[wp-trac] [WordPress Trac] #37968: HTML validation errors in admin tool

[WordPress Trac]

#37968: HTML validation errors in admin tool
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 Reporter:  mdgl            |       Owner:  SergeyBiryukov
     Type:  defect (bug)    |      Status:  reviewing
 Priority:  normal          |   Milestone:  4.7
Component:  Administration  |     Version:  trunk
 Severity:  normal          |  Resolution:
 Keywords:                  |     Focuses:
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Comment (by mdgl):

 I found another similar validation problem in the Appearance - Menus
 screen. It's tempting to ask who tests this stuff, but in fact modern
 browsers are very relaxed with HTML parsing and seem to correct obvious
 errors automatically, so in practice this kind of bug is becoming very
 difficult to spot!

 Class `Walker_Nav_Menu_Edit` is used to populate the "Menu Structure"
 panel with the menu to be edited. If the menu contains nested items,
 however the current code attempts to output a nested list of just `<li>`
 elements which is not valid HTML without an intervening `<ul>` (or
 `<ol>`).

 The solution I think is to follow the example of class
 `Walker_Nav_Menu_Checklist` and override the `start_lvl()` and `end_lvl()`
 methods to output the necessary additional `<ul>` and `</ul>` markup. See
 the forthcoming patch for a suggestion. Tab indents and closing tag
 comments could perhaps be further improved.

 Unfortunately, this change also causes the display of the nested menu
 items to be indented rather more than previously. Some CSS changes are
 probably required as well, but I'm not sure of the best place to do that -
 the current CSS seems rather over-specified, perhaps as a result of trying
 to work around the invalid markup.

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Ticket URL: <https://core.trac.wordpress.org/ticket/37968#comment:2>
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