ajax: Specified that "?" in data is replaced

[AurelioDeRosa]

Fixes gh-999

[dmethvin]

I think this is too broad a statement, see this http://jsbin.com/dicigovevo/edit?html,console and also #878 which is a bit of a dup. There's some lengthy discussion in https://bugs.jquery.com/ticket/8417 .

The essence of the problem is that when users send their own plain string (instead of an object) as data they must ensure that it is either formatted properly as form-url-encoded data or else specify a contentType that says how the data is encoded. It is not possible for form-url-encoded data to contain ?? by the definition of the format.

I kept trying to explain it all and I ended up with something like this, which is probably 3 paragraphs.

Data to be sent to the server. If the HTTP method is one that cannot have an entity body, such as GET, the data is appended to the URL. When data is an object, jQuery generates the data string from the object's key/value pairs unless the processData option is set to false. For example, { a: "bc", d: "e,f" } is converted to the string "a=bc&d=e%2Cf". If the value is an array, jQuery serializes multiple values with same key based on the value of the traditional setting (described below). For example, { a: [1,2] } becomes the string "a%5B%5D=1&a%5B%5D=2" with the default traditional: false setting. When data is passed as a string it should already be encoded using the correct encoding for contentType, which by default is application/x-www-form-urlencoded. If the string contains a double question mark (??) it is replaced with a value generated by jQuery that is unique for each copy of the library on the page (e.g. jQuery21406515378922229067_1479880736745).

[mgol]

@dmethvin it seems that your version is pretty different to the one in this PR. Could you report it as a PR? We'd be able to close this one then (I'm trying to clear up stale PRs).

[mgol]

@dmethvin ping

[AurelioDeRosa]

Agree with @mgol. @dmethvin's text is much more complete, so happy to close mine in favor of a PR fro him.

[mgol]

@dmethvin Ping about #1005 (comment)

[mgol]

I submitted @dmethvin's text in #1171 so let's close this one.