Use esm where possible

It makes the code of CLI utilities simpler. make test still uses
@babel/plugin-transform-modules-commonjs, however, so that fluent-react can
transpile the JSX in tests.

Author: stasm

fluent-syntax/makefile

@@ -25,7 +25,7 @@ compat.js: $(SOURCES)
 
 .PHONY: test-without-babel-polyfill
 test-without-babel-polyfill:
-	@mocha --recursive --ui tdd --require mocha_setup test/**/*_test.js
+	@mocha --recursive --ui tdd --require esm test/**/*_test.js
 
 clean:
 	@rm -f $(PACKAGE).js compat.js

fluent-syntax/mocha_setup.js

@@ -5,10 +5,7 @@
 const fs = require('fs');
 const program = require('commander');
 
-require('@babel/register')({
-  plugins: ['@babel/plugin-transform-modules-commonjs']
-});
-
+require = require('esm')(module);
 const FluentSyntax = require('../../../fluent-syntax/src');
 const parser = new FluentSyntax.FluentParser({
   withSpans: false,

fluent/test/fixtures_behavior/make_fixtures.js

@@ -18,6 +18,7 @@
     "commander": "^2.12",
     "eslint": "^4.18.1",
     "eslint-plugin-mocha": "^4.11.0",
+    "esm": "^3.0.34",
     "fuzzer": "^0.2.1",
     "gh-pages": "^1.1.0",
     "jsdoc": "^3.5.5",

package.json

@@ -5,9 +5,7 @@
 const fs = require('fs');
 const program = require('commander');
 
-require('@babel/register')({
-  plugins: ["@babel/plugin-transform-modules-commonjs"]
-});
+require = require('esm')(module);
 const FluentSyntax = require('../fluent-syntax/src');
 
 program

tools/fluentfmt.js

@@ -8,10 +8,10 @@ const program = require('commander');
 
 require('@babel/register')({
   plugins: [
-    "@babel/plugin-proposal-async-generator-functions",
-    "@babel/plugin-transform-modules-commonjs"
+    '@babel/plugin-proposal-async-generator-functions',
   ]
 });
+require = require('esm')(module);
 require('../fluent-intl-polyfill/src');
 const Fluent = require('../fluent/src');
 

tools/format.js

@@ -7,9 +7,7 @@ const readline = require('readline');
 const program = require('commander');
 const fuzzer = require('fuzzer');
 
-require('@babel/register')({
-  plugins: ["@babel/plugin-transform-modules-commonjs"]
-});
+require = require('esm')(module);
 
 fuzzer.seed(Math.random() * 1000000000);
 

tools/fuzz.js

@@ -5,9 +5,7 @@
 const fs = require('fs');
 const program = require('commander');
 
-require('@babel/register')({
-  plugins: ["@babel/plugin-transform-modules-commonjs"]
-});
+require = require('esm')(module);
 const FluentSyntax = require('../fluent-syntax/src');
 
 program

tools/parse.js

@@ -5,9 +5,7 @@
 const fs = require('fs');
 const program = require('commander');
 
-require('@babel/register')({
-  plugins: ["@babel/plugin-transform-modules-commonjs"]
-});
+require = require('esm')(module);
 const FluentSyntax = require('../fluent-syntax/src');
 
 program