New rule: require-imports-alphabetized

Requires imports to be alphabetised

Fixes #2049
Closes gh-2091

lib/config/configuration.js

@@ -956,6 +956,7 @@ Configuration.prototype.registerDefaultRules = function() {
     this.registerRule(require('../rules/require-enhanced-object-literals'));
     this.registerRule(require('../rules/require-array-destructuring'));
     this.registerRule(require('../rules/disallow-var'));
+    this.registerRule(require('../rules/require-imports-alphabetized'));
     /* ES6 only (end) */
 
     this.registerRule(require('../rules/require-curly-braces'));

lib/rules/require-imports-alphabetized.js

@@ -0,0 +1,94 @@
+/**
+ * Requires imports to be alphabetised
+ *
+ * Types: `Boolean`
+ *
+ * Values: `true` to require imports to be ordered (A-Z)
+ *
+ * #### Example
+ *
+ * ```js
+ * "requireImportAlphabetized": true
+ * ```
+ *
+ * ##### Valid
+ *
+ * ```js
+ * import a from 'a';
+ * import c from 'c';
+ * import z from 'z';
+ * ```
+ *
+ * ##### Invalid
+ *
+ * ```js
+ * import a from 'a';
+ * import z from 'z';
+ * import c from 'c';
+ * ```
+ */
+
+var assert = require('assert');
+
+module.exports = function() {
+};
+
+module.exports.prototype = {
+
+    configure: function(option) {
+        assert(
+            option === true,
+            this.getOptionName() + ' option requires true value'
+        );
+    },
+
+    getOptionName: function() {
+        return 'requireImportAlphabetized';
+    },
+
+    check: function(file, errors) {
+
+        var previous;
+        var current;
+
+        var createSpecHash = function(specifier) {
+
+            var imported = '';
+            var local = '';
+
+            if (specifier.imported && specifier.imported.name) {
+                imported = specifier.imported.name;
+            }
+
+            if (specifier.local && specifier.local.name) {
+                local = specifier.local.name;
+            }
+
+            return imported === local ? imported : imported + local;
+
+        };
+
+        file.iterateNodesByType(
+            'ImportDeclaration',
+            function(node) {
+
+                current = '';
+
+                for (var i = 0; i < node.specifiers.length; i++) {
+                    current += createSpecHash(node.specifiers[i]);
+                }
+
+                if (node.source && node.source.value) {
+                    current += node.source.value;
+                }
+
+                if (previous && previous > current) {
+                    errors.add('imports must be alphabetized',
+                        node.loc.start.line, node.loc.start.column);
+                }
+
+                previous = current;
+            }
+        );
+    }
+};

test/specs/rules/require-imports-alphabetized.js

@@ -0,0 +1,92 @@
+var Checker = require('../../../lib/checker');
+var expect = require('chai').expect;
+
+describe('rules/require-imports-aplhabetized', function() {
+    var checker;
+
+    beforeEach(function() {
+        checker = new Checker();
+        checker.registerDefaultRules();
+        checker.configure({ requireImportAlphabetized: true });
+    });
+
+    it('should report no errors when there are no imports', function() {
+        var code = '// no imports here;\n' +
+            'var looping = function(n) {\n' +
+                'var a = 0, b = 1, f = 1;\n' +
+                'for(var i = 2; i <= n; i++) {\n' +
+                    'f = a + b;\n' +
+                    'a = b;\n' +
+                    'b = f;\n' +
+                '}\n' +
+                'return f; \n' +
+            '};';
+
+        expect(checker.checkString(code)).to.have.no.errors();
+    });
+
+    it('should report no errors for ordered imports', function() {
+        var code = 'import A from \'A\';\nimport C from \'C\';\nimport Z from \'Z\';';
+        expect(checker.checkString(code)).to.have.no.errors();
+    });
+
+    it('should report no errors for ordered import multiline', function() {
+        var code = 'import A\n from\n \'A\';\nimport C\n from \'C\';\nimport Z\n from \'Z\';';
+        expect(checker.checkString(code)).to.have.no.errors();
+    });
+
+    it('should report one error for un-ordered imports', function() {
+        var code = 'import A from \'A\';\nimport Z from \'Z\';\nimport B from \'B\';';
+        expect(checker.checkString(code)).to.have.one.error();
+    });
+
+    it('should report no errors for ordered named imports', function() {
+        var code = 'import { A as myNamed1, named2 } from \'src/mylib\';\n' +
+        'import { B as myNamed1, named2 } from \'src/mylib\';\n' +
+        'import { C as myNamed1, named2 } from \'src/mylib\';';
+
+        expect(checker.checkString(code)).to.have.no.errors();
+    });
+
+    it('should report one error for un-ordered named imports', function() {
+        var code = 'import { Z as myNamed1, named2 } from \'src/mylib\';\n' +
+        'import { B as myNamed1, named2 } from \'src/mylib\';\n' +
+        'import { C as myNamed1, named2 } from \'src/mylib\';';
+
+        expect(checker.checkString(code)).to.have.one.error();
+    });
+
+    it('should report no errors for ordered module as an object import', function() {
+        var code = 'import * from \'src/A\';\n' +
+        'import * from \'src/B\';\n' +
+        'import * from \'src/C\';';
+
+        expect(checker.checkString(code)).to.have.no.error();
+    });
+
+    it('should report one error for un-ordered module as an object import', function() {
+        var code = 'import * from \'src/A\';\n' +
+        'import * from \'src/Z\';\n' +
+        'import * from \'src/C\';';
+
+        expect(checker.checkString(code)).to.have.one.error();
+    });
+
+    it('should report no errors for ordered module import', function() {
+        var code = 'import \'src/A\';\n' +
+        'import \'src/B\';\n' +
+        'import \'src/C\';';
+
+        expect(checker.checkString(code)).to.have.no.error();
+    });
+
+    it('should report one error for un-ordered module import', function() {
+        var code = 'import \'src/Z\';\n import \'src/B\';\nimport \'src/C\';';
+        expect(checker.checkString(code)).to.have.one.error();
+    });
+
+    it('should report multiple errors for un-ordered module import', function() {
+        var code = 'import \'src/C\';\n import \'src/B\';\nimport \'src/A\';';
+        expect(checker.checkString(code)).to.have.validation.errors.from('requireImportAlphabetized');
+    });
+});