@typescript-eslint/eslint-plugin
Version:
TypeScript plugin for ESLint
159 lines (158 loc) • 7.1 kB
JavaScript
;
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}) : function(o, v) {
o["default"] = v;
});
var __importStar = (this && this.__importStar) || (function () {
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};
})();
Object.defineProperty(exports, "__esModule", { value: true });
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-unsafe-type-assertion',
meta: {
type: 'problem',
docs: {
description: 'Disallow type assertions that narrow a type',
requiresTypeChecking: true,
},
messages: {
unsafeOfAnyTypeAssertion: 'Unsafe assertion from {{type}} detected: consider using type guards or a safer assertion.',
unsafeToAnyTypeAssertion: 'Unsafe assertion to {{type}} detected: consider using a more specific type to ensure safety.',
unsafeToUnconstrainedTypeAssertion: "Unsafe type assertion: '{{type}}' could be instantiated with an arbitrary type which could be unrelated to the original type.",
unsafeTypeAssertion: "Unsafe type assertion: type '{{type}}' is more narrow than the original type.",
unsafeTypeAssertionAssignableToConstraint: "Unsafe type assertion: the original type is assignable to the constraint of type '{{type}}', but '{{type}}' could be instantiated with a different subtype of its constraint.",
},
schema: [],
},
defaultOptions: [],
create(context) {
const services = (0, util_1.getParserServices)(context);
const checker = services.program.getTypeChecker();
function getAnyTypeName(type) {
return tsutils.isIntrinsicErrorType(type) ? 'error typed' : '`any`';
}
function isObjectLiteralType(type) {
return (tsutils.isObjectType(type) &&
tsutils.isObjectFlagSet(type, ts.ObjectFlags.ObjectLiteral));
}
function checkExpression(node) {
const expressionType = services.getTypeAtLocation(node.expression);
const assertedType = services.getTypeAtLocation(node.typeAnnotation);
if (expressionType === assertedType) {
return;
}
// handle cases when asserting unknown ==> any.
if ((0, util_1.isTypeAnyType)(assertedType) && (0, util_1.isTypeUnknownType)(expressionType)) {
context.report({
node,
messageId: 'unsafeToAnyTypeAssertion',
data: {
type: '`any`',
},
});
return;
}
const unsafeExpressionAny = (0, util_1.isUnsafeAssignment)(expressionType, assertedType, checker, node.expression);
if (unsafeExpressionAny) {
context.report({
node,
messageId: 'unsafeOfAnyTypeAssertion',
data: {
type: getAnyTypeName(unsafeExpressionAny.sender),
},
});
return;
}
const unsafeAssertedAny = (0, util_1.isUnsafeAssignment)(assertedType, expressionType, checker, node.typeAnnotation);
if (unsafeAssertedAny) {
context.report({
node,
messageId: 'unsafeToAnyTypeAssertion',
data: {
type: getAnyTypeName(unsafeAssertedAny.sender),
},
});
return;
}
// Use the widened type in case of an object literal so `isTypeAssignableTo()`
// won't fail on excess property check.
const expressionWidenedType = isObjectLiteralType(expressionType)
? checker.getWidenedType(expressionType)
: expressionType;
const isAssertionSafe = checker.isTypeAssignableTo(expressionWidenedType, assertedType);
if (isAssertionSafe) {
return;
}
// Produce a more specific error message when targeting a type parameter
if (tsutils.isTypeParameter(assertedType)) {
const assertedTypeConstraint = checker.getBaseConstraintOfType(assertedType);
if (!assertedTypeConstraint) {
// asserting to an unconstrained type parameter is unsafe
context.report({
node,
messageId: 'unsafeToUnconstrainedTypeAssertion',
data: {
type: checker.typeToString(assertedType),
},
});
return;
}
// special case message if the original type is assignable to the
// constraint of the target type parameter
const isAssignableToConstraint = checker.isTypeAssignableTo(expressionWidenedType, assertedTypeConstraint);
if (isAssignableToConstraint) {
context.report({
node,
messageId: 'unsafeTypeAssertionAssignableToConstraint',
data: {
type: checker.typeToString(assertedType),
},
});
return;
}
}
// General error message
context.report({
node,
messageId: 'unsafeTypeAssertion',
data: {
type: checker.typeToString(assertedType),
},
});
}
return {
'TSAsExpression, TSTypeAssertion'(node) {
checkExpression(node);
},
};
},
});