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1/**
2 * @fileoverview A rule to control the style of variable initializations.
3 * @author Colin Ihrig
4 */
5
6"use strict";
7
8//------------------------------------------------------------------------------
9// Helpers
10//------------------------------------------------------------------------------
11
12/**
13 * Checks whether or not a given node is a for loop.
14 * @param {ASTNode} block A node to check.
15 * @returns {boolean} `true` when the node is a for loop.
16 */
17function isForLoop(block) {
18    return block.type === "ForInStatement" ||
19    block.type === "ForOfStatement" ||
20    block.type === "ForStatement";
21}
22
23/**
24 * Checks whether or not a given declarator node has its initializer.
25 * @param {ASTNode} node A declarator node to check.
26 * @returns {boolean} `true` when the node has its initializer.
27 */
28function isInitialized(node) {
29    const declaration = node.parent;
30    const block = declaration.parent;
31
32    if (isForLoop(block)) {
33        if (block.type === "ForStatement") {
34            return block.init === declaration;
35        }
36        return block.left === declaration;
37    }
38    return Boolean(node.init);
39}
40
41//------------------------------------------------------------------------------
42// Rule Definition
43//------------------------------------------------------------------------------
44
45module.exports = {
46    meta: {
47        type: "suggestion",
48
49        docs: {
50            description: "require or disallow initialization in variable declarations",
51            category: "Variables",
52            recommended: false,
53            url: "https://eslint.org/docs/rules/init-declarations"
54        },
55
56        schema: {
57            anyOf: [
58                {
59                    type: "array",
60                    items: [
61                        {
62                            enum: ["always"]
63                        }
64                    ],
65                    minItems: 0,
66                    maxItems: 1
67                },
68                {
69                    type: "array",
70                    items: [
71                        {
72                            enum: ["never"]
73                        },
74                        {
75                            type: "object",
76                            properties: {
77                                ignoreForLoopInit: {
78                                    type: "boolean"
79                                }
80                            },
81                            additionalProperties: false
82                        }
83                    ],
84                    minItems: 0,
85                    maxItems: 2
86                }
87            ]
88        },
89        messages: {
90            initialized: "Variable '{{idName}}' should be initialized on declaration.",
91            notInitialized: "Variable '{{idName}}' should not be initialized on declaration."
92        }
93    },
94
95    create(context) {
96
97        const MODE_ALWAYS = "always",
98            MODE_NEVER = "never";
99
100        const mode = context.options[0] || MODE_ALWAYS;
101        const params = context.options[1] || {};
102
103        //--------------------------------------------------------------------------
104        // Public API
105        //--------------------------------------------------------------------------
106
107        return {
108            "VariableDeclaration:exit"(node) {
109
110                const kind = node.kind,
111                    declarations = node.declarations;
112
113                for (let i = 0; i < declarations.length; ++i) {
114                    const declaration = declarations[i],
115                        id = declaration.id,
116                        initialized = isInitialized(declaration),
117                        isIgnoredForLoop = params.ignoreForLoopInit && isForLoop(node.parent);
118                    let messageId = "";
119
120                    if (mode === MODE_ALWAYS && !initialized) {
121                        messageId = "initialized";
122                    } else if (mode === MODE_NEVER && kind !== "const" && initialized && !isIgnoredForLoop) {
123                        messageId = "notInitialized";
124                    }
125
126                    if (id.type === "Identifier" && messageId) {
127                        context.report({
128                            node: declaration,
129                            messageId,
130                            data: {
131                                idName: id.name
132                            }
133                        });
134                    }
135                }
136            }
137        };
138    }
139};
140