Remove code which loads legacy libolm

Now that we use the Rust crypto stack
(https://github.com/matrix-org/matrix-react-sdk/pull/12630), the legacy olm
library is unneeded. Remove all the dedicated cruft for loading it.

(All this crap is why matrix-sdk-crypto-wasm has to base64 its wasm artifact,
cf https://github.com/matrix-org/matrix-rust-sdk/pull/1167.)

src/vector/index.ts

@@ -105,7 +105,6 @@ async function start(): Promise<void> {
         rageshakePromise,
         setupLogStorage,
         preparePlatform,
-        loadOlm,
         loadConfig,
         loadLanguage,
         loadTheme,
@@ -143,7 +142,6 @@ async function start(): Promise<void> {
             }
         }
 
-        const loadOlmPromise = loadOlm();
         // set the platform for react sdk
         preparePlatform();
         // load config requires the platform to be ready
@@ -210,7 +208,6 @@ async function start(): Promise<void> {
         // app load critical path starts here
         // assert things started successfully
         // ##################################
-        await loadOlmPromise;
         await loadModulesPromise;
         await loadThemePromise;
         await loadLanguagePromise;

src/vector/init.tsx

@@ -17,10 +17,6 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-// eslint-disable-next-line @typescript-eslint/ban-ts-comment
-// @ts-ignore
-import olmWasmPath from "@matrix-org/olm/olm.wasm";
-import Olm from "@matrix-org/olm";
 import * as ReactDOM from "react-dom";
 import * as React from "react";
 import * as languageHandler from "matrix-react-sdk/src/languageHandler";
@@ -76,48 +72,6 @@ export async function loadConfig(): Promise<void> {
     }
 }
 
-export function loadOlm(): Promise<void> {
-    /* Load Olm. We try the WebAssembly version first, and then the legacy,
-     * asm.js version if that fails. For this reason we need to wait for this
-     * to finish before continuing to load the rest of the app. In future
-     * we could somehow pass a promise down to react-sdk and have it wait on
-     * that so olm can be loading in parallel with the rest of the app.
-     *
-     * We also need to tell the Olm js to look for its wasm file at the same
-     * level as index.html. It really should be in the same place as the js,
-     * ie. in the bundle directory, but as far as I can tell this is
-     * completely impossible with webpack. We do, however, use a hashed
-     * filename to avoid caching issues.
-     */
-    return Olm.init({
-        locateFile: () => olmWasmPath,
-    })
-        .then(() => {
-            logger.log("Using WebAssembly Olm");
-        })
-        .catch((wasmLoadError) => {
-            logger.log("Failed to load Olm: trying legacy version", wasmLoadError);
-            return new Promise((resolve, reject) => {
-                const s = document.createElement("script");
-                s.src = "olm_legacy.js"; // XXX: This should be cache-busted too
-                s.onload = resolve;
-                s.onerror = reject;
-                document.body.appendChild(s);
-            })
-                .then(() => {
-                    // Init window.Olm, ie. the one just loaded by the script tag,
-                    // not 'Olm' which is still the failed wasm version.
-                    return window.Olm.init();
-                })
-                .then(() => {
-                    logger.log("Using legacy Olm");
-                })
-                .catch((legacyLoadError) => {
-                    logger.log("Both WebAssembly and asm.js Olm failed!", legacyLoadError);
-                });
-        });
-}
-
 export async function loadLanguage(): Promise<void> {
     const prefLang = SettingsStore.getValue("language", null, /*excludeDefault=*/ true);
     let langs: string[] = [];

webpack.config.js

@@ -274,10 +274,6 @@ module.exports = (env, argv) => {
                 // there is no need for webpack to parse them - they can just be
                 // included as-is.
                 /highlight\.js[\\/]lib[\\/]languages/,
-
-                // olm takes ages for webpack to process, and it's already heavily
-                // optimised, so there is little to gain by us uglifying it.
-                /olm[\\/](javascript[\\/])?olm\.js$/,
             ],
             rules: [
                 useHMR && {
@@ -443,20 +439,6 @@ module.exports = (env, argv) => {
                         },
                     ],
                 },
-                {
-                    // the olm library wants to load its own wasm, rather than have webpack do it.
-                    // We therefore use the `file-loader` to tell webpack to dump the contents to
-                    // a separate file and return the name, and override the default `type` for `.wasm` files
-                    // (which is `webassembly/experimental` under webpack 4) to stop webpack trying to interpret
-                    // the filename as webassembly. (see also https://github.com/webpack/webpack/issues/6725)
-                    test: /olm\.wasm$/,
-                    loader: "file-loader",
-                    type: "javascript/auto",
-                    options: {
-                        name: "[name].[hash:7].[ext]",
-                        outputPath: ".",
-                    },
-                },
                 {
                     // Fix up the name of the opus-recorder worker (react-sdk dependency).
                     // We more or less just want it to be clear it's for opus and not something else.
@@ -498,8 +480,11 @@ module.exports = (env, argv) => {
                     },
                 },
                 {
-                    // Same deal as olm.wasm: the decoderWorker wants to load the wasm artifact
+                    // The decoderWorker wants to load its own wasm, rather than have webpack do it.
-                    // itself.
+                    // We therefore use the `file-loader` to tell webpack to dump the contents to
+                    // a separate file and return the name, and override the default `type` for `.wasm` files
+                    // (which is `webassembly/experimental` under webpack 4) to stop webpack trying to interpret
+                    // the filename as webassembly. (see also https://github.com/webpack/webpack/issues/6725)
                     test: /decoderWorker\.min\.wasm$/,
                     loader: "file-loader",
                     type: "javascript/auto",
@@ -750,7 +735,6 @@ module.exports = (env, argv) => {
                     { from: "vector-icons/**", context: path.resolve(__dirname, "res") },
                     { from: "decoder-ring/**", context: path.resolve(__dirname, "res") },
                     { from: "media/**", context: path.resolve(__dirname, "node_modules/matrix-react-sdk/res/") },
-                    "node_modules/@matrix-org/olm/olm_legacy.js",
                     { from: "config.json", noErrorOnMissing: true },
                     "contribute.json",
                 ],