Avoid parsing plain-text errors as JSON

It's somewhat unhelpful to spam over the actual error from the reverse-proxy or
whatever with a SyntaxError.

package.json

@@ -49,6 +49,7 @@
   "dependencies": {
     "another-json": "^0.2.0",
     "browser-request": "^0.3.3",
+    "content-type": "^1.0.2",
     "q": "^1.4.1",
     "request": "^2.53.0"
   },

spec/integ/matrix-client-methods.spec.js

@@ -49,13 +49,13 @@ describe("MatrixClient", function() {
             httpBackend.when(
                 "POST", "/_matrix/media/v1/upload",
             ).check(function(req) {
-                expect(req.data).toEqual(buf);
+                expect(req.rawData).toEqual(buf);
                 expect(req.queryParams.filename).toEqual("hi.txt");
                 expect(req.queryParams.access_token).toEqual(accessToken);
                 expect(req.headers["Content-Type"]).toEqual("text/plain");
                 expect(req.opts.json).toBeFalsy();
                 expect(req.opts.timeout).toBe(undefined);
-            }).respond(200, "content");
+            }).respond(200, "content", true);
 
             const prom = client.uploadContent({
                 stream: buf,
@@ -86,7 +86,7 @@ describe("MatrixClient", function() {
                 "POST", "/_matrix/media/v1/upload",
             ).check(function(req) {
                 expect(req.opts.json).toBeFalsy();
-            }).respond(200, JSON.stringify({ "content_uri": "uri" }));
+            }).respond(200, { "content_uri": "uri" });
 
             client.uploadContent({
                 stream: buf,
@@ -102,16 +102,15 @@ describe("MatrixClient", function() {
         });
 
         it("should parse errors into a MatrixError", function(done) {
-            // opts.json is false, so request returns unparsed json.
             httpBackend.when(
                 "POST", "/_matrix/media/v1/upload",
             ).check(function(req) {
-                expect(req.data).toEqual(buf);
+                expect(req.rawData).toEqual(buf);
                 expect(req.opts.json).toBeFalsy();
-            }).respond(400, JSON.stringify({
+            }).respond(400, {
                 "errcode": "M_SNAFU",
                 "error": "broken",
-            }));
+            });
 
             client.uploadContent({
                 stream: buf,

spec/mock-request.js

@@ -126,10 +126,15 @@ HttpBackend.prototype = {
                 }
                 testResponse = matchingReq.response;
                 console.log("    responding to %s", matchingReq.path);
+
                 let body = testResponse.body;
                 if (Object.prototype.toString.call(body) == "[object Function]") {
                     body = body(req.path, req.data);
                 }
+
+                if (!testResponse.rawBody) {
+                    body = JSON.stringify(body);
+                }
                 req.callback(
                     testResponse.err, testResponse.response, body,
                 );
@@ -210,17 +215,22 @@ ExpectedRequest.prototype = {
     /**
      * Respond with the given data when this request is satisfied.
      * @param {Number} code The HTTP status code.
-     * @param {Object|Function} data The HTTP JSON body. If this is a function,
+     * @param {Object|Function?} data The response body object. If this is a function,
-     * it will be invoked when the JSON body is required (which should be returned).
+     * it will be invoked when the response body is required (which should be returned).
+     * @param {Boolean} rawBody true if the response should be returned directly rather
+     * than json-stringifying it first.
      */
-    respond: function(code, data) {
+    respond: function(code, data, rawBody) {
         this.response = {
             response: {
                 statusCode: code,
-                headers: {},
+                headers: {
+                    'content-type': 'application/json',
+                },
             },
-            body: data,
+            body: data || "",
             err: null,
+            rawBody: rawBody || false,
         };
     },
 
@@ -265,6 +275,12 @@ function Request(opts, callback) {
     });
 
     Object.defineProperty(this, 'data', {
+        get: function() {
+            return opts.body ? JSON.parse(opts.body) : opts.body;
+        },
+    });
+
+    Object.defineProperty(this, 'rawData', {
         get: function() {
             return opts.body;
         },

src/http-api.js

@@ -19,6 +19,8 @@ limitations under the License.
  * @module http-api
  */
 const q = require("q");
+const parseContentType = require('content-type').parse;
+
 const utils = require("./utils");
 
 // we use our own implementation of setTimeout, so that if we get suspended in
@@ -623,7 +625,31 @@ module.exports.MatrixHttpApi.prototype = {
             }
         }
 
+        const headers = utils.extend({}, opts.headers || {});
         const json = opts.json === undefined ? true : opts.json;
+        let bodyParser = opts.bodyParser;
+
+        // we handle the json encoding/decoding here, because request and
+        // browser-request make a mess of it. Specifically, they attempt to
+        // json-decode plain-text error responses, which in turn means that the
+        // actual error gets swallowed by a SyntaxError.
+
+        if (json) {
+            if (data) {
+                data = JSON.stringify(data);
+                headers['content-type'] = 'application/json';
+            }
+
+            if (!headers['accept']) {
+                headers['accept'] = 'application/json';
+            }
+
+            if (bodyParser === undefined) {
+                bodyParser = function(rawBody) {
+                    return JSON.parse(rawBody);
+                };
+            }
+        }
 
         const defer = q.defer();
 
