Orion/Dependency resolution

Dependency resolution refers to the ability to resolve a type of cross-file dependency to a file in the workspace at development time. Examples of dependencies within our scope are:

• src and href attributes in an HTML file
• @import statements in a CSS file
• define([ deps.. ]) and require([ deps.. ]) in a JS file (AMD modules)
• require( "dep/path" ) in a JS file (Node.js/CommonJS)
• importScripts( urls.. ) in a JS file (web worker API)

Dependency resolution is a prerequisite feature to cross-file type inference and content assist. This document deals with the simplest possible case of dependency resolution: deciding whether the referenced file exists or not. In other words, if we implement everything in this document, it should be trivial to write a validator that puts a red *X* on missing resources in HTML, CSS, and JS files (for the JS contexts: Node, AMD, worker).

Concepts

• Dependency: a reference to some logical path (LP).
• Logical path (LP): whatever goes inside the src="..", @import "..", require(..), etc.
  • The LP is opaque to everything but a Resolver, which can translate LP to a workspace path.
  • Example: in JS, depending on the context, the LP can be a commonJS module path (Node.js), a path in the local file system (Node.js), a web path (browser/worker), or an AMD module ID.
• Resolver: resolves a LP to a workspace path (WP).
  • Workspace paths can be fetched/parsed by the tooling using the usual Orion FileClient API.
• Web Path Configuration (WPD): captures the path-translation info necessary to map from an LP that is a web location.
  • The notion of WPD is important because a resource's location on a web server is generally not the same as its location in the workspace. For example, a file located at a repo path of /src/webapp/static/js/foo.js may be exposed on the web as /admin/js/foo.js.
  • The WPD is of interest to any Resolvers that may encounter web paths as LPs.
  • A WPD is a subset of the site structure defined by an Orion site configuration. Should factor out any commonality here.