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argv.js advanced topics

This file will cover the usage, contents and configuration topics in more detail.

Basics

For basics see README.md

Contents

Configuration

Parser(<spec>)
	-> <parser>

The <spec> object is "merged" into the <parser> instance overriding or extending it's API/data.

The <parser> expects/handles the following data in the <spec> object:

  • the configuration attributes and methods
    Attributes and methods used to configure, modify, extend or overload parser functionality.

    Note that these attributes are the same attributes inherited by <parser> and are simply merged into the new instance created by Parser(..), thus there are no restrictions on what attributes/methods can be overloaded or extended in this way, but care must be taken when overloading elements that were not designed to be overloaded.

  • option/command definitions
    The keys for these are prefixed either by "-" for options or by "@" for commands and are either objects, functions or parser instances.

    The only difference between an option and a command is that the former are passed to the script with a "-" or "--" prefix (by default) and the later are passed by name without prefixes.

    In all other regards options and commands are the same.

  • option/command aliases
    An alias is an option/command key with a string value.
    That value references a different option or command, i.e. is an option/command name.

    Looping (referencing the original alias) or dead-end (referencing non-existent options) aliases are ignored.

Option/command configuration

<option>.handler(..)

Option handler.

'-option': {
	handler: function(opts, key, value){
		// handle the option...
		// ...
	},
},

or a shorthand:

'-option': function(opts, key, value){
	// handle the option...
	// ...
},

The handler gets called if the option is given or if it was not explicitly given but has a default value set.

opts contains the mutable list of arguments passed to the script starting just after the currently handled option/command. If the handler needs to handle it's own arguments it can modify this list in place and the parser will continue from the resulting state.

One use-case for this would be and option handler that needs to handle it's arguments in a custom manner, for example for handling multiple arguments.

key is the actual normalized ([<prefix-char>]<name-str>) option/command triggering the .handler(..).

This can be useful to identify the actual option triggering the handler when using aliases, if a single handler is used for multiple options, or when it is needed to handle a specific prefix differently (a-la find's syntax with +option and -option having different semantics).

value gets the value passed to the option.

A value can be passed either explicitly passed (via = syntax), implicitly parsed from the argv via the <option>.arg definition or is undefined otherwise.

A handler can return one of the THEN, STOP or ParserError instance to control further parsing and/or execution. (See: THEN / STOP for more info.)

<option>.doc

Option/command documentation string used in -help.

doc: <string> | <array-of-strings>,

If an array of strings is given each string will be printed on a separate line.

If this is set to false the option will be hidden from -help.

<option>.priority

Option/command priority in the -help.

Can be a positive or negative number or undefined.

Ordering is as follows:

  • options in descending positive .priority,
  • options with undefined .priority in order of definition,
  • options in descending negative .priority.

Note that options and commands are grouped separately.

The built-in options -help, -version and -quiet have a priority of 99 so that they appear the the top of the -help list.

Any option defining .required and not defining an explicit .priority will be sorted via <parser>.requiredOptionPriority (80 by default).

<option>.arg

Option/command argument definition.

arg: '<arg-name>'
arg: '<arg-name> | <key>'

If defined and no explicit value is passed to the option command (via =) then the parser will consume the directly next non-option if present in argv as a value, passing it to the <option>.type handler, if defined, then the <option>.handler(..), if defined, or setting it to <key> otherwise.

Sets the option/command argument name given in -help for the option and the key where the value will be written.

The <key> is not used if <option>.handler(..) is defined.

<option>.type

Option/command argument type definition.

The given type handler will be used to convert the option value before it is passed to the handler or set to the given <key>.

Supported types:

  • "string" (default behavior)
  • "bool"
  • "int"
  • "float"
  • "number"
  • "date" – expects a new Date(..) compatible date string
  • "list" – expects a ","-separated value, split and written as an Array object

Type handlers are defined in Parser.typeHandlers or can be overwritten by <spec>.typeHandlers.

If not set values are written as strings.

