function scope all variables to reduce side effects

Without passing -f (--function), set commands in functions will clobber same-name shell variables that were already set. For example, if you do 'set commands_selected 1' and then execute _fzf_search_history, commands_selected will change value.

I chose -f over -l or a combination of the two to emulate Python's variable scopes, in which all variables declared within a function are function scoped. This makes reasoning about variables easier and more intuitive.

functions/_fzf_preview_changed_file.fish

@@ -7,13 +7,13 @@ function _fzf_preview_changed_file --argument-names path_status --description "S
     # remove quotes because they'll be interpreted literally by git diff
     # no need to requote when referencing $path because fish does not perform word splitting
     # https://fishshell.com/docs/current/fish_for_bash_users.html
-    set -l path (string unescape (string sub --start 4 $path_status))
+    set -f path (string unescape (string sub --start 4 $path_status))
     # first letter of short format shows index, second letter shows working tree
     # https://git-scm.com/docs/git-status/2.35.0#_short_format
-    set -l index_status (string sub --length 1 $path_status)
-    set -l working_tree_status (string sub --start 2 --length 1 $path_status)
+    set -f index_status (string sub --length 1 $path_status)
+    set -f working_tree_status (string sub --start 2 --length 1 $path_status)
 
-    set diff_opts --color=always
+    set -f diff_opts --color=always
 
     if test $index_status = '?'
         _fzf_report_diff_type Untracked
@@ -32,7 +32,7 @@ function _fzf_preview_changed_file --argument-names path_status --description "S
             # https://stackoverflow.com/questions/73954214
             if test $index_status = R
                 # diff the post-rename path with the original path, otherwise the diff will show the entire file as being added
-                set orig_and_new_path (string split --max 1 -- ' -> ' $path)
+                set -f orig_and_new_path (string split --max 1 -- ' -> ' $path)
                 git diff --staged $diff_opts -- $orig_and_new_path[1] $orig_and_new_path[2]
                 # path currently has the form of "original -> current", so we need to correct it before it's used below
                 set path $orig_and_new_path[2]

functions/_fzf_preview_file.fish

@@ -2,7 +2,7 @@
 function _fzf_preview_file --description "Print a preview for the given file based on its file type."
     # because there's no way to guarantee that _fzf_search_directory passes the path to _fzf_preview_file
     # as one argument, we collect all the arguments into one single variable and treat that as the path
-    set file_path $argv
+    set -f file_path $argv
 
     if test -L "$file_path" # symlink
         # notify user and recurse on the target of the symlink, which can be any of these file types

functions/_fzf_report_diff_type.fish

@@ -5,10 +5,10 @@
 # ╰────────╯
 function _fzf_report_diff_type --argument-names diff_type --description "Print a distinct colored header meant to preface a git patch."
     # number of "-" to draw is the length of the string to box + 2 for padding
-    set repeat_count (math 2 + (string length $diff_type))
-    set line (string repeat --count $repeat_count ─)
-    set top_border ╭$line╮
-    set btm_border ╰$line╯
+    set -f repeat_count (math 2 + (string length $diff_type))
+    set -f line (string repeat --count $repeat_count ─)
+    set -f top_border ╭$line╮
+    set -f btm_border ╰$line╯
 
     set_color yellow
     echo $top_border

functions/_fzf_search_directory.fish

@@ -2,27 +2,27 @@ function _fzf_search_directory --description "Search the current directory. Repl
     # Directly use fd binary to avoid output buffering delay caused by a fd alias, if any.
     # Debian-based distros install fd as fdfind and the fd package is something else, so
     # check for fdfind first. Fall back to "fd" for a clear error message.
-    set fd_cmd (command -v fdfind || command -v fd  || echo "fd")
-    set --append fd_cmd --color=always $fzf_fd_opts
+    set -f fd_cmd (command -v fdfind || command -v fd  || echo "fd")
+    set -f --append fd_cmd --color=always $fzf_fd_opts
 
