Description of the project

Yet another parsing command line for scripts. This is not an attempt to reinvent the wheel. It is part of my learning of NodeJS and I wanted to adapt the ideas I had put in practice with command line parsing in bash scripts.

Common issue in parameters parsing

Usually, a set scripts is written on a long time period. The scripts are built around a common thema (your environment) and then may need to use the same set of options. But it is quite common, among different scripts, to have parameters with different names that designates the same thing. That is what I call the parameters inconsistency issue.

I encountered this problem in a mission where I had to maintain and improve a huge set of bash scripts. This was a big issue to remember what was the syntax for the options of one script or another (one with underscore instead of hyphen, one with long option that had a different spelling than the same option in another script).

The idea to avoid the parameters inconsistency

I tried to apply the ideas I had in bash to javascript programs. The bash library is stored in a different repository so you can have a look if you are interested in the tool.

The library provides a file listing the parameters in a JSON structure. You can provide your own file that matches this structure and details your own parameters.

Using this file in a set of scripts guarantees the same naming and the same syntax for all the scripts. If the documentation of an option changes from a script to another, you simply have to override the documentation of this option.

Parameters you don't want to have an option for

If you think that one (or some parameters) should not have a dedicated option, they are collected in a special value of the output parameter : _unassigned .

Structure of the parameters file

The file containing the options is a json file. This is the structure :

{
	name : {
		doc: "",
		shortOption: "",
		longOption: "",
		value: ""
	}
}

The field value is the default value for the option.

Declare the supported arguments of a script

You simply need to declare an array named (for instance) allowedOptions with the names of the parameters :

var allowedOptions = [
	'name1',
	'name2'
];

Any supported option must be defined in this array. Mandatory parameters are handled in another place. Then use the pickOptions function :

var parser = require('./lib-parsing.js');
var globalParameters = parser.defineGlobalParameters('./parameters.json');
var allowedOptions = [
	'name1',
	'name2'
];
var supportedSet = globalParameters.pickOptions(allowedOptions);

Declare a parameter as mandatory

To declare mandatory parameters, you have to define the following array :

var parser = require('./lib-parsing.js');
var globalOptions = parser.defineGlobalParameters('./parameters.json');
var allowedOptions = [
	'name1',
	'name2'
];
var mandatoryParameters = [
	'name2'
];
var supportedSet = globalOptions.pickOptions(allowedOptions).
    markOptionsAsMandatory(mandatoryParameters);

The idea is to keep the file parameters.json generic since it is a general definition of the available options. Some options might be mandatory for some scripts and not mandatory for others. So the definition of mandatory must be set elsewhere than in the global definition.

Automatic generation of the documentation

Of course, as the other libraries, the documentation is automatically built. The documentation can be ouputed in different formats. This allows the publication of the documentation in different tools.

Planned supported output format are :

• txt for the console
• JSON

Based on JSON, it should be possible to convert to any other textual documentation format.

Using the command line parsing

The parsing of the command line generates a parameter object that stores only the name and the value of the parameter.

// Load the parsing library
var parsing = require("parsing");

// Use your parameter file
var specificOptions = parser.defineGlobalParameters(pathToYourFile).
    pickOptions(yourArrayOfSpecificOptions).
    markOptionsAsMandatory(theMandatoryOptions);

// parse the command line
parameters = specificOptions.parseCommandLine();

Overriding the documentation of an option

Simply overrides the following value :

specificOptions.overrideDocumentation("name", "New documentation.");

It works the same for the value of a parameter :

overrideDefaultValue("name", "New Value.");

Support for allowed values for the parameter ??

To be done.

Support for multiple values

To be done.

Support for interdependent options

To be done

Supplying a json as arguments and validate it

To be done