Fix: forward engine exit code from impeccable.cmd (#836)

Bare `exit /b` dropped the process code when the launcher was cmd /c's entry point (PowerShell, Node spawn), so Windows skill runs treated detector findings as success.

AI assistance: implemented by Cursor Grok 4.6.

Co-authored-by: Cursor <cursoragent@cursor.com>

crates/live/src/live_accept.rs

@@ -1093,12 +1093,26 @@ fn extract_inner_by_attr(text: &str, attr: &str) -> Option<String> {
     None
 }
 
+/// Drop leading and trailing blank lines while keeping a single empty line
+/// when the inner text is only whitespace.
+fn trim_surrounding_blank_lines(lines: Vec<String>) -> Vec<String> {
+    let mut start = 0usize;
+    let mut end = lines.len();
+    while end - start > 1 && trim(&lines[start]).is_empty() {
+        start += 1;
+    }
+    while end - start > 1 && trim(&lines[end - 1]).is_empty() {
+        end -= 1;
+    }
+    lines[start..end].to_vec()
+}
+
 /// JS: extractOriginal(lines, block)
 fn extract_original(lines: &[String], block: &MarkerBlock) -> Vec<String> {
     let text = strip_style_and_join(lines, block);
     match extract_inner_by_attr(&text, "data-impeccable-variant=\"original\"") {
         None => Vec::new(),
-        Some(inner) => inner.split('\n').map(String::from).collect(),
+        Some(inner) => trim_surrounding_blank_lines(inner.split('\n').map(String::from).collect()),
     }
 }
 
@@ -1113,13 +1127,7 @@ fn extract_variant(
         &text,
         &format!("data-impeccable-variant=\"{}\"", variant_num),
     )?;
-    let mut result: Vec<String> = inner.split('\n').map(String::from).collect();
-    while result.len() > 1 && trim(&result[0]).is_empty() {
-        result.remove(0);
-    }
-    while result.len() > 1 && trim(result.last().unwrap()).is_empty() {
-        result.pop();
-    }
+    let result = trim_surrounding_blank_lines(inner.split('\n').map(String::from).collect());
     if result.is_empty() {
         None
     } else {
@@ -1249,6 +1257,55 @@ fn find_session_file(id: &str, cwd: &str) -> Option<(String, String, Vec<String>
     Some((file, content, lines))
 }
 
+#[cfg(test)]
+mod discard_tests {
+    use super::*;
+
+    #[test]
+    fn discard_restores_the_original_without_blank_lines_around_it() {
+        let nanos = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map(|d| d.as_nanos())
+            .unwrap_or(0);
+        let dir = std::env::temp_dir().join(format!(
+            "impeccable-discard-{}-{nanos}",
+            std::process::id()
+        ));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let file = dir.join("Login.tsx");
+        let src = [
+            "      </div>",
+            "      <div data-impeccable-variants=\"ab12cd34\" data-impeccable-variant-count=\"3\" style={{ display: \"contents\" }}>",
+            "        {/* impeccable-variants-start ab12cd34 */}",
+            "        <style data-impeccable-css=\"ab12cd34\">{`",
+            "          @scope ([data-impeccable-variant=\"1\"]) { :scope > .x { color: red; } }",
+            "        `}</style>",
+            "        {/* Original */}",
+            "        <div data-impeccable-variant=\"original\">",
+            "          <Bar title=\"Log in\" />",
+            "        </div>",
+            "        {/* Variants: insert below this line */}",
+            "        <div data-impeccable-variant=\"1\">",
+            "          <Bar title=\"Log in\" />",
+            "        </div>",
+            "        {/* impeccable-variants-end ab12cd34 */}",
+            "      </div>",
+            "    </AuthPage>",
+        ];
+        let lines: Vec<String> = src.iter().map(|s| s.to_string()).collect();
+        let path = file.to_string_lossy().into_owned();
+        std::fs::write(&file, lines.join("\n")).unwrap();
+        handle_discard_unlocked("ab12cd34", &lines, &path).unwrap();
+        let out = std::fs::read_to_string(&file).unwrap();
+        let _ = std::fs::remove_dir_all(&dir);
+        assert_eq!(
+            out,
+            "      </div>\n      <Bar title=\"Log in\" />\n    </AuthPage>"
+        );
+    }
+}
+
 #[cfg(test)]
 mod bake_tests {
     use super::*;

