Bug: 'with' fails when context variable from outer scope

[swernerx]

Description

Python's with context manager statement is not being converted and remains as invalid TypeScript syntax.

Python Input

with open(file, 'rb') as f:
    data = f.read()

with ctx as handle:
    process(handle)

with nullcontext() as nc:
    do_something()

Current Output (v1.3.3)

with open(file, 'rb') as f:  // ❌ INVALID! 'with' is different in JS
    let data = f.read();

with ctx as handle:  // ❌ INVALID!
    process(handle);

Expected Output

const f = open(file, 'rb')
try {
  const data = f.read()
} finally {
  f[Symbol.dispose]?.() ?? f.close?.()
}

// Or simpler without dispose:
const handle = ctx
try {
  process(handle)
} finally {
  handle.close?.()
}

Note

Earlier versions of python2ts correctly converted with statements to try/finally blocks (I saw this in simple test cases). This might be a regression or only happens in specific contexts.

Affected Files

Found ~60 occurrences in NumPy migration.

Priority

🔴 Critical - Causes ~200 errors

[swernerx]

The with...as context manager is already correctly converted:

with open(file, 'rb') as f:
    data = f.read()

→

const f = open(file, "rb")
try {
  const data = f.read()
} finally {
  f[Symbol.dispose]?.() ?? f.close?.()
}

This works in the current main branch. The fix hasn't been released to npm yet (still at v1.3.3).

[swernerx]

Found the specific edge case!

The bug occurs when the context variable is defined in a previous scope (e.g., if/else block):

# ✅ Works (inline context):
with open(file, 'rb') as f:
    data = f.read()

# ❌ Fails (context from previous scope):
if condition:
    ctx = nullcontext()
else:
    ctx = open(file, 'wb')
with ctx as f:  # ctx defined above!
    f.write(data)

Current Output:

if (condition) {
  let ctx = nullcontext();
} else {
  let ctx = open(file, 'wb');
}
with ctx as f:  // ❌ Not converted!
    f.write(data)

Expected:

let ctx;
if (condition) {
  ctx = nullcontext();
} else {
  ctx = open(file, 'wb');
}
const f = ctx;
try {
  f.write(data);
} finally {
  f[Symbol.dispose]?.() ?? f.close?.();
}

This pattern is common when choosing context managers conditionally.