Don't strip newline in esc_url() when protocol is mailto:

[danielbachhuber]

esc_url() strips encoded newlines when it shouldn't.

The genesis of newline stripping is r4148. mailto was added as a mentioned protocol in r8743, but it doesn't appear there was any technical change, only the PHPdoc mention.

Here's the failing testcase:

$body = <<<EOT
Hi there,

I thought you might want to sign up for this newsletter
EOT;
$email_link = 'mailto:?body=' . rawurlencode( $body );

// Expected: mailto:?body=Hi%20there%2C%0A%0AI%20thought%20you%20might%20want%20to%20sign%20up%20for%20this%20newsletter
var_export( $email_link );

// Actual: mailto:?body=Hi%20there%2CI%20thought%20you%20might%20want%20to%20sign%20up%20for%20this%20newsletter
$email_link = esc_url( $email_link );
var_export( $email_link );

[danielbachhuber]

Don't strip newline in esc_url when protocol is mailto:

[dd32]

This feels like a wontfix edgecase to me..

[jorbin]

I think that this is an edgecase, but one worth supporting. mailto is an acceptable protocal to be run through esc_url and it allows new lines. The fact that this contains unit tests means that the cost of the supporting the edge case is low.

[dd32]

I'm fine with letting it in if others feel strongly, but I still think it's an significant edge-case that doesn't realistically need to be supported.

The unit tests should be expanded to cover other use-cases as well. It should show it in action, and that it still works as intended for other url forms (assuming that there isn't another test that handles that already)

[jorbin]

In 33064:

Don't strip newline in esc_url() when protocol is mailto:

The mailto protocol is a bit different than the other protocols in that new lines are something you might realistically want to include. Includes tests to make sure that http protocol urls that contain mailto: aren't affected. Tests for stripping newlines in general already exist.

Fixes #31632
Props danielbachhuber