Keep the prior behavior of overwriting File.page

[oprypin]

unless the page value is a strict subclass of Page

• Addresses Allow plugins to provide their own Page #3367 (comment)

@squidfunk @ultrabug

[squidfunk]

LGTM. So, the regressions that we've seen should be gone, but judging from the code, you decided to issue warnings if a plugin overwrites Page. Are we planning to switch to the behavior proposed in #3367 in MkDocs 1.6?

[oprypin]

You'll be able to move forward with your plugin in 1.5.3 because you're working with strict subclasses and they're supported without warning. For other cases I kept old behavior and added warnings.

[squidfunk]

Thanks, yes, I was asking what the plans for 1.6 were, because the warning is not entirely clear to me:

warnings.warn(
  "A plugin has set File.page to an instance of Page and it got overwritten. "
  "The behavior of this will change in MkDocs 1.6.",
  DeprecationWarning,
)

Will this be an error that terminates the build in MkDocs 1.6?

[oprypin]

Here's the list of cases:

• Strict subclass: 1.5.3 just accepts it and 1.6.0 still just accepts it
• Page: 1.5.3 ignores/overwrites it with warning, 1.6.0 just accepts it   ← what you're asking about
• Other type: 1.5.3 ignores/overwrites it with warning, 1.6.0 errors
• None: always ignore/overwrite

[squidfunk]

Perfect, thanks!

[ultrabug]

Awesome thanks!