set environment with brew shellenv

init.fish

@@ -1,24 +1,22 @@
-if type -q brew
-  set -l brew_paths /usr/local/bin /usr/bin /bin /usr/local/sbin /usr/sbin /sbin
+if status is-login
+  # check $HOMEBREW_BIN and set $brew
+  set -q HOMEBREW_BIN
+    and set -l brew $HOMEBREW_BIN
+    or set -l brew /usr/local/bin/brew
 
-  # Append all existing brew paths to PATH
-  set -l existing_brew_paths
-  for brew_path in $brew_paths
-    if test -d $brew_path
-      set PATH $PATH $brew_path
-      set existing_brew_paths $existing_brew_paths $brew_path
-    end
-  end
-
-  # Remove brew paths from tail to head that were not recently added
-  set -l number_of_paths_to_ignore (math (count $PATH) - (count $existing_brew_paths))
-  for i in (seq (count $PATH))[-1..1]
-    if test $i -le $number_of_paths_to_ignore
-      if contains $PATH[$i] $brew_paths
-        set -e PATH[$i]
-      end
-    end
-  end
-else
-  echo "Please install 'brew' first!"
+  # By default, `brew shellenv` sets $fish_user_paths as a global variable instead of directly
+  # setting $PATH. This behavior should be avoided and thus is overriden here, since setting 
+  # a global $fish_user_paths will shadow the universal $fish_user_paths, which is supposed 
+  # to be set manually by users by design.
+  if type -q $brew; and set cmd ($brew shellenv | sed 's/fish_user_paths/PATH/g') ^ /dev/null
+    # initialized brew shell environment if $brew is valid
+    eval $cmd
+    set -gx HOMEBREW_BIN $brew
+    set -gxp PATH
+  else
+    echo "Error! 'brew' not found at $brew."
+    echo "Please make sure Homebrew is installed and \$HOMEBREW_BIN is correctly set!"
+    echo "To install Homebrew, please check https://brew.sh"
+    echo "Note that setting \$HOMEBREW_BIN is optional if the default Homebrew installation path is used."
+  end >& 2
 end