Ajax: Don't process data property on no-entity-body requests

[dmethvin]

Fixes gh-3438

Summary

The description in gh-3438 is pretty detailed. Basically, don't process settings.data if settings.processData is false. This allows a settings.beforeSend hook to have its way with the original data and, for example, serialize it to JSON on the URL.

I'd consider this a long-standing bug and the current documentation would imply it should have worked this way all along. It should be safe to include in a minor release.

Checklist

• All authors have signed the CLA at https://cla.js.foundation/jquery/jquery
• New tests have been added to show the fix or feature works
• Grunt build and unit tests pass locally with these changes
• [-] If needed, a docs issue/PR was created at https://github.com/jquery/api.jquery.com

[mention-bot]

@dmethvin, thanks for your PR! By analyzing the history of the files in this pull request, we identified @markelog, @jaubourg and @gibson042 to be potential reviewers.

[jaubourg]

👎 see my comment on the issue

(and sorry to be late to the party)

[gibson042]

I'm still in favor of this change, but I observed while combing through the code that modifying an ajax URL in beforeSend (as in the example) breaks our caching logic. We may want to open an issue for ensuring that cacheURL always corresponds to the request as issued.

P.S. It's great to see you here, @jaubourg. And you're not late at all.

[jaubourg]

Hey @gibson042, nice to see you too :)

[timmywil]

What @jaubourg said makes sense to me. It's not that the data should be ignored, it's that it should not be processed. It should still get used if passed. Otherwise, why pass it a GET request at all? Also, I don't see a use case for passing a non string in a !hasContent request.

[gibson042]

This is my interpretation of desired behavior as discussed in the meeting. It should be implemented in this PR and documented in https://github.com/jquery/api.jquery.com/blob/master/entries/jQuery.ajax.xml#L145 .

processData (default: true)
Type: Boolean
When true, non-string request data is serialized with $.param, and data is additionally re-encoded for payloads with contentType "application/x-www-form-urlencoded" (the default) or moved into URL query parameters for methods which are issued without a payload (e.g., "GET" and "HEAD"). When false, such processing is skipped (except for the special case of string data, which is still moved into the URL of no-content requests).

[jbedard]

indentation?