require-await.js

   1 /**
   2  * @fileoverview Rule to disallow async functions which have no `await` expression.
   3  * @author Toru Nagashima
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const astUtils = require("./utils/ast-utils");
  13
  14 //------------------------------------------------------------------------------
  15 // Helpers
  16 //------------------------------------------------------------------------------
  17
  18 /**
  19  * Capitalize the 1st letter of the given text.
  20  * @param {string} text The text to capitalize.
  21  * @returns {string} The text that the 1st letter was capitalized.
  22  */
  23 function capitalizeFirstLetter(text) {
  24     return text[0].toUpperCase() + text.slice(1);
  25 }
  26
  27 //------------------------------------------------------------------------------
  28 // Rule Definition
  29 //------------------------------------------------------------------------------
  30
  31 module.exports = {
  32     meta: {
  33         type: "suggestion",
  34
  35         docs: {
  36             description: "disallow async functions which have no `await` expression",
  37             category: "Best Practices",
  38             recommended: false,
  39             url: "https://eslint.org/docs/rules/require-await"
  40         },
  41
  42         schema: []
  43     },
  44
  45     create(context) {
  46         const sourceCode = context.getSourceCode();
  47         let scopeInfo = null;
  48
  49         /**
  50          * Push the scope info object to the stack.
  51          * @returns {void}
  52          */
  53         function enterFunction() {
  54             scopeInfo = {
  55                 upper: scopeInfo,
  56                 hasAwait: false
  57             };
  58         }
  59
  60         /**
  61          * Pop the top scope info object from the stack.
  62          * Also, it reports the function if needed.
  63          * @param {ASTNode} node The node to report.
  64          * @returns {void}
  65          */
  66         function exitFunction(node) {
  67             if (node.async && !scopeInfo.hasAwait && !astUtils.isEmptyFunction(node)) {
  68                 context.report({
  69                     node,
  70                     loc: astUtils.getFunctionHeadLoc(node, sourceCode),
  71                     message: "{{name}} has no 'await' expression.",
  72                     data: {
  73                         name: capitalizeFirstLetter(
  74                             astUtils.getFunctionNameWithKind(node)
  75                         )
  76                     }
  77                 });
  78             }
  79
  80             scopeInfo = scopeInfo.upper;
  81         }
  82
  83         return {
  84             FunctionDeclaration: enterFunction,
  85             FunctionExpression: enterFunction,
  86             ArrowFunctionExpression: enterFunction,
  87             "FunctionDeclaration:exit": exitFunction,
  88             "FunctionExpression:exit": exitFunction,
  89             "ArrowFunctionExpression:exit": exitFunction,
  90
  91             AwaitExpression() {
  92                 if (!scopeInfo) {
  93                     return;
  94                 }
  95
  96                 scopeInfo.hasAwait = true;
  97             },
  98             ForOfStatement(node) {
  99                 if (!scopeInfo) {
 100                     return;
 101                 }
 102
 103                 if (node.await) {
 104                     scopeInfo.hasAwait = true;
 105                 }
 106             }
 107         };
 108     }
 109 };