From 4c932edabc8e8bc38b8140db0d86411066335f3f Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Tue, 13 Jan 2026 23:12:27 +0000
Subject: [PATCH] fix: make postinstall patcher idempotent

---
 CHANGELOG.md                    |  5 ++++
 scripts/postinstall.js          | 20 ++++++++++++++
 src/postinstall-patcher.test.ts | 46 +++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 58ff1f56a..6dd789686 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## 2026.1.13 (Unreleased)
+
+### Fixes
+- Postinstall: treat already-applied pnpm patches as no-ops to avoid npm/bun install failures.
+
 ## 2026.1.12-2
 
 ### Fixes
diff --git a/scripts/postinstall.js b/scripts/postinstall.js
index 4627b6dc1..c14686f55 100644
--- a/scripts/postinstall.js
+++ b/scripts/postinstall.js
@@ -149,6 +149,26 @@ function writeFileLines(targetPath, lines, hadTrailingNewline) {
 
 function applyHunk(lines, hunk, offset) {
   let cursor = hunk.oldStart - 1 + offset;
+  const expected = [];
+  for (const raw of hunk.lines) {
+    const marker = raw[0];
+    if (marker === " " || marker === "+") {
+      expected.push(raw.slice(1));
+    }
+  }
+  if (cursor >= 0 && cursor + expected.length <= lines.length) {
+    let alreadyApplied = true;
+    for (let i = 0; i < expected.length; i += 1) {
+      if (lines[cursor + i] !== expected[i]) {
+        alreadyApplied = false;
+        break;
+      }
+    }
+    if (alreadyApplied) {
+      const delta = hunk.newLines - hunk.oldLines;
+      return offset + delta;
+    }
+  }
 
   for (const raw of hunk.lines) {
     const marker = raw[0];
diff --git a/src/postinstall-patcher.test.ts b/src/postinstall-patcher.test.ts
index 79afd2c51..2a468e157 100644
--- a/src/postinstall-patcher.test.ts
+++ b/src/postinstall-patcher.test.ts
@@ -74,6 +74,52 @@ index 0000000..1111111 100644
     fs.rmSync(dir, { recursive: true, force: true });
   });
 
+  it("treats already-applied hunks as no-ops", () => {
+    const dir = makeTempDir();
+    const target = path.join(dir, "lib");
+    fs.mkdirSync(target);
+
+    const filePath = path.join(target, "main.js");
+    const original = `${[
+      "var QRCode = require('./../vendor/QRCode'),",
+      "    QRErrorCorrectLevel = require('./../vendor/QRCode/QRErrorCorrectLevel'),",
+      '    black = "\\033[40m  \\033[0m",',
+      '    white = "\\033[47m  \\033[0m",',
+      "    toCell = function (isBlack) {",
+    ].join("\n")}\n`;
+    fs.writeFileSync(filePath, original, "utf-8");
+
+    const patchText = `diff --git a/lib/main.js b/lib/main.js
+index 0000000..1111111 100644
+--- a/lib/main.js
++++ b/lib/main.js
+@@ -1,5 +1,5 @@
+-var QRCode = require('./../vendor/QRCode'),
+-    QRErrorCorrectLevel = require('./../vendor/QRCode/QRErrorCorrectLevel'),
++var QRCode = require('./../vendor/QRCode/index.js'),
++    QRErrorCorrectLevel = require('./../vendor/QRCode/QRErrorCorrectLevel.js'),
+     black = "\\033[40m  \\033[0m",
+     white = "\\033[47m  \\033[0m",
+     toCell = function (isBlack) {
+`;
+
+    applyPatchSet({ patchText, targetDir: dir });
+    applyPatchSet({ patchText, targetDir: dir });
+
+    const updated = fs.readFileSync(filePath, "utf-8");
+    expect(updated).toBe(
+      `${[
+        "var QRCode = require('./../vendor/QRCode/index.js'),",
+        "    QRErrorCorrectLevel = require('./../vendor/QRCode/QRErrorCorrectLevel.js'),",
+        '    black = "\\033[40m  \\033[0m",',
+        '    white = "\\033[47m  \\033[0m",',
+        "    toCell = function (isBlack) {",
+      ].join("\n")}\n`,
+    );
+
+    fs.rmSync(dir, { recursive: true, force: true });
+  });
+
   it("handles multiple hunks with offsets", () => {
     const dir = makeTempDir();
     const filePath = path.join(dir, "file.txt");