     # $fzf_dir_opts is the deprecated version of $fzf_directory_opts
-    set fzf_arguments --multi --ansi $fzf_dir_opts $fzf_directory_opts
-    set token (commandline --current-token)
+    set -f fzf_arguments --multi --ansi $fzf_dir_opts $fzf_directory_opts
+    set -f token (commandline --current-token)
     # expand any variables or leading tilde (~) in the token
-    set expanded_token (eval echo -- $token)
+    set -f expanded_token (eval echo -- $token)
     # unescape token because it's already quoted so backslashes will mess up the path
-    set unescaped_exp_token (string unescape -- $expanded_token)
+    set -f unescaped_exp_token (string unescape -- $expanded_token)
 
     # If the current token is a directory and has a trailing slash,
     # then use it as fd's base directory.
     if string match --quiet -- "*/" $unescaped_exp_token && test -d "$unescaped_exp_token"
         set --append fd_cmd --base-directory=$unescaped_exp_token
         # use the directory name as fzf's prompt to indicate the search is limited to that directory
         set --prepend fzf_arguments --prompt="Search Directory $unescaped_exp_token> " --preview="_fzf_preview_file $expanded_token{}"
-        set file_paths_selected $unescaped_exp_token($fd_cmd 2>/dev/null | _fzf_wrapper $fzf_arguments)
+        set -f file_paths_selected $unescaped_exp_token($fd_cmd 2>/dev/null | _fzf_wrapper $fzf_arguments)
     else
         set --prepend fzf_arguments --prompt="Search Directory> " --query="$unescaped_exp_token" --preview='_fzf_preview_file {}'
-        set file_paths_selected ($fd_cmd 2>/dev/null | _fzf_wrapper $fzf_arguments)
+        set -f file_paths_selected ($fd_cmd 2>/dev/null | _fzf_wrapper $fzf_arguments)
     end
 
 

functions/_fzf_search_git_log.fish

@@ -4,9 +4,9 @@ function _fzf_search_git_log --description "Search the output of git log and pre
     else
         if not set --query fzf_git_log_format
             # %h gives you the abbreviated commit hash, which is useful for saving screen space, but we will have to expand it later below
-            set fzf_git_log_format '%C(bold blue)%h%C(reset) - %C(cyan)%ad%C(reset) %C(yellow)%d%C(reset) %C(normal)%s%C(reset)  %C(dim normal)[%an]%C(reset)'
+            set -f fzf_git_log_format '%C(bold blue)%h%C(reset) - %C(cyan)%ad%C(reset) %C(yellow)%d%C(reset) %C(normal)%s%C(reset)  %C(dim normal)[%an]%C(reset)'
         end
-        set selected_log_lines (
+        set -f selected_log_lines (
             git log --no-show-signature --color=always --format=format:$fzf_git_log_format --date=short | \
             _fzf_wrapper --ansi \
                 --multi \
@@ -18,9 +18,9 @@ function _fzf_search_git_log --description "Search the output of git log and pre
         )
         if test $status -eq 0
             for line in $selected_log_lines
-                set abbreviated_commit_hash (string split --field 1 " " $line)
-                set full_commit_hash (git rev-parse $abbreviated_commit_hash)
-                set --append commit_hashes $full_commit_hash
+                set -f abbreviated_commit_hash (string split --field 1 " " $line)
+                set -f full_commit_hash (git rev-parse $abbreviated_commit_hash)
+                set -f --append commit_hashes $full_commit_hash
             end
             commandline --current-token --replace (string join ' ' $commit_hashes)
         end

functions/_fzf_search_git_status.fish

@@ -2,7 +2,7 @@ function _fzf_search_git_status --description "Search the output of git status.
     if not git rev-parse --git-dir >/dev/null 2>&1
         echo '_fzf_search_git_status: Not in a git repository.' >&2
     else
-        set selected_paths (
+        set -f selected_paths (
             # Pass configuration color.status=always to force status to use colors even though output is sent to a pipe
             git -c color.status=always status --short |
             _fzf_wrapper --ansi \
@@ -16,7 +16,7 @@ function _fzf_search_git_status --description "Search the output of git status.
         if test $status -eq 0
             # git status --short automatically escapes the paths of most files for us so not going to bother trying to handle
             # the few edges cases of weird file names that should be extremely rare (e.g. "this;needs;escaping")
-            set cleaned_paths
+            set -f cleaned_paths
 
             for path in $selected_paths
                 if test (string sub --length 1 $path) = R

functions/_fzf_search_history.fish

@@ -6,7 +6,7 @@ function _fzf_search_history --description "Search command history. Replace the
     end
 
