Add a fish completion script

This is only rudimentary support as allowed by `NIX_GET_COMPLETIONS`.

In the future, we could use complete’s `--wraps` argument to autocomplete arguments for programs after `nix shell -c`.
This commit is contained in:
Jan Tojnar 2021-06-02 00:45:03 +02:00
parent 323e5450a1
commit bee71e1bb1
3 changed files with 39 additions and 0 deletions

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@ -12,6 +12,7 @@ makefiles = \
src/resolve-system-dependencies/local.mk \
scripts/local.mk \
misc/bash/local.mk \
misc/fish/local.mk \
misc/zsh/local.mk \
misc/systemd/local.mk \
misc/launchd/local.mk \

37
misc/fish/completion.fish Normal file
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@ -0,0 +1,37 @@
function _nix_complete
# Get the current command up to a cursor.
# - Behaves correctly even with pipes and nested in commands like env.
# - TODO: Returns the command verbatim (does not interpolate variables).
# That might not be optimal for arguments like -f.
set -l nix_args (commandline --current-process --tokenize --cut-at-cursor)
# --cut-at-cursor with --tokenize removes the current token so we need to add it separately.
# https://github.com/fish-shell/fish-shell/issues/7375
# Can be an empty string.
set -l current_token (commandline --current-token --cut-at-cursor)
# Nix wants the index of the argv item to complete but the $nix_args variable
# also contains the program name (argv[0]) so we would need to subtract 1.
# But the variable also misses the current token so it cancels out.
set -l nix_arg_to_complete (count $nix_args)
env NIX_GET_COMPLETIONS=$nix_arg_to_complete $nix_args $current_token
end
function _nix_accepts_files
set -l response (_nix_complete)
# First line is either filenames or no-filenames.
test $response[1] = 'filenames'
end
function _nix
set -l response (_nix_complete)
# Skip the first line since it handled by _nix_accepts_files.
# Tail lines each contain a command followed by a tab character and, optionally, a description.
# This is also the format fish expects.
string collect -- $response[2..-1]
end
# Disable file path completion if paths do not belong in the current context.
complete --command nix --condition 'not _nix_accepts_files' --no-files
complete --command nix --arguments '(_nix)'

1
misc/fish/local.mk Normal file
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$(eval $(call install-file-as, $(d)/completion.fish, $(datarootdir)/fish/vendor_completions.d/nix.fish, 0644))