A proper implementation of fzf-tab

completions/fzf_configure_bindings.fish

@@ -6,3 +6,4 @@ complete fzf_configure_bindings --long git_status --description "Change the key
 complete fzf_configure_bindings --long history --description "Change the key binding for searching history"
 complete fzf_configure_bindings --long processes --description "Change the key binding for searching processes"
 complete fzf_configure_bindings --long variables --description "Change the key binding for searching variables"
+complete fzf_configure_bindings --long completions --description "Change the key binding for searching completions"

functions/_fzf_search_completions.fish

@@ -0,0 +1,189 @@
+# External limitations:
+# - fish-shell/fish-shell#9577: folders ending in '=' break fish's internal path completion
+#   (It thinks that it has to complete from / because `a_folder=/` looks like an argument to fish.
+# - fish cannot give reliable context information on completions. Knowing whether a completion
+#   is a file or argument can only be determined via a heuristic.
+# - Completion is slow. Not because this script is slow but because fish's `complete` command
+#   can take several seconds even for just 100 entries. Just run `time complete --escape --do-complete l`
+#   to see for yourself.
+set --global _fzf_search_completions_min_description_offset 14
+function _fzf_search_completions --description "Shell completion using fzf"
+	# Produce a list of completions from which to choose
+	# and do nothing if there is nothing to select from
+	set -l cmd (commandline -co) (commandline -t)
+	set -l completions (complete --escape --do-complete "$cmd")
+	test (count $completions) -eq 0; and return
+
+	set -l results
+	set -l first_completion (string split --fields 1 --max 1 --right \t -- $completions[1])
+
+	# A prefix that will be prepended before each selected completion
+	set -l each_prefix ""
+
+	# Only skip fzf if there is a single completion and it starts with the expected completion prefix.
+	# Otherwise, the completion originates from a match in the description which the user might
+	# want to review first (e.g. man ima<TAB> might match `feh`, an image viewer)
+	if test (count $completions) -eq 1; and test (string sub -l (string length -- (commandline -ct)) -- $first_completion) = (commandline -ct)
+		# If there is only one option then we don't need fzf
+		set results $first_completion
+	else
+		# Preprocess the whole list and extract the actual completion any the corresponding description (if any)
+		# From here on, make sure to use -- (argument list end) and zero termination everywhere to prevent introducing
+		# new edge-cases where characters are interpreted wrongly
+		set -l actual_completions
+		set -l descriptions
+		for i in (seq (count $completions))
+			# split on \t from the right, at most one time and use the first (left) field.
+			# This is the actual completion
+			set --append actual_completions (string split --fields 1 --max 1 --right \t -- $completions[$i])
+			# The other field is the description, if it exists (otherwise set empty).
+			set --append descriptions (string split --fields 2 --max 1 --right \t -- $completions[$i] ; or echo "")
+		end
+
+		# Find the common prefix of all completions. Yes this seems to be a hard
+		# thing to do in fish if it should be fast. No external process may be
+		# spawned as this is too slow. So fish internals it is :/
+		set -l common_prefix $completions[1]
+		set -l common_prefix_length (string length -- $common_prefix)
+		for comp in $actual_completions[2..]
+			if test (string sub -l $common_prefix_length -- $comp) != $common_prefix
+				set -l new_common_prefix_length 0
+				set -l try_common_prefix_length (math min $common_prefix_length,(string length -- $comp))
+				# Binary search for new common prefix
+				set -l step $try_common_prefix_length
+				while test $step != 0
+					set step (math --scale 0 $step / 2)
+					# Adjust range to the left or right depending on whether the current new prefix matches
+					set -l xs (string sub -l $try_common_prefix_length -- $comp $common_prefix)
+					set -l op (test $xs[1] = $xs[2]; and printf "+"; and set new_common_prefix_length $try_common_prefix_length; or printf "-")
+					set try_common_prefix_length (math --scale 0 $try_common_prefix_length $op (math max 1,$step))
+				end
+				set common_prefix_length $new_common_prefix_length
+				set common_prefix (string sub -l $new_common_prefix_length -- $common_prefix)
+				# Stop if there is no common prefix
+				test $common_prefix_length = 0; and break
+			end
+		end
+
+		# If the common prefix includes a / we are completing a file path.
+		# Strip the prefix until the last / completely and later re-add it on the replaced token
+		set -l path_prefix (string match --regex --groups-only -- '^(.*/)[^/]*$' $common_prefix)