crates/skills/tests/launcher_contract_tests.rs

@@ -57,6 +57,28 @@ fn cmd_launcher_asset_naming_matches_engine() {
     assert!(!cmd.contains("npm i -g"));
 }
 
+#[test]
+fn cmd_launcher_forwards_engine_exit_code() {
+    // Bare `exit /b` drops the process exit code when this file is cmd.exe's
+    // entry point (cmd /c, PowerShell, Node spawn). Forward %errorlevel%
+    // after each engine invocation instead.
+    let cmd = launcher_file("impeccable.cmd");
+    for (i, line) in cmd.lines().enumerate() {
+        assert_ne!(
+            line.trim(),
+            "exit /b",
+            "impeccable.cmd line {}: bare exit /b drops the process code: {line}",
+            i + 1
+        );
+    }
+    let forward = "exit /b %errorlevel%";
+    assert_eq!(
+        cmd.matches(forward).count(),
+        2,
+        "PATH candidate and :run must both forward the engine exit code"
+    );
+}
+
 #[test]
 fn cmd_launcher_has_no_multiline_parenthesized_blocks() {
     // cmd.exe expands %var% inside a parenthesized block at parse time, so a

skill/scripts/impeccable.cmd

@@ -59,7 +59,7 @@ if errorlevel 1 goto download
 call :probe impeccable
 if not "%probe_ok%"=="1" goto download
 impeccable %*
-exit /b
+exit /b %errorlevel%
 
 :download
 rem Last resort: fetch this version's binary from the release channel into
@@ -166,7 +166,7 @@ exit /b 127
 
 :run
 "%run%" %*
-exit /b
+exit /b %errorlevel%
 
 :probe
 rem Sets probe_ok=1 when %1 answers the engine handshake: prints

tests/launcher-download.test.mjs

@@ -174,6 +174,34 @@ test('launcher downloads and runs a verified executable', async t => {
   assert.equal(result.requests.length, 2);
 });
 
+test('cmd launcher forwards engine exit code through cmd /c', { skip: WINDOWS ? false : 'Windows-only cmd /c exit-code forwarding' }, async t => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'impeccable-launcher-exit-'));
+  t.after(() => fs.rmSync(root, { recursive: true, force: true }));
+  const home = path.join(root, 'home');
+  fs.mkdirSync(home);
+  const launcher = path.join(root, 'impeccable.cmd');
+  fs.copyFileSync(path.join(ROOT, 'skill/scripts/impeccable.cmd'), launcher);
+  const env = {
+    PATH: `${process.env.SystemRoot}\\System32;${process.env.SystemRoot}`,
+    HOME: home, USERPROFILE: home, TEMP: root, TMP: root,
+    IMPECCABLE_HOME: path.join(root, 'cache'),
+    IMPECCABLE_BIN: COMSPEC,
+    SystemRoot: process.env.SystemRoot,
+    ComSpec: COMSPEC,
+    PROCESSOR_ARCHITECTURE: 'AMD64',
+  };
+  const run = (args) => new Promise((resolve, reject) => {
+    const child = spawn(COMSPEC, ['/d', '/s', '/c', `""${launcher}" ${args}"`], { env, cwd: root, windowsVerbatimArguments: true, timeout: 20000 });
+    child.on('error', reject);
+    child.on('close', (status, signal) => resolve({ status, signal }));
+  });
+  for (const [args, expected] of [['/c exit 2', 2], ['/c exit 1', 1], ['/c exit 0', 0]]) {
+    const result = await run(args);
+    assert.equal(result.signal, null, JSON.stringify(result));
+    assert.equal(result.status, expected, args);
+  }
+});
+
 for (const scenario of ['removed', 'emptied', 'empty-download', 'no-sidecar', 'empty-sidecar', 'mismatch', 'hash-failure', 'removed-during-hash', 'removed-before-move', 'removed-after-move', 'emptied-after-move', 'move-failure']) {
   test(`launcher refuses ${scenario} with an accurate diagnostic`, async t => {
     const result = await exercise(t, scenario);

