Fix fish for ShellDirectiveNoSpace and file comp

For fish shell we achieve ShellDirectiveNoSpace by outputing a fake
second completion with an extra character.  However, this extra
character was being added after the description string, instead of
before.  This commit fixes that.

It also cleans up the script of useless code, now that fish completion
details are better understood.

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

fish_completions.go

@@ -28,9 +28,9 @@ function __%[1]s_debug
 end
 
 function __%[1]s_perform_completion
-    __%[1]s_debug "Starting __%[1]s_perform_completion with: $argv"
+    __%[1]s_debug "Starting __%[1]s_perform_completion"
 
-    set args (string split -- " " "$argv")
+    set args (string split -- " " (commandline -c))
     set lastArg "$args[-1]"
 
     __%[1]s_debug "args: $args"
@@ -71,31 +71,22 @@ function __%[1]s_perform_completion
     printf "%%s\n" "$directiveLine"
 end
 
-# This function does three things:
-# 1- Obtain the completions and store them in the global __%[1]s_comp_results
-# 2- Set the __%[1]s_comp_do_file_comp flag if file completion should be performed
-#    and unset it otherwise
-# 3- Return true if the completion results are not empty
+# This function does two things:
+# - Obtain the completions and store them in the global __%[1]s_comp_results
+# - Return false if file completion should be performed
 function __%[1]s_prepare_completions
+    __%[1]s_debug ""
+    __%[1]s_debug "========= starting completion logic =========="
+
     # Start fresh
-    set --erase __%[1]s_comp_do_file_comp
     set --erase __%[1]s_comp_results
 
-    # Check if the command-line is already provided.  This is useful for testing.
-    if not set --query __%[1]s_comp_commandLine
-        # Use the -c flag to allow for completion in the middle of the line
-        set __%[1]s_comp_commandLine (commandline -c)
-    end
-    __%[1]s_debug "commandLine is: $__%[1]s_comp_commandLine"
-
-    set results (__%[1]s_perform_completion "$__%[1]s_comp_commandLine")
-    set --erase __%[1]s_comp_commandLine
+    set results (__%[1]s_perform_completion)
     __%[1]s_debug "Completion results: $results"
 
     if test -z "$results"
         __%[1]s_debug "No completion, probably due to a failure"
         # Might as well do file completion, in case it helps
-        set --global __%[1]s_comp_do_file_comp 1
         return 1
     end
 
@@ -119,7 +110,6 @@ function __%[1]s_prepare_completions
     if test $compErr -eq 1
         __%[1]s_debug "Received error directive: aborting."
         # Might as well do file completion, in case it helps
-        set --global __%[1]s_comp_do_file_comp 1
         return 1
     end
 
@@ -128,7 +118,6 @@ function __%[1]s_prepare_completions
     if test $filefilter -eq 1; or test $dirfilter -eq 1
         __%[1]s_debug "File extension filtering or directory filtering not supported"
         # Do full file completion instead
-        set --global __%[1]s_comp_do_file_comp 1
         return 1
     end
 
@@ -137,27 +126,51 @@ function __%[1]s_prepare_completions
 
     __%[1]s_debug "nospace: $nospace, nofiles: $nofiles"
 
-    # Important not to quote the variable for count to work
-    set numComps (count $__%[1]s_comp_results)
-    __%[1]s_debug "numComps: $numComps"
-
-    if test $numComps -eq 1; and test $nospace -ne 0
-        # To support the "nospace" directive we trick the shell
-        # by outputting an extra, longer completion.
-        __%[1]s_debug "Adding second completion to perform nospace directive"
-        set --append __%[1]s_comp_results $__%[1]s_comp_results[1].
+    # If we want to prevent a space, or if file completion is NOT disabled,
+    # we need to count the number of valid completions.
+    # To do so, we will filter on prefix as the completions we have received
+    # may not already be filtered so as to allow fish to math on different
+    # criteria than prefix.
+    if test $nospace -ne 0; or test $nofiles -eq 0
+        set prefix (commandline -t)
+        __%[1]s_debug "prefix: $prefix"
+
+        set completions
+        for comp in $__%[1]s_comp_results
+            if test (string match -e -r "^$prefix" "$comp")
+                set -a completions $comp
+            end
+        end
+        set --global __%[1]s_comp_results $completions
+        __%[1]s_debug "Filtered completions are: $__%[1]s_comp_results"
+
+        # Important not to quote the variable for count to work
+        set numComps (count $__%[1]s_comp_results)
+        __%[1]s_debug "numComps: $numComps"
+
+        if test $numComps -eq 1; and test $nospace -ne 0
+            # To support the "nospace" directive we trick the shell
+            # by outputting an extra, longer completion.
+            # We must first split on \t to get rid of the descriptions because
+            # the extra character we add to the fake second completion must be
+            # before the description.  We don't need descriptions anyway since
+            # there is only a single real completion which the shell will expand
+            # immediately.
+            __%[1]s_debug "Adding second completion to perform nospace directive"
+            set split (string split --max 1 \t $__%[1]s_comp_results[1])
+            set --global __%[1]s_comp_results $split[1] $split[1].
+            __%[1]s_debug "Completions are now: $__%[1]s_comp_results"
+        end
+
+        if test $numComps -eq 0; and test $nofiles -eq 0
+            # To be consistent with bash and zsh, we only trigger file
+            # completion when there are no other completions
+            __%[1]s_debug "Requesting file completion"
+            return 1
+        end
     end
 
-    if test $numComps -eq 0; and test $nofiles -eq 0
-        __%[1]s_debug "Requesting file completion"
-        set --global __%[1]s_comp_do_file_comp 1
-    end
-
-    # If we don't want file completion, we must return true even if there
-    # are no completions found.  This is because fish will perform the last
-    # completion command, even if its condition is false, if no other
-    # completion command was triggered
-    return (not set --query __%[1]s_comp_do_file_comp)
+    return 0
 end
 
 # Since Fish completions are only loaded once the user triggers them, we trigger them ourselves
@@ -170,16 +183,8 @@ complete --do-complete "%[2]s " > /dev/null 2>&1
 # Remove any pre-existing completions for the program since we will be handling all of them.
 complete -c %[2]s -e
 
-# The order in which the below two lines are defined is very important so that __%[1]s_prepare_completions
-# is called first.  It is __%[1]s_prepare_completions that sets up the __%[1]s_comp_do_file_comp variable.
-#
-# This completion will be run second as complete commands are added FILO.
-# It triggers file completion choices when __%[1]s_comp_do_file_comp is set.
-complete -c %[2]s -n 'set --query __%[1]s_comp_do_file_comp'
-
-# This completion will be run first as complete commands are added FILO.
-# The call to __%[1]s_prepare_completions will setup both __%[1]s_comp_results and __%[1]s_comp_do_file_comp.
-# It provides the program's completion choices.
+# The call to __%[1]s_prepare_completions will setup __%[1]s_comp_results
+# which provides the program's completion choices.
 complete -c %[2]s -n '__%[1]s_prepare_completions' -f -a '$__%[1]s_comp_results'
 
 `, nameForVar, name, compCmd,