From 6a33412bb5ed0d3ee7d3b436961141be6e4cab42 Mon Sep 17 00:00:00 2001
From: Dmitry Kakurin <dmitryk@microsoft.com>
Date: Fri, 3 Jan 2020 19:27:05 -0800
Subject: [PATCH 1/2] Fixed Path.absname to correctly handle UNC paths on
 Windows

absname was incorrectly converting `//host/path` to `/host/path`

Added Windows-only Unit Tests for:
* Path.absname for UNC path (fixed here)
* Path.type for UNC path (was already correct, but not tested)
---
 lib/elixir/lib/path.ex               | 9 +++++++--
 lib/elixir/test/elixir/path_test.exs | 8 ++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/elixir/lib/path.ex b/lib/elixir/lib/path.ex
index 090899aa726..f2fbd02b87b 100644
--- a/lib/elixir/lib/path.ex
+++ b/lib/elixir/lib/path.ex
@@ -95,6 +95,8 @@ defmodule Path do
     absname(absname_join(name), cwd)
   end
 
+  @slash [?/, ?\\]
+
   # Joins a list
   defp absname_join([name1, name2 | rest]), do: absname_join([absname_join(name1, name2) | rest])
 
@@ -110,6 +112,11 @@ defmodule Path do
     do_absname_join(rest, relativename, [?:, uc_letter + ?a - ?A], :win32)
   end
 
+  defp do_absname_join(<<c1, c2, rest::binary>>, relativename, [], :win32)
+       when c1 in @slash and c2 in @slash do
+    do_absname_join(rest, relativename, '//', :win32)
+  end
+
   defp do_absname_join(<<?\\, rest::binary>>, relativename, result, :win32),
     do: do_absname_join(<<?/, rest::binary>>, relativename, result, :win32)
 
@@ -254,8 +261,6 @@ defmodule Path do
   defp unix_pathtype([list | rest]) when is_list(list), do: unix_pathtype(list ++ rest)
   defp unix_pathtype(relative), do: {:relative, relative}
 
-  @slash [?/, ?\\]
-
   defp win32_pathtype([list | rest]) when is_list(list), do: win32_pathtype(list ++ rest)
 
   defp win32_pathtype([char, list | rest]) when is_list(list),
diff --git a/lib/elixir/test/elixir/path_test.exs b/lib/elixir/test/elixir/path_test.exs
index 4ad0c99367e..d870b683a9f 100644
--- a/lib/elixir/test/elixir/path_test.exs
+++ b/lib/elixir/test/elixir/path_test.exs
@@ -39,6 +39,11 @@ defmodule PathTest do
   describe "Windows" do
     @describetag :windows
 
+    test "absname/1" do
+      assert Path.absname("//host/path") == "//host/path"
+      assert Path.absname("\\\\host\\path") == "//host/path"
+    end
+
     test "relative/1" do
       assert Path.relative("C:/usr/local/bin") == "usr/local/bin"
       assert Path.relative("C:\\usr\\local\\bin") == "usr\\local\\bin"
@@ -67,6 +72,9 @@ defmodule PathTest do
       assert Path.type("/usr/local/bin") == :volumerelative
       assert Path.type('usr/local/bin') == :relative
       assert Path.type("../usr/local/bin") == :relative
+
+      assert Path.type("//host/path") == :absolute
+      assert Path.type("\\\\host\\path") == :absolute
     end
 
     test "split/1" do

From 85f13b882439964fc2247887de8340e09dc6bf10 Mon Sep 17 00:00:00 2001
From: Dmitry Kakurin <dmitryk@microsoft.com>
Date: Mon, 6 Jan 2020 12:26:16 -0800
Subject: [PATCH 2/2] Added tests for mixed slashes

---
 lib/elixir/test/elixir/path_test.exs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/elixir/test/elixir/path_test.exs b/lib/elixir/test/elixir/path_test.exs
index d870b683a9f..6d1daafa156 100644
--- a/lib/elixir/test/elixir/path_test.exs
+++ b/lib/elixir/test/elixir/path_test.exs
@@ -42,6 +42,8 @@ defmodule PathTest do
     test "absname/1" do
       assert Path.absname("//host/path") == "//host/path"
       assert Path.absname("\\\\host\\path") == "//host/path"
+      assert Path.absname("\\/host\\path") == "//host/path"
+      assert Path.absname("/\\host\\path") == "//host/path"
     end
 
     test "relative/1" do
@@ -75,6 +77,8 @@ defmodule PathTest do
 
       assert Path.type("//host/path") == :absolute
       assert Path.type("\\\\host\\path") == :absolute
+      assert Path.type("/\\host\\path") == :absolute
+      assert Path.type("\\/host\\path") == :absolute
     end
 
     test "split/1" do