tests/oracle/golden/live-accept-html-discard-then-accept.json

@@ -16,6 +16,6 @@
   "files": {
     ".impeccable/live/accept-receipts/ab12cd34.json": "{\n  \"id\": \"ab12cd34\",\n  \"operation\": \"discard\",\n  \"variantId\": null,\n  \"result\": {\n    \"handled\": true,\n    \"file\": \"index.html\",\n    \"carbonize\": false\n  },\n  \"completedAt\": \"<ISO>\"\n}\n",
     ".impeccable/live/config.json": "{\n  \"files\": [\"index.html\", \"public/**/*.html\"],\n  \"insertBefore\": \"</body>\",\n  \"commentSyntax\": \"html\"\n}\n",
-    "index.html": "<!DOCTYPE html>\n<html lang=\"en\">\n  <head>\n    <meta charset=\"UTF-8\" />\n    <title>Oracle Live HTML Fixture</title>\n    <style>\n      .hero-title { font-size: 2rem; }\n      .hero-hook { color: #555; }\n    </style>\n  </head>\n  <body>\n    <main class=\"page\">\n\n      <h1 id=\"hero\" class=\"hero-title\">Oracle Fixture</h1>\n\n      <p class=\"hero-hook\">Minimal static page for oracle live-mode goldens.</p>\n      <section id=\"features\" class=\"feature-grid\">\n        <article class=\"feature-card\">One</article>\n        <article class=\"feature-card\">Two</article>\n      </section>\n      <aside class=\"side-note\">\n        <h2 class=\"note-title\">Aside</h2>\n        <p>Nested content.</p>\n      </aside>\n    </main>\n  </body>\n</html>\n"
+    "index.html": "<!DOCTYPE html>\n<html lang=\"en\">\n  <head>\n    <meta charset=\"UTF-8\" />\n    <title>Oracle Live HTML Fixture</title>\n    <style>\n      .hero-title { font-size: 2rem; }\n      .hero-hook { color: #555; }\n    </style>\n  </head>\n  <body>\n    <main class=\"page\">\n      <h1 id=\"hero\" class=\"hero-title\">Oracle Fixture</h1>\n      <p class=\"hero-hook\">Minimal static page for oracle live-mode goldens.</p>\n      <section id=\"features\" class=\"feature-grid\">\n        <article class=\"feature-card\">One</article>\n        <article class=\"feature-card\">Two</article>\n      </section>\n      <aside class=\"side-note\">\n        <h2 class=\"note-title\">Aside</h2>\n        <p>Nested content.</p>\n      </aside>\n    </main>\n  </body>\n</html>\n"
   }
 }

