Add API to clear local cache

README.md

@@ -38,10 +38,18 @@ start
   = grammar
 ```
 
-When you ```@import``` another grammar, that grammar's topmost rule becomes accessible in the context of the current grammar under one of two possible rule names: 
+When you ```@import``` another grammar, that grammar's topmost rule becomes accessible in the context of the current grammar under one of two possible rule names:
    - A name you provide explicitly through the use of the optional "as" parameter
    - The basename of the file, corrected to be a valid Javascript identifier (so if the file were called /foo/bar/my-grammar.peg, the rule name would be my_grammar).
 
+pegjs-import will cache rules it has parsed.  You can clear this local cache by calling `clearCache`:
+```javascript
+  var pegimport = require('pegjs-import');
+
+  pegimport.clearCache();
+```
+
+
 ## Changes from stock PEG.js behavior
 
 * You cannot supply ```options.allowedStartRules``` anymore. The only allowed start rule is always the first rule in the grammar.

index.js

@@ -102,4 +102,9 @@ function buildParser(filename, options) {
   return newParser;
 
 };
-module.exports = { buildParser: buildParser };
+
+function clearCache() {
+  parsers = {};
+}
+
+module.exports = { buildParser: buildParser, clearCache: clearCache };

package.json

@@ -19,7 +19,8 @@
   },
   "devDependencies": {
     "chai": "^1.9.2",
-    "mocha": "^1.21.5"
+    "mocha": "^1.21.5",
+    "mock-fs": "^3.8.0"
   },
   "author": "Harry Schmidt",
   "license": "MIT",

test/spec/core.js

@@ -1,8 +1,9 @@
-
 'use strict';
 
 var pegimport = require('../../index'),
-  peg = require('pegjs');
+  peg = require('pegjs'),
+  path = require('path'),
+  mockFs = require('mock-fs');
 
 describe('peg-import', function() {
 
@@ -66,4 +67,43 @@ describe('peg-import', function() {
 
   });
 
+  describe('caching', function() {
+    var absoluteFilename = path.resolve('test/fixtures/import.peg')
+
+    afterEach(function() {
+      mockFs.restore();
+    });
+
+    function enableMock() {
+      var stubbedFixture = 'start = a:.* { return "abc" }';
+
+      mockFs({
+        'test/fixtures': {
+          'import.peg': stubbedFixture
+        }
+      });
+    }
+
+    function result() {
+      return pegimport.buildParser(absoluteFilename).parse('123');
+    }
+
+    it('works with absolute filenames', function() {
+      expect(result()).to.deep.equal(['1', '2', '3']);
+
+      enableMock();
+
+      expect(result()).to.not.equal('abc');
+    });
+
+    it('can be cleared', function() {
+      expect(result()).to.deep.equal(['1', '2', '3']);
+
+      enableMock();
+      pegimport.clearCache();
+
+      expect(result()).to.equal('abc');
+    });
+
+  });
 });