From 15fe7abdca687a563d2e2d063eef3e2334059fb8 Mon Sep 17 00:00:00 2001
From: Evan Jarrett <evan@evanjarrett.com>
Date: Fri, 26 Dec 2025 10:02:54 -0600
Subject: [PATCH] appview/fragments/diff, types/diff: fix anchor on deleted
 files for sidebar navigation

Signed-off-by: Evan Jarrett <evan@evanjarrett.com>
---
 .../pages/templates/repo/fragments/diff.html  |   2 +-
 types/diff.go                                 |   3 +
 types/diff_test.go                            | 112 ++++++++++++++++++
 3 files changed, 116 insertions(+), 1 deletion(-)
 create mode 100644 types/diff_test.go

diff --git a/appview/pages/templates/repo/fragments/diff.html b/appview/pages/templates/repo/fragments/diff.html
index 1f17636a..88748532 100644
--- a/appview/pages/templates/repo/fragments/diff.html
+++ b/appview/pages/templates/repo/fragments/diff.html
@@ -17,7 +17,7 @@
     {{ else }}
     {{ range $idx, $hunk := $diff }}
       {{ with $hunk }}
-        <details open id="file-{{ .Name.New }}" class="group border border-gray-200 dark:border-gray-700 w-full mx-auto rounded bg-white dark:bg-gray-800 drop-shadow-sm" tabindex="{{ add $idx 1 }}">
+        <details open id="file-{{ .Id }}" class="group border border-gray-200 dark:border-gray-700 w-full mx-auto rounded bg-white dark:bg-gray-800 drop-shadow-sm" tabindex="{{ add $idx 1 }}">
           <summary class="list-none cursor-pointer sticky top-0">
             <div id="diff-file-header" class="rounded cursor-pointer bg-white dark:bg-gray-800 flex justify-between">
               <div id="left-side-items" class="p-2 flex gap-2 items-center overflow-x-auto">
diff --git a/types/diff.go b/types/diff.go
index 8cdea07c..5eb0fc5f 100644
--- a/types/diff.go
+++ b/types/diff.go
@@ -74,6 +74,9 @@ func (d *NiceDiff) ChangedFiles() []string {
 
 // used by html elements as a unique ID for hrefs
 func (d *Diff) Id() string {
+	if d.IsDelete {
+		return d.Name.Old
+	}
 	return d.Name.New
 }
 
diff --git a/types/diff_test.go b/types/diff_test.go
new file mode 100644
index 00000000..cde4ff64
--- /dev/null
+++ b/types/diff_test.go
@@ -0,0 +1,112 @@
+package types
+
+import "testing"
+
+func TestDiffId(t *testing.T) {
+	tests := []struct {
+		name     string
+		diff     Diff
+		expected string
+	}{
+		{
+			name: "regular file uses new name",
+			diff: Diff{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "", New: "src/main.go"},
+			},
+			expected: "src/main.go",
+		},
+		{
+			name: "new file uses new name",
+			diff: Diff{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "", New: "src/new.go"},
+				IsNew: true,
+			},
+			expected: "src/new.go",
+		},
+		{
+			name: "deleted file uses old name",
+			diff: Diff{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "src/deleted.go", New: ""},
+				IsDelete: true,
+			},
+			expected: "src/deleted.go",
+		},
+		{
+			name: "renamed file uses new name",
+			diff: Diff{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "src/old.go", New: "src/renamed.go"},
+				IsRename: true,
+			},
+			expected: "src/renamed.go",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.diff.Id(); got != tt.expected {
+				t.Errorf("Diff.Id() = %q, want %q", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestChangedFilesMatchesDiffId(t *testing.T) {
+	// ChangedFiles() must return values matching each Diff's Id()
+	// so that sidebar links point to the correct anchors.
+	// Tests existing, deleted, new, and renamed files.
+	nd := NiceDiff{
+		Diff: []Diff{
+			{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "", New: "src/modified.go"},
+			},
+			{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "src/deleted.go", New: ""},
+				IsDelete: true,
+			},
+			{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "", New: "src/new.go"},
+				IsNew: true,
+			},
+			{
+				Name: struct {
+					Old string `json:"old"`
+					New string `json:"new"`
+				}{Old: "src/old.go", New: "src/renamed.go"},
+				IsRename: true,
+			},
+		},
+	}
+
+	changedFiles := nd.ChangedFiles()
+
+	if len(changedFiles) != len(nd.Diff) {
+		t.Fatalf("ChangedFiles() returned %d items, want %d", len(changedFiles), len(nd.Diff))
+	}
+
+	for i, diff := range nd.Diff {
+		if changedFiles[i] != diff.Id() {
+			t.Errorf("ChangedFiles()[%d] = %q, but Diff.Id() = %q", i, changedFiles[i], diff.Id())
+		}
+	}
+}
-- 
2.43.0