From 48b62e66cdbca267080274d7d76947073d7f58d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johannes=20M=C3=BCller?= <straightshoota@gmail.com>
Date: Tue, 6 Mar 2018 20:11:24 +0000
Subject: [PATCH] Fix File.extname to handle path with dot in directory name

---
 spec/std/file_spec.cr | 1 +
 src/file.cr           | 6 +++---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/spec/std/file_spec.cr b/spec/std/file_spec.cr
index fe6c1f520edc..cd143e8a77d6 100644
--- a/spec/std/file_spec.cr
+++ b/spec/std/file_spec.cr
@@ -291,6 +291,7 @@ describe "File" do
     File.extname("/foo/bar/.profile.sh").should eq(".sh")
     File.extname("/foo/bar/foo.").should eq("")
     File.extname("test").should eq("")
+    File.extname("/foo.bar/baz").should eq("")
   end
 
   it "constructs a path from parts" do
diff --git a/src/file.cr b/src/file.cr
index 67766919d514..96d816b6d9c1 100644
--- a/src/file.cr
+++ b/src/file.cr
@@ -294,12 +294,12 @@ class File < IO::FileDescriptor
   # File.extname("foo.cr") # => ".cr"
   # ```
   def self.extname(filename) : String
-    filename.check_no_null_byte
+    filename = basename(filename)
 
     dot_index = filename.rindex('.')
 
-    if dot_index && dot_index != filename.size - 1 && filename[dot_index - 1] != SEPARATOR
-      filename[dot_index, filename.size - dot_index]
+    if dot_index && dot_index != 0 && dot_index != filename.size - 1
+      filename[dot_index..-1]
     else
       ""
     end