'NoneType' has no attribute 'tell' can be avoided by raising FileNotFoundError.

[Poikilos]

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Software Versions

• Python: 3.9
• OS: Linux (Devuan Chimera)
• Kivy: 2.1.0
• Kivy installation method: pip

Describe the bug When an image is not found, an obscure error appears: 'NoneType' has no attribute 'tell'

Expected behavior A meaningful exception (probably FileNotFoundError) should be raised before the problem becomes obscure in later code.

To Reproduce A short, runnable example that reproduces the issue with latest kivy master. example1.py in https://github.com/kivy/kivy3

Code and Logs and screenshots kivy_venv/lib/python3.9/site-packages/kivy/core/image/init.py

        filename = resource_find(filename)

Additional context There are several users who have been confused by the error:

• kivy's fork of kivy3 currently has the problem (diagnosing the simple problem of a missing file was difficult since the error message was unclear; I am the user in this case).
• https://github.com/viblo/pymunk/issues/166 (It confused more than one user in this case)
• https://www.forexfactory.com/thread/614471-free-machine-learning-tool-with-a-graphical-user-interface?page=2 (This is not a kivy example but is in imagehdr.py which kivy uses).

To be clear, the error goes away in the example code if a png file named "empty.png" is manually placed in the folder (The fact that it is not there is a kivy3 issue). The kivy issue is merely that the error message is unclear, and the suggested fix provides a better error message.

suggested fix Before the resource_find call, add:

        original_path = str(filename)

After the resource_find call, add:

        if filename is None:
            raise FileNotFoundError(original_path + " was not found.")

Other considerations:

• If you rather not have a crash when images are missing, maybe use kivy/default.png and simply show an error rather than raise an exception.

[Vricken]

I was working with images and got the ‘NoneType’… , I was very confused to say the least. This however brought me clarity. I personally think this is a very good suggestion which can avoid confusion to many people.

[Julian-O]

I was going to mark this as easy, but I realised:

• There is no mention of where the code that is calling tell - why isn't it checking?
• What about all the other calls to resource_find?
• resource.py's`resource_find already checks the filename is not Falsy.
• Why is the filename None when the file doesn't exist?

This may be a bug, but I am not sure the proposed solution is tackling the root cause.

[ElliotGarbus]

Creating a simple test, I do not see the reported issue with Kivy. Kivy V2.2.1

from kivy.app import App
from kivy.uix.image import Image


class Reproduce7844App(App):
    def build(self):
        image = Image(source='missing_file.png')
        return image


Reproduce7844App().run()

The log contains the following error message: [ERROR ] [Image ] Not found <missing_file.png>

@Poikilos Is there a reproducer available for kivy? Does my example capture the use case you highlighted?

[github-actions[bot]]

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