1 | /**
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2 | * @fileoverview Rule to flag use of an lexical declarations inside a case clause
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3 | * @author Erik Arvidsson
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4 | */
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5 | ;
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6 |
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7 | //------------------------------------------------------------------------------
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8 | // Rule Definition
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9 | //------------------------------------------------------------------------------
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10 |
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11 | module.exports = {
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12 | meta: {
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13 | docs: {
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14 | description: "disallow lexical declarations in case clauses",
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15 | category: "Best Practices",
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16 | recommended: true,
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17 | url: "https://eslint.org/docs/rules/no-case-declarations"
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18 | },
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19 |
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20 | schema: [],
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21 |
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22 | messages: {
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23 | unexpected: "Unexpected lexical declaration in case block."
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24 | }
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25 | },
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26 |
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27 | create(context) {
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28 |
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29 | /**
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30 | * Checks whether or not a node is a lexical declaration.
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31 | * @param {ASTNode} node A direct child statement of a switch case.
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32 | * @returns {boolean} Whether or not the node is a lexical declaration.
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33 | */
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34 | function isLexicalDeclaration(node) {
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35 | switch (node.type) {
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36 | case "FunctionDeclaration":
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37 | case "ClassDeclaration":
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38 | return true;
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39 | case "VariableDeclaration":
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40 | return node.kind !== "var";
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41 | default:
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42 | return false;
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43 | }
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44 | }
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45 |
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46 | return {
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47 | SwitchCase(node) {
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48 | for (let i = 0; i < node.consequent.length; i++) {
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49 | const statement = node.consequent[i];
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50 |
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51 | if (isLexicalDeclaration(statement)) {
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52 | context.report({
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53 | node,
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54 | messageId: "unexpected"
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55 | });
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56 | }
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57 | }
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58 | }
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59 | };
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60 |
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61 | }
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62 | };
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