From 3edee32bb9d89ff4cf51faba029012558be4452e Mon Sep 17 00:00:00 2001
From: "Brian J. Cardiff" <bcardiff@gmail.com>
Date: Mon, 4 Jun 2018 18:45:53 +0200
Subject: [PATCH] Add File.same?(path1, path2) with follow_symlinks option
 (#6161)

---
 spec/std/file_spec.cr                | 23 +++++++++++++++++++++--
 src/crystal/system/unix/file_info.cr |  2 +-
 src/file.cr                          |  6 ++++++
 src/file/info.cr                     |  4 ++--
 4 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/spec/std/file_spec.cr b/spec/std/file_spec.cr
index 65de5d0c3624..650f3f44807f 100644
--- a/spec/std/file_spec.cr
+++ b/spec/std/file_spec.cr
@@ -230,13 +230,32 @@ describe "File" do
         File.link(in_path, out_path)
         File.exists?(out_path).should be_true
         File.symlink?(out_path).should be_false
-        File.info(in_path).should eq(File.info(out_path))
+        File.same?(in_path, out_path).should be_true
       ensure
         File.delete(out_path) if File.exists?(out_path)
       end
     end
   end
 
+  describe "same?" do
+    it "compares following symlinks only if requested" do
+      file = "#{__DIR__}/data/test_file.txt"
+      symlink = "#{__DIR__}/data/test_file_symlink.txt"
+      other = "#{__DIR__}/data/test_file.ini"
+
+      begin
+        File.symlink(file, symlink)
+
+        File.same?(file, symlink).should be_false
+        File.same?(file, symlink, follow_symlinks: true).should be_true
+        File.same?(file, symlink, follow_symlinks: false).should be_false
+        File.same?(file, other).should be_false
+      ensure
+        File.delete(symlink) if File.exists?(symlink)
+      end
+    end
+  end
+
   describe "symlink" do
     it "creates a symbolic link" do
       in_path = "#{__DIR__}/data/test_file.txt"
@@ -244,7 +263,7 @@ describe "File" do
       begin
         File.symlink(in_path, out_path)
         File.symlink?(out_path).should be_true
-        File.info(in_path).should eq(File.info(out_path))
+        File.same?(in_path, out_path, follow_symlinks: true).should be_true
       ensure
         File.delete(out_path) if File.exists?(out_path)
       end
diff --git a/src/crystal/system/unix/file_info.cr b/src/crystal/system/unix/file_info.cr
index 94052f15c99e..3b42496b96fd 100644
--- a/src/crystal/system/unix/file_info.cr
+++ b/src/crystal/system/unix/file_info.cr
@@ -54,7 +54,7 @@ struct Crystal::System::FileInfo < ::File::Info
     @stat.st_gid.to_u32
   end
 
-  def ==(other : ::File::Info) : Bool
+  def same_file?(other : ::File::Info) : Bool
     @stat.st_dev == other.@stat.st_dev && @stat.st_ino == other.@stat.st_ino
   end
 end
diff --git a/src/file.cr b/src/file.cr
index 82f503881e84..8064a2cf9251 100644
--- a/src/file.cr
+++ b/src/file.cr
@@ -82,6 +82,12 @@ class File < IO::FileDescriptor
     Crystal::System::File.exists?(path)
   end
 
+  # Returns `true` if *path1* and *path2* represents the same file.
+  # The comparison take symlinks in consideration if *follow_symlinks* is `true`.
+  def self.same?(path1 : String, path2 : String, follow_symlinks = false) : Bool
+    info(path1, follow_symlinks).same_file? info(path2, follow_symlinks)
+  end
+
   # Returns the size of *filename* bytes. Raises `Errno` if the file at *path*
   # does not exist.
   #
diff --git a/src/file/info.cr b/src/file/info.cr
index 0f323f8292af..0df61ab3fd05 100644
--- a/src/file/info.cr
+++ b/src/file/info.cr
@@ -99,11 +99,11 @@ class File
     # The group ID that the file belongs to.
     abstract def group : UInt32
 
-    # Two `File::Info`s are equal if and only if they are of the same file.
+    # Returns true if this `Info` and *other* are of the same file.
     #
     # On unix, this compares device and inode fields, and will compare equal for
     # hard linked files.
-    abstract def ==(other : File::Info)
+    abstract def same_file?(other : File::Info) : Bool
 
     # Returns true if this `Info` represents a standard file. Shortcut for
     # `type.file?`.