Redirect sitemap.xml to wp-sitemap.xml if about to return a 404

[kraftbj]

Issue Number

Fixes #144

Description

sitemap.xml is a common location of a site's sitemap. In instances where there is not an existing sitemap.xml either on the file system or served by another plugin, the Core WP-Sitemaps plugin will redirect to the wp-sitemap.xml URL to help improve discoverability and allowed those who have submitted sitemap.xml to search engines to be able to drop-in without change.

Type of change

Please select the relevant options:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (change which improves an existing feature. E.g., performance improvement, docs update, etc.)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Steps to test

• Visit your testing site's sitemap.xml (assuming your server is set to have WP serve that URL, e.g. with pretty permalinks on with .htaccess set for Apache or via the server block in Nginx).
• On master, a WP-served 404 will be returned.
• On this branch, it will 302 redirect to wp-sitemap.xml

Acceptance criteria

• My code follows WordPress coding standards.
• I have performed a self-review of my own code.
• If the changes are visual, I have cross browser / device tested.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.
• I have added test instructions that prove my fix is effective or that my feature works.

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[kraftbj]

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[kraftbj]

Noting from today's Slack meeting, this PR is on ice until we settle on the URL format.

If we keep wp-sitemap.xml as the file name for our sitemaps, this is needed. If we go with a sitemap.xml option that doesn't conflict with existing implementations, this can be closed.

[pfefferle]

should we also remove the 0.3.0 milestone?

[svandragt]

Looks good to me, do we want any tests here? @swissspidy

[swissspidy]

If it's possible, sure. But let's wait first whether we actually keep the wp- URLs (#149 (comment))

[swissspidy]

@kraftbj just an FYI that last week we decided to stick with wp-sitemap.xml.

Do you think we can add a test here? WP core itself doesn't test handle_404, so maybe it's not easily doable.

[kraftbj]

Will pick this back up and see what I can out together.

[swissspidy]

Merging this one for now as it works as expected. Not critical to have a test for an HTTP redirect, but could always be added in a new PR.