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5 | "use strict";
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6 |
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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 | type: "suggestion",
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14 |
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15 | docs: {
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16 | description: "enforce the consistent use of either `function` declarations or expressions",
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17 | category: "Stylistic Issues",
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18 | recommended: false,
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19 | url: "https://eslint.org/docs/rules/func-style"
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20 | },
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21 |
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22 | schema: [
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23 | {
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24 | enum: ["declaration", "expression"]
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25 | },
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26 | {
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27 | type: "object",
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28 | properties: {
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29 | allowArrowFunctions: {
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30 | type: "boolean",
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31 | default: false
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32 | }
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33 | },
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34 | additionalProperties: false
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35 | }
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36 | ],
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37 |
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38 | messages: {
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39 | expression: "Expected a function expression.",
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40 | declaration: "Expected a function declaration."
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41 | }
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42 | },
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43 |
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44 | create(context) {
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45 |
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46 | const style = context.options[0],
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47 | allowArrowFunctions = context.options[1] && context.options[1].allowArrowFunctions,
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48 | enforceDeclarations = (style === "declaration"),
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49 | stack = [];
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50 |
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51 | const nodesToCheck = {
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52 | FunctionDeclaration(node) {
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53 | stack.push(false);
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54 |
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55 | if (!enforceDeclarations && node.parent.type !== "ExportDefaultDeclaration") {
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56 | context.report({ node, messageId: "expression" });
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57 | }
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58 | },
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59 | "FunctionDeclaration:exit"() {
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60 | stack.pop();
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61 | },
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62 |
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63 | FunctionExpression(node) {
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64 | stack.push(false);
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65 |
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66 | if (enforceDeclarations && node.parent.type === "VariableDeclarator") {
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67 | context.report({ node: node.parent, messageId: "declaration" });
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68 | }
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69 | },
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70 | "FunctionExpression:exit"() {
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71 | stack.pop();
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72 | },
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73 |
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74 | ThisExpression() {
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75 | if (stack.length > 0) {
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76 | stack[stack.length - 1] = true;
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77 | }
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78 | }
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79 | };
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80 |
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81 | if (!allowArrowFunctions) {
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82 | nodesToCheck.ArrowFunctionExpression = function() {
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83 | stack.push(false);
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84 | };
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85 |
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86 | nodesToCheck["ArrowFunctionExpression:exit"] = function(node) {
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87 | const hasThisExpr = stack.pop();
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88 |
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89 | if (enforceDeclarations && !hasThisExpr && node.parent.type === "VariableDeclarator") {
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90 | context.report({ node: node.parent, messageId: "declaration" });
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91 | }
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92 | };
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93 | }
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94 |
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95 | return nodesToCheck;
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96 |
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97 | }
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98 | };
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