| "use strict"; |
| var __importDefault = (this && this.__importDefault) || function (mod) { |
| return (mod && mod.__esModule) ? mod : { "default": mod }; |
| }; |
| var __importStar = (this && this.__importStar) || function (mod) { |
| if (mod && mod.__esModule) return mod; |
| var result = {}; |
| if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) result[k] = mod[k]; |
| result["default"] = mod; |
| return result; |
| }; |
| Object.defineProperty(exports, "__esModule", { value: true }); |
| const tsutils_1 = require("tsutils"); |
| const typescript_1 = __importDefault(require("typescript")); |
| const util = __importStar(require("../util")); |
| exports.default = util.createRule({ |
| name: 'no-unnecessary-type-assertion', |
| meta: { |
| docs: { |
| description: 'Warns if a type assertion does not change the type of an expression', |
| category: 'Best Practices', |
| recommended: false, |
| }, |
| fixable: 'code', |
| messages: { |
| unnecessaryAssertion: 'This assertion is unnecessary since it does not change the type of the expression.', |
| contextuallyUnnecessary: 'This assertion is unnecessary since the receiver accepts the original type of the expression.', |
| }, |
| schema: [ |
| { |
| type: 'object', |
| properties: { |
| typesToIgnore: { |
| type: 'array', |
| items: { |
| type: 'string', |
| }, |
| }, |
| }, |
| }, |
| ], |
| type: 'suggestion', |
| }, |
| defaultOptions: [{}], |
| create(context, [options]) { |
| const sourceCode = context.getSourceCode(); |
| const parserServices = util.getParserServices(context); |
| const checker = parserServices.program.getTypeChecker(); |
| const compilerOptions = parserServices.program.getCompilerOptions(); |
| /** |
| * Sometimes tuple types don't have ObjectFlags.Tuple set, like when they're being matched against an inferred type. |
| * So, in addition, check if there are integer properties 0..n and no other numeric keys |
| */ |
| function couldBeTupleType(type) { |
| const properties = type.getProperties(); |
| if (properties.length === 0) { |
| return false; |
| } |
| let i = 0; |
| for (; i < properties.length; ++i) { |
| const name = properties[i].name; |
| if (String(i) !== name) { |
| if (i === 0) { |
| // if there are no integer properties, this is not a tuple |
| return false; |
| } |
| break; |
| } |
| } |
| for (; i < properties.length; ++i) { |
| if (String(+properties[i].name) === properties[i].name) { |
| return false; // if there are any other numeric properties, this is not a tuple |
| } |
| } |
| return true; |
| } |
| /** |
| * Returns the contextual type of a given node. |
| * Contextual type is the type of the target the node is going into. |
| * i.e. the type of a called function's parameter, or the defined type of a variable declaration |
| */ |
| function getContextualType(checker, node) { |
| const parent = node.parent; |
| if (!parent) { |
| return; |
| } |
| if (tsutils_1.isCallExpression(parent) || tsutils_1.isNewExpression(parent)) { |
| if (node === parent.expression) { |
| // is the callee, so has no contextual type |
| return; |
| } |
| } |
| else if (tsutils_1.isVariableDeclaration(parent) || |
| tsutils_1.isPropertyDeclaration(parent) || |
| tsutils_1.isParameterDeclaration(parent)) { |
| return parent.type |
| ? checker.getTypeFromTypeNode(parent.type) |
| : undefined; |
| } |
| else if (![typescript_1.default.SyntaxKind.TemplateSpan, typescript_1.default.SyntaxKind.JsxExpression].includes(parent.kind)) { |
| // parent is not something we know we can get the contextual type of |
| return; |
| } |
| // TODO - support return statement checking |
| return checker.getContextualType(node); |
| } |
| /** |
| * Returns true if there's a chance the variable has been used before a value has been assigned to it |
| */ |
| function isPossiblyUsedBeforeAssigned(node) { |
| const declaration = util.getDeclaration(checker, node); |
| if (!declaration) { |
| // don't know what the declaration is for some reason, so just assume the worst |
| return true; |
| } |
| if ( |
| // non-strict mode doesn't care about used before assigned errors |