+		if test $status = 0
+			set -l path_prefix_length (string length -- $path_prefix)
+			set -l new_start (math 1 + $path_prefix_length)
+			for i in (seq (count $completions))
+				set completions[$i] (string sub -s $new_start -- $completions[$i])
+				set actual_completions[$i] (string sub -s $new_start -- $actual_completions[$i])
+			end
+
+			# We have a path-like prefix and will therefore strip this common prefix from all
+			# completions to un-clutter the menu.
+			set each_prefix (string sub -l $path_prefix_length -- $common_prefix)
+			set common_prefix_length (math $common_prefix_length - $path_prefix_length)
+			set common_prefix (string sub -s $new_start -- $common_prefix)
+		end
+
+		# Detect whether descriptions are present and the length of each completion.
+		set -l has_descriptions false
+		set -l longest_completion $_fzf_search_completions_min_description_offset
+		for i in (seq (count $completions))
+			if string match --quiet -- "*"\t"*" $completions[$i]
+				set has_descriptions true
+
+				# Here we additionally remember the longest completion to align the descriptions in fzf later
+				set longest_completion (math max $longest_completion,(string length -- $actual_completions[$i]))
+				set completions[$i] $actual_completions[$i]\t(set_color -i yellow)$descriptions[$i](set_color normal)
+			end
+		end
+
+		# FIXME Would technically work, but not sure it's worth the effort to match the descriptions
+		# after filtering.
+		# Remove tokens from the completion list that are already present on the current commandline.
+		#set -l all_tokens (commandline -o)
+		#set -l current_token_index (math 1 + (count (commandline -co)))
+		#set --erase all_tokens[$current_token_index]
+		#set -l remaining (comm --zero-terminated -23 (string join0 -- $actual_completions | psub) (string join0 -- $all_tokens | sort | psub) | string split0)
+
+		# TODO pressing / in a completion should add the completion and immediately start a new completion
+		test $has_descriptions = true; and set -l fzf_complete_description_opts \
+			--tabstop=(math 2 + $longest_completion)
+		set -l fzf_output (
+			string join0 -- $completions \
+			| _fzf_wrapper \
+				--read0 \
+				--print0 \
+				--ansi \
+				--multi \
+				--bind=tab:down,btab:up,change:top,ctrl-space:toggle \
+				--tiebreak=begin \
+				--query=$common_prefix \
+				--print-query \
+				$fzf_complete_description_opts \
+				$fzf_complete_opts \
+			| string split0)
+
+		switch $pipestatus[2]
+			case 0
+				# If something was selected, discard the current query
+				set results $fzf_output[2..-1]
+			case 1
+				# User accepted without selecting anything, thus we will
+				# use just the current query
+				set results $fzf_output[1]
+			case '*'
+				# Fzf failed, do nothing.
+				commandline -f repaint
+				return
+		end
+
+		# Strip anything after last \t (the descriptions)
+		for i in (seq (count $results))
+			set results[$i] (string split --fields 1 --max 1 --right \t -- $results[$i])
+		end
+	end
+
+	set -l prefix ""
+	set -l suffix " "
+	# By default we want to append a space to completed options.
+	# While this is always true when competing multiple things, there
+	# are some cases in which we don't want to add a space:
+	if test (count $results) -eq 1
+		# When a completion ends in a / we usually want to keep adding to that completion.
+		# This may be because it is a directory (or link to a directory), or just
+		# an option that takes a category/name tuple like `emerge app-shells/fish`.
+		# Also, completions like ~something are directories.
+		#
+		# In a similar manner, completions ending in = are usually part of an argument
+		# that expects a parameter (like --color= or dd if=). The same logic applies here.
+		set -l first_char (string sub -l 1 -- $results[1])
+		set -l last_char (string sub -s -1 -- $results[1])
+		if test $last_char = =; or test $last_char = /
+			set suffix ""
+		else if string match --regex --quiet -- '^~[^/]*$' $results[1]
+			set suffix "/"
+		end
+	end
+
+	if not contains -- "--" (commandline -co)
+		# If a path is being completed and it starts with --, we add -- to terminate argument interpreting.
+		# Technically not always correct (the program may not accept --), but the alternative is worse
+		# and this will make the user notice it.
+		for r in $results
+			test - = (string sub -l 1 -- $r); and test -e $r; and set prefix "-- "; and break
+		end
+	end
+
+	# If each_prefix is set, we need to apply it to each result
+	# before replacing the token
+	if test -n $each_prefix
+		set -l new_tokens
+		for r in $results
+			set -a new_tokens $each_prefix$r
+		end
+		commandline -t -- "$prefix$new_tokens$suffix"
+	else
+		commandline -t -- "$prefix$results$suffix"
+	end
+
+	commandline -f repaint
+end

