yang-cc

YANG model-driven application core composer

ycc is the command line utility providing gcc-style schema composition/compilation.

It provides a useful abstraction on top of yang-js for dealing with schema file(s) in the local filesystem.

The core composer utilizes a new YANG language extension called composition which contains one or more specification and module extensions and a new extracts extension to base64 encoded data with the generated results for the specification. The new YANG language extensions are defined in yang-composition.yang schema and implemented in yang-composition.yaml specification. It basically generates portable compiled output which contains one or more schema(s) and specification(s). The generated output can then be sent across the wire and loaded by another instance of the Composer to re-create the identical instance of the core.

This software is brought to you by Corenova. We'd love to hear your feedback. Please feel free to reach me at peter@corenova.com anytime with questions, suggestions, etc.

Installation

$ npm install -g yang-cc

You must have node >= 0.10.28 as a minimum requirement to use yang-cc.

Usage

Usage: ycc [options] file...
 
Options:
  -I, --include [dir...]  Add directory to compiler search path
  -L, --link [dir...]     Add directory to linker search path
  -o, --output <file>     Place output into <file>

Using the provided ycc utility produces a core composition output which can then be loaded and placed into runtime by an engine such as yang-forge. It can also be loaded by yang-cc composer instance as well to restore back to the original Core.

Any relative paths specified in -I or -L is resolved using process.cwd() where the ycc command is being executed.

API

Here's an example for using this module:

var ycc = require('yang-cc');
var core = 
  ycc
    .set({ basedir: __dirname })
    .include('./some-local-dir')
    .link('./other-local-dir')
    .load('foo.yang','bar.yang');
 
console.log(core.dump());

load (file/schema...)

This is the primary method for passing in various filenames as well as schema object/string to the Composer for producing a newly compiled Core containing one or more schemas and specifications along with their dependencies.

The ability to dynamically discover dependencies from the local filesystem search path is one of the key capabilities provided by the yang-cc module over the yang-js.

By referencing various include directories prior to issuing the load method, any include and import statements found within the schema(s) being composed will be dynamically located and if found, compiled and bundled as part of the resulting Core.

For example, the yang-cc module itself includes the standard directory, which contains a handful of common YANG schema assets:

This is purely a convenience reference so that such assets do not need to be present inside the project directory where new YANG schemas are being composed.

This call returns a new Core instance.

include (dir...)

This call registers existing local directories into internal search-path for dynamic resolution for schemas and specifications. If supplied as a relative path, it will be prepended with the specified basedir property. If basedir is undefined, it will default to using process.cwd(). It will always use basedir as the first directory when attempting to locate the file(s) whether additional include() directories have been registered or not.

It will dynamically attempt to resolve files passed in without extensions to look for .yaml, .yml, and .yang files with that same name.

This call returns the current Composer instance for call chaining purposes.

link (dir...)

This call similarly registers existing local directories as in the include case above but it is used for dynamic resolutions for features and rpcs. It is utilized internally while compiling a schema in order to locate handler functions for the declared feature and rpc statements.

It will dynamically attempt to resolve the feature/rpc names inside the registered linker directories by looking for .js and .coffee files.

Here's an example (coffeescript):

ycc = require 'yang-cc'
core = ycc
  .link './lib'
  .load 'foo.yang', 'bar.yang'

If foo.yang schema contains references to feature example { ... } and rpc create { ... }, then during schema compilation, the Composer will attempt to look for following files:

• ./foo/feature/example.js
• ./foo/feature/example.coffee
• ./lib/foo/feature/example.js
• ./lib/foo/feature/example.coffee
• ./foo/rpc/create.js
• ./foo/rpc/create.coffee
• ./lib/foo/rpc/create.js
• ./lib/foo/rpc/create.coffee

Please note that it automatically prepends <module name>/<type> when attempting to locate the handler function file. This is to ensure that discovered assets are namespace protected when associated during respective schema compilation.

This call returns the current Composer instance for call chaining purposes.

use / resolve

The Composer provides similar use/resolve capabilities inherited from the underlying yang-js parser/compiler module. The key differences are that the use also performs filename resolution by searching the includes directories and that the resolve attempts to dynamically resolve missing definitions from the local filesystem.

compile / preprocess / parse / ...

The yang-cc module extends the yang-js parser/compiler module. In turn, it inherits all methods available from the super class.

For additional details on other methods available on this module, please check the documentation found inside the yang-js parser/compiler project.

Core

TBD - need to write documentation on how to interact with the generated Core instance.

License

Apache 2.0