@@ -662,7 +688,7 @@ module.exports.MatrixHttpApi.prototype = {
                     withCredentials: false,
                     qs: queryParams,
                     body: data,
-                    json: json,
+                    json: false,
                     timeout: localTimeoutMs,
                     headers: opts.headers || {},
                     _matrix_opts: this.opts,
@@ -675,13 +701,9 @@ module.exports.MatrixHttpApi.prototype = {
                         }
                     }
 
-                    // if json is falsy, we won't parse any error response, so need
-                    // to do so before turning it into a MatrixError
-                    const parseErrorJson = !json;
                     const handlerFn = requestCallback(
                         defer, callback, self.opts.onlyData,
-                        parseErrorJson,
+                        bodyParser,
-                        opts.bodyParser,
                     );
                     handlerFn(err, response, body);
                 },
@@ -718,15 +740,18 @@ module.exports.MatrixHttpApi.prototype = {
  * that will either resolve or reject the given defer as well as invoke the
  * given userDefinedCallback (if any).
  *
- * If onlyData is true, the defer/callback is invoked with the body of the
+ * HTTP errors are transformed into javascript errors and the deferred is rejected.
- * response, otherwise the result code.
  *
- * If parseErrorJson is true, we will JSON.parse the body if we get a 4xx error.
+ * If bodyParser is given, it is used to transform the body of the successful
+ * responses before passing to the defer/callback.
+ *
+ * If onlyData is true, the defer/callback is invoked with the body of the
+ * response, otherwise the result object (with `code` and `data` fields)
  *
  */
 const requestCallback = function(
     defer, userDefinedCallback, onlyData,
-    parseErrorJson, bodyParser,
+    bodyParser,
 ) {
     userDefinedCallback = userDefinedCallback || function() {};
 
@@ -734,19 +759,12 @@ const requestCallback = function(
         if (!err) {
             try {
                 if (response.statusCode >= 400) {
-                    if (parseErrorJson) {
+                    err = parseErrorResponse(response, body);
-                        // we won't have json-decoded the response.
-                        body = JSON.parse(body);
-                    }
-                    err = new module.exports.MatrixError(body);
                 } else if (bodyParser) {
                     body = bodyParser(body);
                 }
             } catch (e) {
-                err = e;
+                err = new Error(`Error parsing server response: ${e}`);
-            }
-            if (err) {
-                err.httpStatus = response.statusCode;
             }
         }
 
@@ -756,6 +774,9 @@ const requestCallback = function(
         } else {
             const res = {
                 code: response.statusCode,
+
+                // XXX: why do we bother with this? it doesn't work for
+                // XMLHttpRequest, so clearly we don't use it.
                 headers: response.headers,
                 data: body,
             };
@@ -765,6 +786,67 @@ const requestCallback = function(
     };
 };
 
+/**
+ * Attempt to turn an HTTP error response into a Javascript Error.
+ *
+ * If it is a JSON response, we will parse it into a MatrixError. Otherwise
+ * we return a generic Error.
+ *
+ * @param {XMLHttpRequest|http.IncomingMessage} response response object
+ * @param {String} body raw body of the response
+ * @returns {Error}
+ */
+function parseErrorResponse(response, body) {
+    const httpStatus = response.statusCode;
+    const contentType = getResponseContentType(response);
+
+    let err;
+    if (contentType) {
+        if (contentType.type === 'application/json') {
+            err = new module.exports.MatrixError(JSON.parse(body));
+        } else if (contentType.type === 'text/plain') {
+            err = new Error(`Server returned ${httpStatus} error: ${body}`);
+        }
+    }
+
+    if (!err) {
+        err = new Error(`Server returned ${httpStatus} error`);
+    }
+    err.httpStatus = httpStatus;
+    return err;
+}
+
+
+/**
+ * extract the Content-Type header from the response object, and
+ * parse it to a `{type, parameters}` object.
+ *
+ * returns null if no content-type header could be found.
+ *
+ * @param {XMLHttpRequest|http.IncomingMessage} response response object
+ * @returns {{type: String, parameters: Object}?} parsed content-type header, or null if not found
+ */
+function getResponseContentType(response) {
+    let contentType;
+    if (response.getResponseHeader) {
+        // XMLHttpRequest provides getResponseHeader
+        contentType = response.getResponseHeader("Content-Type");
+    } else if (response.headers) {
+        // request provides http.IncomingMessage which has a message.headers map
+        contentType = response.headers['content-type'] || null;
+    }
+
+    if (!contentType) {
+        return null;
+    }
+
+    try {
+        return parseContentType(contentType);
+    } catch(e) {
+        throw new Error(`Error parsing Content-Type '${contentType}': ${e}`);
+    }
+}
+
 /**
  * Construct a Matrix error. This is a JavaScript Error with additional
  * information specific to the standard Matrix error response.