250 lines
12 KiB
Plaintext
250 lines
12 KiB
Plaintext
"use strict";
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var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
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if (k2 === undefined) k2 = k;
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var desc = Object.getOwnPropertyDescriptor(m, k);
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if (!desc || ("get" in desc ? !m.__esModule : desc.writable || desc.configurable)) {
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desc = { enumerable: true, get: function() { return m[k]; } };
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}
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Object.defineProperty(o, k2, desc);
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}) : (function(o, m, k, k2) {
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if (k2 === undefined) k2 = k;
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o[k2] = m[k];
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}));
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var __setModuleDefault = (this && this.__setModuleDefault) || (Object.create ? (function(o, v) {
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Object.defineProperty(o, "default", { enumerable: true, value: v });
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}) : function(o, v) {
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o["default"] = v;
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});
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var __importStar = (this && this.__importStar) || function (mod) {
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if (mod && mod.__esModule) return mod;
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var result = {};
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if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
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__setModuleDefault(result, mod);
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return result;
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};
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Object.defineProperty(exports, "__esModule", { value: true });
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const utils_1 = require("@typescript-eslint/utils");
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const tsutils = __importStar(require("ts-api-utils"));
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const ts = __importStar(require("typescript"));
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const util_1 = require("../util");
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exports.default = (0, util_1.createRule)({
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name: 'no-unnecessary-type-assertion',
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meta: {
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docs: {
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description: 'Disallow type assertions that do not change the type of an expression',
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recommended: 'recommended',
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requiresTypeChecking: true,
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},
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fixable: 'code',
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messages: {
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unnecessaryAssertion: 'This assertion is unnecessary since it does not change the type of the expression.',
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contextuallyUnnecessary: 'This assertion is unnecessary since the receiver accepts the original type of the expression.',
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},
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schema: [
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{
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type: 'object',
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additionalProperties: false,
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properties: {
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typesToIgnore: {
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description: 'A list of type names to ignore.',
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type: 'array',
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items: {
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type: 'string',
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},
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},
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},
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},
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],
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type: 'suggestion',
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},
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defaultOptions: [{}],
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create(context, [options]) {
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const services = (0, util_1.getParserServices)(context);
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const checker = services.program.getTypeChecker();
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const compilerOptions = services.program.getCompilerOptions();
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/**
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* Sometimes tuple types don't have ObjectFlags.Tuple set, like when they're being matched against an inferred type.
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* So, in addition, check if there are integer properties 0..n and no other numeric keys
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*/
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function couldBeTupleType(type) {
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const properties = type.getProperties();
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if (properties.length === 0) {
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return false;
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}
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let i = 0;
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for (; i < properties.length; ++i) {
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const name = properties[i].name;
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if (String(i) !== name) {
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if (i === 0) {
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// if there are no integer properties, this is not a tuple
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return false;
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}
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break;
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}
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}
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for (; i < properties.length; ++i) {
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if (String(+properties[i].name) === properties[i].name) {
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return false; // if there are any other numeric properties, this is not a tuple
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}
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}
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return true;
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}
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/**
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* Returns true if there's a chance the variable has been used before a value has been assigned to it
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*/
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function isPossiblyUsedBeforeAssigned(node) {
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const declaration = (0, util_1.getDeclaration)(services, node);
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if (!declaration) {
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// don't know what the declaration is for some reason, so just assume the worst
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return true;
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}
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if (
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// non-strict mode doesn't care about used before assigned errors
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tsutils.isStrictCompilerOptionEnabled(compilerOptions, 'strictNullChecks') &&
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// ignore class properties as they are compile time guarded
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// also ignore function arguments as they can't be used before defined
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ts.isVariableDeclaration(declaration) &&
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// is it `const x!: number`
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declaration.initializer === undefined &&
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declaration.exclamationToken === undefined &&
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declaration.type !== undefined) {
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// check if the defined variable type has changed since assignment
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const declarationType = checker.getTypeFromTypeNode(declaration.type);
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const type = (0, util_1.getConstrainedTypeAtLocation)(services, node);
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if (declarationType === type) {
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// possibly used before assigned, so just skip it
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// better to false negative and skip it, than false positive and fix to compile erroring code
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//
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// no better way to figure this out right now
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// https://github.com/Microsoft/TypeScript/issues/31124
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return true;
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}
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}
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return false;
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}
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function isConstAssertion(node) {
