errno.EROFS isn't available but its error string is

[ricknun]

CircuitPython version

Adafruit CircuitPython 9.1.4 on 2024-09-17; Adafruit Circuit Playground Bluefruit with nRF52840

Code/REPL

...
import errno
...
try:
    with open("/textfile.txt", "a") as fp:
        ...
except OSError as e:
    print(e)  # for example prints "[Errno 30] Read-only filesystem"
    if e.errno == 30:
    ...

Behavior

The provided code works fine. The "print(e)" results in the string "[Errno 30] Read-only filesystem" and "if e.errno == 30" works as expected. But if I replace "30" with "errno.EROFS" (as described at https://docs.circuitpython.org/en/latest/docs/library/errno.html) I get "During handling of the above exception, another exception occurred" and "AttributeError: 'module' object has no attribute 'EROFS'".

Description

I would expect to have either both the string and enum (hopefully, since this is such a common error), or neither.

Additional information

See https://forums.adafruit.com/viewtopic.php?p=1032465 where this issue was discussed with Dan Halbert. Most important, I think the list of strings and list of enums in moderrno.c should agree and both include Read-Only File System. Less important (but it sure would have helped me), the documentation at https://docs.circuitpython.org/en/latest/docs/library/errno.html could be improved from "The codes available may vary per CircuitPython build" (please avoid disclaimers like this) to where to find the list that applies to my situation.

[ricknun]

I just noticed Dan addressed this yesterday. See #9731.

[ricknun]

But I don't think Dan's issue #9731 addresses my request above for improved documentation...

[dhalbert]

Less important (but it sure would have helped me), the documentation at https://docs.circuitpython.org/en/latest/docs/library/errno.html could be improved from "The codes available may vary per CircuitPython build" (please avoid disclaimers like this) to where to find the list that applies to my situation.

I have opened #9737 to cover this.