unified-signatures.test.ts

import rule from '../../src/rules/unified-signatures';
import { RuleTester } from '../RuleTester';

//------------------------------------------------------------------------------
// Tests
//------------------------------------------------------------------------------

const ruleTester = new RuleTester({ parser: '@typescript-eslint/parser' });

ruleTester.run('unified-signatures', rule, {
  valid: [
    `
function g(): void;
function g(a: number, b: number): void;
function g(a?: number, b?: number): void {}
 `,
    `
function rest(...xs: number[]): void;
function rest(xs: number[], y: string): void;
function rest(...args: any[]) {}
`,
    `
class C {
    constructor();
    constructor(a: number, b: number);
    constructor(a?: number, b?: number) {}

    a(): void;
    a(a: number, b: number): void;
    a(a?: number, b?: number): void {}
}
`,
    // No error for arity difference greater than 1.
    `
interface I {
    a2(): void;
    a2(x: number, y: number): void;
}
`,
    // No error for different return types.
    `
interface I {
    a4(): void;
    a4(x: number): number;
}
`,
    // No error if one takes a type parameter and the other doesn't.
    `
interface I {
    a5<T>(x: T): T;
    a5(x: number): number;
}
`,
    // No error if one is a rest parameter and other isn't.
    `
interface I {
    b2(x: string): void;
    b2(...x: number[]): void;
}
`,
    // No error if both are rest parameters. (https://github.com/Microsoft/TypeScript/issues/5077)
    `
interface I {
    b3(...x: number[]): void;
    b3(...x: string[]): void;
}
`,
    // No error if one is optional and the other isn't.
    `
interface I {
    c3(x: number): void;
    c3(x?: string): void;
}
`,
    // No error if they differ by 2 or more parameters.
    `
interface I {
    d2(x: string, y: number): void;
    d2(x: number, y: string): void;
}
`,
    // No conflict between static/non-static members.
    `
declare class D {
    static a();
    a(x: number);
}
`,
    // Allow separate overloads if one is generic and the other isn't.
    `
interface Generic<T> {
    x(): void;
    x(x: T[]): void;
}
`,
    // Allow signatures if the type is not equal.
    `
interface I {
  f(x1:number): void;
  f(x1:boolean, x2?: number): void;
}
`,
    // AllowType parameters that are not equal
    `
function f<T extends number>(x: T[]): void;
function f<T extends string>(x: T): void;
 `,
  ],
  invalid: [
    {
      code: `
function f(x: number): void;
function f(x: string): void;
function f(x: any): any {
    return x;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: 'string',
          },
          line: 3,
          column: 12,
        },
      ],
    },
    {
      code: `
function opt(xs?: number[]): void;
function opt(xs: number[], y: string): void;
function opt(...args: any[]) {}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 3,
          column: 28,
        },
      ],
    },
    {
      // For 3 or more overloads, mentions the line.
      code: `
interface I {
    a0(): void;
    a0(x: string): string;
    a0(x: number): void;
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'This overload and the one on line 3 can be combined into one signature',
          },
          line: 5,
          column: 8,
        },
      ],
    },
    {
      // Error for extra parameter.
      code: `
interface I {
    a1(): void;
    a1(x: number): void;
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 8,
        },
      ],
    },
    {
      // Error for arity difference greater than 1 if the additional parameters are all optional/rest.
      code: `
interface I {
    a3(): void;
    a3(x: number, y?: number, ...z: number[]): void;
}
`,
      errors: [
        {
          messageId: 'omittingRestParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 31,
        },
      ],
    },
    {
      // Error if only one defines a rest parameter.
      code: `
interface I {
    b(): void;
    b(...x: number[]): void;
}
`,
      errors: [
        {
          messageId: 'omittingRestParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 7,
        },
      ],
    },
    {
      // Error if only one defines an optional parameter.
      code: `
interface I {
    c(): void;
    c(x?: number): void;
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 7,
        },
      ],
    },
    {
      // Error if both are optional.
      code: `
interface I {
    c2(x?: number): void;
    c2(x?: string): void;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: 'string',
          },
          line: 4,
          column: 8,
        },
      ],
    },
    {
      // Error for different types (could be a union)
      code: `
interface I {
    d(x: number): void;
    d(x: string): void;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: 'string',
          },
          line: 4,
          column: 7,
        },
      ],
    },
    {
      // Works for type literal and call signature too.
      code: `
type T = {
    (): void;
    (x: number): void;
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 6,
        },
      ],
    },
    {
      // Works for constructor.
      code: `
declare class C {
    constructor();
    constructor(x: number);
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 17,
        },
      ],
    },
    {
      // Works with unions.
      code: `
interface I {
    f(x: number);
    f(x: string | boolean);
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: 'string | boolean',
          },
          line: 4,
          column: 7,
        },
      ],
    },
    {
      // Works with tuples.
      code: `
interface I {
    f(x: number);
    f(x: [string, boolean]);
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: '[string, boolean]',
          },
          line: 4,
          column: 7,
        },
      ],
    },
    {
      code: `
interface Generic<T> {
    y(x: T[]): void;
    y(x: T): void;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'T[]',
            type2: 'T',
          },
          line: 4,
          column: 7,
        },
      ],
    },
    {
      // Check type parameters when equal
      code: `
function f<T>(x: T[]): void;
function f<T>(x: T): void;
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'T[]',
            type2: 'T',
          },
          line: 3,
          column: 15,
        },
      ],
    },
    {
      // Verifies type parameters and constraints
      code: `
function f<T extends number>(x: T[]): void;
function f<T extends number>(x: T): void;
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'T[]',
            type2: 'T',
          },
          line: 3,
          column: 30,
        },
      ],
    },
    {
      // Works with abstract
      code: `
abstract class Foo {
    public abstract f(x: number): void;
    public abstract f(x: string): void;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: 'string',
          },
          line: 4,
          column: 23,
        },
      ],
    },
    {
      // Works with literals
      code: `
interface Foo {
    "f"(x: string): void;
    "f"(x: number): void;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'string',
            type2: 'number',
          },
          line: 4,
          column: 9,
        },
      ],
    },
    {
      // Works with new constructor
      code: `
interface Foo {
    new(x: string): Foo;
    new(x: number): Foo;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'string',
            type2: 'number',
          },
          line: 4,
          column: 9,
        },
      ],
    },
    {
      // Works with new computed properties
      code: `
enum Enum {
    Func = "function",
}

