no-misused-promises.js
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"use strict";
var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
Object.defineProperty(o, k2, { enumerable: true, get: function() { return m[k]; } });
}) : (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
o[k2] = m[k];
}));
var __setModuleDefault = (this && this.__setModuleDefault) || (Object.create ? (function(o, v) {
Object.defineProperty(o, "default", { enumerable: true, value: v });
}) : function(o, v) {
o["default"] = v;
});
var __importStar = (this && this.__importStar) || function (mod) {
if (mod && mod.__esModule) return mod;
var result = {};
if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
__setModuleDefault(result, mod);
return result;
};
Object.defineProperty(exports, "__esModule", { value: true });
const experimental_utils_1 = require("@typescript-eslint/experimental-utils");
const tsutils = __importStar(require("tsutils"));
const ts = __importStar(require("typescript"));
const util = __importStar(require("../util"));
exports.default = util.createRule({
name: 'no-misused-promises',
meta: {
docs: {
description: 'Avoid using promises in places not designed to handle them',
category: 'Best Practices',
recommended: 'error',
requiresTypeChecking: true,
},
messages: {
voidReturn: 'Promise returned in function argument where a void return was expected.',
conditional: 'Expected non-Promise value in a boolean conditional.',
},
schema: [
{
type: 'object',
properties: {
checksConditionals: {
type: 'boolean',
},
checksVoidReturn: {
type: 'boolean',
},
},
},
],
type: 'problem',
},
defaultOptions: [
{
checksConditionals: true,
checksVoidReturn: true,
},
],
create(context, [{ checksConditionals, checksVoidReturn }]) {
const parserServices = util.getParserServices(context);
const checker = parserServices.program.getTypeChecker();
const checkedNodes = new Set();
const conditionalChecks = {
ConditionalExpression: checkTestConditional,
DoWhileStatement: checkTestConditional,
ForStatement: checkTestConditional,
IfStatement: checkTestConditional,
LogicalExpression: checkConditional,
'UnaryExpression[operator="!"]'(node) {
checkConditional(node.argument, true);
},
WhileStatement: checkTestConditional,
};
const voidReturnChecks = {
CallExpression: checkArguments,
NewExpression: checkArguments,
};
function checkTestConditional(node) {
if (node.test) {
checkConditional(node.test, true);
}
}
/**
* This function analyzes the type of a node and checks if it is a Promise in a boolean conditional.
* It uses recursion when checking nested logical operators.
* @param node The AST node to check.
* @param isTestExpr Whether the node is a descendant of a test expression.
*/
function checkConditional(node, isTestExpr = false) {
// prevent checking the same node multiple times
if (checkedNodes.has(node)) {
return;
}
checkedNodes.add(node);
if (node.type === experimental_utils_1.AST_NODE_TYPES.LogicalExpression) {
// ignore the left operand for nullish coalescing expressions not in a context of a test expression
if (node.operator !== '??' || isTestExpr) {
checkConditional(node.left, isTestExpr);
}
// we ignore the right operand when not in a context of a test expression
if (isTestExpr) {
checkConditional(node.right, isTestExpr);
}
return;
}
const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node);
if (isAlwaysThenable(checker, tsNode)) {
context.report({
messageId: 'conditional',
node,
});
}
}
function checkArguments(node) {
const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node);
const voidParams = voidFunctionParams(checker, tsNode);
if (voidParams.size === 0) {
return;
}
for (const [index, argument] of node.arguments.entries()) {
if (!voidParams.has(index)) {
continue;
}
const tsNode = parserServices.esTreeNodeToTSNodeMap.get(argument);
if (returnsThenable(checker, tsNode)) {
context.report({
messageId: 'voidReturn',
node: argument,
});
}
}
}
return Object.assign(Object.assign({}, (checksConditionals ? conditionalChecks : {})), (checksVoidReturn ? voidReturnChecks : {}));
},
});
// Variation on the thenable check which requires all forms of the type (read:
// alternates in a union) to be thenable. Otherwise, you might be trying to
// check if something is defined or undefined and get caught because one of the
// branches is thenable.
function isAlwaysThenable(checker, node) {
const type = checker.getTypeAtLocation(node);
for (const subType of tsutils.unionTypeParts(checker.getApparentType(type))) {
const thenProp = subType.getProperty('then');
// If one of the alternates has no then property, it is not thenable in all
// cases.
if (thenProp === undefined) {
return false;
}
// We walk through each variation of the then property. Since we know it
// exists at this point, we just need at least one of the alternates to
// be of the right form to consider it thenable.
const thenType = checker.getTypeOfSymbolAtLocation(thenProp, node);
let hasThenableSignature = false;
for (const subType of tsutils.unionTypeParts(thenType)) {
for (const signature of subType.getCallSignatures()) {
if (signature.parameters.length !== 0 &&
isFunctionParam(checker, signature.parameters[0], node)) {
hasThenableSignature = true;
break;
}
}
// We only need to find one variant of the then property that has a
// function signature for it to be thenable.
if (hasThenableSignature) {
break;
}
}
// If no flavors of the then property are thenable, we don't consider the
// overall type to be thenable
if (!hasThenableSignature) {
return false;
}
}
// If all variants are considered thenable (i.e. haven't returned false), we
// consider the overall type thenable
return true;
}
function isFunctionParam(checker, param, node) {
const type = checker.getApparentType(checker.getTypeOfSymbolAtLocation(param, node));
for (const subType of tsutils.unionTypeParts(type)) {
if (subType.getCallSignatures().length !== 0) {
return true;
}
}
return false;
}
// Get the positions of parameters which are void functions (and not also
// thenable functions). These are the candidates for the void-return check at
// the current call site.
function voidFunctionParams(checker, node) {
const voidReturnIndices = new Set();
const thenableReturnIndices = new Set();
const type = checker.getTypeAtLocation(node.expression);
for (const subType of tsutils.unionTypeParts(type)) {
// Standard function calls and `new` have two different types of signatures
const signatures = ts.isCallExpression(node)
? subType.getCallSignatures()
: subType.getConstructSignatures();
for (const signature of signatures) {
for (const [index, parameter] of signature.parameters.entries()) {
const type = checker.getTypeOfSymbolAtLocation(parameter, node.expression);
for (const subType of tsutils.unionTypeParts(type)) {
for (const signature of subType.getCallSignatures()) {
const returnType = signature.getReturnType();
if (tsutils.isTypeFlagSet(returnType, ts.TypeFlags.Void)) {
voidReturnIndices.add(index);
}
else if (tsutils.isThenableType(checker, node.expression, returnType)) {
thenableReturnIndices.add(index);
}
}
}
}
}
}
// If a certain positional argument accepts both thenable and void returns,
// a promise-returning function is valid
for (const thenable of thenableReturnIndices) {
voidReturnIndices.delete(thenable);
}
return voidReturnIndices;
}
// Returns true if the expression is a function that returns a thenable
function returnsThenable(checker, node) {
const type = checker.getApparentType(checker.getTypeAtLocation(node));
for (const subType of tsutils.unionTypeParts(type)) {
for (const signature of subType.getCallSignatures()) {
const returnType = signature.getReturnType();
if (tsutils.isThenableType(checker, node, returnType)) {
return true;
}
}
}
return false;
}
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