Exoskeleton is a Scala library for to make it easy to write command-line applications which
interact through tab-completion in
implementing a simple,
functional API to
define the execution of parameters.
- unified programmatic tab-completions for
- automatic installation of completion scripts for each shell
- tab-completions can be generated programmatically on-demand
- high-level APIs for programs following common tab-completion patterns
- low-level APIs for more fine-grained control over completions
- fully functional API
- can be used with GraalVM to eliminate JVM startup time
Exoskeleton has not yet been published as a binary, though work is ongoing to fix this.
Exoskeleton provides the
Application trait, akin to
App in the Scala
Standard Library. In addition to a
main method, the
complete method, which should be implemented to return a sequence
of tab-completions based on the current state of the command-line, which is
passed in as an input parameter.
For a shell to offer tab-completions for a command to the user, it needs to
find definitions for the possible ways of completing the arguments to that
command. In general, this is done by searching a sequence of possible
locations for a file with a predictable name based on the command name (e.g.
cmd, this file will be called
cmd.fish). These locations
are usually defined in an environment variable, containing at least some
default initial values, but potentially with additional paths added to it
during the shell startup script, e.g.
The way a completion script works will be different for every shell, because their tab-completion systems all work differently, but each shell typically provides a command for specifying command completions which will be called from the completion script. Completion scripts for most commands define a static set of completions (which may be dependent on the state of the command-line being completed).
Exoskeleton, however, defines very general completion scripts for each shell
it supports, which all run the command whose parameters are being completed
in “completion mode”, effectively calling the Exoskeleton application’s
complete method. The completion scripts receive a response from the
Exoskeleton application, in aformat that is specific to each shell, which is
transformed into calls to the completion command for that particular shell.
Generation of completion scripts
Source files may be generated by running,
java -cp exoskeleton.jar exoskeleton.Generate <shell> <command> <dir>
where shell is one of
fish, command is the name of
the command that completions are being provided for, and dir is the
directory in which the script should be written.
The following Scala One libraries are dependencies of Exoskeleton:
No other Scala One libraries are dependents of Exoskeleton.
Exoskeleton is classified as fledgling. For reference, Scala One projects are categorized into one of the following five stability levels:
- embryonic: for experimental or demonstrative purposes only, without any guarantees of longevity
- fledgling: of proven utility, seeking contributions, but liable to significant redesigns
- maturescent: major design decisions broady settled, seeking probatory adoption and refinement
- dependable: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version
- adamantine: proven, reliable and production-ready, with no further breaking changes ever anticipated
Projects at any stability level, even embryonic projects, are still ready to be used, but caution should be taken if there is a mismatch between the project's stability level and the importance of your own project.
Exoskeleton is designed to be small. Its entire source code currently consists of 341 lines of code.
Exoskeleton can be built on Linux or Mac OS with Fury, however the approach to building is currently in a state of flux, and is likely to change.
Contributors to Exoskeleton are welcome and encouraged. New contributors may like to look for issues marked beginner.
We suggest that all contributors read the Contributing Guide to make the process of contributing to Exoskeleton easier.
Please do not contact project maintainers privately with questions unless there is a good reason to keep them private. While it can be tempting to repsond to such questions, private answers cannot be shared with a wider audience, and it can result in duplication of effort.
Exoskeleton was designed and developed by Jon Pretty, and commercial support and training is available from Propensive OÜ.
Exoskeleton is a library for interacting with shells, which are their exterior skeletons—or Exoskeletons.
Exoskeleton is copyright © 2017-23 Jon Pretty & Propensive OÜ, and is made available under the Apache 2.0 License.