@typescript-eslint/eslint-plugin
Version:
TypeScript plugin for ESLint
251 lines (250 loc) • 11 kB
JavaScript
"use strict";
var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
var desc = Object.getOwnPropertyDescriptor(m, k);
if (!desc || ("get" in desc ? !m.__esModule : desc.writable || desc.configurable)) {
desc = { enumerable: true, get: function() { return m[k]; } };
}
Object.defineProperty(o, k2, desc);
}) : (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 () {
var ownKeys = function(o) {
ownKeys = Object.getOwnPropertyNames || function (o) {
var ar = [];
for (var k in o) if (Object.prototype.hasOwnProperty.call(o, k)) ar[ar.length] = k;
return ar;
};
return ownKeys(o);
};
return function (mod) {
if (mod && mod.__esModule) return mod;
var result = {};
if (mod != null) for (var k = ownKeys(mod), i = 0; i < k.length; i++) if (k[i] !== "default") __createBinding(result, mod, k[i]);
__setModuleDefault(result, mod);
return result;
};
})();
Object.defineProperty(exports, "__esModule", { value: true });
const utils_1 = require("@typescript-eslint/utils");
const tsutils = __importStar(require("ts-api-utils"));
const ts = __importStar(require("typescript"));
const util_1 = require("../util");
exports.default = (0, util_1.createRule)({
name: 'no-useless-default-assignment',
meta: {
type: 'suggestion',
docs: {
description: 'Disallow default values that will never be used',
recommended: 'strict',
requiresTypeChecking: true,
},
fixable: 'code',
messages: {
preferOptionalSyntax: 'Using `= undefined` to make a parameter optional adds unnecessary runtime logic. Use the `?` optional syntax instead.',
uselessDefaultAssignment: 'Default value is useless because the {{ type }} is not optional.',
uselessUndefined: 'Default value is useless because it is undefined. Optional {{ type }}s are already undefined by default.',
},
schema: [],
},
defaultOptions: [],
create(context) {
const services = (0, util_1.getParserServices)(context);
const checker = services.program.getTypeChecker();
function canBeUndefined(type) {
if ((0, util_1.isTypeAnyType)(type) || (0, util_1.isTypeUnknownType)(type)) {
return true;
}
return tsutils
.unionConstituents(type)
.some(part => (0, util_1.isTypeFlagSet)(part, ts.TypeFlags.Undefined));
}
function getPropertyType(objectType, propertyName) {
const symbol = objectType.getProperty(propertyName);
if (!symbol) {
return null;
}
return checker.getTypeOfSymbol(symbol);
}
function getArrayElementType(arrayType, elementIndex) {
if (checker.isTupleType(arrayType)) {
const tupleArgs = checker.getTypeArguments(arrayType);
if (elementIndex < tupleArgs.length) {
return tupleArgs[elementIndex];
}
}
return arrayType.getNumberIndexType() ?? null;
}
function checkAssignmentPattern(node) {
if (node.right.type === utils_1.AST_NODE_TYPES.Identifier &&
node.right.name === 'undefined') {
const tsNode = services.esTreeNodeToTSNodeMap.get(node);
if (ts.isParameter(tsNode) &&
tsNode.type &&
canBeUndefined(checker.getTypeFromTypeNode(tsNode.type))) {
reportPreferOptionalSyntax(node);
return;
}
const type = node.parent.type === utils_1.AST_NODE_TYPES.Property ||
node.parent.type === utils_1.AST_NODE_TYPES.ArrayPattern
? 'property'
: 'parameter';
reportUselessUndefined(node, type);
return;
}
const parent = node.parent;
if (parent.type === utils_1.AST_NODE_TYPES.ArrowFunctionExpression ||
parent.type === utils_1.AST_NODE_TYPES.FunctionExpression) {
const paramIndex = parent.params.indexOf(node);
if (paramIndex !== -1) {
const tsFunc = services.esTreeNodeToTSNodeMap.get(parent);
if (ts.isFunctionLike(tsFunc)) {
const contextualType = checker.getContextualType(tsFunc);
if (!contextualType) {
return;
}
const signatures = contextualType.getCallSignatures();
if (signatures.length === 0 ||
