noVoidTypeReturn

Diagnostic Category: lint/correctness/noVoidTypeReturn

TypeScript and TSX

Since: v1.0.0

Description

Disallow returning a value from a function with the return type ‘void’

‘void’ signals the absence of value. The returned value is likely to be ignored by the caller. Thus, returning a value when the return type of function is ‘void’, is undoubtedly an error.

Only returning without a value is allowed, as it’s a control flow statement.

Examples

Invalid

class A {
    f(): void {
        return undefined;
    }
}

code-block.ts:3:9 lint/correctness/noVoidTypeReturn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The function should not return a value because its return type is void.
  
    1 │ class A {
    2 │     f(): void {
  > 3 │         return undefined;
      │         ^^^^^^^^^^^^^^^^^
    4 │     }
    5 │ }
  
  ℹ The function is here:
  
    1 │ class A {
  > 2 │     f(): void {
      │     ^^^^^^^^^^^
  > 3 │         return undefined;
  > 4 │     }
      │     ^
    5 │ }
    6 │ 
  
  ℹ ‘void’ signals the absence of value. The returned value is likely to be ignored by the caller.

const a = {
    f(): void {
        return undefined;
    }
}

code-block.ts:3:9 lint/correctness/noVoidTypeReturn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The function should not return a value because its return type is void.
  
    1 │ const a = {
    2 │     f(): void {
  > 3 │         return undefined;
      │         ^^^^^^^^^^^^^^^^^
    4 │     }
    5 │ }
  
  ℹ The function is here:
  
    1 │ const a = {
  > 2 │     f(): void {
      │     ^^^^^^^^^^^
  > 3 │         return undefined;
  > 4 │     }
      │     ^
    5 │ }
    6 │ 
  
  ℹ ‘void’ signals the absence of value. The returned value is likely to be ignored by the caller.

function f(): void {
    return undefined;
}

code-block.ts:2:5 lint/correctness/noVoidTypeReturn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The function should not return a value because its return type is void.
  
    1 │ function f(): void {
  > 2 │     return undefined;
      │     ^^^^^^^^^^^^^^^^^
    3 │ }
    4 │ 
  
  ℹ The function is here:
  
  > 1 │ function f(): void {
      │ ^^^^^^^^^^^^^^^^^^^^
  > 2 │     return undefined;
  > 3 │ }
      │ ^
    4 │ 
  
  ℹ ‘void’ signals the absence of value. The returned value is likely to be ignored by the caller.

export default function(): void {
    return undefined;
}

code-block.ts:2:5 lint/correctness/noVoidTypeReturn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The function should not return a value because its return type is void.
  
    1 │ export default function(): void {
  > 2 │     return undefined;
      │     ^^^^^^^^^^^^^^^^^
    3 │ }
    4 │ 
  
  ℹ The function is here:
  
  > 1 │ export default function(): void {
      │                ^^^^^^^^^^^^^^^^^^
  > 2 │     return undefined;
  > 3 │ }
      │ ^
    4 │ 
  
  ℹ ‘void’ signals the absence of value. The returned value is likely to be ignored by the caller.

const g = (): void => {
    return undefined;
};

code-block.ts:2:5 lint/correctness/noVoidTypeReturn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The function should not return a value because its return type is void.
  
    1 │ const g = (): void => {
  > 2 │     return undefined;
      │     ^^^^^^^^^^^^^^^^^
    3 │ };
    4 │ 
  
  ℹ The function is here:
  
  > 1 │ const g = (): void => {
      │           ^^^^^^^^^^^^^
  > 2 │     return undefined;
  > 3 │ };
      │ ^
    4 │ 
  
  ℹ ‘void’ signals the absence of value. The returned value is likely to be ignored by the caller.

const h = function(): void {
    return undefined;
};

code-block.ts:2:5 lint/correctness/noVoidTypeReturn ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The function should not return a value because its return type is void.
  
    1 │ const h = function(): void {
  > 2 │     return undefined;
      │     ^^^^^^^^^^^^^^^^^
    3 │ };
    4 │ 
  
  ℹ The function is here:
  
  > 1 │ const h = function(): void {
      │           ^^^^^^^^^^^^^^^^^^
  > 2 │     return undefined;
  > 3 │ };
      │ ^
    4 │ 
  
  ℹ ‘void’ signals the absence of value. The returned value is likely to be ignored by the caller.

Valid

class A {
    f() {
        return undefined;
    }
}

class B {
    f(): void {}
}

function f(): void {
    return;
}

How to configure

{
  "linter": {
    "rules": {
      "correctness": {
        "noVoidTypeReturn": "error"
      }
    }
  }
}