| tsutils_1.isStrictCompilerOptionEnabled(compilerOptions, 'strictNullChecks') && |
| // ignore class properties as they are compile time guarded |
| // also ignore function arguments as they can't be used before defined |
| tsutils_1.isVariableDeclaration(declaration) && |
| // is it `const x!: number` |
| declaration.initializer === undefined && |
| declaration.exclamationToken === undefined && |
| declaration.type !== undefined) { |
| // check if the defined variable type has changed since assignment |
| const declarationType = checker.getTypeFromTypeNode(declaration.type); |
| const type = util.getConstrainedTypeAtLocation(checker, node); |
| if (declarationType === type) { |
| // possibly used before assigned, so just skip it |
| // better to false negative and skip it, than false postiive and fix to compile erroring code |
| // |
| // no better way to figure this out right now |
| // https://github.com/Microsoft/TypeScript/issues/31124 |
| return true; |
| } |
| } |
| return false; |
| } |
| return { |
| TSNonNullExpression(node) { |
| const originalNode = parserServices.esTreeNodeToTSNodeMap.get(node); |
| const type = util.getConstrainedTypeAtLocation(checker, originalNode.expression); |
| if (!util.isNullableType(type)) { |
| if (isPossiblyUsedBeforeAssigned(originalNode.expression)) { |
| return; |
| } |
| context.report({ |
| node, |
| messageId: 'unnecessaryAssertion', |
| fix(fixer) { |
| return fixer.removeRange([ |
| originalNode.expression.end, |
| originalNode.end, |
| ]); |
| }, |
| }); |
| } |
| else { |
| // we know it's a nullable type |
| // so figure out if the variable is used in a place that accepts nullable types |
| const contextualType = getContextualType(checker, originalNode); |
| if (contextualType) { |
| // in strict mode you can't assign null to undefined, so we have to make sure that |
| // the two types share a nullable type |
| const typeIncludesUndefined = util.isTypeFlagSet(type, typescript_1.default.TypeFlags.Undefined); |
| const typeIncludesNull = util.isTypeFlagSet(type, typescript_1.default.TypeFlags.Null); |
| const contextualTypeIncludesUndefined = util.isTypeFlagSet(contextualType, typescript_1.default.TypeFlags.Undefined); |
| const contextualTypeIncludesNull = util.isTypeFlagSet(contextualType, typescript_1.default.TypeFlags.Null); |
| if ((typeIncludesUndefined && contextualTypeIncludesUndefined) || |
| (typeIncludesNull && contextualTypeIncludesNull)) { |
| context.report({ |
| node, |
| messageId: 'contextuallyUnnecessary', |
| fix(fixer) { |
| return fixer.removeRange([ |
| originalNode.expression.end, |
| originalNode.end, |
| ]); |
| }, |
| }); |
| } |
| } |
| } |
| }, |
| 'TSAsExpression, TSTypeAssertion'(node) { |
| if (options && |
| options.typesToIgnore && |
| options.typesToIgnore.indexOf(sourceCode.getText(node.typeAnnotation)) !== -1) { |
| return; |
| } |
| const originalNode = parserServices.esTreeNodeToTSNodeMap.get(node); |
| const castType = checker.getTypeAtLocation(originalNode); |
| if (tsutils_1.isTypeFlagSet(castType, typescript_1.default.TypeFlags.Literal) || |
| (tsutils_1.isObjectType(castType) && |
| (tsutils_1.isObjectFlagSet(castType, typescript_1.default.ObjectFlags.Tuple) || |
| couldBeTupleType(castType)))) { |
| // It's not always safe to remove a cast to a literal type or tuple |
| // type, as those types are sometimes widened without the cast. |
| return; |
| } |
| const uncastType = checker.getTypeAtLocation(originalNode.expression); |
| if (uncastType === castType) { |
| context.report({ |
| node, |
| messageId: 'unnecessaryAssertion', |
| fix(fixer) { |
| return originalNode.kind === typescript_1.default.SyntaxKind.TypeAssertionExpression |
| ? fixer.removeRange([ |
| originalNode.getStart(), |
| originalNode.expression.getStart(), |
| ]) |
| : fixer.removeRange([ |
| originalNode.expression.end, |
| originalNode.end, |
| ]); |
| }, |
| }); |
| } |
| // TODO - add contextually unnecessary check for this |
| }, |
| }; |
| }, |
| }); |
| //# sourceMappingURL=no-unnecessary-type-assertion.js.map |
