Bring path verification and add normalization (#1016)

* Bring path verification and add normalization

* Normalize user home

Co-authored-by: Jonatan Kłosko <jonatanklosko@gmail.com>

lib/livebook/config.ex

@@ -55,9 +55,11 @@ defmodule Livebook.Config do
   """
   @spec home() :: String.t()
   def home do
-    Application.get_env(:livebook, :home) || System.user_home() || File.cwd!()
+    Application.get_env(:livebook, :home) || user_home() || File.cwd!()
   end
 
+  defp user_home(), do: System.user_home() |> Path.expand()
+
   @doc """
   Returns the configuration path.
   """

lib/livebook/file_system/file.ex

@@ -29,7 +29,13 @@ defmodule Livebook.FileSystem.File do
 
     path =
       if path do
-        FileSystem.resolve_path(file_system, default_path, path)
+        resolved_path = FileSystem.resolve_path(file_system, default_path, path)
+
+        unless path == resolved_path do
+          raise ArgumentError, "expected an expanded absolute path, got: #{inspect(path)}"
+        end
+
+        path
       else
         default_path
       end

test/livebook/file_system/file_test.exs

@@ -6,18 +6,22 @@ defmodule Livebook.FileSystem.FileTest do
   alias Livebook.FileSystem
 
   describe "new/2" do
-    test "resolves relative paths" do
+    test "raises an error when a relative path is given" do
       file_system = FileSystem.Local.new()
 
-      assert FileSystem.File.new(file_system, "file.txt").path ==
-               Path.join(File.cwd!(), "file.txt")
+      assert_raise ArgumentError, ~s{expected an expanded absolute path, got: "file.txt"}, fn ->
+        FileSystem.File.new(file_system, "file.txt")
+      end
     end
 
-    test "resolves unexpanded paths" do
+    test "raises an error when a unexpanded path is given" do
       file_system = FileSystem.Local.new()
 
-      assert FileSystem.File.new(file_system, "/dir/nested/../file.txt").path ==
-               Path.expand("/dir/file.txt")
+      assert_raise ArgumentError,
+                   ~s{expected an expanded absolute path, got: "/dir/nested/../file.txt"},
+                   fn ->
+                     FileSystem.File.new(file_system, "/dir/nested/../file.txt")
+                   end
     end
 
     test "uses default file system path if non is given" do