fix: elixir path discovery (#248)

* fix(port): use markers to parse shell PATH

* whoops, forgot to remove the old one

Author: soisyourface

apps/expert/lib/expert/port.ex

@@ -15,6 +15,8 @@ defmodule Expert.Port do
 
   @type open_opts :: [open_opt]
 
+  @path_marker "__EXPERT_PATH__"
+
   @doc """
   Launches elixir in a port.
 
@@ -62,32 +64,38 @@ defmodule Expert.Port do
     # or we get an incomplete PATH not including erl or any other version manager
     # managed programs.
 
+    # Disable shell session history to reduce noise
     env = [{"SHELL_SESSIONS_DISABLE", "1"}]
 
-    path =
+    args =
       case Path.basename(shell) do
         # Ideally, it should contain the path to shell (e.g. `/usr/bin/fish`),
         # but it might contain only the name of the shell (e.g. `fish`).
         "fish" ->
           # Fish uses space-separated PATH, so we use the built-in `string join` command
           # to join the entries with colons and have a standard colon-separated PATH output
           # as in bash, which is expected by `:os.find_executable/2`.
-          {path, 0} =
-            System.cmd(shell, ["-l", "-c", "cd #{directory} && string join ':' $PATH"], env: env)
+          # Also, no -i flag
+          cmd =
+            "cd #{directory}; printf \"#{@path_marker}:%s:#{@path_marker}\" (string join ':' $PATH)"
 
-          path
+          ["-l", "-c", cmd]
 
         _ ->
-          {path, 0} =
-            System.cmd(shell, ["-i", "-l", "-c", "cd #{directory} && echo $PATH"], env: env)
-
-          path
+          cmd = "cd #{directory} && printf \"#{@path_marker}:%s:#{@path_marker}\" \"$PATH\""
+          ["-i", "-l", "-c", cmd]
       end
 
-    path
-    |> String.trim()
-    |> String.split("\n")
-    |> List.last()
+    {output, _} = System.cmd(shell, args, env: env)
+
+    # This ignores banners (start) and logout garbage (end)
+    case Regex.run(~r/#{@path_marker}:(.*?):#{@path_marker}/s, output) do
+      [_, clean_path] ->
+        clean_path
+
+      nil ->
+        output |> String.trim() |> String.split("\n") |> List.last()
+    end
   end
 
   @doc """