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require-variadic-function-argument

Requires that variadic functions must be supplied with at least one argument.

Rule Details​

Variadic functions are functions that take a variable amount of arguments. However, as far as the TypeScript compiler is concerned, passing no arguments at all to a variadic function is legal. But doing this is usually a bug. For example:

const myArray = [1, 2, 3];
myArray.push(); // Oops!

Here, the author of the code made a typo and forgot to supply the thing to be inserted into the array. Thus, the myArray.push line is a no-op.

To protect against these kinds of errors, this rule requires that you always pass at least one argument to a variadic function.

Hard-Coded Exceptions​

This rule is hard-coded to not throw an error with console methods (such as console.log or console.error), since:

  1. It is relatively common to use these functions with no arguments in order to print a newline.
  2. The TypeScript signatures for those functions are weird in that they have a rest parameter as the second parameter instead of the first one.

Additionally, this rule will not be flagged for setTimeout or setInterval, since those rest parameters are optional.

JSDoc Exceptions​

Sometimes, a variadic function can be written to intentionally allow for zero arguments. If this is the case, you can use a @allowEmptyVariadic JSDoc tag inside of the JSDoc comment for the function. Then, this rule will ignore any calls of that function.

For example, something like the following:

/**
 * Helper function to get all of the cars in the database. By default, it will return every car.
 *
 * You can optionally specify one or more car types to return only the cars that match the specified
 * car types.
 *
 * @allowEmptyVariadic
 */
function getCars(...carTypes: CarType[]) {}

Options and Defaults​

{
  "rules": {
    "complete/require-variadic-function-argument": "error"
  }
}

This rule is not configurable.

Resources​