Bring back m.request - it's too useful.

It mostly delegates to `fetch`.

Also, kill `m.withProgress` as that only existed because there was no `m.request`.

src/entry/mithril.esm.js

@@ -4,16 +4,16 @@ import {debouncer, throttler} from "../std/rate-limit.js"
 import {link, route} from "../std/router.js"
 import {match, p, query} from "../std/path-query.js"
 import {tracked, trackedList} from "../std/tracked.js"
+import fetch from "../std/fetch.js"
 import init from "../std/init.js"
 import lazy from "../std/lazy.js"
-import withProgress from "../std/with-progress.js"
 
 m.route = route
 m.link = link
 m.p = p
 m.query = query
 m.match = match
-m.withProgress = withProgress
+m.fetch = fetch
 m.lazy = lazy
 m.init = init
 m.tracked = tracked

src/std/fetch.js

@@ -0,0 +1,71 @@
+/* global fetch */
+
+import {checkCallback} from "../util.js"
+
+var mfetch = async (url, opts = {}) => {
+	checkCallback(opts.onprogress, true, "opts.onprogress")
+	checkCallback(opts.extract, true, "opts.extract")
+
+	try {
+		var response = await fetch(url, opts)
+
+		if (opts.onprogress && response.body) {
+			var reader = response.body.getReader()
+			var rawLength = response.headers.get("content-length") || ""
+			// This is explicit coercion, but ESLint is frequently too dumb to detect it correctly.
+			// Another example: https://github.com/eslint/eslint/issues/14623
+			// eslint-disable-next-line no-implicit-coercion
+			var total = (/^\d+$/).test(rawLength) ? +rawLength : -1
+			var current = 0
+
+			response = new Response(new ReadableStream({
+				type: "bytes",
+				start: (ctrl) => reader || ctrl.close(),
+				cancel: (reason) => reader.cancel(reason),
+				async pull(ctrl) {
+					var result = await reader.read()
+					if (result.done) {
+						ctrl.close()
+					} else {
+						current += result.value.length
+						ctrl.enqueue(result.value)
+						opts.onprogress(current, total)
+					}
+				},
+			}), response)
+		}
+
+		if (response.ok) {
+			if (opts.extract) {
+				return await opts.extract(response)
+			}
+
+			switch (opts.responseType || "json") {
+				case "json": return await response.json()
+				case "formdata": return await response.formData()
+				case "arraybuffer": return await response.arrayBuffer()
+				case "blob": return await response.blob()
+				case "text": return await response.text()
+				case "document":
+					// eslint-disable-next-line no-undef
+					return new DOMParser()
+						.parseFromString(await response.text(), response.headers.get("content-type") || "text/html")
+				default:
+					throw new TypeError(`Unknown response type: ${opts.responseType}`)
+			}
+		}
+
+		var message = (await response.text()) || response.statusText
+	} catch (e) {
+		var cause = e
+		var message = e.message
+	}
+
+	var e = new Error(message)
+	e.status = response ? response.status : 0
+	e.response = response
+	e.cause = cause
+	throw e
+}
+
+export {mfetch as default}