tests/oracle/golden/live-accept-html-discard.json

@@ -6,6 +6,6 @@
   "files": {
     ".impeccable/live/accept-receipts/ab12cd34.json": "{\n  \"id\": \"ab12cd34\",\n  \"operation\": \"discard\",\n  \"variantId\": null,\n  \"result\": {\n    \"handled\": true,\n    \"file\": \"index.html\",\n    \"carbonize\": false\n  },\n  \"completedAt\": \"<ISO>\"\n}\n",
     ".impeccable/live/config.json": "{\n  \"files\": [\"index.html\", \"public/**/*.html\"],\n  \"insertBefore\": \"</body>\",\n  \"commentSyntax\": \"html\"\n}\n",
-    "index.html": "<!DOCTYPE html>\n<html lang=\"en\">\n  <head>\n    <meta charset=\"UTF-8\" />\n    <title>Oracle Live HTML Fixture</title>\n    <style>\n      .hero-title { font-size: 2rem; }\n      .hero-hook { color: #555; }\n    </style>\n  </head>\n  <body>\n    <main class=\"page\">\n\n      <h1 id=\"hero\" class=\"hero-title\">Oracle Fixture</h1>\n\n      <p class=\"hero-hook\">Minimal static page for oracle live-mode goldens.</p>\n      <section id=\"features\" class=\"feature-grid\">\n        <article class=\"feature-card\">One</article>\n        <article class=\"feature-card\">Two</article>\n      </section>\n      <aside class=\"side-note\">\n        <h2 class=\"note-title\">Aside</h2>\n        <p>Nested content.</p>\n      </aside>\n    </main>\n  </body>\n</html>\n"
+    "index.html": "<!DOCTYPE html>\n<html lang=\"en\">\n  <head>\n    <meta charset=\"UTF-8\" />\n    <title>Oracle Live HTML Fixture</title>\n    <style>\n      .hero-title { font-size: 2rem; }\n      .hero-hook { color: #555; }\n    </style>\n  </head>\n  <body>\n    <main class=\"page\">\n      <h1 id=\"hero\" class=\"hero-title\">Oracle Fixture</h1>\n      <p class=\"hero-hook\">Minimal static page for oracle live-mode goldens.</p>\n      <section id=\"features\" class=\"feature-grid\">\n        <article class=\"feature-card\">One</article>\n        <article class=\"feature-card\">Two</article>\n      </section>\n      <aside class=\"side-note\">\n        <h2 class=\"note-title\">Aside</h2>\n        <p>Nested content.</p>\n      </aside>\n    </main>\n  </body>\n</html>\n"
   }
 }

tests/oracle/golden/live-accept-jsx-discard.json

@@ -6,7 +6,7 @@
   "files": {
     ".impeccable/live/accept-receipts/ab12cd34.json": "{\n  \"id\": \"ab12cd34\",\n  \"operation\": \"discard\",\n  \"variantId\": null,\n  \"result\": {\n    \"handled\": true,\n    \"file\": \"src/App.jsx\",\n    \"carbonize\": false\n  },\n  \"completedAt\": \"<ISO>\"\n}\n",
     ".impeccable/live/config.json": "{\n  \"files\": [\"index.html\"],\n  \"insertBefore\": \"</body>\",\n  \"commentSyntax\": \"html\"\n}\n",
-    "src/App.jsx": "export default function App() {\n  return (\n    <main className=\"page\">\n\n      <h1 className=\"hero-title\">Vite Fixture</h1>\n\n      <p className=\"hero-hook\">Minimal React tree for oracle live-mode goldens.</p>\n      <section id=\"features\" className=\"feature-grid\">\n        <article className=\"feature-card\">One</article>\n        <article className=\"feature-card\">Two</article>\n      </section>\n      <ul className=\"item-list\">\n        {items.map((item) => (\n          <li key={item.id} className=\"item-row\">{item.title}</li>\n        ))}\n      </ul>\n    </main>\n  );\n}\n\nconst items = [\n  { id: 1, title: 'First' },\n  { id: 2, title: 'Second' },\n];\n",
+    "src/App.jsx": "export default function App() {\n  return (\n    <main className=\"page\">\n      <h1 className=\"hero-title\">Vite Fixture</h1>\n      <p className=\"hero-hook\">Minimal React tree for oracle live-mode goldens.</p>\n      <section id=\"features\" className=\"feature-grid\">\n        <article className=\"feature-card\">One</article>\n        <article className=\"feature-card\">Two</article>\n      </section>\n      <ul className=\"item-list\">\n        {items.map((item) => (\n          <li key={item.id} className=\"item-row\">{item.title}</li>\n        ))}\n      </ul>\n    </main>\n  );\n}\n\nconst items = [\n  { id: 1, title: 'First' },\n  { id: 2, title: 'Second' },\n];\n",
     "src/main.jsx": "import { createRoot } from 'react-dom/client';\nimport App from './App.jsx';\n\ncreateRoot(document.getElementById('root')).render(<App />);\n",
     "src/Panel.tsx": "type PanelProps = { title: string; children?: React.ReactNode };\n\nexport function Panel({ title, children }: PanelProps) {\n  return (\n    <section className=\"panel\">\n      <header className=\"panel-header\">\n        <h2 className=\"panel-title\">{title}</h2>\n      </header>\n      <div className=\"panel-body\">{children}</div>\n    </section>\n  );\n}\n"
   }

