imageio v3 cannot read metadata of tiff files it created itself

import imageio.v3 as iio, numpy as np; iio.imwrite("test.tiff", np.empty((10, 10, 3), "u1")); print(iio.immeta("test.tiff"))

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.10/site-packages/imageio/v3.py", line 264, in immeta
    metadata = img_file.metadata(**call_kwargs)
  File "/usr/lib/python3.10/site-packages/imageio/core/legacy_plugin_wrapper.py", line 308, in metadata
    raise ValueError(
ValueError: Legacy plugins don't support excluding applied metadata fields.

This is as of imageio 2.19.5.

[FirefoxMetzger]

@anntzer I’ve created a PR that will ignore exclude_applied for legacy plugins.

I don’t think it is a perfect solution, because now it can be surprising for the end-user to see that they get metadata they may not have expected to see, but I can see how it is the lesser of two evils. I will have a think if we can add something to the docs or if we should create a logging message for this.

[anntzer]

Assuming that no legacy plugin ever has the ability to exclude applied metadata, I would just silently ignore exclude_applied=True for such plugins. Asking people to explicitly exclude_applied=True is pretty bad for usability (if you’re trying to write generic library code you’d basically end up having to always put exclude_applied=True as you can’t know what format you’ll get from your callers) and putting a warning is even worse (you basically have to make the catch_warnings dance).