Use & enforce snake_case naming convention on config.json settings (#8062)

* Document and support the established naming convention for config opts

This change:
* Rename `ConfigOptions` to `IConfigOptions` to match code convention/style, plus move it to a dedicated file
* Update comments and surrounding documentation
* Define every single documented option (from element-web's config.md)
* Enable a linter to enforce the convention
* Invent a translation layer for a different change to use
* No attempt to fix build errors from doing this (at this stage)

* Add demo of lint rule in action

* Fix all obvious instances of SdkConfig case conflicts

* Fix tests to use SdkConfig directly

* Add docs to make unset() calling safer

* Appease the linter

* Update documentation to match snake_case_config

* Fix more instances of square brackets off SdkConfig

src/utils/AutoDiscoveryUtils.tsx

@@ -207,7 +207,7 @@ export default class AutoDiscoveryUtils {
         const hsResult = discoveryResult['m.homeserver'];
         const isResult = discoveryResult['m.identity_server'];
 
-        const defaultConfig = SdkConfig.get()["validated_server_config"];
+        const defaultConfig = SdkConfig.get("validated_server_config");
 
         // Validate the identity server first because an invalid identity server causes
         // an invalid homeserver, which may not be picked up correctly.

src/utils/IdentityServerUtils.ts

@@ -21,7 +21,7 @@ import SdkConfig from '../SdkConfig';
 import { MatrixClientPeg } from '../MatrixClientPeg';
 
 export function getDefaultIdentityServerUrl(): string {
-    return SdkConfig.get()['validated_server_config']['isUrl'];
+    return SdkConfig.get("validated_server_config").isUrl;
 }
 
 export function useDefaultIdentityServer(): void {

src/utils/SnakedObject.ts

@@ -0,0 +1,36 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export function snakeToCamel(s: string): string {
+    return s.replace(/._./g, v => `${v[0]}${v[2].toUpperCase()}`);
+}
+
+export class SnakedObject<T = Record<string, any>> {
+    public constructor(private obj: T) {
+    }
+
+    public get<K extends string & keyof T>(key: K, altCaseName?: string): T[K] {
+        const val = this.obj[key];
+        if (val !== undefined) return val;
+
+        return this.obj[altCaseName ?? snakeToCamel(key)];
+    }
+
+    // Make JSON.stringify() pretend that everything is fine
+    public toJSON() {
+        return this.obj;
+    }
+}

src/utils/pages.ts

@@ -14,23 +14,37 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { ConfigOptions } from "../SdkConfig";
+import { logger } from "matrix-js-sdk/src/logger";
 
-export function getHomePageUrl(appConfig: ConfigOptions): string | null {
-    const pagesConfig = appConfig.embeddedPages;
-    let pageUrl = pagesConfig?.homeUrl;
+import { IConfigOptions } from "../IConfigOptions";
+import { SnakedObject } from "./SnakedObject";
+
+export function getHomePageUrl(appConfig: IConfigOptions): string | null {
+    const config = new SnakedObject(appConfig);
+
+    const pagesConfig = config.get("embedded_pages");
+    let pageUrl = pagesConfig ? (new SnakedObject(pagesConfig).get("home_url")) : null;
 
     if (!pageUrl) {
         // This is a deprecated config option for the home page
         // (despite the name, given we also now have a welcome
         // page, which is not the same).
-        pageUrl = appConfig.welcomePageUrl;
+        pageUrl = (<any>appConfig).welcomePageUrl;
+        if (pageUrl) {
+            logger.warn(
+                "You are using a deprecated config option: `welcomePageUrl`. Please use " +
+                "`embedded_pages.home_url` instead, per https://github.com/vector-im/element-web/issues/21428",
+            );
+        }
     }
 
     return pageUrl;
 }
 
-export function shouldUseLoginForWelcome(appConfig: ConfigOptions): boolean {
-    const pagesConfig = appConfig.embeddedPages;
-    return pagesConfig?.loginForWelcome === true;
+export function shouldUseLoginForWelcome(appConfig: IConfigOptions): boolean {
+    const config = new SnakedObject(appConfig);
+    const pagesConfig = config.get("embedded_pages");
+    return pagesConfig
+        ? ((new SnakedObject(pagesConfig).get("login_for_welcome")) === true)
+        : false;
 }

src/utils/permalinks/Permalinks.ts

@@ -413,7 +413,7 @@ export function getPrimaryPermalinkEntity(permalink: string): string {
 }
 
 function getPermalinkConstructor(): PermalinkConstructor {
-    const elementPrefix = SdkConfig.get()['permalinkPrefix'];
+    const elementPrefix = SdkConfig.get("permalink_prefix");
     if (elementPrefix && elementPrefix !== matrixtoBaseUrl) {
         return new ElementPermalinkConstructor(elementPrefix);
     }
@@ -423,7 +423,7 @@ function getPermalinkConstructor(): PermalinkConstructor {
 
 export function parsePermalink(fullUrl: string): PermalinkParts {
     try {
-        const elementPrefix = SdkConfig.get()['permalinkPrefix'];
+        const elementPrefix = SdkConfig.get("permalink_prefix");
         if (decodeURIComponent(fullUrl).startsWith(matrixtoBaseUrl)) {
             return new MatrixToPermalinkConstructor().parsePermalink(decodeURIComponent(fullUrl));
         } else if (fullUrl.startsWith("matrix:")) {

src/utils/presence.ts

@@ -19,7 +19,7 @@ import SdkConfig from "../SdkConfig";
 
 export function isPresenceEnabled() {
     const hsUrl = MatrixClientPeg.get().baseUrl;
-    const urls = SdkConfig.get()['enable_presence_by_hs_url'];
+    const urls = SdkConfig.get("enable_presence_by_hs_url");
     if (!urls) return true;
     if (urls[hsUrl] || urls[hsUrl] === undefined) return true;
     return false;