add `function --shadow-builtin` flag

It's currently too easy for someone to bork their shell by doing something
like `function test; return 0; end`. That's obviously a silly, contrived,
example but the point is that novice users who learn about functions are
prone to do something like that without realizing it will bork the shell. Even
expert users who know about the `test` builtin might forget that, say, `pwd`
is a builtin.

This change adds a `--shadow-builtin` flag that must be specified to
indicate you know what you're doing.

Fixes #3000

1 files changed, 5 insertions, 13 deletions

diff --git a/share/functions/__fish_config_interactive.fish b/share/functions/__fish_config_interactive.fish
index 7b306e3d..ec891ddd 100644
--- a/share/functions/__fish_config_interactive.fish
+++ b/share/functions/__fish_config_interactive.fish
@@ -4,9 +4,7 @@
 # This function is called by the __fish_on_interactive function, which is defined in config.fish.
 #
 function __fish_config_interactive -d "Initializations that should be performed when entering interactive mode"
-
-
-    # Make sure this function is only run once
+    # Make sure this function is only run once.
     if set -q __fish_config_interactive_done
         return
     end
@@ -27,7 +25,6 @@ function __fish_config_interactive -d "Initializations that should be performed
     #
     # If we are starting up for the first time, set various defaults
     #
-
     if not set -q __fish_init_1_50_0
         if not set -q fish_greeting
             set -l line1 (printf (_ 'Welcome to fish, the friendly interactive shell') )
@@ -97,25 +94,22 @@ function __fish_config_interactive -d "Initializations that should be performed
         #
         # Directory history colors
         #
-
         set -q fish_color_history_current
         or set -U fish_color_history_current cyan
     end
 
     #
-    # Generate man page completions if not present
+    # Generate man page completions if not present.
     #
-
     if not test -d $userdatadir/fish/generated_completions
         #fish_update_completions is a function, so it can not be directly run in background.
         eval "$__fish_bin_dir/fish -c 'fish_update_completions > /dev/null ^/dev/null' &"
     end
 
     #
-    # Print a greeting
-    # fish_greeting can be a function (preferred) or a variable
+    # Print a greeting.
+    # fish_greeting can be a function (preferred) or a variable.
     #
-
     if functions -q fish_greeting
         fish_greeting
     else
@@ -130,7 +124,6 @@ function __fish_config_interactive -d "Initializations that should be performed
     # fish_color_cwd changes value. Like all event handlers, it can't be
     # autoloaded.
     #
-
     function __fish_repaint --on-variable fish_color_cwd --description "Event handler, repaints the prompt when fish_color_cwd changes"
         if status --is-interactive
             set -e __fish_prompt_cwd
@@ -149,7 +142,6 @@ function __fish_config_interactive -d "Initializations that should be performed
     # Completions for SysV startup scripts. These aren't bound to any
     # specific command, so they can't be autoloaded.
     #
-
     complete -x -p "/etc/init.d/*" -a start --description 'Start service'
     complete -x -p "/etc/init.d/*" -a stop --description 'Stop service'
     complete -x -p "/etc/init.d/*" -a status --description 'Print service status'
@@ -293,7 +285,7 @@ function __fish_config_interactive -d "Initializations that should be performed
 
         # Don't allow setting color other than what linux offers (see #2001)
         functions -e set_color
-        function set_color
+        function set_color --shadow-builtin
             set -l term_colors black red green yellow blue magenta cyan white normal
             for a in $argv
                 if not contains -- $a $term_colors