Scenic File Name Causes InvalidScenarioError

[Eric-Vin]

System Details

1. Python 3.11.11
2. Scenic 3.1.0a1 (Main branch as of commit 20292f3)
3. Apple M4 26.0.1
4. NA

Detailed Description

The name of a scenic file can cause a conflict resulting in an InvalidScenarioError. I have reproduced this bug only with Metadrive, though it may affect other models/simulators.

Scenic File in Question:

param map = localPath('assets/maps/CARLA/Town01.xodr')
param use2DMap = True
model scenic.simulators.metadrive.model
ego = new Car

Run with command: scenic --2d NAME.scenic (NAME is important, see steps to reproduce).

Error: InvalidScenarioError: Scenic world model itself uses the "model" statement

Steps To Reproduce

First create a file called foo.scenic in the top level Scenic directory. Running scenic --2d foo.scenic results in no error.

Rename the file to metadrive.scenic. Running scenic --2d metadrive.scenic results in the error above.

Copy the file and rename one to foo.scenic, so that there are two identical files with the names foo.scenic and metadrive.scenic. Running scenic --2d foo.scenic or scenic --2d metadrive.scenic results in the above error, even though foo.scenic does not reference metadrive.scenic at all.

Issue Submission Checklist

• I am reporting an issue, not asking a question
• I checked the open and closed issues, forum, etc. and have not found any solution
• I have provided all necessary code, etc. to reproduce the issue

[dfremont]

The problem is that metadrive.scenic shadows the metadrive package (like if you had a metadrive.py file), so when Scenic does import metadrive it ends up importing this code recursively instead of the actual MetaDrive module. This isn't supposed to happen, since you're not allowed to import Scenic modules inside Python modules, but our check to catch such imports is fooled in this case because the import is ultimately during Scenic compilation:

1. metadrive.scenic does model scenic.simulators.metadrive.model, triggering import of the latter;
2. scenic/simulators/metadrive/__init__.py does import metadrive;
3. The ScenicFileFinder allows metadrive.scenic to fulfill that import since we are in the middle of compiling a Scenic program (in step 1).

I can look into making our check more robust, but in the mean time you should avoid giving Scenic files the same names as top-level packages.