55
66"use strict" ;
77
8+ //------------------------------------------------------------------------------
9+ // Helpers
10+ //------------------------------------------------------------------------------
11+
12+ var SCOPE_NODE_TYPE = / ^ (?: P r o g r a m | B l o c k S t a t e m e n t | S w i t c h S t a t e m e n t | F o r S t a t e m e n t | F o r I n S t a t e m e n t | F o r O f S t a t e m e n t ) $ / ;
13+
14+ /**
15+ * Gets the scope node which directly contains a given node.
16+ *
17+ * @param {ASTNode } node - A node to get. This is a `VariableDeclaration` or
18+ * an `Identifier`.
19+ * @returns {ASTNode } A scope node. This is one of `Program`, `BlockStatement`,
20+ * `SwitchStatement`, `ForStatement`, `ForInStatement`, and
21+ * `ForOfStatement`.
22+ */
23+ function getScopeNode ( node ) {
24+ while ( node ) {
25+ if ( SCOPE_NODE_TYPE . test ( node . type ) ) {
26+ return node ;
27+ }
28+
29+ node = node . parent ;
30+ }
31+
32+ /* istanbul ignore next : unreachable */
33+ return null ;
34+ }
35+
36+ /**
37+ * Checks whether a given variable is redeclared or not.
38+ *
39+ * @param {escope.Variable } variable - A variable to check.
40+ * @returns {boolean } `true` if the variable is redeclared.
41+ */
42+ function isRedeclared ( variable ) {
43+ return variable . defs . length >= 2 ;
44+ }
45+
46+ /**
47+ * Checks whether a given variable is used from outside of the specified scope.
48+ *
49+ * @param {ASTNode } scopeNode - A scope node to check.
50+ * @returns {Function } The predicate function which checks whether a given
51+ * variable is used from outside of the specified scope.
52+ */
53+ function isUsedFromOutsideOf ( scopeNode ) {
54+
55+ /**
56+ * Checks whether a given reference is inside of the specified scope or not.
57+ *
58+ * @param {escope.Reference } reference - A reference to check.
59+ * @returns {boolean } `true` if the reference is inside of the specified
60+ * scope.
61+ */
62+ function isOutsideOfScope ( reference ) {
63+ var scope = scopeNode . range ;
64+ var id = reference . identifier . range ;
65+
66+ return id [ 0 ] < scope [ 0 ] || id [ 1 ] > scope [ 1 ] ;
67+ }
68+
69+ return function ( variable ) {
70+ return variable . references . some ( isOutsideOfScope ) ;
71+ } ;
72+ }
73+
874//------------------------------------------------------------------------------
975// Rule Definition
1076//------------------------------------------------------------------------------
@@ -17,19 +83,80 @@ module.exports = {
1783 recommended : false
1884 } ,
1985
20- schema : [ ]
86+ schema : [ ] ,
87+ fixable : "code"
2188 } ,
2289
2390 create : function ( context ) {
91+ var sourceCode = context . getSourceCode ( ) ;
92+
93+ /**
94+ * Checks whether it can fix a given variable declaration or not.
95+ * It cannot fix if the following cases:
96+ *
97+ * - A variable is declared on a SwitchCase node.
98+ * - A variable is redeclared.
99+ * - A variable is used from outside the scope.
100+ *
101+ * ## A variable is declared on a SwitchCase node.
102+ *
103+ * If this rule modifies 'var' declarations on a SwitchCase node, it
104+ * would generate the warnings of 'no-case-declarations' rule. And the
105+ * 'eslint:recommended' preset includes 'no-case-declarations' rule, so
106+ * this rule doesn't modify those declarations.
107+ *
108+ * ## A variable is redeclared.
109+ *
110+ * The language spec disallows redeclarations of `let` declarations.
111+ * Those variables would cause syntax errors.
112+ *
113+ * ## A variable is used from outside the scope.
114+ *
115+ * The language spec disallows accesses from outside of the scope for
116+ * `let` declarations. Those variables would cause reference errors.
117+ *
118+ * @param {ASTNode } node - A variable declaration node to check.
119+ * @returns {boolean } `true` if it can fix the node.
120+ */
121+ function canFix ( node ) {
122+ var variables = context . getDeclaredVariables ( node ) ;
123+ var scopeNode = getScopeNode ( node ) ;
124+
125+ return ! (
126+ node . parent . type === "SwitchCase" ||
127+ variables . some ( isRedeclared ) ||
128+ variables . some ( isUsedFromOutsideOf ( scopeNode ) )
129+ ) ;
130+ }
131+
132+ /**
133+ * Reports a given variable declaration node.
134+ *
135+ * @param {ASTNode } node - A variable declaration node to report.
136+ * @returns {void }
137+ */
138+ function report ( node ) {
139+ var varToken = sourceCode . getFirstToken ( node ) ;
140+
141+ context . report ( {
142+ node : node ,
143+ message : "Unexpected var, use let or const instead." ,
144+
145+ fix : function ( fixer ) {
146+ if ( canFix ( node ) ) {
147+ return fixer . replaceText ( varToken , "let" ) ;
148+ }
149+ return null ;
150+ }
151+ } ) ;
152+ }
24153
25154 return {
26155 VariableDeclaration : function ( node ) {
27156 if ( node . kind === "var" ) {
28- context . report ( node , "Unexpected var, use let or const instead." ) ;
157+ report ( node ) ;
29158 }
30159 }
31-
32160 } ;
33-
34161 }
35162} ;
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