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