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no-throw-literal.ts
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no-throw-literal.ts
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import * as ts from 'typescript';
import * as util from '../util';
import {
TSESTree,
AST_NODE_TYPES,
} from '@typescript-eslint/experimental-utils';
export default util.createRule({
name: 'no-throw-literal',
meta: {
type: 'problem',
docs: {
description: 'Disallow throwing literals as exceptions',
category: 'Best Practices',
recommended: false,
requiresTypeChecking: true,
},
schema: [],
messages: {
object: 'Expected an error object to be thrown.',
undef: 'Do not throw undefined.',
},
},
defaultOptions: [],
create(context) {
const parserServices = util.getParserServices(context);
const program = parserServices.program;
const checker = program.getTypeChecker();
function isErrorLike(type: ts.Type): boolean {
const symbol = type.getSymbol();
if (symbol?.getName() === 'Error') {
const declarations = symbol.getDeclarations() ?? [];
for (const declaration of declarations) {
const sourceFile = declaration.getSourceFile();
if (program.isSourceFileDefaultLibrary(sourceFile)) {
return true;
}
}
}
const baseTypes = type.getBaseTypes() ?? [];
for (const baseType of baseTypes) {
if (isErrorLike(baseType)) {
return true;
}
}
return false;
}
function tryGetThrowArgumentType(node: TSESTree.Node): ts.Type | null {
switch (node.type) {
case AST_NODE_TYPES.Identifier:
case AST_NODE_TYPES.CallExpression:
case AST_NODE_TYPES.NewExpression:
case AST_NODE_TYPES.MemberExpression: {
const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node);
return checker.getTypeAtLocation(tsNode);
}
case AST_NODE_TYPES.AssignmentExpression:
return tryGetThrowArgumentType(node.right);
case AST_NODE_TYPES.SequenceExpression:
return tryGetThrowArgumentType(
node.expressions[node.expressions.length - 1],
);
case AST_NODE_TYPES.LogicalExpression: {
const left = tryGetThrowArgumentType(node.left);
return left ?? tryGetThrowArgumentType(node.right);
}
case AST_NODE_TYPES.ConditionalExpression: {
const consequent = tryGetThrowArgumentType(node.consequent);
return consequent ?? tryGetThrowArgumentType(node.alternate);
}
default:
return null;
}
}
function checkThrowArgument(node: TSESTree.Node): void {
if (
node.type === AST_NODE_TYPES.AwaitExpression ||
node.type === AST_NODE_TYPES.YieldExpression
) {
return;
}
const type = tryGetThrowArgumentType(node);
if (type) {
if (type.flags & ts.TypeFlags.Undefined) {
context.report({ node, messageId: 'undef' });
return;
}
if (
type.flags & (ts.TypeFlags.Any | ts.TypeFlags.Unknown) ||
isErrorLike(type)
) {
return;
}
}
context.report({ node, messageId: 'object' });
}
return {
ThrowStatement(node): void {
if (node.argument) {
checkThrowArgument(node.argument);
}
},
};
},
});