17 Adding a raco Command

The set of commands supported by raco can be extended by installed packages, PLaneT packages, and other collections. A command is added by defining raco-commands in the "info.rkt" library of a collection (see "info.rkt" File Format), and then raco setup (as called directly or as part of a package or PLaneT installation) must index the "info.rkt" file.

The value bound to raco-commands must be a list of command specifications, where each specification is a list of four values:

(list command-string

implementation-module-path

description-string

prominence)

The command-string is the command name. Any unambiguous prefix of a command name can be supplied to raco to invoke the command.

The implementation-module-path names the implementation though a module path (in the sense of module-path?). The module is loaded and invoked through dynamic-require to run the command. The module can access command-line arguments through the current-command-line-arguments parameter, which is adjusted before loading the command module to include only the arguments to the command. The current-command-name parameter is also set to the command name used to load the command. When raco help is used on a command, the command is launched with an initial --help argument in current-command-line-arguments.

The description-string is a short string used to describe the command in response to raco help. The description should not be capitalized or end with a period.

The prominence value should be a read number or #f. A #f value means that the command should not be included in the short list of “frequently used commands.” A number indicates the relative prominence of the command; the help command has a value of 110, and probably no command should be more prominent. The pack tool, which is currently ranked as the least-prominent of the frequently used commands, has a value of 10.

As an example, the "info.rkt" of the "compiler" collection might contain the

(define raco-commands

'(("make" compiler/commands/make "compile source to bytecode" 100)

("decompile" compiler/commands/decompile "decompile bytecode" #f)))

so that make is treated as a frequently used command, while decompile is available as an infrequently used command.

17.1 Command Argument Parsing

A command implementation can use this parameter to determine whether it was invoked via raco or through some other means.

The result of this function is suitable for use with command-line. For example, the decompile tool parses command-line arguments with

(define source-files

(command-line

#:program (short-program+command-name)

#:args source-or-bytecode-file

source-or-bytecode-file))

so that raco decompile --help prints