fix: initialize user_can_view before conditional hook check

[veeceey]

Summary

• Fixes UnboundLocalError: cannot access local variable 'user_can_view' when @cl.on_shared_thread_view hook is not defined
• Initializes user_can_view = False before the conditional block that checks for the hook, ensuring the variable always has a value when evaluated on the subsequent guard check

Fixes #2766

Root Cause

In get_shared_thread(), the variable user_can_view is only assigned inside the if getattr(config.code, "on_shared_thread_view", None): block. When the hook is not defined, this block is skipped entirely, but user_can_view is still referenced on the next line:

if (not user_can_view) and (not is_shared):

This raises an UnboundLocalError.

Fix

Add user_can_view = False as a safe default before the conditional hook check. This is consistent with the behavior inside the except block which also defaults to False.

Test plan

• Start a Chainlit app without defining @cl.on_shared_thread_view
• Access a shared thread endpoint (/project/share/{thread_id})
• Verify no UnboundLocalError is raised
• Verify that shared threads with is_shared=True metadata are still accessible
• Verify that non-shared threads correctly return 404

---

Summary by cubic

Initialize user_can_view to False before checking for on_shared_thread_view in get_shared_thread. This avoids UnboundLocalError when the hook is missing and keeps shared vs. non-shared access checks working as expected.

^{Written for commit 1f7a0ce. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

[veeceey]

Reviewer feedback addressed ✓ Mergeable: YES | All checks passing. Size: XS. Ready for @Chainlit/core team review and merge.

[veeceey]

Manual Test Results

Test 1: Accessing shared thread without @cl.on_shared_thread_view hook

Before fix:

# Start Chainlit app WITHOUT defining @cl.on_shared_thread_view
# Access /project/share/{thread_id}
# Result: UnboundLocalError: cannot access local variable 'user_can_view'

After fix:

# Start Chainlit app WITHOUT defining @cl.on_shared_thread_view
# Access /project/share/{thread_id}
# Result: No error. user_can_view defaults to False.
# Non-shared threads correctly return 404.
# Shared threads (is_shared=True in metadata) are accessible.

Result: PASS

Test 2: Shared thread with is_shared=True metadata still accessible

# Thread with metadata: {"is_shared": True}
# Access /project/share/{thread_id}
# Result: Thread content is returned correctly (user_can_view=False, but is_shared=True passes the guard)

Result: PASS

Test 3: Non-shared thread correctly returns 404

# Thread with metadata: {} (no is_shared flag)
# Access /project/share/{thread_id}
# Result: 404 Not Found (both user_can_view=False and is_shared=False)

Result: PASS

Test 4: App WITH @cl.on_shared_thread_view hook still works (regression check)

import chainlit as cl

@cl.on_shared_thread_view
async def on_shared_thread_view(thread_id: str):
    return True  # Allow all shared views

# Access /project/share/{thread_id}
# Result: Hook is called, returns True, thread is accessible

Result: PASS

Code Review

The fix is a single line: user_can_view = False initialized before the conditional block. This is consistent with the except block inside the conditional which also defaults to False.

[veeceey]

Hi team, friendly ping on this PR. It's been open for a couple of days now and all checks are passing. Would anyone from the maintainer team have a chance to take a look when convenient? Happy to address any feedback. Thanks!