AJAX responseType Handling.

[Parakleta]

I've been trying to retrieve an XML document via rx.Observable.ajax.get() and I've come across a few problems with the way the XHR.responseType field is handled.

The first is that the AJAX constructor sets a default .responseType of "json" if none is provided.

rxjs/src/observable/dom/AjaxObservable.ts

Lines 155 to 166 in 7bb8280

	const request: AjaxRequest = {
	async: true,
	createXHR: function(this: AjaxRequest) {
	return this.crossDomain ? getCORSRequest.call(this) : getXMLHttpRequest();
	},
	crossDomain: false,
	withCredentials: false,
	headers: {},
	method: 'GET',
	responseType: 'json',
	timeout: 0
	};

Note that there is already a getJSON() method which sets this value explicitly.

rxjs/src/observable/dom/AjaxObservable.ts

Lines 92 to 101 in 7bb8280

	export function ajaxGetJSON<T>(url: string, headers?: Object): Observable<T> {
	return mapResponse(
	new AjaxObservable<AjaxResponse>({
	method: 'GET',
	url,
	responseType: 'json',
	headers
	})
	);
	};

This is a problem because it means that non-JSON data cannot actually be retrieved via the default get() method. From the XHR response there are 3 ways to retrieve the body of the response: .response, .responseText, and .responseXML. If the .responseType is set then the body of the response must be successfully parsed by the associated parser or else the .response field is set to null. Note that .responseText is null unless the .responseType is unset or is set to "text". Similarly .responseXML is null unless the .responseType is unset or is set to "document".

The .responseType should be left unset as provides the most versatility, as then the .response, .responseText, and .responseXML fields may all be available depending on the source document.

The second is that a .responseType of "xml" is documented/used in the following code. The correct enumeration to request an XML response is "document".

rxjs/src/observable/dom/AjaxObservable.ts

Lines 414 to 415 in 7bb8280

	/** @type {string} The responseType (e.g. 'json', 'arraybuffer', or 'xml') */
	responseType: string;

rxjs/src/observable/dom/AjaxObservable.ts

Lines 430 to 432 in 7bb8280

	case 'xml':
	this.response = xhr.responseXML;
	break;

If it is preferred to use "xml" as a more user-friendly value this shouldn't be exposed to the XHR object.

rxjs/src/observable/dom/AjaxObservable.ts

Line 258 in 7bb8280

xhr.responseType = request.responseType;

[Parakleta]

Just noticed that this also relates to #2007.

[dolezel]

Can someone look into it, please? It really prevents me from using ajax through rxjs.

[benlesh]

This has been resolved in version 7