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return (node.type === utils_1.AST_NODE_TYPES.TSTypeReference &&
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node.typeName.type === utils_1.AST_NODE_TYPES.Identifier &&
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node.typeName.name === 'const');
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}
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return {
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TSNonNullExpression(node) {
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if (node.parent.type === utils_1.AST_NODE_TYPES.AssignmentExpression &&
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node.parent.operator === '=') {
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if (node.parent.left === node) {
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context.report({
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node,
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messageId: 'contextuallyUnnecessary',
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fix(fixer) {
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return fixer.removeRange([
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node.expression.range[1],
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node.range[1],
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]);
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},
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});
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}
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// for all other = assignments we ignore non-null checks
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// this is because non-null assertions can change the type-flow of the code
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// so whilst they might be unnecessary for the assignment - they are necessary
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// for following code
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return;
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}
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const originalNode = services.esTreeNodeToTSNodeMap.get(node);
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const type = (0, util_1.getConstrainedTypeAtLocation)(services, node.expression);
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if (!(0, util_1.isNullableType)(type)) {
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if (node.expression.type === utils_1.AST_NODE_TYPES.Identifier &&
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isPossiblyUsedBeforeAssigned(node.expression)) {
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return;
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}
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context.report({
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node,
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messageId: 'unnecessaryAssertion',
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fix(fixer) {
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return fixer.removeRange([node.range[1] - 1, node.range[1]]);
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},
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});
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}
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else {
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// we know it's a nullable type
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// so figure out if the variable is used in a place that accepts nullable types
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const contextualType = (0, util_1.getContextualType)(checker, originalNode);
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if (contextualType) {
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// in strict mode you can't assign null to undefined, so we have to make sure that
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// the two types share a nullable type
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const typeIncludesUndefined = (0, util_1.isTypeFlagSet)(type, ts.TypeFlags.Undefined);
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const typeIncludesNull = (0, util_1.isTypeFlagSet)(type, ts.TypeFlags.Null);
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const contextualTypeIncludesUndefined = (0, util_1.isTypeFlagSet)(contextualType, ts.TypeFlags.Undefined);
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const contextualTypeIncludesNull = (0, util_1.isTypeFlagSet)(contextualType, ts.TypeFlags.Null);
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// make sure that the parent accepts the same types
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// i.e. assigning `string | null | undefined` to `string | undefined` is invalid
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const isValidUndefined = typeIncludesUndefined
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? contextualTypeIncludesUndefined
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: true;
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const isValidNull = typeIncludesNull
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? contextualTypeIncludesNull
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: true;
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if (isValidUndefined && isValidNull) {
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context.report({
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node,
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messageId: 'contextuallyUnnecessary',
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fix(fixer) {
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return fixer.removeRange([
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node.expression.range[1],
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node.range[1],
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]);
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},
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});
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}
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}
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}
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},
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'TSAsExpression, TSTypeAssertion'(node) {
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if (options.typesToIgnore?.includes(context.sourceCode.getText(node.typeAnnotation)) ||
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isConstAssertion(node.typeAnnotation)) {
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return;
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}
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const castType = services.getTypeAtLocation(node);
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if ((0, util_1.isTypeFlagSet)(castType, ts.TypeFlags.Literal) ||
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(tsutils.isObjectType(castType) &&
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(tsutils.isObjectFlagSet(castType, ts.ObjectFlags.Tuple) ||
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couldBeTupleType(castType)))) {
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// It's not always safe to remove a cast to a literal type or tuple
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// type, as those types are sometimes widened without the cast.
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return;
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}
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const uncastType = services.getTypeAtLocation(node.expression);
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if (uncastType === castType) {
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context.report({
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node,
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messageId: 'unnecessaryAssertion',
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fix(fixer) {
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if (node.type === utils_1.AST_NODE_TYPES.TSTypeAssertion) {
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const openingAngleBracket = context.sourceCode.getTokenBefore(node.typeAnnotation, token => token.type === utils_1.AST_TOKEN_TYPES.Punctuator &&
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token.value === '<');
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const closingAngleBracket = context.sourceCode.getTokenAfter(node.typeAnnotation, token => token.type === utils_1.AST_TOKEN_TYPES.Punctuator &&
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token.value === '>');
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// < ( number ) > ( 3 + 5 )
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// ^---remove---^
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return fixer.removeRange([
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openingAngleBracket.range[0],
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closingAngleBracket.range[1],
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]);
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}
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// `as` is always present in TSAsExpression
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const asToken = context.sourceCode.getTokenAfter(node.expression, token => token.type === utils_1.AST_TOKEN_TYPES.Identifier &&
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token.value === 'as');
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const tokenBeforeAs = context.sourceCode.getTokenBefore(asToken, {
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includeComments: true,
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});
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// ( 3 + 5 ) as number
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// ^--remove--^
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return fixer.removeRange([tokenBeforeAs.range[1], node.range[1]]);
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},
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});
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}
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// TODO - add contextually unnecessary check for this
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},
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};
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},
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});
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//# sourceMappingURL=no-unnecessary-type-assertion.js.map |