OpenAutoComplete 📝

Shell-agnostic, declarative CLI autocomplete specification

Specification: SPECIFICATION.md

Nowadays, app developers have to provide autocompletion scripts for their applications for every shell possible by themselves. Usually, they provide autocompletions for bash, zsh and fish, and other shells have to support these completions (and this task is not easy, if even possible).

We want to have a single way an application could provide its autocompletion specification for the user's shell.

Ready-to-use definition files can be located here: https://github.com/openautocomplete/completions.

Basic principles

Declarative

The spec should have means to create CLI autocompletion in a declarative way, mostly without using shell scripting.

Shell-agnostic

There should not be a great problem to write autocompletion module for every shell available with minimum usage of non-standard tools. Our target shells: bash, zsh, fish, PowerShell and others.

Standards-based

OAC uses JSON, so the Runtime implementers can use jq for Unix shells, ConvertFrom-Json in PowerShell and other common approaches to parse OAC document.

Backwards-compatible with legacy applications

The spec should have means to describe most of the today's application CLIs.

Roadmap

Every single item in the roadmap is a subject for discussion

Enumerations support

Argument completion with values, being a part of some sort of enumeration:

• path (file/directory) (with regex/wildcard filter)
• storage-volume -- mounted volume. On Unix-like: "/home", "/" (use df?)
• packages (installed/not installed). Tricky one.
• PIDs
• process names
• something else

Enumerations from command output

This is for commands, like tar, thar can provide some machine-readable list, that could be parsed using a simple regex, and turned into an enumeration list. Also, this could be used for commands, that can provide their own autocompletion lists, like dotnet.

Delegation to another OAC instance

This could be used for delegating command autocompletion to another instance. Better with an example.

Consider a Python Django package. python -m django <TAB><TAB>

We provide python autocompletion by ourselves, and after -m <arg> it contains delegation pattern. When the user invokes autocompletion (double TAB), the Runtime gets definitions for python, then proceeds to a command inside delegation, and tries to get OAC definitions for django package (how?). If successful, it returns a list of currently available django commands: [check, compilemessages, createcachetable, dbshell, diffsettings, dumpdata, flush, inspectdb, ...]

shell-dependent scripting for delegations or enumerations

Well, to make completions more powerful, some sort of shell-dependent scriptiong would be useful (but discouraged). We should think about safety considerations, though.