Defining a new global type handler:

// check if a value is email-compatible...
argv.Parser.typeHandlers.email = function(value, ...options){
	if(!/[a-zA-Z][a-zA-Z.-]*@[a-zA-Z.-]+/.test(value)){
		throw new TypeRrror('email: format error:', value) }
	return value }

Defining a local to parser instance type handler:

var parser = new Parser({
	// Note that inheriting from the global type handlers is required 
	// only if one needs to use the global types, otherwise just setting
	// a bare object is enough...
	typeHandlers: Object.assign(Object.create(Parser.typeHandlers), {
		email: function(value, ...options){
			// ...
		},
		// ...
	}),

	// ...
})

<option>.collect

Option value collection mode.

The given handler will be used to collect values passed to multiple occurrences of the option and write the result to <key>.

Supported collection modes:

  • "list" – group values into an Array object
  • "set" – group values into a Set object
  • "string" – concatenate values into a string.
    This also supports an optional separator, for example "string|\t" will collect values into a string joining them with a tab (i.e. "\t").
    Default separator is: " "
  • "toggle" – toggle option value (bool).
    Note that the actual value assigned to an option is ignored here and can be omitted.

Type handlers are defined in Parser.valueCollectors or can be overwritten by <spec>.valueCollectors.

<option>.collect can be used in conjunction with <option>.type to both convert and collect values.

If not set, each subsequent option will overwrite the previously set value.

Defining a global value collector:

// '+' prefixed flags will add values to set while '-' prefixed flag will 
// remove value from set...
argv.Parser.valueCollectors.Set = function(value, current, key){ 
	current = current || new Set()
	return key[0] != '-' ?
		current.add(value) 
		: (cur.delete(value), current) }

Defining handlers local to a parser instance handler is the same as for type handlers above.

<option>.env

Determines the environment variable to be used as the default value for option/command, if set.

If this is set, the corresponding environment variable is non-zero and <option>.handler(..) is defined, the handler will be called regardless of weather the option was given by the user or not.

<option>.default

Sets the default value for option/command's value.

If this is set to a value other than undefined and <option>.handler(..) is defined, the handler will be called regardless of weather the option was given by the user or not.

<option>.required

Sets weather the parser should complain/err if option/command is not given.

Note that this also implicitly prioritizes the option, for more info see: <option>.priority.

<option>.valueRequired

Sets weather the parser should complain/err if option/value value is not given.

Built-in options

Disabling or redefining a built-in option

To disable a built-in option simply assign undefined, false or null to it.

		// disable help...
		'-help': undefined,

Redefining or extending options is done by either shadowing it completely or by overloading it partially.

		// redefine and option...
		'-version': {
			doc: 'an alternative version',
			handler: function(){
				console.log('1.2.3') 
				return argv.STOP } },

		// extend...
		'-quiet': Object.assign(
			Object.create(argv.Parser.prototype['-quiet']),
			{
				// hide -quiet from -help
				doc: false,
			}),

- / --

Stop processing further options.

This can be used to terminate nested parsers or to stop option processing in the root parser to handle the rest of the options in <parser>.then(..), for example.

-* / @*

Handle options/commands for which no definition is found.

By default -* will:

  • on root parser: print an "unhandled option/command" error and terminate.
  • on nested parser: delegate the option to the parent.

By default @* is an alias to -*.

<parser>.delegateUnknownToParent

Controls the default behavior of a nested parser when encountering an unknown option.

If true (default) the option will be delegated to the parent parser. If false behave the same way as the root parser, i.e. printing an error.

-v / --version

This will output the value of .version and exit.

-q / --quiet

This will turn quiet mode on.

In quiet mode <parser>.print(..) will not print anything.

Passing --help or --version will disable quiet mode and print normally.

Note that this will only set <parser>.quiet to true and disable output of <parser>.print(..), any user code needs to either also use <parser>.print(..) for output (not always practical) or respect <parser>.quiet.

-h / --help

By default -help will output in the following format:

<usage>

<doc>

Options:
	<option-spec> <option-val>		
				- <option-doc>
				  (<opt-required>, <opt-default>, <opt-env>)
	...

Dynamic options:
	...

Commands:
	...

Examples:
	...

<footer>

All sections are optional and will not be rendered if they contain no data.

Value placeholders

All documentation strings can contain special placeholders that will get replaced with appropriate values when rendering help.

