Shellac Protocol Proposal V2

• Back to Shell Autocompletion
• Original Shellac Protocol Proposal

Requirements

• Shell-agnostic. You can't force zsh to parse bash strings!
• Compatible with existing completion scripts. e.g. _openstack use case. Most migrations should be a trivial wrapper.
• Probably: Should be implementable in pure bash and zsh.

Design Sketch

Compared to the original Shellac Protocol Proposal

• Remove mention of coprocesses! That is orthogonal. It's just a process now.
• Input side:
  • shellac-provider -- command --myflag 1 --myflag2 f
• Output:
  • { key, value, key, value } in NUL terminated strings
  • Arrays are prefixed with length

Example:

["candidates", "2", "one", "two", "descriptions", "2", "desc1", "desc2"]

This is printed on stdout as a series of NUL-terminated strings.

• Read with read -d $'\0' in bash

Finding Completions for binaries

Look in $SHELLAC_HOME_DIR/plugins/openstack/complete for openstack.

$SHELLAC_HOME = ~/.local/shellac on Linux.

TODO: details.

Extensibility

• Input format is extensible with new flags
• Output format is extensible with new "keys".
  • right now we have "candidates" and "descriptions", but we can have more.

Migration

From bash completion

• Easy, just take COMPREPLY and print as "candidates". Descriptions are left blank.

From subcommands

• Easy, just write a shell wrapper:

#!/bin/sh
exec npm complete "$@"

What's Wrong with complete -C in bash?

• line-oriented protocol
• COMP_CWORDS is wrong

TODO: Write up more!

Test Cases

See Shellac Test Cases.

Links

• https://www.redox-os.org/news/rsoc-ion-ux-2/
• https://www.redox-os.org/news/rsoc-ion-ux-3/
• https://www.redox-os.org/news/rsoc-ion-ux-4-5/