eslint/lib/rules/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 /** @type {import('../shared/types').Rule} */
  32 module.exports = {
  33     meta: {
  34         type: "suggestion",
  35
  36         docs: {
  37             description: "Disallow async functions which have no `await` expression",
  38             recommended: false,
  39             url: "https://eslint.org/docs/rules/require-await"
  40         },
  41
  42         schema: [],
  43
  44         messages: {
  45             missingAwait: "{{name}} has no 'await' expression."
  46         }
  47     },
  48
  49     create(context) {
  50         const sourceCode = context.getSourceCode();
  51         let scopeInfo = null;
  52
  53         /**
  54          * Push the scope info object to the stack.
  55          * @returns {void}
  56          */
  57         function enterFunction() {
  58             scopeInfo = {
  59                 upper: scopeInfo,
  60                 hasAwait: false
  61             };
  62         }
  63
  64         /**
  65          * Pop the top scope info object from the stack.
  66          * Also, it reports the function if needed.
  67          * @param {ASTNode} node The node to report.
  68          * @returns {void}
  69          */
  70         function exitFunction(node) {
  71             if (!node.generator && node.async && !scopeInfo.hasAwait && !astUtils.isEmptyFunction(node)) {
  72                 context.report({
  73                     node,
  74                     loc: astUtils.getFunctionHeadLoc(node, sourceCode),
  75                     messageId: "missingAwait",
  76                     data: {
  77                         name: capitalizeFirstLetter(
  78                             astUtils.getFunctionNameWithKind(node)
  79                         )
  80                     }
  81                 });
  82             }
  83
  84             scopeInfo = scopeInfo.upper;
  85         }
  86
  87         return {
  88             FunctionDeclaration: enterFunction,
  89             FunctionExpression: enterFunction,
  90             ArrowFunctionExpression: enterFunction,
  91             "FunctionDeclaration:exit": exitFunction,
  92             "FunctionExpression:exit": exitFunction,
  93             "ArrowFunctionExpression:exit": exitFunction,
  94
  95             AwaitExpression() {
  96                 if (!scopeInfo) {
  97                     return;
  98                 }
  99
 100                 scopeInfo.hasAwait = true;
 101             },
 102             ForOfStatement(node) {
 103                 if (!scopeInfo) {
 104                     return;
 105                 }
 106
 107                 if (node.await) {
 108                     scopeInfo.hasAwait = true;
 109                 }
 110             }
 111         };
 112     }
 113 };