From 5a189cbe66a5ef632d8a5e1c8ba5df6cbcc4caa9 Mon Sep 17 00:00:00 2001
From: Cody Byrnes <byrnes.cody@gmail.com>
Date: Fri, 9 Mar 2018 06:09:41 -0800
Subject: [PATCH] Fix: File.extname edge case for dot in path with no extension
 (#5790)

---
 spec/std/file_spec.cr | 6 ++++++
 src/file.cr           | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/spec/std/file_spec.cr b/spec/std/file_spec.cr
index fe6c1f520edc..19e4f4f527a0 100644
--- a/spec/std/file_spec.cr
+++ b/spec/std/file_spec.cr
@@ -290,6 +290,12 @@ describe "File" do
     File.extname("/foo/bar/.profile").should eq("")
     File.extname("/foo/bar/.profile.sh").should eq(".sh")
     File.extname("/foo/bar/foo.").should eq("")
+    File.extname("/foo.bar/baz").should eq("")
+    File.extname("test.cr").should eq(".cr")
+    File.extname("test.cr.cz").should eq(".cz")
+    File.extname(".test").should eq("")
+    File.extname(".test.cr").should eq(".cr")
+    File.extname(".test.cr.cz").should eq(".cz")
     File.extname("test").should eq("")
   end
 
diff --git a/src/file.cr b/src/file.cr
index 67766919d514..53e8f35ceaf1 100644
--- a/src/file.cr
+++ b/src/file.cr
@@ -298,7 +298,7 @@ class File < IO::FileDescriptor
 
     dot_index = filename.rindex('.')
 
-    if dot_index && dot_index != filename.size - 1 && filename[dot_index - 1] != SEPARATOR
+    if dot_index && dot_index != filename.size - 1 && dot_index - 1 > (filename.rindex(SEPARATOR) || 0)
       filename[dot_index, filename.size - dot_index]
     else
       ""