxQY=

internal/reporter/github.go

@@ -53,7 +53,7 @@ func (gr GithubReporter) commentPosition(p PendingComment) (side string, line in
 		if nearest := p.changedLines.NearestBefore(oldLine); nearest > 0 {
 			return "LEFT", nearest
 		}
-		return "LEFT", oldLine
+		// No deleted lines in the diff, fall through to RIGHT side.
 	}
 	if p.changedLines.HasAfter(p.line) {
 		return "RIGHT", p.line

internal/reporter/github_test.go

@@ -886,6 +886,61 @@ func TestGitHubReporter(t *testing.T) {
 				},
 			}),
 		},
+		{
+			description: "anchor before with only added lines in diff",
+			owner:       "foo",
+			repo:        "bar",
+			token:       "something",
+			prNum:       123,
+			maxComments: 50,
+			timeout:     time.Second,
+			httpHandler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if r.Method == http.MethodGet && r.URL.Path == "/api/v3/repos/foo/bar/pulls/123/reviews" {
+					_, _ = w.Write([]byte(`[]`))
+					return
+				}
+				if r.Method == http.MethodGet && r.URL.Path == "/api/v3/repos/foo/bar/pulls/123/comments" {
+					_, _ = w.Write([]byte(`[]`))
+					return
+				}
+				if r.Method == http.MethodPost && r.URL.Path == "/api/v3/repos/foo/bar/pulls/123/comments" {
+					body, _ := io.ReadAll(r.Body)
+					b := strings.TrimSpace(strings.TrimRight(string(body), "\n\t\r"))
+					// Diff only has added lines, no deleted lines to attach to.
+					// Falls through to RIGHT side, moved to nearest added line: 5.
+					if b != `{"body":":stop_sign: **Fatal** reported by [pint](https://cloudflare.github.io/pint/) **mock** check.\n\n------\n\nsyntax error\n\n<details>\n<summary>More information</summary>\nsyntax details\n</details>\n\n------\n\n:information_source: To see documentation covering this check and instructions on how to resolve it [click here](https://cloudflare.github.io/pint/checks/mock.html).\n","path":"foo.txt","line":5,"side":"RIGHT","commit_id":"HEAD"}` {
+						t.Errorf("Unexpected comment: %s", b)
+						t.FailNow()
+					}
+				}
+				_, _ = w.Write([]byte(""))
+			}),
+			summary: reporter.NewSummary([]reporter.Report{
+				{
+					Path: discovery.Path{
+						Name:          "foo.txt",
+						SymlinkTarget: "foo.txt",
+					},
+
+					Changes: discovery.Changes{
+						OldPath: "",
+						Lines:   git.LineNumbers{{Before: 0, After: 5}},
+					},
+					Rule: mockFile.Groups[0].Rules[0],
+					Problem: checks.Problem{
+						Lines: diags.LineRange{
+							First: 3,
+							Last:  3,
+						},
+						Reporter: "mock",
+						Summary:  "syntax error",
+						Details:  "syntax details",
+						Severity: checks.Fatal,
+						Anchor:   checks.AnchorBefore,
+					},
+				},
+			}),
+		},
 		{
 			description: "review comment",
 			owner:       "foo",

internal/reporter/gitlab.go

@@ -434,13 +434,17 @@ func reportToGitLabDiscussion(pending PendingComment, ver *gitlab.MergeRequestDi
 
 	// GitLab requires comments on lines present in the diff.
 	// If the target line is not in the diff, move it to the nearest changed line.
+	var useBefore bool
 	if pending.anchor == checks.AnchorBefore {
-		if !pending.changedLines.HasBefore(line) {
-			if nearest := pending.changedLines.NearestBefore(line); nearest > 0 {
-				line = nearest
-			}
+		if pending.changedLines.HasBefore(line) {
+			useBefore = true
+		} else if nearest := pending.changedLines.NearestBefore(line); nearest > 0 {
+			line = nearest
+			useBefore = true
 		}
-	} else {
+		// No deleted lines in the diff, fall through to RIGHT side.
+	}
+	if !useBefore {
 		if !pending.changedLines.HasAfter(line) {
 			if nearest := pending.changedLines.NearestAfter(line); nearest > 0 {
 				line = nearest
@@ -450,14 +454,11 @@ func reportToGitLabDiscussion(pending PendingComment, ver *gitlab.MergeRequestDi
 	}
 
 	switch {
-	// Deleted line: only old_line, no new_line.
-	case pending.anchor == checks.AnchorBefore:
+	case useBefore:
 		d.Position.OldLine = new(int64(line))
 		d.Position.NewLine = nil
-	// Added line (oldLine==0): only new_line, no old_line.
 	case oldLine == 0:
 		d.Position.NewLine = new(int64(line))
-	// Context line with known old->new mapping: both old_line and new_line.
 	case oldLine > 0:
 		d.Position.NewLine = new(int64(line))
 		d.Position.OldLine = new(int64(oldLine))

internal/reporter/gitlab_test.go

@@ -1026,7 +1026,7 @@ Below is the list of checks that were disabled for each Prometheus server define
 						OldPath:      new(mockPath),
 						NewPath:      new(mockPath),
 						PositionType: new("text"),
-						OldLine:      new(int64(3)),
+						NewLine:      new(int64(3)),
 					}),
 				}).ReturnJSON(gitlab.Response{})
 			}),