flutter_flutter/specs/modules.md

Sky module system

This document describes the Sky module system.

Overview

The Sky module system is based on the import element. In its most basic form, you import a module as follows:

<import src="path/to/module.sky" />

As these import elements are inserted into a document, the document's list of outstanding dependencies grows. When an imported module completes, it is removed from the document's list of outstanding dependencies.

Before executing any script elements, the parser waits until the list of outstanding dependencies is empty. After the parser has finished parsing, the document waits until its list of outstanding dependencies is empty before the module it represents is marked complete.

Module API

Within a script in a module, the module identifier is bound to the Module object that represents the module:

interface Module : EventTarget {
  constructor (Application application, Document document); // O(1)
  attribute any exports; // O(1) // defaults to the module's document
  readonly attribute Document document; // O(1) // the module's document
  readonly attribute Application application; // O(1)
}

Exporting values

A module can export a value by assigning the exports property of its Module object. By default, the exports property of a Module is its Document object, so that a script-less import is still useful (it exposes its contents, e.g. templates that the import might have been written to provide).

Naming modules

The as attribute on the import element binds a name to the imported module:

<import src="path/to/chocolate.sky" as="chocolate" />

The parser executes the contents of script elements inside a module as if they were executed as follow:

(new Function(module, name_1, ..., name_n, source_code)).call(
  source_module, value_1, ..., value_n);

Where name_1 through name_n are the names bound to the various named imports in the script element's document, source_code is the text content of the script element, source_module`` is the Moduleobject of the script element's module, andvalue_1throughvalue_n``` are the values exported by the various named imports in the script element's document.

When an import fails to load, the as name for the import gets bound to undefined.