  • $SCRIPTNAME replaced with the value of .scriptName,
  • $VERSION replaced with .version,
  • $LICENSE replaced with .license.
Automatically defined values

These values are set by the parser just before parsing starts:

  • .script - full script path, usually this is the value of argv[0],
  • .scriptName - base name of the script,
  • .scriptPath - path of the script.

These will be overwritten when the parser is called.

<parser>.doc

Script documentation.

<spec>.doc = <string> | <function>

Default value: undefined

<parser>.usage

Basic usage hint.

<spec>.usage = <string> | <function> | undefined

Default value: "$SCRIPTNAME [OPTIONS]"

<parser>.packageJson

The path to the metadata JSON file.

<spec>.packageJson = <string> | <function> | undefined

If not set package.json will be searched for in the same directory as the main script.

Default value: undefined.

<parser>.version

Version number.

<spec>.usage = <string> | <function> | undefined

If this is not defined it will be read from the project metadata, if none is found "0.0.0" will be printed by -version.

Default value: undefined

<parser>.author

Author name/contacts.

<spec>.author = <string> | <function> | undefined

If not set project metadata is used, if found.

Default value: undefined

<parser>.license

Short license information.

<spec>.usage = <string> | <function> | undefined

If not set project metadata is used, if found.

Default value: undefined

<parser>.examples
<spec>.usage = <string> | <list> | <function> | undefined

Example list format:

[
	[<example-code>, <example-doc>, ...],
	...
]

Default value: undefined

<parser>.footer

Additional information.

<spec>.footer = <string> | <function> | undefined

Default value: undefined

More control over help...

For more info on help formatting see <parser>.help* attributes in the source.

Nested parsers

An option/command handler can be a parser instance.

From the point of view of the nested parser nothing is different – it gets passed the remaining list of arguments and handles it on it's own.

The containing parser treats the nested parser just like any normal handler with it's attributes and API.

Note that if the nested parser consumes the rest of the arguments, the containing parser is left with an empty list and it will stop parsing and return normally.

A way to explicitly stop the nested parser processing at a specific point in the argument list is to pass it a - argument at that point.

For example:

$ script -a nested -b -c - -x -y -z

Here script will handle -a then delegate to nested which in turn will consume -b, -c and on - return, rest of the arguments are again handled by script.

This is similar to the way programming languages handle passing arguments to functions, for example in Lisp this is similar to:

(script a (nested b c) x y z)

And in C-like-call-syntax languages like C/Python/JavaScript/... this would (a bit less cleanly) be:

script(a, nested(b, c), x, y, z)

The difference here is that nested has control over what it handles, and depending on its definition, can either override the default - option as well as stop handling arguments at any point it chooses (similar to words in stack languages like Fort or Factor).

Components and API

THEN / STOP

Values that if returned by option/command handlers can control the parse flow.

  • THEN – Stop parsing and call <parser>.then(..) callbacks.
  • STOP – Stop parsing and call <parser>.stop(..) callbacks, skipping <parser>.then(..).

THEN is useful when we want to stop option processing and trigger the post-parse stage (i.e. calling <parser>.then(..)) for example to pass the rest of the options to some other command.

STOP is used for options like -help when no post-parsing is needed.

ParserError(..)

A base error constructor.

If an instance of ParserError is thrown by the handler:

ParserError can also be returned form the handler, this has almost the same effect as throwing it but the error will not be automatically reported.

The following error constructors are also defined:

  • ParserTypeError(..)
  • ParserValueError(..)

Parser(..)

Construct a parser instance

Parser(<spec>)
	-> <parser>

See <parser>(..) for more info.

<parser>.onArgs(..)

Add callback triggered when one or more arguments are passed to the parser.

<parser>.onArgs(<callback>)
	-> <parser>

callback(<args>)
	-> <obj>

Note that this is triggered before parsing begins.

<parser>.onNoArgs(..)

Add callback triggered when no arguments are passed to the parser.

<parser>.onNoArgs(<callback>)
	-> <parser>

callback(<args>)
	-> <obj>

Note that this is triggered before parsing begins.

<parser>.then(..)

Add callback to then "event".

