From df849df0865778650fb64f9e232e641f06f652f2 Mon Sep 17 00:00:00 2001
From: Garry Tan <garrytan@gmail.com>
Date: Mon, 16 Mar 2026 09:43:41 -0500
Subject: [PATCH] feat: support await in $B js and eval commands
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Auto-wrap await expressions in async IIFE context so
$B js "await fetch(...)" works without SyntaxError.

- hasAwait() strips comments before detection
- js: expression wrapping (async()=>(expr))()
- eval: smart wrapping — single-line=expression, multi-line=block
- 6 new unit tests covering async, false-positive, and return semantics
---
 browse/src/read-commands.ts  | 16 ++++++++++-
 browse/test/commands.test.ts | 54 ++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/browse/src/read-commands.ts b/browse/src/read-commands.ts
index 53efec8a..a7d76352 100644
--- a/browse/src/read-commands.ts
+++ b/browse/src/read-commands.ts
@@ -11,6 +11,12 @@ import type { Page } from 'playwright';
 import * as fs from 'fs';
 import * as path from 'path';
 
+/** Detect await keyword, ignoring comments. Accepted risk: await in string literals triggers wrapping (harmless). */
+function hasAwait(code: string): boolean {
+  const stripped = code.replace(/\/\/.*$/gm, '').replace(/\/\*[\s\S]*?\*\//g, '');
+  return /\bawait\b/.test(stripped);
+}
+
 // Security: Path validation to prevent path traversal attacks
 const SAFE_DIRECTORIES = ['/tmp', process.cwd()];
 
@@ -118,7 +124,8 @@ export async function handleReadCommand(
     case 'js': {
       const expr = args[0];
       if (!expr) throw new Error('Usage: browse js <expression>');
-      const result = await page.evaluate(expr);
+      const wrapped = hasAwait(expr) ? `(async()=>(${expr}))()` : expr;
+      const result = await page.evaluate(wrapped);
       return typeof result === 'object' ? JSON.stringify(result, null, 2) : String(result ?? '');
     }
 
@@ -128,6 +135,13 @@ export async function handleReadCommand(
       validateReadPath(filePath);
       if (!fs.existsSync(filePath)) throw new Error(`File not found: ${filePath}`);
       const code = fs.readFileSync(filePath, 'utf-8');
+      if (hasAwait(code)) {
+        const trimmed = code.trim();
+        const isSingleExpr = trimmed.split('\n').length === 1;
+        const wrapped = isSingleExpr ? `(async()=>(${trimmed}))()` : `(async()=>{\n${code}\n})()`;
+        const result = await page.evaluate(wrapped);
+        return typeof result === 'object' ? JSON.stringify(result, null, 2) : String(result ?? '');
+      }
       const result = await page.evaluate(code);
       return typeof result === 'object' ? JSON.stringify(result, null, 2) : String(result ?? '');
     }
diff --git a/browse/test/commands.test.ts b/browse/test/commands.test.ts
index a3e201d9..d8aaeab6 100644
--- a/browse/test/commands.test.ts
+++ b/browse/test/commands.test.ts
@@ -144,6 +144,60 @@ describe('Inspection', () => {
     expect(obj.b).toBe(2);
   });
 
+  test('js supports await expressions', async () => {
+    const result = await handleReadCommand('js', ['await Promise.resolve(42)'], bm);
+    expect(result).toBe('42');
+  });
+
+  test('js does not false-positive on await substring', async () => {
+    const result = await handleReadCommand('js', ['(() => { const awaitable = 5; return awaitable })()'], bm);
+    expect(result).toBe('5');
+  });
+
+  test('eval supports await in single-line file', async () => {
+    const tmp = '/tmp/eval-await-test.js';
+    fs.writeFileSync(tmp, 'await Promise.resolve("hello from eval")');
+    try {
+      const result = await handleReadCommand('eval', [tmp], bm);
+      expect(result).toBe('hello from eval');
+    } finally {
+      fs.unlinkSync(tmp);
+    }
+  });
+
+  test('eval does not wrap when await is only in a comment', async () => {
+    const tmp = '/tmp/eval-comment-test.js';
+    fs.writeFileSync(tmp, '// no need to await this\ndocument.title');
+    try {
+      const result = await handleReadCommand('eval', [tmp], bm);
+      expect(result).toBe('Test Page - Basic');
+    } finally {
+      fs.unlinkSync(tmp);
+    }
+  });
+
+  test('eval multi-line with await and explicit return', async () => {
+    const tmp = '/tmp/eval-multiline-await.js';
+    fs.writeFileSync(tmp, 'const data = await Promise.resolve("multi");\nreturn data;');
+    try {
+      const result = await handleReadCommand('eval', [tmp], bm);
+      expect(result).toBe('multi');
+    } finally {
+      fs.unlinkSync(tmp);
+    }
+  });
+
+  test('eval multi-line with await but no return gives empty string', async () => {
+    const tmp = '/tmp/eval-multiline-no-return.js';
+    fs.writeFileSync(tmp, 'const data = await Promise.resolve("lost");\ndata;');
+    try {
+      const result = await handleReadCommand('eval', [tmp], bm);
+      expect(result).toBe('');
+    } finally {
+      fs.unlinkSync(tmp);
+    }
+  });
+
   test('css returns computed property', async () => {
     const result = await handleReadCommand('css', ['h1', 'color'], bm);
     // Navy color