SNOW-2317965: Refactor context_configure_development_features

[sfc-gh-yixie]

1. Which Jira issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-2317965

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.
   • I acknowledge that I have ensured my changes to be thread-safe. Follow the link for more information: Thread-safe Developer Guidelines
   • If adding any arguments to public Snowpark APIs or creating new public Snowpark APIs, I acknowledge that I have ensured my changes include AST support. Follow the link for more information: AST Support Guidelines

3. Please describe how your code solves the related issue.

   1. When context_configure_development_features is called, call an internal API to enable AST instead of the public session.ast_enabled = True.
   2. Refactored to be able to config dev features if there are no active sessions or multiple sessions. When a new session is created, the new session reads the developer feature config.

[graphite-app]

Type mismatch: Returns an empty list [] but the function signature declares return type as Set["Session"]. This should return an empty set instead.

return set()

While iteration works with both lists and sets, this type inconsistency could cause runtime errors if callers use Set-specific methods like .add(), .union(), etc. or type checkers will flag this as an error.

Suggested change

	return []
	return set()

Spotted by Graphite Agent



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[sfc-gh-yixie]

Updated manually

[graphite-app]

Race condition: _get_active_sessions() returns the actual _active_sessions set without holding the lock during iteration. If another thread adds/removes a session while iterating at line 86, it will raise RuntimeError: Set changed size during iteration.

Fix by making a copy:

sessions = snowflake.snowpark.session._get_active_sessions(
    require_at_least_one=False
).copy()  # Make a copy to avoid iteration issues

Alternatively, the _get_active_sessions() function should return a copy instead of the actual set to prevent unsafe access to the mutex-protected data structure.

Suggested change

	sessions = snowflake.snowpark.session._get_active_sessions(
	require_at_least_one=False
	)
	try:
	session = get_active_session()
	if session is None:
	_logger.warning(
	"No active session found. Please create a session first and call "
	"`configure_development_features()` after creating the session.",
	)
	return
	_enable_dataframe_trace_on_error = enable_dataframe_trace_on_error
	_enable_trace_sql_errors_to_dataframe = enable_trace_sql_errors_to_dataframe
	session.ast_enabled = True
	for active_session in sessions:
	active_session._set_ast_enabled_internal(True)
	sessions = snowflake.snowpark.session._get_active_sessions(
	require_at_least_one=False
	).copy() # Make a copy to avoid iteration issues
	try:
	for active_session in sessions:
	active_session._set_ast_enabled_internal(True)

Spotted by Graphite Agent



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