<parser>.then(<callback>)
	-> <parser>

callback(<unhandled>, <root-value>, <rest>)
	-> <obj>

then is triggered when parsing is done or stopped from an option handler by returning THEN.

<parser>.stop(..)

Add callback to stop "event".

<parser>.stop(<callback>)
	-> <parser>

callback(<arg>, <rest>)
	-> <obj>

stop is triggered when a handler returns STOP.

<parser>.error(..)

Add callback to error "event".

<parser>.error(<callback>)
	-> <parser>

callback(<reason>, <arg>, <rest>)
	-> <obj>

error is triggered when a handler returns ERROR.

<parser>.off(..)

Remove callback from "event".

	<parser>.off(<event>, <callback>)
		-> <parser>

<parser>(..)

Execute the parser instance.

Run the parser on process.argv implicitly:

<parser>()
	-> <result>

Explicitly pass a list of arguments where <argv>[0] is treated as the script path.

<parser>(<argv>)
	-> <result>

Explicitly pass both a list of arguments and script path.

<parser>(<argv>, <main>)
	-> <result>

If <main> is present in <argv> all the arguments before it will be ignored, otherwise the whole list is processed as if <main> was its head.

Parser.chain(..) (EXPERIMENTAL)

Chain several parsers for staggering option/command processing.

Parser.chain(<spec>, <spec>, ..)
	-> <parser>

This creates a chain of parsers, each processing only the arguments it defines and passes the rest to the next in chain. This is useful for defining arguments that need to be processed out of order and before anything else.

This is similar to chaining parsers via .then(..) but with additional setup:

  • all parsers except the last will have:
    • .splitOptions set to false
    • "-" set to undefined
    • "-help" set to undefined enabling -help pass-through
    • "-*" and "@*" set to undefined enabling arguments pass-through
  • the last parser will have:
    • all the options from the other parsers merged into it for complete docs/-help
    • .splitOptions set to false

XXX the resulting <parsed> object will only contain data from the last parser, this may change in the future...

XXX not sure about the .splitOptions restriction on the last parser yet, but it definitely should not include the options from preceding parsers...

Advanced parser API

<parser>.print(..) / <parser>.printError(..)

Handle how <parser> prints things.

<parser>.print(..) and <parser>.printError(..) are very similar but handle different cases, similar to console.log(..) and console.error(..)

<parser>.print(...)
	-> <parser>

<parser>.printError(...)
	-> <parser>
<parser>.printError(<error>, ...)
	-> <error>

Both support callback binding:

<parser>.print(<func>)
	-> <parser>

<parser>.printError(<func>)
	-> <parser>

Both <parser>.print(..) and <parser>.printError(..) can safely be overloaded if the callback feature is not going to be used by the user – the print callbacks are not used internally.

For full callback API see: extra.afterCallback(..) in argv.js.

<parser>.handlerDefault(..)

Called when <option>.handler(..) is not defined.

By default this sets option values on the parsed object.

<parser>.handleArgumentValue(..)

Handle argument value conversion.

By default this handles the <option>.type mechanics.

If this is set to false values will be set as-is.

<parser>.handleErrorExit(..)

Handle exit on error.

By default this will call process.exit(1) for the root parser and does nothing for nested parsers.

If set to false the parser will simply return like any normal function.

<parser>.handle(..)

Manually trigger <arg> handling.

<parser>.handle(<arg>, <rest>, <key>, <value>)
	-> <res>

This is intended to be used for delegating handling from one handler to another. Note that this does not handle errors or other protocols handled by <parser>(..), this only calls the <arg> handler (or if it was not defined the default handler) so it is not recommended for this to be called from outside an option handler method/function.

This is not intended for overloading.

<parser>.setHandlerValue(..)

Set handler value manually, this uses <handler>.arg and if not set <key> to write <value> on the parsed object.

<parser>.setHandlerValue(<handler>, <key>, <value>)
	-> <parser>

This is useful when extending argv.js, for client code values can be set directly.

This is not intended for overloading.

External utilities

normalizeIndent(..) / normalizeTextIndent(..)

argv.js uses and exposes object.js' text normalization functions for convenient text/code formatting, see original documentation for more info.

More...

For more info see the source.