From a414ef1cd556805ee834fc0ee7e90276f22a3aa0 Mon Sep 17 00:00:00 2001
From: Mradul Singh <msingh@dealmeridian.com>
Date: Thu, 12 Nov 2026 12:10:20 +0530
Subject: [PATCH] parser: only drop "\ No newline" marker lines

The parser removed every "\ No newline at end of file" string from
the whole input before splitting it into lines. When the diff is for
a patch file, content lines like " \ No newline at end of file" lost
that text and showed up as " ", "-" or "+".

Now only lines that start with "\ " are skipped. This matches how
git apply finds the marker, and it also skips translated markers
from GNU diff.

Fixes #598
---
 src/__tests__/diff-parser-tests.ts | 80 ++++++++++++++++++++++++++++++
 src/diff-parser.ts                 |  9 ++--
 2 files changed, 84 insertions(+), 5 deletions(-)

diff --git a/src/__tests__/diff-parser-tests.ts b/src/__tests__/diff-parser-tests.ts
index dde2778e..880be683 100644
--- a/src/__tests__/diff-parser-tests.ts
+++ b/src/__tests__/diff-parser-tests.ts
@@ -2514,5 +2514,85 @@ describe('DiffParser', () => {
         ]
       `);
     });
+
+    it('should keep "\\ No newline at end of file" text inside content lines', () => {
+      const diff =
+        'diff --git a/fix.patch b/fix.patch\n' +
+        'index 0000001..0ddf2ba 100644\n' +
+        '--- a/fix.patch\n' +
+        '+++ b/fix.patch\n' +
+        '@@ -1,4 +1,4 @@\n' +
+        ' @@ -1 +1 @@\n' +
+        '-+old\n' +
+        '-\\ No newline at end of file\n' +
+        '++new\n' +
+        '+\\ No newline at end of file\n' +
+        ' \\ No newline at end of file\n' +
+        '\\ No newline at end of file\n';
+
+      const result = parse(diff);
+      expect(result).toMatchInlineSnapshot(`
+        [
+          {
+            "addedLines": 2,
+            "blocks": [
+              {
+                "header": "@@ -1,4 +1,4 @@",
+                "lines": [
+                  {
+                    "content": " @@ -1 +1 @@",
+                    "newNumber": 1,
+                    "oldNumber": 1,
+                    "type": "context",
+                  },
+                  {
+                    "content": "-+old",
+                    "newNumber": undefined,
+                    "oldNumber": 2,
+                    "type": "delete",
+                  },
+                  {
+                    "content": "-\\ No newline at end of file",
+                    "newNumber": undefined,
+                    "oldNumber": 3,
+                    "type": "delete",
+                  },
+                  {
+                    "content": "++new",
+                    "newNumber": 2,
+                    "oldNumber": undefined,
+                    "type": "insert",
+                  },
+                  {
+                    "content": "+\\ No newline at end of file",
+                    "newNumber": 3,
+                    "oldNumber": undefined,
+                    "type": "insert",
+                  },
+                  {
+                    "content": " \\ No newline at end of file",
+                    "newNumber": 4,
+                    "oldNumber": 4,
+                    "type": "context",
+                  },
+                ],
+                "newStartLine": 1,
+                "oldStartLine": 1,
+                "oldStartLine2": null,
+              },
+            ],
+            "checksumAfter": "0ddf2ba",
+            "checksumBefore": "0000001",
+            "deletedLines": 2,
+            "isCombined": false,
+            "isGitDiff": true,
+            "language": "patch",
+            "mode": "100644",
+            "newName": "fix.patch",
+            "oldName": "fix.patch",
+          },
+        ]
+      `);
+    });
   });
 });
diff --git a/src/diff-parser.ts b/src/diff-parser.ts
index 83d9c630..f3bf95f8 100644
--- a/src/diff-parser.ts
+++ b/src/diff-parser.ts
@@ -93,10 +93,7 @@ export function parse(diffInput: string, config: DiffParserConfig = {}): DiffFil
   const combinedNewFile = /^new file mode (\d{6})/;
   const combinedDeletedFile = /^deleted file mode (\d{6}),(\d{6})/;
 
-  const diffLines = diffInput
-    .replace(/\\ No newline at end of file/g, '')
-    .replace(/\r\n?/g, '\n')
-    .split('\n');
+  const diffLines = diffInput.replace(/\r\n?/g, '\n').split('\n');
 
   /* Add previous block(if exists) before start a new file */
   function saveBlock(): void {
@@ -261,7 +258,9 @@ export function parse(diffInput: string, config: DiffParserConfig = {}): DiffFil
     // Unmerged paths, and possibly other non-diffable files
     // https://github.com/scottgonzalez/pretty-diff/issues/11
     // Also, remove some useless lines
-    if (!line || line.startsWith('*')) {
+    // Lines starting with "\ " are markers like "\ No newline at end of file"
+    // (the message text can be translated, so only the prefix is checked)
+    if (!line || line.startsWith('*') || line.startsWith('\\ ')) {
       return;
     }