alias: don't add --wraps for wrappers with the same name

These aliases seem to be common, see #7389 and others.  This prevents
recursion on that example, so `alias ssh "env TERM=screen ssh"` will just
have the same completions as ssh.

Checking the last token is a heuristic which hopefully works for most
cases. Users are encouraged to use functions instead of aliases.

CHANGELOG.rst

@@ -91,6 +91,7 @@ Scripting improvements
 -  ``abbr --erase`` no longer errors on an unset abbreviation (#7376).
 -  ``test -t``, for testing whether file descriptors are connected to a terminal, works for file descriptors 0, 1, and 2 (#4766). It can still return incorrect results in other cases (#1228).
 -  Trying to run fish scripts with Windows line endings (CRLF) produces a sensible error (#2783).
+-  An ``alias`` that delegates to a command with the same name no longer triggers an error about recursive completion (#7389).
 
 Interactive improvements
 ------------------------

share/functions/alias.fish

@@ -11,8 +11,6 @@ function alias --description 'Creates a function wrapping a command'
     set -l name
     set -l body
     set -l prefix
-    set -l first_word
-    set -l wrapped_cmd
 
     if not set -q argv[1]
         # Print the known aliases.
@@ -46,7 +44,8 @@ function alias --description 'Creates a function wrapping a command'
 
     # Extract the first command from the body.
     printf '%s\n' $body | read -l --list words
-    set first_word $words[1]
+    set -l first_word $words[1]
+    set -l last_word $words[-1]
 
     # Prevent the alias from immediately running into an infinite recursion if
     # $body starts with the same command as $name.
@@ -59,8 +58,16 @@ function alias --description 'Creates a function wrapping a command'
     end
     set -l cmd_string (string escape -- "alias $argv")
 
-    set wrapped_cmd (string escape -- $body)
-    echo "function $name --wraps $wrapped_cmd --description $cmd_string; $prefix $body \$argv; end" | source
+    # Do not define wrapper completion if we have "alias foo 'foo xyz'" or "alias foo 'sudo foo'"
+    # This is to prevent completions from recursively calling themselves (#7389).
+    # The latter will have rare false positives but it's more important to
+    # prevent recursion for this high-level command.
+    set -l wraps
+    if test $first_word != $name; and test $last_word != $name
+        set wraps --wraps (string escape -- $body)
+    end
+
+    echo "function $name $wraps --description $cmd_string; $prefix $body \$argv; end" | source
     if set -q _flag_save
         funcsave $name
     end

tests/checks/alias.fish

@@ -31,3 +31,19 @@ functions d
 # CHECK: function d --wraps=\'/mnt/c/Program\ Files\ \(x86\)/devenv.exe\'\ /Edit --description alias\ d\ \'/mnt/c/Program\ Files\ \(x86\)/devenv.exe\'\ /Edit
 # CHECK: '/mnt/c/Program Files (x86)/devenv.exe' /Edit $argv;
 # CHECK: end
+
+# Use "command" to prevent recusion, and don't add --wraps to avoid accidental recursion in completion.
+alias e 'e --option=value'
+functions e
+# CHECK: # Defined in - @ line 1
+# CHECK: function e --description 'alias e e --option=value'
+# CHECK: command e --option=value $argv;
+# CHECK: end
+
+# Don't add --wraps if it looks like a wrapper command to avoid accidental recursion in completion.
+alias f 'wrapper around f'
+functions f
+# CHECK: # Defined in - @ line 1
+# CHECK: function f --description 'alias f wrapper around f'
+# CHECK: wrapper around f $argv;
+# CHECK: end