fix: Permit single-line JSON comments (#1361)

Strip comments from _locales/*/messages.json.

And set an explicit encoding in readFile so that the return value is a
string instead of a Buffer.

src/cmd/build.js

@@ -4,6 +4,7 @@ import {createWriteStream} from 'fs';
 
 import {fs} from 'mz';
 import parseJSON from 'parse-json';
+import stripJsonComments from 'strip-json-comments';
 import defaultEventToPromise from 'event-to-promise';
 
 import defaultSourceWatcher from '../watcher';
@@ -71,14 +72,14 @@ export async function getDefaultLocalizedName(
   let extensionName: string = manifestData.name;
 
   try {
-    messageContents = await fs.readFile(messageFile);
+    messageContents = await fs.readFile(messageFile, {encoding: 'utf-8'});
   } catch (error) {
     throw new UsageError(
       `Error reading messages.json file at ${messageFile}: ${error}`);
   }
 
   try {
-    messageData = parseJSON(String(messageContents), messageFile);
+    messageData = parseJSON(stripJsonComments(messageContents), messageFile);
   } catch (error) {
     throw new UsageError(
       `Error parsing messages.json ${error}`);

src/util/manifest.js

@@ -38,7 +38,7 @@ export default async function getValidatedManifest(
   let manifestContents;
 
   try {
-    manifestContents = await fs.readFile(manifestFile);
+    manifestContents = await fs.readFile(manifestFile, {encoding: 'utf-8'});
   } catch (error) {
     throw new InvalidManifest(
       `Could not read manifest.json file at ${manifestFile}: ${error}`);
@@ -47,8 +47,7 @@ export default async function getValidatedManifest(
   let manifestData;
 
   try {
-    manifestData = parseJSON(stripJsonComments(manifestContents.toString()),
-                             manifestFile);
+    manifestData = parseJSON(stripJsonComments(manifestContents), manifestFile);
   } catch (error) {
     throw new InvalidManifest(
       `Error parsing manifest.json at ${manifestFile}: ${error}`);

tests/unit/test-cmd/test.build.js

@@ -116,6 +116,33 @@ describe('build', () => {
     );
   });
 
+  it('handles comments in messages.json', () => {
+    return withTempDir(
+      (tmpDir) => {
+        const messageFileName = path.join(tmpDir.path(), 'messages.json');
+        fs.writeFileSync(
+          messageFileName,
+          `{"extensionName": {
+              "message": "example extension", // comments
+              "description": "example with comments"
+            }
+          }`
+        );
+
+        return getDefaultLocalizedName({
+          messageFile: messageFileName,
+          manifestData: {
+            name: '__MSG_extensionName__',
+            version: '0.0.1',
+          },
+        })
+          .then((result) => {
+            assert.match(result, /example extension/);
+          });
+      }
+    );
+  });
+
   it('checks locale file for malformed json', () => {
     return withTempDir(
       (tmpDir) => {