fix(scripts): harden patch-modernz handling

scripts/patch-modernz.sh

@@ -4,19 +4,28 @@ set -euo pipefail
 
 TARGET="${HOME}/.config/mpv/scripts/modernz.lua"
 
-while [[ $# -gt 0 ]]; do
-    case "$1" in
-        --target)
-            TARGET="$2"
-            shift 2
-            ;;
-        --help|-h)
-            cat <<'EOF'
+usage() {
+    cat <<'EOF'
 Usage: patch-modernz.sh [--target /path/to/modernz.lua]
 
 Applies the local ModernZ OSC sidebar-resize patch to an existing modernz.lua.
 If the target file does not exist, the script exits without changing anything.
 EOF
+}
+
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --target)
+            if [[ $# -lt 2 || -z "${2:-}" || "$2" == -* ]]; then
+                echo "patch-modernz: --target requires a non-empty file path" >&2
+                usage >&2
+                exit 1
+            fi
+            TARGET="$2"
+            shift 2
+            ;;
+        --help|-h)
+            usage
             exit 0
             ;;
         *)
@@ -37,7 +46,7 @@ if grep -q 'get_external_video_margin_ratio' "$TARGET" \
     exit 0
 fi
 
-patch --forward --quiet "$TARGET" <<'PATCH'
+if ! patch --forward --quiet "$TARGET" <<'PATCH'
 --- a/modernz.lua
 +++ b/modernz.lua
 @@ -931,6 +931,26 @@ local function reset_margins()
@@ -140,5 +149,9 @@ patch --forward --quiet "$TARGET" <<'PATCH'
      if val and user_opts.visibility == "auto" and not user_opts.showonselect then
          osc_visible(false)
 PATCH
+then
+    echo "patch-modernz: failed to apply patch to $TARGET" >&2
+    exit 1
+fi
 
 echo "patch-modernz: patched $TARGET"

scripts/patch-modernz.test.ts

@@ -0,0 +1,76 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import { spawnSync } from 'node:child_process';
+import test from 'node:test';
+
+function withTempDir<T>(fn: (dir: string) => T): T {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-patch-modernz-test-'));
+  try {
+    return fn(dir);
+  } finally {
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+}
+
+function writeExecutable(filePath: string, contents: string): void {
+  fs.writeFileSync(filePath, contents, 'utf8');
+  fs.chmodSync(filePath, 0o755);
+}
+
+test('patch-modernz rejects a missing --target value', () => {
+  withTempDir((root) => {
+    const result = spawnSync('bash', ['scripts/patch-modernz.sh', '--target'], {
+      cwd: process.cwd(),
+      encoding: 'utf8',
+      env: {
+        ...process.env,
+        HOME: path.join(root, 'home'),
+      },
+    });
+
+    assert.equal(result.status, 1, result.stderr || result.stdout);
+    assert.match(result.stderr, /--target requires a non-empty file path/);
+    assert.match(result.stderr, /Usage: patch-modernz\.sh/);
+  });
+});
+
+test('patch-modernz reports patch failures explicitly', () => {
+  withTempDir((root) => {
+    const binDir = path.join(root, 'bin');
+    const target = path.join(root, 'modernz.lua');
+    const patchLog = path.join(root, 'patch.log');
+
+    fs.mkdirSync(binDir, { recursive: true });
+    fs.mkdirSync(path.dirname(target), { recursive: true });
+    fs.writeFileSync(target, 'original', 'utf8');
+
+    writeExecutable(
+      path.join(binDir, 'patch'),
+      `#!/usr/bin/env bash
+set -euo pipefail
+cat > "${patchLog}"
+exit 1
+`,
+    );
+
+    const result = spawnSync(
+      'bash',
+      ['scripts/patch-modernz.sh', '--target', target],
+      {
+        cwd: process.cwd(),
+        encoding: 'utf8',
+        env: {
+          ...process.env,
+          HOME: path.join(root, 'home'),
+          PATH: `${binDir}:${process.env.PATH || ''}`,
+        },
+      },
+    );
+
+    assert.equal(result.status, 1, result.stderr || result.stdout);
+    assert.match(result.stderr, /failed to apply patch to/);
+    assert.equal(fs.readFileSync(patchLog, 'utf8').includes('modernz.lua'), true);
+  });
+});