Functions.md

Functions

DScript specifications can utilize functions which contain the logic of what should happen. A typical function looks like:

Example

function myFunction(arg: Arguments): Result {
    // Method statements go here
};

In this example the name of the function is myFunction. It has a single argument named arg which is of type Arguments.

Arguments.

Functions can take multiple arguments separated by a comma. Arguments can be declared to be optional by placing a question mark (?) after the name of the argument.

function myHelper(requiredArg: string, optionalArg?: string): string {
   return "result";
};

While functions can take multiple arguments, for primary Sdk functions like tool wrappers or functions that represent building something complex like a static library, managed executable etc. It is highly recommended to take a single argument that is an interface. This will allow the easiest composition and extension for others later.

Return value

Since all logic in BuildXL is side-effect free, it doesn't make sense to not have a return value. Therefore methods that return void are not allowed in DScript as you might as well not even call the function.

Guidelines

Functions have the same visibility rules as other declarations using export and @@public. Function names are recommended to be camelCase

Method statements

The following statement types are allowed inside methods:

• const and let declarations. If you don't reassign the variable you should use const.

   const x = 10;
   let y = [1];

• Assignment declaration of let variables:

  y = y.push(2);

• if statement:

  if (x === 10) {
      // more statements
  }

• for of enumerations:

  for (let item of y) {
      // more statements
  }

• return statement

  return 10;

• switch statements

  switch (x) {
      case 10: 
          // more statements
          break;
      case 20: 
          // more statements
          break;
      default: 
          // more statements
          break;
  }

• block statements

  {
       // more statements
  }