Separate script to rebuild msg/json/en.json, qqq.json etc.

There are some files in msg/json/ (currently en.json, qqq.json,
constants.json and synonyms.json) that are generated by
scripts/i18n/js_to_json.py as part of the language file build process
- but this only needs to be done when messages.js is updated and
and usually requires some manual cleanup, so remove this step from the
existing buildLangfiles gulp script and create a separate command
('npm run generate:langfiles') to do this when required.

gulpfile.js

@@ -23,6 +23,7 @@ var cleanupTasks = require('./scripts/gulpfiles/cleanup_tasks');
 module.exports = {
   deployDemos: appengineTasks.deployDemos,
   default: buildTasks.build,
+  generateLangfiles: buildTasks.generateLangfiles,
   build: buildTasks.build,
   buildCore: buildTasks.core,
   buildBlocks: buildTasks.blocks,

msg/messages.js

@@ -8,13 +8,15 @@
  * @fileoverview English strings.
  * @author fraser@google.com (Neil Fraser)
  *
- * After modifying this file, either run "build.py" from the parent directory,
+ * After modifying this file, run:
- * or run (from this directory):
+ *
- * ../scripts/i18n/js_to_json.py
+ *     npm run generate:langfiles
- * to regenerate json/{en,qqq,synonyms}.json.
+ *
+ * to regenerate json/{en,qqq,constants,synonyms}.json.
  *
  * To convert all of the json files to .js files, run:
- * ../scripts/i18n/create_messages.py json/*.json
+ *
+ *     npm run build:langfiles
  */
 'use strict';
 

package.json

@@ -32,6 +32,7 @@
     "deployDemos": "gulp deployDemos",
     "format": "git-clang-format",
     "format:sortrequires": "gulp sortRequires",
+    "generate:langfiles": "gulp generateLangfiles",
     "license": "gulp checkLicenses",
     "lint": "eslint .",
     "package": "gulp package",

scripts/gulpfiles/build_tasks.js

@@ -408,18 +408,41 @@ goog.require('Blockly.requires');
   });
 };
 
+/**
+ * This task regenrates msg/json/en.js and msg/json/qqq.js from
+ * msg/messages.js.
+ */
+function generateLangfiles(done) {
+  // Run js_to_json.py
+  const jsToJsonCmd = `python scripts/i18n/js_to_json.py \
+      --input_file ${path.join('msg', 'messages.js')} \
+      --output_dir ${path.join('msg', 'json')} \
+      --quiet`;
+  execSync(jsToJsonCmd, { stdio: 'inherit' });
+
+  console.log(`
+Regenerated several flies in msg/json/.  Now run
+
+    git diff msg/json/*.json
+
+and check that operation has not overwritten any modifications made to
+hints, etc. by the TranslateWiki volunteers.  If it has, backport
+their changes to msg/messages.js and re-run 'npm run generate:langfiles'.
+
+Once you are satisfied that any new hints have been backported you may
+go ahead and commit the changes, but note that the generate script
+will have removed the translator credits - be careful not to commit
+this removal!
+`);
+
+  done();
+};
+
 /**
  * This task builds Blockly's lang files.
  *     msg/*.js
  */
 function buildLangfiles(done) {
-  // Run js_to_json.py
-  const jsToJsonCmd = `python ./scripts/i18n/js_to_json.py \
---input_file ${path.join('msg', 'messages.js')} \
---output_dir ${path.join('msg', 'json')} \
---quiet`;
-  execSync(jsToJsonCmd, { stdio: 'inherit' });
-
   // Run create_messages.py
   let json_files = fs.readdirSync(path.join('msg', 'json'));
   json_files = json_files.filter(file => file.endsWith('json') &&
@@ -514,6 +537,7 @@ module.exports = {
   build: build,
   core: buildCore,
   blocks: buildBlocks,
+  generateLangfiles: generateLangfiles,
   langfiles: buildLangfiles,
   uncompressed: buildUncompressed,
   compressed: buildCompressed,