[feat] added no-empty-character-class rule (closes #8)

Author: buzinas

README.md

@@ -215,7 +215,7 @@ The following rules point out areas where you might have made mistakes.
     "no-duplicate-case": true
     ```
 
-* [no-empty-character-class](http://eslint.org/docs/rules/no-empty-character-class) => no-empty-character-class (tslint-eslint-rules) [TODO](https://github.com/buzinas/tslint-eslint-rules/issues/8)
+* [no-empty-character-class](http://eslint.org/docs/rules/no-empty-character-class) => no-empty-character-class (tslint-eslint-rules)
   * Description: disallow the use of empty character classes in regular expressions (recommended)
   * Usage
 

eslint_tslint.json

@@ -11,6 +11,7 @@
     "no-unexpected-multiline": true,
     "no-invalid-regexp": true,
     "no-inner-declarations": [true, "both"],
-    "no-regex-spaces": true
+    "no-regex-spaces": true,
+    "no-empty-character-class": true
   }
 }

src/rules/noEmptyCharacterClassRule.ts

@@ -0,0 +1,24 @@
+/// <reference path='helper.d.ts' />
+// import {ts, Lint} from './helper';
+
+export class Rule extends Lint.Rules.AbstractRule {
+  public static FAILURE_STRING = `don't use empty classes in regular expressions`;
+
+  public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+    const walker = new NoEmptyCharacterClassWalker(sourceFile, this.getOptions());
+    return this.applyWithWalker(walker);
+  }
+}
+
+class NoEmptyCharacterClassWalker extends Lint.RuleWalker {
+  protected visitRegularExpressionLiteral(node: ts.LiteralExpression) {
+    this.validateEmptyCharacterClass(node);
+    super.visitRegularExpressionLiteral(node);
+  }
+
+  private validateEmptyCharacterClass(node: ts.LiteralExpression) {
+    if (!(/^\/([^\\[]|\\.|\[([^\\\]]|\\.)+\])*\/[gim]*$/.test(node.getText()))) {
+      this.addFailure(this.createFailure(node.getStart(), node.getWidth(), Rule.FAILURE_STRING));
+    }
+  }
+}

src/test/rules/noEmptyCharacterClassRuleTests.ts

@@ -0,0 +1,37 @@
+/// <reference path='../../../typings/mocha/mocha.d.ts' />
+import {makeTest} from './helper';
+
+const rule = 'no-empty-character-class';
+const scripts = {
+  valid: [
+    'var foo = /^abc[a-zA-Z]/;',
+    'var regExp = new RegExp(\'^abc[]\');',
+    'var foo = /^abc/;',
+    'var foo = /[\\[]/;',
+    'var foo = /[\\]]/;',
+    'var foo = /[a-zA-Z\\[]/;',
+    'var foo = /[[]/;',
+    'var foo = /[\\[a-z[]]/;',
+    'var foo = /[\\-\\[\\]\\/\\{\\}\\(\\)\\*\\+\\?\\.\\\\^\\$\\|]/g;',
+    'var foo = /\\s*:\\s*/gim;'
+  ],
+  invalid: [
+    'var foo = /^abc[]/;',
+    'var foo = /foo[]bar/;',
+    'if (foo.match(/^abc[]/)) {}',
+    'if (/^abc[]/.test(foo)) {}',
+    'var foo = /[]]/;',
+    'var foo = /\\[[]/;',
+    'var foo = /\\[\\[\\]a-z[]/;'
+  ]
+};
+
+describe(rule, function test() {
+  it('should pass when not using empty character classes in regular expressions', function testValid() {
+    makeTest(rule, scripts.valid, true);
+  });
+
+  it('should fail when using empty character classes in regular expressions', function testInvalid() {
+    makeTest(rule, scripts.invalid, false);
+  });
+});