Prefix hashes with underscores based on CSS spec

Author: Alexey Litvinov

.npmignore

@@ -2,5 +2,5 @@
 .gitignore
 .npmignore
 .travis.yml
-test.js
+test
 yarn.lock

package.json

@@ -4,7 +4,7 @@
   "description": "Helper for building generic names, similar to webpack",
   "main": "index.js",
   "scripts": {
-    "test": "tape test.js"
+    "test": "tape test/*.js"
   },
   "repository": {
     "type": "git",

test/cssspec.js

@@ -0,0 +1,45 @@
+'use strict';
+
+const genericNames = require('../index');
+const test = require('tape');
+
+// According to the CSS spec, identifiers cannot
+// start with a digit, two hyphens, or a hyphen
+// followed by a digit.
+//
+// relates: https://github.com/webpack/css-loader/commit/da27c07d0df25a38699344c13b6614c53a469fd9
+
+test('identity', t => {
+  const generate = genericNames('[local]');
+
+  t.equal(generate('foo', '/test/case/source.css'), 'foo');
+  t.end();
+});
+
+test('leading digit', t => {
+  const generate = genericNames('0[local]');
+
+  t.equal(generate('foo', '/test/case/source.css'), '_0foo');
+  t.end();
+});
+
+test('leading digit in the token', t => {
+  const generate = genericNames('[local]');
+
+  t.equal(generate('0foo', '/test/case/source.css'), '_0foo');
+  t.end();
+});
+
+test('leading two hyphens', t => {
+  const generate = genericNames('--[local]');
+
+  t.equal(generate('foo', '/test/case/source.css'), '_--foo');
+  t.end();
+});
+
+test('leading hyphen and digit', t => {
+  const generate = genericNames('-0[local]');
+
+  t.equal(generate('foo', '/test/case/source.css'), '_-0foo');
+  t.end();
+});

test.js renamed to test/index.js

@@ -1,6 +1,6 @@
 'use strict';
 
-const genericNames = require('./index');
+const genericNames = require('../index');
 const test = require('tape');
 
 const pattern = '[name]__[local]___[hash:base64:5]';