polyfills: bundle our own fetch polyfill

It's vendored and slightly adapted whatwg-fetch to start with.

package.json

@@ -29,7 +29,6 @@
     "urlpattern-polyfill": "^10.0.0",
     "uuid": "10.0.0",
     "web-streams-polyfill": "^4.0.0",
-    "whatwg-fetch": "^3.6.20",
     "whatwg-url": "^14.0.0"
   },
   "devDependencies": {

src/js/polyfills/fetch/body.js

@@ -0,0 +1,195 @@
+function isDataView(obj) {
+    return obj && isPrototypeOf(DataView.prototype, obj);
+}
+
+function consumed(body) {
+    if (body._noBody) {
+        return;
+    }
+
+    if (body.bodyUsed) {
+        return Promise.reject(new TypeError('Already read'));
+    }
+
+    body.bodyUsed = true;
+}
+
+function fileReaderReady(reader) {
+    return new Promise(function(resolve, reject) {
+        reader.onload = function() {
+            resolve(reader.result);
+        };
+
+        reader.onerror = function() {
+            reject(reader.error);
+        };
+    });
+}
+
+function readBlobAsArrayBuffer(blob) {
+    var reader = new FileReader();
+    var promise = fileReaderReady(reader);
+
+    reader.readAsArrayBuffer(blob);
+
+    return promise;
+}
+
+function readBlobAsText(blob) {
+    var reader = new FileReader();
+    var promise = fileReaderReady(reader);
+    var match = /charset=([A-Za-z0-9_-]+)/.exec(blob.type);
+    var encoding = match ? match[1] : 'utf-8';
+
+    reader.readAsText(blob, encoding);
+
+    return promise;
+}
+
+function readArrayBufferAsText(buf) {
+    var view = new Uint8Array(buf);
+    var chars = new Array(view.length);
+
+    for (var i = 0; i < view.length; i++) {
+        chars[i] = String.fromCharCode(view[i]);
+    }
+
+    return chars.join('');
+}
+
+function bufferClone(buf) {
+    if (buf.slice) {
+        return buf.slice(0);
+    } else {
+        const view = new Uint8Array(buf.byteLength);
+
+        view.set(new Uint8Array(buf));
+
+        return view.buffer;
+    }
+}
+
+function isPrototypeOf(a, b) {
+    return Object.prototype.isPrototypeOf.call(a, b);
+}
+
+export const BodyMixin = {
+    bodyUsed: false,
+
+    _initBody(body) {
+        this._bodyInit = body;
+
+        if (!body) {
+            this._noBody = true;
+            this._bodyText = '';
+        } else if (typeof body === 'string') {
+            this._bodyText = body;
+        } else if (isPrototypeOf(Blob.prototype, body)) {
+            this._bodyBlob = body;
+        } else if (isPrototypeOf(FormData.prototype, body)) {
+            this._bodyFormData = body;
+        } else if (isPrototypeOf(URLSearchParams.prototype, body)) {
+            this._bodyText = body.toString();
+        } else if (isDataView(body)) {
+            this._bodyArrayBuffer = bufferClone(body.buffer);
+        } else if (isPrototypeOf(ArrayBuffer.prototype, body) || ArrayBuffer.isView(body)) {
+            this._bodyArrayBuffer = bufferClone(body);
+        } else {
+            this._bodyText = body = Object.prototype.toString.call(body);
+        }
+
+        if (!this.headers.get('content-type')) {
+            if (typeof body === 'string') {
+                this.headers.set('content-type', 'text/plain;charset=UTF-8');
+            } else if (this._bodyBlob && this._bodyBlob.type) {
+                this.headers.set('content-type', this._bodyBlob.type);
+            } else if (isPrototypeOf(URLSearchParams.prototype, body)) {
+                this.headers.set('content-type', 'application/x-www-form-urlencoded;charset=UTF-8');
+            }
+        }
+    },
+
+    blob() {
+        const rejected = consumed(this);
+
+        if (rejected) {
+            return rejected;
+        }
+
+        if (this._bodyBlob) {
+            return Promise.resolve(this._bodyBlob);
+        } else if (this._bodyArrayBuffer) {
+            return Promise.resolve(new Blob([ this._bodyArrayBuffer ]));
+        } else if (this._bodyFormData) {
+            throw new Error('could not read FormData body as blob');
+        } else {
+            return Promise.resolve(new Blob([ this._bodyText ]));
+        }
+    },
+
+    arrayBuffer() {
+        if (this._bodyArrayBuffer) {
+            var isConsumed = consumed(this);
+
+            if (isConsumed) {
+                return isConsumed;
+            } else if (ArrayBuffer.isView(this._bodyArrayBuffer)) {
+                return Promise.resolve(
+                    this._bodyArrayBuffer.buffer.slice(
+                        this._bodyArrayBuffer.byteOffset,
+                        this._bodyArrayBuffer.byteOffset + this._bodyArrayBuffer.byteLength
+                    )
+                );
+            } else {
+                return Promise.resolve(this._bodyArrayBuffer);
+            }
+        } else {
+            return this.blob().then(readBlobAsArrayBuffer);
+        }
+    },
+
+    text() {
+        const rejected = consumed(this);
+
+        if (rejected) {
+            return rejected;
+        }
+
+        if (this._bodyBlob) {
+            return readBlobAsText(this._bodyBlob);
+        } else if (this._bodyArrayBuffer) {
+            return Promise.resolve(readArrayBufferAsText(this._bodyArrayBuffer));
+        } else if (this._bodyFormData) {
+            throw new Error('could not read FormData body as text');
+        } else {
+            return Promise.resolve(this._bodyText);
+        }
+    },
+
+    formData() {
+        return this.text().then(decode);
+    },
+
+    json() {
+        return this.text().then(JSON.parse);
+    },
+};
+
+function decode(body) {
+    const form = new FormData();
+
+    body
+        .trim()
+        .split('&')
+        .forEach(function(bytes) {
+            if (bytes) {
+                const split = bytes.split('=');
+                const name = split.shift().replace(/\+/g, ' ');
+                const value = split.join('=').replace(/\+/g, ' ');
+
+                form.append(decodeURIComponent(name), decodeURIComponent(value));
+            }
+        });
+
+    return form;
+}