tests/oracle/golden/live-accept-svelte-fallback-source-wrapper.json

@@ -17,6 +17,6 @@
     ".impeccable/live/accept-receipts/ab12cd34.json": "{\n  \"id\": \"ab12cd34\",\n  \"operation\": \"discard\",\n  \"variantId\": null,\n  \"result\": {\n    \"handled\": true,\n    \"file\": \"src/routes/+page.svelte\",\n    \"carbonize\": false\n  },\n  \"completedAt\": \"<ISO>\"\n}\n",
     ".impeccable/live/config.json": "{\n  \"files\": [\"src/app.html\"],\n  \"insertBefore\": \"</body>\",\n  \"commentSyntax\": \"html\"\n}\n",
     "src/app.html": "<!DOCTYPE html>\n<html lang=\"en\">\n  <head>\n    <meta charset=\"utf-8\" />\n    <title>SvelteKit Fixture</title>\n    %sveltekit.head%\n  </head>\n  <body data-sveltekit-preload-data=\"hover\">\n    <div style=\"display: contents\">%sveltekit.body%</div>\n  </body>\n</html>\n",
-    "src/routes/+page.svelte": "<script>\n  let title = 'SvelteKit Fixture';\n  let expenses = [\n    { id: 1, label: 'Coffee', amount: 3 },\n    { id: 2, label: 'Lunch', amount: 12 },\n  ];\n</script>\n\n<main class=\"page\">\n\n  <h1 class=\"hero-title\">{title}</h1>\n\n  <p class=\"hero-hook\">Minimal SvelteKit route for oracle live-mode goldens.</p>\n  <ul class=\"expense-list\">\n    {#each expenses as expense (expense.id)}\n      <li class=\"expense-row\">{expense.label}: {expense.amount}</li>\n    {/each}\n  </ul>\n  <section id=\"features\" class=\"feature-grid\">\n    <article class=\"feature-card\">One</article>\n    <article class=\"feature-card\">Two</article>\n  </section>\n</main>\n\n<style>\n  .hero-title { font-size: 2rem; }\n  .expense-list { list-style: none; padding: 0; }\n  .expense-row { padding: 4px 0; }\n</style>\n"
+    "src/routes/+page.svelte": "<script>\n  let title = 'SvelteKit Fixture';\n  let expenses = [\n    { id: 1, label: 'Coffee', amount: 3 },\n    { id: 2, label: 'Lunch', amount: 12 },\n  ];\n</script>\n\n<main class=\"page\">\n  <h1 class=\"hero-title\">{title}</h1>\n  <p class=\"hero-hook\">Minimal SvelteKit route for oracle live-mode goldens.</p>\n  <ul class=\"expense-list\">\n    {#each expenses as expense (expense.id)}\n      <li class=\"expense-row\">{expense.label}: {expense.amount}</li>\n    {/each}\n  </ul>\n  <section id=\"features\" class=\"feature-grid\">\n    <article class=\"feature-card\">One</article>\n    <article class=\"feature-card\">Two</article>\n  </section>\n</main>\n\n<style>\n  .hero-title { font-size: 2rem; }\n  .expense-list { list-style: none; padding: 0; }\n  .expense-row { padding: 4px 0; }\n</style>\n"
   }
 }