From c655a2bf8758ef04f84caed01b2bbf83df242ba8 Mon Sep 17 00:00:00 2001
From: Connor Peet <connor@peet.io>
Date: Thu, 1 May 2025 15:37:37 -0700
Subject: [PATCH] fix: infinite loop in TS library

We observed that GPT 4.1 sometimes omits the space afte `@@` in edit
chunks. This causes an infinite loop in the TS library. This change make
the parser a little more robust to this case.
---
 codex-cli/src/utils/agent/apply-patch.ts | 22 ++++++++++------------
 codex-cli/tests/apply-patch.test.ts      | 18 ++++++++++++++++++
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/codex-cli/src/utils/agent/apply-patch.ts b/codex-cli/src/utils/agent/apply-patch.ts
index 525404c30..b9f940870 100644
--- a/codex-cli/src/utils/agent/apply-patch.ts
+++ b/codex-cli/src/utils/agent/apply-patch.ts
@@ -95,6 +95,8 @@ export class DiffError extends Error {}
 // Parser (patch text -> Patch)
 // -----------------------------------------------------------------------------
 
+const CHUNK_DELIMITER = '@@';
+
 class Parser {
   current_files: Record<string, string>;
   lines: Array<string>;
@@ -200,16 +202,12 @@ class Parser {
         END_OF_FILE_PREFIX,
       ])
     ) {
-      const defStr = this.read_str("@@ ");
-      let sectionStr = "";
-      if (!defStr && this.lines[this.index] === "@@") {
-        sectionStr = this.lines[this.index]!;
-        this.index += 1;
-      }
-      if (!(defStr || sectionStr || index === 0)) {
-        throw new DiffError(`Invalid Line:\n${this.lines[this.index]}`);
-      }
-      if (defStr.trim()) {
+			const sectionStr = this.read_str("@@", true);
+			const defStr = sectionStr.slice(CHUNK_DELIMITER.length).trim();
+			if (!(sectionStr || index === 0)) {
+				throw new DiffError(`Invalid Line:\n${this.lines[this.index]}`);
+			}
+      if (defStr) {
         let found = false;
         // ------------------------------------------------------------------
         // Equality helpers using the canonicalisation from find_context_core.
@@ -261,11 +259,11 @@ class Parser {
           !found &&
           !fileLines
             .slice(0, index)
-            .some((s) => canonLocal(s.trim()) === canonLocal(defStr.trim()))
+            .some((s) => canonLocal(s.trim()) === canonLocal(defStr))
         ) {
           for (let i = index; i < fileLines.length; i++) {
             if (
-              canonLocal(fileLines[i]!.trim()) === canonLocal(defStr.trim())
+              canonLocal(fileLines[i]!.trim()) === canonLocal(defStr)
             ) {
               index = i + 1;
               this.fuzz += 1;
diff --git a/codex-cli/tests/apply-patch.test.ts b/codex-cli/tests/apply-patch.test.ts
index e1532c01b..ffbe90e97 100644
--- a/codex-cli/tests/apply-patch.test.ts
+++ b/codex-cli/tests/apply-patch.test.ts
@@ -344,3 +344,21 @@ test("apply_commit correctly performs move / rename operations", () => {
   expect(writes).toEqual({ "new.txt": "new" });
   expect(removals).toEqual(["old.txt"]);
 });
+
+test("text_to_patch + patch_to_commit tolerant to missing edit space", () => {
+  const originalFiles = {
+    "a.txt": "section1\n[old code1]\nsection2\n[old code2]",
+  };
+
+  const patch = `*** Begin Patch\n*** Update File: a.txt\n@@section1\n-[old code1]\n+[new code1}\n@@section2\n-[old code2]\n+[new code2}\n*** End Patch`;
+
+  const [parsedPatch] = text_to_patch(patch, originalFiles);
+  const commit = patch_to_commit(parsedPatch, originalFiles).changes;
+
+  expect(commit["a.txt"]).toEqual({
+    type: ActionType.UPDATE,
+    move_path: undefined,
+    old_content: "section1\n[old code1]\nsection2\n[old code2]",
+    new_content: "section1\n[new code1}\nsection2\n[new code2}",
+  });
+});