Add expectNotType assertion - fixes #56

readme.md

@@ -154,6 +154,10 @@ These options will be overridden if a `tsconfig.json` file is found in your proj
 
 Check that the type of `value` is identical to type `T`.
 
+### expectNotType<T>(value)
+
+Check that the type of `value` is not identical to type `T`.
+
 ### expectAssignable<T>(value)
 
 Check that the type of `value` is assignable to type `T`.

source/lib/assertions/assert.ts

@@ -8,6 +8,17 @@ export const expectType = <T>(value: T) => {		// tslint:disable-line:no-unused
 	// Do nothing, the TypeScript compiler handles this for us
 };
 
+/**
+ * Check that the type of `value` is not identical to type `T`.
+ *
+ * @param value - Value that should be identical to type `T`.
+ */
+// @ts-ignore
+export const expectNotType = <T>(value: any) => {		// tslint:disable-line:no-unused
+	// TODO Use a `not T` type when possible https://github.com/microsoft/TypeScript/pull/29317
+	// Do nothing, the TypeScript compiler handles this for us
+};
+
 /**
  * Check that the type of `value` is assignable to type `T`.
  *

source/lib/assertions/handlers/identicality.ts

@@ -0,0 +1,85 @@
+import {CallExpression} from '../../../../libraries/typescript/lib/typescript';
+import {TypeChecker} from '../../entities/typescript';
+import {Diagnostic} from '../../interfaces';
+import {makeDiagnostic} from '../../utils';
+
+/**
+ * Verifies that the argument of the assertion is identical to the generic type of the assertion.
+ *
+ * @param checker - The TypeScript type checker.
+ * @param nodes - The `expectType` AST nodes.
+ * @return List of custom diagnostics.
+ */
+export const isIdentical = (checker: TypeChecker, nodes: Set<CallExpression>): Diagnostic[] => {
+	const diagnostics: Diagnostic[] = [];
+
+	if (!nodes) {
+		return diagnostics;
+	}
+
+	for (const node of nodes) {
+		if (!node.typeArguments) {
+			// Skip if the node does not have generics
+			continue;
+		}
+
+		// Retrieve the type to be expected. This is the type inside the generic.
+		const expectedType = checker.getTypeFromTypeNode(node.typeArguments[0]);
+
+		// Retrieve the argument type. This is the type to be checked.
+		const argumentType = checker.getTypeAtLocation(node.arguments[0]);
+
+		if (!checker.isTypeAssignableTo(argumentType, expectedType)) {
+			// The argument type is not assignable to the expected type. TypeScript will catch this for us.
+			continue;
+		}
+
+		if (!checker.isTypeAssignableTo(expectedType, argumentType)) {
+			/**
+			 * The expected type is not assignable to the argument type, but the argument type is
+			 * assignable to the expected type. This means our type is too wide.
+			 */
+			diagnostics.push(makeDiagnostic(node, `Parameter type \`${checker.typeToString(expectedType)}\` is declared too wide for argument type \`${checker.typeToString(argumentType)}\`.`));
+		} else if (!checker.isTypeIdenticalTo(expectedType, argumentType)) {
+			/**
+			 * The expected type and argument type are assignable in both directions. We still have to check
+			 * if the types are identical. See https://github.com/Microsoft/TypeScript/blob/master/doc/spec.md#3.11.2.
+			 */
+			diagnostics.push(makeDiagnostic(node, `Parameter type \`${checker.typeToString(expectedType)}\` is not identical to argument type \`${checker.typeToString(argumentType)}\`.`));
+		}
+	}
+
+	return diagnostics;
+};
+
+/**
+ * Verifies that the argument of the assertion is not identical to the generic type of the assertion.
+ *
+ * @param checker - The TypeScript type checker.
+ * @param nodes - The `expectType` AST nodes.
+ * @return List of custom diagnostics.
+ */
+export const isNotIdentical = (checker: TypeChecker, nodes: Set<CallExpression>): Diagnostic[] => {
+	const diagnostics: Diagnostic[] = [];
+
+	if (!nodes) {
+		return diagnostics;
+	}
+
+	for (const node of nodes) {
+		if (!node.typeArguments) {
+			// Skip if the node does not have generics
+			continue;
+		}
+
+		// Retrieve the type to be expected. This is the type inside the generic.
+		const expectedType = checker.getTypeFromTypeNode(node.typeArguments[0]);
+		const argumentType = checker.getTypeAtLocation(node.arguments[0]);
+
+		if (checker.isTypeIdenticalTo(expectedType, argumentType)) {
+			diagnostics.push(makeDiagnostic(node, `Parameter type \`${checker.typeToString(expectedType)}\` is identical to argument type \`${checker.typeToString(argumentType)}\`.`));
+		}
+	}
+
+	return diagnostics;
+};

source/lib/assertions/handlers/index.ts

@@ -1,6 +1,6 @@
 export {Handler} from './handler';
 