     # Delinate commands throughout pipeline using null rather than newlines because commands can be multi-line
-    set commands_selected (
+    set -f commands_selected (
         # Reference https://devhints.io/strftime to understand strftime format symbols
         builtin history --null --show-time="%m-%d %H:%M:%S │ " |
         _fzf_wrapper --read0 \

functions/_fzf_search_processes.fish

@@ -1,8 +1,8 @@
 function _fzf_search_processes --description "Search all running processes. Replace the current token with the pid of the selected process."
     # use all caps to be consistent with ps default format
     # snake_case because ps doesn't seem to allow spaces in the field names
-    set ps_preview_fmt (string join ',' 'pid' 'ppid=PARENT' 'user' '%cpu' 'rss=RSS_IN_KB' 'start=START_TIME' 'command')
-    set processes_selected (
+    set -f ps_preview_fmt (string join ',' 'pid' 'ppid=PARENT' 'user' '%cpu' 'rss=RSS_IN_KB' 'start=START_TIME' 'command')
+    set -f processes_selected (
         ps -A -opid,command | \
         _fzf_wrapper --multi \
                     --prompt="Search Processes> " \
@@ -18,7 +18,7 @@ function _fzf_search_processes --description "Search all running processes. Repl
 
     if test $status -eq 0
         for process in $processes_selected
-            set --append pids_selected (string split --no-empty --field=1 -- " " $process)
+            set -f --append pids_selected (string split --no-empty --field=1 -- " " $process)
         end
 
         # string join to replace the newlines outputted by string split with spaces

functions/_fzf_search_variables.fish

@@ -13,14 +13,14 @@ function _fzf_search_variables --argument-names set_show_output set_names_output
     # 1. it's not included in $set_names_output
     # 2. it tends to be a very large value => increases computation time
     # 3._fzf_search_history is a much better way to examine history anyway
-    set all_variable_names (string match --invert history <$set_names_output)
+    set -f all_variable_names (string match --invert history <$set_names_output)
 
-    set current_token (commandline --current-token)
+    set -f current_token (commandline --current-token)
     # Use the current token to pre-populate fzf's query. If the current token begins
     # with a $, remove it from the query so that it will better match the variable names
-    set cleaned_curr_token (string replace -- '$' '' $current_token)
+    set -f cleaned_curr_token (string replace -- '$' '' $current_token)
 
-    set variable_names_selected (
+    set -f variable_names_selected (
         printf '%s\n' $all_variable_names |
         _fzf_wrapper --preview "_fzf_extract_var_info {} $set_show_output" \
             --prompt="Search Variables> " \

functions/_fzf_wrapper.fish

@@ -1,8 +1,8 @@
 function _fzf_wrapper --description "Prepares some environment variables before executing fzf."
     # Make sure fzf uses fish to execute preview commands, some of which
     # are autoloaded fish functions so don't exist in other shells.
-    # Use --local so that it doesn't clobber SHELL outside of this function.
-    set --local --export SHELL (command --search fish)
+    # Use --function so that it doesn't clobber SHELL outside this function.
+    set -f --export SHELL (command --search fish)
 
     # If FZF_DEFAULT_OPTS is not set, then set some sane defaults.
     # See https://github.com/junegunn/fzf#environment-variables

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 -f options_spec h/help 'directory=?' 'git_log=?' 'git_status=?' 'history=?' 'processes=?' 'variables=?'
     argparse --max-args=0 --ignore-unknown $options_spec -- $argv 2>/dev/null
     if test $status -ne 0
         echo "Invalid option or a positional argument was provided." >&2
@@ -16,7 +16,7 @@ function fzf_configure_bindings --description "Installs the default key bindings
     else
         # Initialize with default key sequences and then override or disable them based on flags
         # index 1 = directory, 2 = git_log, 3 = git_status, 4 = history, 5 = processes, 6 = variables
-        set key_sequences \e\cf \e\cl \e\cs \cr \e\cp \cv # \c = control, \e = escape
+        set -f key_sequences \e\cf \e\cl \e\cs \cr \e\cp \cv # \c = control, \e = escape
         set --query _flag_directory && set key_sequences[1] "$_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"