URLInput component needs a custom 'placeholder' attribute

[r-a-y]

Editor's Update 2019-12-05 (by @aduth): A placeholder prop now exists for URLInput as of #17846, but is not yet documented. The task should now reflect the need for documentation.

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Describe the bug
Similar to other block components like RichText, the URLInput block needs to have a configurable placeholder attribute so custom blocks can set a different value other than the default Paste URL or type to search

It currently does not allow for one:
https://github.com/WordPress/gutenberg/blob/master/packages/editor/src/components/url-input/index.js#L243

Additional context

• Tested on Gutenberg 4.3.0

I also encountered other bugs with URLInput that I'll file new issues for.

[gziolo]

Placeholder for URLInput is hardcoded as of today:

gutenberg/packages/block-editor/src/components/url-input/index.js

Line 244 in 392df98

placeholder={ __( 'Paste URL or type to search' ) }

Please note that this component was moved to @wordpress/block-editor package.

[luckyape]

the hard coded placeholder provides a challenging user experience for disableSuggestions: true

[HardeepAsrani]

Yea, it's weird to have the "or search" option when there's a prop to disable suggestions. I can take over this if an affirmative decision is made. :)

[aduth]

URLInput now has a placeholder prop as of #17846

It does not yet appear to be documented, so this issue should remain open until that is resolved.

[PypWalters]

I believe this ticket can be closed now that #36799 has been merged.