[wp-trac] [WordPress Trac] #45157: Upgrading from 4.9.9 to 5.0-alpha-43815 with Gutenberg plugin installed gets whitescreen of death

[WordPress Trac]

#45157: Upgrading from 4.9.9 to 5.0-alpha-43815 with Gutenberg plugin installed
gets whitescreen of death
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 Reporter:  timhibberd    |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  5.0
Component:  General       |     Version:  5.0
 Severity:  major         |  Resolution:
 Keywords:  needs-patch   |     Focuses:
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Comment (by mcsf):

 > I think the only way forward now, if we want to be safe, is to finally
 switch the plugin to requiring 5.0.0 as the minimum WP version and
 removing all the declarations that core already provides.

 I hate this, though, because the plugin should keep working for whoever
 can't upgrade immediately. Which makes me think of something I'd
 considered in some other issue or ticket:

 Instead of letting the plugin rely on `class_exists`/`function_exists`,
 which are prone to failure, let it more aggressively skip loading of files
 depending on `$wp_version` (in short, if it starts with `'5.'`, then skip
 loading of these entities). Meanwhile, they could even be moved to a
 `lib/4.9-compat` directory for added clarity.

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Ticket URL: <https://core.trac.wordpress.org/ticket/45157#comment:15>
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