1 | /**
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2 | * @fileoverview Rule to disallow async functions which have no `await` expression.
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3 | * @author Toru Nagashima
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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 | //------------------------------------------------------------------------------
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9 | // Requirements
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10 | //------------------------------------------------------------------------------
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11 |
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12 | const astUtils = require("../ast-utils");
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13 |
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14 | //------------------------------------------------------------------------------
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15 | // Helpers
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16 | //------------------------------------------------------------------------------
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17 |
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18 | /**
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19 | * Capitalize the 1st letter of the given text.
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20 | *
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21 | * @param {string} text - The text to capitalize.
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22 | * @returns {string} The text that the 1st letter was capitalized.
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23 | */
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24 | function capitalizeFirstLetter(text) {
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25 | return text[0].toUpperCase() + text.slice(1);
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26 | }
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27 |
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28 | //------------------------------------------------------------------------------
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29 | // Rule Definition
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30 | //------------------------------------------------------------------------------
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31 |
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32 | module.exports = {
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33 | meta: {
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34 | docs: {
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35 | description: "disallow async functions which have no `await` expression",
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36 | category: "Best Practices",
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37 | recommended: false
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38 | },
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39 | schema: []
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40 | },
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41 |
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42 | create(context) {
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43 | const sourceCode = context.getSourceCode();
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44 | let scopeInfo = null;
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45 |
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46 | /**
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47 | * Push the scope info object to the stack.
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48 | *
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49 | * @returns {void}
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50 | */
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51 | function enterFunction() {
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52 | scopeInfo = {
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53 | upper: scopeInfo,
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54 | hasAwait: false
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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 | * Pop the top scope info object from the stack.
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60 | * Also, it reports the function if needed.
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61 | *
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62 | * @param {ASTNode} node - The node to report.
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63 | * @returns {void}
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64 | */
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65 | function exitFunction(node) {
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66 | if (node.async && !scopeInfo.hasAwait && !astUtils.isEmptyFunction(node)) {
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67 | context.report({
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68 | node,
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69 | loc: astUtils.getFunctionHeadLoc(node, sourceCode),
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70 | message: "{{name}} has no 'await' expression.",
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71 | data: {
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72 | name: capitalizeFirstLetter(
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73 | astUtils.getFunctionNameWithKind(node)
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74 | )
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75 | }
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76 | });
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77 | }
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78 |
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79 | scopeInfo = scopeInfo.upper;
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80 | }
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81 |
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82 | return {
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83 | FunctionDeclaration: enterFunction,
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84 | FunctionExpression: enterFunction,
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85 | ArrowFunctionExpression: enterFunction,
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86 | "FunctionDeclaration:exit": exitFunction,
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87 | "FunctionExpression:exit": exitFunction,
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88 | "ArrowFunctionExpression:exit": exitFunction,
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89 |
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90 | AwaitExpression() {
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91 | scopeInfo.hasAwait = true;
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92 | }
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93 | };
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94 | }
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95 | };
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