Fix: Add duplicate name check in rename_image to prevent 500 errors

[Copilot]

Problem

When renaming an image in EXACT, if the new name already exists in the imageset, the system would attempt to perform os.rename() operations without checking for duplicates first. This causes a 500 Internal Server Error because the filesystem operation fails when trying to rename to an existing filename.

Steps to Reproduce

1. Upload two images to an imageset: "image1.jpg" and "image2.jpg"
2. Attempt to rename "image1.jpg" to "image2.jpg"
3. System tries to execute: os.rename("path/image1.jpg", "path/image2.jpg")
4. Operating system fails because "image2.jpg" already exists
5. Django returns a 500 Internal Server Error

Solution

Added duplicate checking logic in images/views.py:rename_image() that queries the database for existing images with the same name or filename before attempting any file operations:

# Check if an image with the new name already exists in the imageset
existing_image = Image.objects.filter(Q(name=newName)|Q(filename=newstem+filenameext), 
                                    image_set=imageset).exclude(id=image.id).first()
if existing_image is not None:
    # Image with this name already exists, redirect without changes
    return redirect(reverse('images:view_imageset', args=(imageset_id,)))

Key Features

• Graceful handling: Instead of crashing with a 500 error, the function now gracefully redirects back to the imageset view without making changes
• Comprehensive checking: Checks both name and filename fields to catch all potential conflicts
• Self-exclusion: Uses .exclude(id=image.id) to allow renaming to the same name (no-op scenario)
• Consistent pattern: Follows the same Q(name=...|Q(filename=...) query pattern used elsewhere in the codebase
• Early exit: Prevents any file system operations when duplicates are detected

Testing

The fix handles all edge cases correctly:

• ✅ Renaming to unique name: succeeds as before
• ✅ Renaming to existing name: fails gracefully (no 500 error)
• ✅ Renaming to same name: succeeds (no-op)
• ✅ Permission checks: maintains existing access control

This is a minimal, surgical fix that resolves the 500 error issue while maintaining backward compatibility and all existing functionality.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Bug: Renaming does not check if filename previously existed already</issue_title>
<issue_description>The title says it all. When renaming an image, we don't check if the filename already exists.
This directly results in a 500 error.

Should be easy to fix, by changing the appropriate lines in images/views.py:rename_image.</issue_description>

<agent_instructions>Create a fix for images/views.py to check all images in the current imageset for the existence of an image of same filename before renaming.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #141

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[maubreville]

Tested successfully.