 // Handlers
-export {strictAssertion} from './strict-assertion';
+export {isIdentical, isNotIdentical} from './identicality';
 export {isNotAssignable} from './assignability';
 export {expectDeprecated, expectNotDeprecated} from './expect-deprecated';

source/lib/assertions/index.ts

@@ -1,10 +1,11 @@
 import {CallExpression} from '../../../libraries/typescript/lib/typescript';
 import {TypeChecker} from '../entities/typescript';
 import {Diagnostic} from '../interfaces';
-import {Handler, strictAssertion, isNotAssignable, expectDeprecated, expectNotDeprecated} from './handlers';
+import {Handler, isIdentical, isNotIdentical, isNotAssignable, expectDeprecated, expectNotDeprecated} from './handlers';
 
 export enum Assertion {
 	EXPECT_TYPE = 'expectType',
+	EXPECT_NOT_TYPE = 'expectNotType',
 	EXPECT_ERROR = 'expectError',
 	EXPECT_ASSIGNABLE = 'expectAssignable',
 	EXPECT_NOT_ASSIGNABLE = 'expectNotAssignable',
@@ -14,7 +15,8 @@ export enum Assertion {
 
 // List of diagnostic handlers attached to the assertion
 const assertionHandlers = new Map<string, Handler | Handler[]>([
-	[Assertion.EXPECT_TYPE, strictAssertion],
+	[Assertion.EXPECT_TYPE, isIdentical],
+	[Assertion.EXPECT_NOT_TYPE, isNotIdentical],
 	[Assertion.EXPECT_NOT_ASSIGNABLE, isNotAssignable],
 	[Assertion.EXPECT_DEPRECATED, expectDeprecated],
 	[Assertion.EXPECT_NOT_DEPRECATED, expectNotDeprecated]

source/test/fixtures/identicality/identical/index.d.ts

@@ -0,0 +1,6 @@
+declare const concat: {
+	(foo: string, bar: string): string;
+	(foo: number, bar: number): number;
+};
+
+export default concat;

source/test/fixtures/identicality/identical/index.js

@@ -0,0 +1,3 @@
+module.exports.default = (foo, bar) => {
+	return foo + bar;
+};

source/test/fixtures/identicality/identical/index.test-d.ts

@@ -0,0 +1,8 @@
+import {expectType} from '../../../..';
+import concat from '.';
+
+expectType<string>(concat('foo', 'bar'));
+expectType<number>(concat(1, 2));
+
+expectType<any>(concat(1, 2));
+expectType<string | number>(concat('unicorn', 'rainbow'));

source/test/fixtures/identicality/identical/package.json

@@ -0,0 +1,3 @@
+{
+	"name": "foo"
+}

source/test/fixtures/identicality/not-identical/index.d.ts

@@ -0,0 +1,6 @@
+declare const concat: {
+	(foo: string, bar: string): string;
+	(foo: number, bar: number): number;
+};
+
+export default concat;

source/test/fixtures/identicality/not-identical/index.js

@@ -0,0 +1,3 @@
+module.exports.default = (foo, bar) => {
+	return foo + bar;
+};

source/test/fixtures/identicality/not-identical/index.test-d.ts

@@ -0,0 +1,7 @@
+import {expectNotType} from '../../../..';
+import concat from '.';
+
+expectNotType<number>(concat('foo', 'bar'));
+expectNotType<string | number>(concat('foo', 'bar'));
+
+expectNotType<string>(concat('unicorn', 'rainbow'));

source/test/fixtures/identicality/not-identical/package.json

@@ -0,0 +1,3 @@
+{
+	"name": "foo"
+}

source/test/identicality.ts

@@ -0,0 +1,21 @@
+import * as path from 'path';
+import test from 'ava';
+import {verify} from './fixtures/utils';
+import tsd from '..';
+
+test('identical', async t => {
+	const diagnostics = await tsd({cwd: path.join(__dirname, 'fixtures/identicality/identical')});
+
+	verify(t, diagnostics, [
+		[7, 0, 'error', 'Parameter type `any` is declared too wide for argument type `number`.'],
+		[8, 0, 'error', 'Parameter type `string | number` is declared too wide for argument type `string`.']
+	]);
+});
+
+test('not identical', async t => {
+	const diagnostics = await tsd({cwd: path.join(__dirname, 'fixtures/identicality/not-identical')});
+
+	verify(t, diagnostics, [
+		[7, 0, 'error', 'Parameter type `string` is identical to argument type `string`.']
+	]);
+});