signatures[0].getDeclaration() === tsFunc) {
return;
}
const params = signatures[0].getParameters();
if (paramIndex < params.length) {
const paramSymbol = params[paramIndex];
if ((paramSymbol.flags & ts.SymbolFlags.Optional) === 0) {
const paramType = checker.getTypeOfSymbol(paramSymbol);
if (!canBeUndefined(paramType)) {
reportUselessDefaultAssignment(node, 'parameter');
}
}
}
}
}
return;
}
if (parent.type === utils_1.AST_NODE_TYPES.Property) {
const propertyType = getTypeOfProperty(parent);
if (!propertyType) {
return;
}
if (!canBeUndefined(propertyType)) {
reportUselessDefaultAssignment(node, 'property');
}
}
else if (parent.type === utils_1.AST_NODE_TYPES.ArrayPattern) {
const sourceType = getSourceTypeForPattern(parent);
if (!sourceType) {
return;
}
if (!checker.isTupleType(sourceType)) {
return;
}
const tupleArgs = checker.getTypeArguments(sourceType);
const elementIndex = parent.elements.indexOf(node);
if (elementIndex < 0 || elementIndex >= tupleArgs.length) {
return;
}
const elementType = tupleArgs[elementIndex];
if (!canBeUndefined(elementType)) {
reportUselessDefaultAssignment(node, 'property');
}
}
}
function getTypeOfProperty(node) {
const objectPattern = node.parent;
const sourceType = getSourceTypeForPattern(objectPattern);
if (!sourceType) {
return null;
}
const propertyName = getPropertyName(node.key);
if (!propertyName) {
return null;
}
return getPropertyType(sourceType, propertyName);
}
function getSourceTypeForPattern(pattern) {
const parent = (0, util_1.nullThrows)(pattern.parent, util_1.NullThrowsReasons.MissingParent);
if (parent.type === utils_1.AST_NODE_TYPES.VariableDeclarator && parent.init) {
const tsNode = services.esTreeNodeToTSNodeMap.get(parent.init);
return checker.getTypeAtLocation(tsNode);
}
if ((0, util_1.isFunction)(parent)) {
const paramIndex = parent.params.indexOf(pattern);
const tsFunc = services.esTreeNodeToTSNodeMap.get(parent);
const signature = (0, util_1.nullThrows)(checker.getSignatureFromDeclaration(tsFunc), util_1.NullThrowsReasons.MissingToken('signature', 'function'));
const params = signature.getParameters();
return checker.getTypeOfSymbol(params[paramIndex]);
}
if (parent.type === utils_1.AST_NODE_TYPES.AssignmentPattern) {
return getSourceTypeForPattern(parent);
}
if (parent.type === utils_1.AST_NODE_TYPES.Property) {
return getTypeOfProperty(parent);
}
if (parent.type === utils_1.AST_NODE_TYPES.ArrayPattern) {
const arrayPattern = parent;
const arrayType = getSourceTypeForPattern(arrayPattern);
if (!arrayType) {
return null;
}
const elementIndex = arrayPattern.elements.indexOf(pattern);
return getArrayElementType(arrayType, elementIndex);
}
return null;
}
function getPropertyName(key) {
switch (key.type) {
case utils_1.AST_NODE_TYPES.Identifier:
return key.name;
case utils_1.AST_NODE_TYPES.Literal:
return String(key.value);
default:
return null;
}
}
function reportUselessDefaultAssignment(node, type) {
context.report({
node: node.right,
messageId: 'uselessDefaultAssignment',
data: { type },
fix: fixer => removeDefault(fixer, node),
});
}
function reportUselessUndefined(node, type) {
context.report({
node: node.right,
messageId: 'uselessUndefined',
data: { type },
fix: fixer => removeDefault(fixer, node),
});
}
function reportPreferOptionalSyntax(node) {
context.report({
node: node.right,
messageId: 'preferOptionalSyntax',
*fix(fixer) {
yield removeDefault(fixer, node);
const { left } = node;
if (left.type === utils_1.AST_NODE_TYPES.Identifier) {
yield fixer.insertTextAfterRange([left.range[0], left.range[0] + left.name.length], '?');
}
},
});
}
function removeDefault(fixer, node) {
const start = node.left.range[1];
const end = node.range[1];
return fixer.removeRange([start, end]);
}
return {
AssignmentPattern: checkAssignmentPattern,
};
},
});