require-variadic-function-argument
💼 This rule is enabled in the ✅ recommended config.
Requires that variadic functions must be supplied with at least one argument.
💠This rule requires type information.
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:
- It is relatively common to use these functions with no arguments in order to print a newline.
- 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​
This rule is not configurable.