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unbound-method.ts
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unbound-method.ts
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import {
AST_NODE_TYPES,
TSESTree,
} from '@typescript-eslint/experimental-utils';
import * as tsutils from 'tsutils';
import * as ts from 'typescript';
import * as util from '../util';
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
interface Config {
ignoreStatic: boolean;
}
export type Options = [Config];
export type MessageIds = 'unbound';
/**
* The following is a list of exceptions to the rule
* Generated via the following script.
* This is statically defined to save making purposely invalid calls every lint run
* ```
SUPPORTED_GLOBALS.flatMap(namespace => {
const object = window[namespace];
return Object.getOwnPropertyNames(object)
.filter(
name =>
!name.startsWith('_') &&
typeof object[name] === 'function',
)
.map(name => {
try {
const x = object[name];
x();
} catch (e) {
if (e.message.includes("called on non-object")) {
return `${namespace}.${name}`;
}
}
});
}).filter(Boolean);
* ```
*/
const nativelyNotBoundMembers = new Set([
'Promise.all',
'Promise.race',
'Promise.resolve',
'Promise.reject',
'Promise.allSettled',
'Object.defineProperties',
'Object.defineProperty',
'Reflect.defineProperty',
'Reflect.deleteProperty',
'Reflect.get',
'Reflect.getOwnPropertyDescriptor',
'Reflect.getPrototypeOf',
'Reflect.has',
'Reflect.isExtensible',
'Reflect.ownKeys',
'Reflect.preventExtensions',
'Reflect.set',
'Reflect.setPrototypeOf',
]);
const SUPPORTED_GLOBALS = [
'Number',
'Object',
'String', // eslint-disable-line @typescript-eslint/internal/prefer-ast-types-enum
'RegExp',
'Symbol',
'Array',
'Proxy',
'Date',
'Infinity',
'Atomics',
'Reflect',
'console',
'Math',
'JSON',
'Intl',
] as const;
const nativelyBoundMembers = SUPPORTED_GLOBALS.map(namespace => {
if (!(namespace in global)) {
// node.js might not have namespaces like Intl depending on compilation options
// https://nodejs.org/api/intl.html#intl_options_for_building_node_js
return [];
}
const object = global[namespace];
return Object.getOwnPropertyNames(object)
.filter(
name =>
!name.startsWith('_') &&
typeof (object as Record<string, unknown>)[name] === 'function',
)
.map(name => `${namespace}.${name}`);
})
.reduce((arr, names) => arr.concat(names), [])
.filter(name => !nativelyNotBoundMembers.has(name));
const isMemberNotImported = (
symbol: ts.Symbol,
currentSourceFile: ts.SourceFile | undefined,
): boolean => {
const { valueDeclaration } = symbol;
if (!valueDeclaration) {
// working around https://github.com/microsoft/TypeScript/issues/31294
return false;
}
return (
!!currentSourceFile &&
currentSourceFile !== valueDeclaration.getSourceFile()
);
};
const getNodeName = (node: TSESTree.Node): string | null =>
node.type === AST_NODE_TYPES.Identifier ? node.name : null;
const getMemberFullName = (
node: TSESTree.MemberExpression | TSESTree.OptionalMemberExpression,
): string => `${getNodeName(node.object)}.${getNodeName(node.property)}`;
export default util.createRule<Options, MessageIds>({
name: 'unbound-method',
meta: {
docs: {
category: 'Best Practices',
description:
'Enforces unbound methods are called with their expected scope',
recommended: 'error',
requiresTypeChecking: true,
},
messages: {
unbound:
'Avoid referencing unbound methods which may cause unintentional scoping of `this`.',
},
schema: [
{
type: 'object',
properties: {
ignoreStatic: {
type: 'boolean',
},
},
additionalProperties: false,
},
],
type: 'problem',
},
defaultOptions: [
{
ignoreStatic: false,
},
],
create(context, [{ ignoreStatic }]) {
const parserServices = util.getParserServices(context);
const checker = parserServices.program.getTypeChecker();
const currentSourceFile = parserServices.program.getSourceFile(
context.getFilename(),
);
return {
'MemberExpression, OptionalMemberExpression'(
node: TSESTree.MemberExpression | TSESTree.OptionalMemberExpression,
): void {
if (isSafeUse(node)) {
return;
}
const objectSymbol = checker.getSymbolAtLocation(
parserServices.esTreeNodeToTSNodeMap.get(node.object),
);
if (
objectSymbol &&
nativelyBoundMembers.includes(getMemberFullName(node)) &&
isMemberNotImported(objectSymbol, currentSourceFile)
) {
return;
}
const originalNode = parserServices.esTreeNodeToTSNodeMap.get(node);
const symbol = checker.getSymbolAtLocation(originalNode);
if (symbol && isDangerousMethod(symbol, ignoreStatic)) {
context.report({
messageId: 'unbound',
node,
});
}
},
};
},
});
function isDangerousMethod(symbol: ts.Symbol, ignoreStatic: boolean): boolean {
const { valueDeclaration } = symbol;
if (!valueDeclaration) {
// working around https://github.com/microsoft/TypeScript/issues/31294
return false;
}
switch (valueDeclaration.kind) {
case ts.SyntaxKind.PropertyDeclaration:
return (
(valueDeclaration as ts.PropertyDeclaration).initializer?.kind ===
ts.SyntaxKind.FunctionExpression
);
case ts.SyntaxKind.MethodDeclaration:
case ts.SyntaxKind.MethodSignature:
return !(
ignoreStatic &&
tsutils.hasModifier(
valueDeclaration.modifiers,
ts.SyntaxKind.StaticKeyword,
)
);
}
return false;
}
function isSafeUse(node: TSESTree.Node): boolean {
const parent = node.parent;
switch (parent?.type) {
case AST_NODE_TYPES.IfStatement:
case AST_NODE_TYPES.ForStatement:
case AST_NODE_TYPES.MemberExpression:
case AST_NODE_TYPES.OptionalMemberExpression:
case AST_NODE_TYPES.SwitchStatement:
case AST_NODE_TYPES.UpdateExpression:
case AST_NODE_TYPES.WhileStatement:
return true;
case AST_NODE_TYPES.CallExpression:
case AST_NODE_TYPES.OptionalCallExpression:
return parent.callee === node;
case AST_NODE_TYPES.ConditionalExpression:
return parent.test === node;
case AST_NODE_TYPES.TaggedTemplateExpression:
return parent.tag === node;
case AST_NODE_TYPES.UnaryExpression:
// the first case is safe for obvious
// reasons. The second one is also fine
// since we're returning something falsy
return ['typeof', '!', 'void', 'delete'].includes(parent.operator);
case AST_NODE_TYPES.BinaryExpression:
return ['instanceof', '==', '!=', '===', '!=='].includes(parent.operator);
case AST_NODE_TYPES.AssignmentExpression:
return parent.operator === '=' && node === parent.left;
case AST_NODE_TYPES.TSNonNullExpression:
case AST_NODE_TYPES.TSAsExpression:
case AST_NODE_TYPES.TSTypeAssertion:
return isSafeUse(parent);
case AST_NODE_TYPES.LogicalExpression:
if (parent.operator === '&&' && parent.left === node) {
// this is safe, as && will return the left if and only if it's falsy
return true;
}
// in all other cases, it's likely the logical expression will return the method ref
// so make sure the parent is a safe usage
return isSafeUse(parent);
}
return false;
}