Add platform-specific build type manifest modifications (#12638)

The build system now supports platform-specific modifications to the
manifest for each build type. The need to customize the `id` on Firefox
motivated this change.

To support this, a new directory was made in each build type directory
for manifest changes. The images currently in this directory were moved
into an `images` subdirectory.

This new `manifest` directory can include each manifest file currently
in `app/manifest`. The `_base.json` file is assumed to exist, but the
platform manifest modifications are optional.

app/build-types/beta/manifest/firefox.json

@@ -0,0 +1,7 @@
+{
+  "applications": {
+    "gecko": {
+      "id": "webextension-beta@metamask.io"
+    }
+  }
+}

app/build-types/flask/manifest/firefox.json

@@ -0,0 +1,7 @@
+{
+  "applications": {
+    "gecko": {
+      "id": "webextension-flask@metamask.io"
+    }
+  }
+}

development/build/manifest.js

@@ -3,8 +3,6 @@ const path = require('path');
 const { merge, cloneDeep } = require('lodash');
 
 const baseManifest = require('../../app/manifest/_base.json');
-const betaManifestModifications = require('../../app/manifest/_beta_modifications.json');
-const flaskManifestModifications = require('../../app/manifest/_flask_modifications.json');
 
 const { createTask, composeSeries } = require('./task');
 const { BuildType } = require('./utils');
@@ -34,7 +32,7 @@ function createManifestTasks({
           cloneDeep(baseManifest),
           platformModifications,
           browserVersionMap[platform],
-          getBuildModifications(buildType),
+          await getBuildModifications(buildType, platform),
         );
         const dir = path.join('.', 'dist', platform);
         await fs.mkdir(dir, { recursive: true });
@@ -113,12 +111,53 @@ async function writeJson(obj, file) {
   return fs.writeFile(file, JSON.stringify(obj, null, 2));
 }
 
-function getBuildModifications(buildType) {
-  const buildModifications = {};
-  if (buildType === BuildType.beta) {
-    Object.assign(buildModifications, betaManifestModifications);
-  } else if (buildType === BuildType.flask) {
-    Object.assign(buildModifications, flaskManifestModifications);
+/**
+ * Get manifest modifications for the given build type, including modifications specific to the
+ * given platform.
+ *
+ * @param {BuildType} buildType - The build type.
+ * @param {string} platform - The platform (i.e. the browser).
+ * @returns {Object} The build modificantions for the given build type and platform.
+ */
+async function getBuildModifications(buildType, platform) {
+  if (!Object.values(BuildType).includes(buildType)) {
+    throw new Error(`Invalid build type: ${buildType}`);
+  } else if (buildType === BuildType.main) {
+    return {};
   }
+
+  const builtTypeManifestDirectoryPath = path.resolve(
+    __dirname,
+    '..',
+    '..',
+    'app',
+    'build-types',
+    buildType,
+    'manifest',
+  );
+
+  const baseBuildTypeModificationsPath = path.join(
+    builtTypeManifestDirectoryPath,
+    '_base.json',
+  );
+  const buildModifications = await readJson(baseBuildTypeModificationsPath);
+
+  const platformBuildTypeModificationsPath = path.join(
+    builtTypeManifestDirectoryPath,
+    `${platform}.json`,
+  );
+  try {
+    const platformBuildTypeModifications = await readJson(
+      platformBuildTypeModificationsPath,
+    );
+    Object.assign(buildModifications, platformBuildTypeModifications);
+  } catch (error) {
+    // Suppress 'ENOENT' error because it indicates there are no platform-specific manifest
+    // modifications for this build type.
+    if (error.code !== 'ENOENT') {
+      throw error;
+    }
+  }
+
   return buildModifications;
 }

development/build/static.js

@@ -23,13 +23,13 @@ module.exports = function createStaticAssetTasks({
   const additionalBuildTargets = {
     [BuildType.beta]: [
       {
-        src: './app/build-types/beta/',
+        src: './app/build-types/beta/images/',
         dest: `images`,
       },
     ],
     [BuildType.flask]: [
       {
-        src: './app/build-types/flask/',
+        src: './app/build-types/flask/images/',
         dest: `images`,
       },
     ],

ui/helpers/utils/build-types.js

@@ -1,8 +1,8 @@
 ///: BEGIN:ONLY_INCLUDE_IN(beta)
-import betaJson from '../../../app/build-types/beta/beta-mascot.json';
+import betaJson from '../../../app/build-types/beta/images/beta-mascot.json';
 ///: END:ONLY_INCLUDE_IN
 ///: BEGIN:ONLY_INCLUDE_IN(flask)
-import flaskJson from '../../../app/build-types/flask/flask-mascot.json';
+import flaskJson from '../../../app/build-types/flask/images/flask-mascot.json';
 ///: END:ONLY_INCLUDE_IN
 
 const assetList = {