write-special-chars-heredoc

Write File Special Characters Workaround

Problem

The write_file tool may fail with [ERROR] unknown error when file content contains special characters such as:

• Apostrophes / single quotes (')
• Backticks (`)
• Template literals (`${variable}`) common in TypeScript/JavaScript
• Complex combinations of quotes and escape sequences

This is especially common when writing TypeScript, JavaScript, shell scripts, or any source file with string interpolation syntax.

Solution: Python Heredoc Workaround

Write a small Python script to /tmp/ that uses triple-quoted strings to embed the file content, then execute it with python3.

Step-by-Step

1. Compose a Python writer script using triple-quoted strings ("""...""").
2. Write the Python script itself to /tmp/ — its content is plain enough that write_file will succeed (no problematic characters in the wrapper).
3. Execute the script with run_shell: python3 /tmp/write_<name>.py

Escaping Rules Inside the Python Script

Character	How to handle
Backslash \	Escape as \\
Triple double-quote """	Escape as \"\"\" or use ''' strings instead
Everything else (backticks, $, ', {})	No escaping needed

Template

#!/usr/bin/env python3
content = """
<YOUR FILE CONTENT HERE>
""".lstrip("\n")

with open("/path/to/target/file.ts", "w") as f:
    f.write(content)

print("File written successfully.")

Concrete Example

Suppose you need to write a TypeScript file with template literals and apostrophes that causes write_file to fail:

Step 1 — Write the Python helper to /tmp/:

Use write_file with path /tmp/write_greeting.py and content:

#!/usr/bin/env python3
content = """
export function greet(name: string): string {
  const msg = `Hello, ${name}! It's a great day.`;
  console.log(`Greeting: ${msg}`);
  return msg;
}
""".lstrip("\n")

with open("/app/src/greeting.ts", "w") as f:
    f.write(content)

print("Written: /app/src/greeting.ts")

Step 2 — Execute the helper:

python3 /tmp/write_greeting.py

Step 3 — Verify:

cat /app/src/greeting.ts

When to Use This Pattern

• write_file returns [ERROR] unknown error for a specific file.
• The file contains TypeScript/JavaScript template literals.
• The file contains mixed quote styles or shell-like special characters.
• Any time direct file writing fails and content cannot be easily sanitized.

Multiple Files

For writing several problematic files in one pass, consolidate them into a single Python script:

#!/usr/bin/env python3
import os

files = {
    "/app/src/component.tsx": """
import React from 'react';

const App = () => (
  <div className={`container`}>
    <h1>It's working!</h1>
  </div>
);

export default App;
""".lstrip("\n"),

    "/app/src/utils.ts": """
export const format = (val: number) => `Value: ${val.toFixed(2)}`;
""".lstrip("\n"),
}

for path, content in files.items():
    os.makedirs(os.path.dirname(path), exist_ok=True)
    with open(path, "w") as f:
        f.write(content)
    print(f"Written: {path}")

Key Advantages

• No shell escaping required — Python triple-quoted strings are literal.
• Handles all TypeScript syntax — template literals, generics, JSX, etc.
• Atomic — the target file is only created if the Python script succeeds.
• Debuggable — the intermediate .py file can be inspected if needed.
• Cleanup (optional): rm /tmp/write_*.py after all files are written.