interface IFoo {
    [Enum.Func](x: string): void;
    [Enum.Func](x: number): void;
}
`,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'string',
            type2: 'number',
          },
          line: 8,
          column: 17,
        },
      ],
    },
    {
      // Works with parameter properties. Note that this is invalid TypeScript syntax.
      code: `
class Foo {
    constructor(readonly x: number);
    constructor(readonly x: string);
}
    `,
      errors: [
        {
          messageId: 'singleParameterDifference',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
            type1: 'number',
            type2: 'string',
          },
          line: 4,
          column: 17,
        },
      ],
    },
    {
      // Works with parameter properties. Note that this is invalid TypeScript syntax.
      code: `
class Foo {
    constructor(readonly x: number);
    constructor(readonly x: number, readonly y: string);
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 37,
        },
      ],
    },
    {
      // Works with parameter properties. Note that this is invalid TypeScript syntax.
      code: `
class Foo {
    constructor(readonly x: number);
    constructor(readonly x: number, readonly y?: string, readonly z?: string);
}
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 4,
          column: 58,
        },
      ],
    },
    {
      code: `
export function foo(line: number): number;
export function foo(line: number, character?: number): number;
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 3,
          column: 35,
        },
      ],
    },
    {
      code: `
declare function foo(line: number): number;
export function foo(line: number, character?: number): number;
`,
      errors: [
        {
          messageId: 'omittingSingleParameter',
          data: {
            failureStringStart:
              'These overloads can be combined into one signature',
          },
          line: 3,
          column: 35,
        },
      ],
    },
  ],
});