functions/fzf_configure_bindings.fish

@@ -4,7 +4,7 @@ function fzf_configure_bindings --description "Installs the default key bindings
     # no need to install bindings if not in interactive mode or running tests
     status is-interactive || test "$CI" = true; or return
 
-    set options_spec h/help 'directory=?' 'git_log=?' 'git_status=?' 'history=?' 'processes=?' 'variables=?'
+    set options_spec h/help 'directory=?' 'git_log=?' 'git_status=?' 'history=?' 'processes=?' 'variables=?' 'completions=?'
     argparse --max-args=0 --ignore-unknown $options_spec -- $argv 2>/dev/null
     if test $status -ne 0
         echo "Invalid option or a positional argument was provided." >&2
@@ -16,13 +16,14 @@ function fzf_configure_bindings --description "Installs the default key bindings
     else
         # Initialize with default key sequences and then override or disable them based on flags
         # index 1 = directory, 2 = git_log, 3 = git_status, 4 = history, 5 = processes, 6 = variables
-        set key_sequences \e\cf \e\cl \e\cs \cr \e\cp \cv # \c = control, \e = escape
+        set key_sequences \e\cf \e\cl \e\cs \cr \e\cp \cv \t # \c = control, \e = escape
         set --query _flag_directory && set key_sequences[1] "$_flag_directory"
         set --query _flag_git_log && set key_sequences[2] "$_flag_git_log"
         set --query _flag_git_status && set key_sequences[3] "$_flag_git_status"
         set --query _flag_history && set key_sequences[4] "$_flag_history"
         set --query _flag_processes && set key_sequences[5] "$_flag_processes"
         set --query _flag_variables && set key_sequences[6] "$_flag_variables"
+        set --query _flag_completions && set key_sequences[7] "$_flag_completions"
 
         # If fzf bindings already exists, uninstall it first for a clean slate
         if functions --query _fzf_uninstall_bindings
@@ -36,6 +37,7 @@ function fzf_configure_bindings --description "Installs the default key bindings
             test -n $key_sequences[4] && bind --mode $mode $key_sequences[4] _fzf_search_history
             test -n $key_sequences[5] && bind --mode $mode $key_sequences[5] _fzf_search_processes
             test -n $key_sequences[6] && bind --mode $mode $key_sequences[6] "$_fzf_search_vars_command"
+            test -n $key_sequences[7] && bind --mode $mode $key_sequences[7] _fzf_search_completions
         end
 
         function _fzf_uninstall_bindings --inherit-variable key_sequences