src/js/polyfills/fetch/fetch.js

@@ -0,0 +1,120 @@
+import { Headers, normalizeName, normalizeValue } from './headers.js';
+import { Request } from './request.js';
+
+
+export function fetch(input, init) {
+    return new Promise(function(resolve, reject) {
+        const request = new Request(input, init);
+
+        if (request.signal && request.signal.aborted) {
+            return reject(new DOMException('Aborted', 'AbortError'));
+        }
+
+        const xhr = new XMLHttpRequest();
+
+        function abortXhr() {
+            xhr.abort();
+        }
+
+        xhr.onload = function() {
+            const options = {
+                statusText: xhr.statusText,
+                headers: parseHeaders(xhr.getAllResponseHeaders() || ''),
+                status: xhr.status,
+                url: xhr.responseURL
+            };
+            const body = xhr.response;
+
+            setTimeout(function() {
+                resolve(new Response(body, options));
+            }, 0);
+        };
+
+        xhr.onerror = function() {
+            setTimeout(function() {
+                reject(new TypeError('Network request failed'));
+            }, 0);
+        };
+
+        xhr.ontimeout = function() {
+            setTimeout(function() {
+                reject(new TypeError('Network request timed out'));
+            }, 0);
+        };
+
+        xhr.onabort = function() {
+            setTimeout(function() {
+                reject(new DOMException('Aborted', 'AbortError'));
+            }, 0);
+        };
+
+        xhr.open(request.method, request.url, true);
+
+        if (request.credentials === 'include') {
+            xhr.withCredentials = true;
+        } else if (request.credentials === 'omit') {
+            xhr.withCredentials = false;
+        }
+
+        // TODO: better use Blob, if / when we support that.
+        xhr.responseType = 'arraybuffer';
+
+        if (init && typeof init.headers === 'object' && !(init.headers instanceof Headers)) {
+            const names = [];
+
+            Object.getOwnPropertyNames(init.headers).forEach(function(name) {
+                names.push(normalizeName(name));
+                xhr.setRequestHeader(name, normalizeValue(init.headers[name]));
+            });
+            request.headers.forEach(function(value, name) {
+                if (names.indexOf(name) === -1) {
+                    xhr.setRequestHeader(name, value);
+                }
+            });
+        } else {
+            request.headers.forEach(function(value, name) {
+                xhr.setRequestHeader(name, value);
+            });
+        }
+
+        if (request.signal) {
+            request.signal.addEventListener('abort', abortXhr);
+
+            xhr.onreadystatechange = function() {
+                // DONE (success or failure)
+                if (xhr.readyState === xhr.DONE) {
+                    request.signal.removeEventListener('abort', abortXhr);
+                }
+            };
+        }
+
+        // TODO: why not use the .body property?
+        xhr.send(typeof request._bodyInit === 'undefined' ? null : request._bodyInit);
+    });
+}
+
+
+function parseHeaders(rawHeaders) {
+    const headers = new Headers();
+
+    // Replace instances of \r\n and \n followed by at least one space or horizontal tab with a space
+    // https://tools.ietf.org/html/rfc7230#section-3.2
+    const preProcessedHeaders = rawHeaders.replace(/\r?\n[\t ]+/g, ' ');
+
+    preProcessedHeaders.split(/\r?\n/).forEach(line => {
+        const parts = line.split(':');
+        const key = parts.shift().trim();
+
+        if (key) {
+            const value = parts.join(':').trim();
+
+            try {
+                headers.append(key, value);
+            } catch (error) {
+                console.warn('Response ' + error.message);
+            }
+        }
+    });
+
+    return headers;
+}