Support specifying the config location manually (outside of the user's profile)

README.md

@@ -143,6 +143,10 @@ $PROFILE` in which case it becomes `Element-$PROFILE`, or it is using one of
 the above created by a pre-1.7 install, in which case it will be `Riot` or
 `Riot-$PROFILE`.
 
+You may also specify a different path entirely for the `config.json` file by
+providing the `--config $YOUR_CONFIG_JSON_FILE` to the process, or via the
+`ELEMENT_DESKTOP_CONFIG_JSON` environment variable.
+
 # Translations
 
 To add a new translation, head to the [translating doc](https://github.com/vector-im/element-web/blob/develop/docs/translating.md).

playwright/e2e/launch/config-options.spec.ts

@@ -0,0 +1,41 @@
+/*
+Copyright 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { resolve } from "node:path";
+
+import { test, expect } from "../../element-desktop-test";
+
+test.describe("App config options", () => {
+    test.describe("Should load custom config via env", () => {
+        test.slow();
+        test.use({
+            extraEnv: {
+                ELEMENT_DESKTOP_CONFIG_JSON: resolve(__dirname, "../..", "fixtures/custom-config.json"),
+            },
+        });
+        test("should launch and use configured homeserver", async ({ page }) => {
+            await page.locator("#matrixchat").waitFor();
+            await page.locator(".mx_Welcome").waitFor();
+            await expect(page).toHaveURL("vector://vector/webapp/#/welcome");
+            await page.getByText("Sign in").click();
+            await page.getByText("matrix.example.org", { exact: true }).waitFor();
+        });
+    });
+    test.describe("Should load custom config via argument", () => {
+        test.slow();
+        test.use({
+            extraArgs: ["--config", resolve(__dirname, "../..", "fixtures/custom-config.json")],
+        });
+        test("should launch and use configured homeserver", async ({ page }) => {
+            await page.locator("#matrixchat").waitFor();
+            await page.locator(".mx_Welcome").waitFor();
+            await expect(page).toHaveURL("vector://vector/webapp/#/welcome");
+            await page.getByText("Sign in").click();
+            await page.getByText("matrix.example.org", { exact: true }).waitFor();
+        });
+    });
+});

playwright/element-desktop-test.ts

@@ -11,15 +11,24 @@ import fs from "node:fs/promises";
 import path from "node:path";
 import os from "node:os";
 
-export const test = base.extend<{ app: ElectronApplication; tmpDir: string }>({
+interface Fixtures {
+    app: ElectronApplication;
+    tmpDir: string;
+    extraEnv: Record<string, string>;
+    extraArgs: string[];
+}
+
+export const test = base.extend<Fixtures>({
+    extraEnv: {},
+    extraArgs: [],
     // eslint-disable-next-line no-empty-pattern
     tmpDir: async ({}, use) => {
         const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "element-desktop-tests-"));
         console.log("Using temp profile directory: ", tmpDir);
         await use(tmpDir);
         await fs.rm(tmpDir, { recursive: true });
     },
-    app: async ({ tmpDir }, use) => {
+    app: async ({ tmpDir, extraEnv, extraArgs }, use) => {
         const args = ["--profile-dir", tmpDir];
 
         const executablePath = process.env["ELEMENT_DESKTOP_EXECUTABLE"];
@@ -29,9 +38,12 @@ export const test = base.extend<{ app: ElectronApplication; tmpDir: string }>({
         }
 
         const app = await electron.launch({
-            env: process.env,
+            env: {
+                ...process.env,
+                ...extraEnv,
+            },
             executablePath,
-            args,
+            args: [...args, ...extraArgs],
         });
 
         app.process().stdout.pipe(process.stdout);

playwright/fixtures/custom-config.json

@@ -0,0 +1,10 @@
+{
+    "default_server_config": {
+        "m.homeserver": {
+            "base_url": "https://matrix.example.org"
+        },
+        "m.identity_server": {
+            "base_url": "https://identity.example.org"
+        }
+    }
+}

src/electron-main.ts

@@ -44,13 +44,19 @@ if (argv["help"]) {
     console.log("  --profile-dir {path}: Path to where to store the profile.");
     console.log("  --profile {name}:     Name of alternate profile to use, allows for running multiple accounts.");
     console.log("  --devtools:           Install and use react-devtools and react-perf.");
+    console.log(
+        `  --config:             Path to the config.json file. May also be specified via the ELEMENT_DESKTOP_CONFIG_JSON environment variable.\n` +
+            `                         Otherwise use the default user location '${app.getPath("userData")}'`,
+    );
     console.log("  --no-update:          Disable automatic updating.");
     console.log("  --hidden:             Start the application hidden in the system tray.");
     console.log("  --help:               Displays this help message.");
     console.log("And more such as --proxy, see:" + "https://electronjs.org/docs/api/command-line-switches");
     app.exit();
 }
 
+const LocalConfigLocation = process.env.ELEMENT_DESKTOP_CONFIG_JSON ?? argv["config"];
+
 // Electron creates the user data directory (with just an empty 'Dictionaries' directory...)
 // as soon as the app path is set, so pick a random path in it that must exist if it's a
 // real user data directory.
@@ -147,7 +153,9 @@ async function loadConfig(): Promise<void> {
 
     try {
         // Load local config and use it to override values from the one baked with the build
-        const localConfig = loadJsonFile(app.getPath("userData"), "config.json");
+        const localConfig = LocalConfigLocation
+            ? loadJsonFile(LocalConfigLocation)
+            : loadJsonFile(app.getPath("userData"), "config.json");
 
         // If the local config has a homeserver defined, don't use the homeserver from the build
         // config. This is to avoid a problem where Riot thinks there are multiple homeservers