Rework make_relative_symlink error handling and move it into keg

Library/Homebrew/extend/pathname.rb

@@ -290,53 +290,9 @@ class Pathname
     (dirname+link).exist?
   end
 
-  # perhaps confusingly, this Pathname object becomes the symlink pointing to
-  # the src paramter.
-  def make_relative_symlink src
+  def make_relative_symlink(src)
     dirname.mkpath
-
-    dirname.cd do
-      # NOTE only system ln -s will create RELATIVE symlinks
-      return if quiet_system("ln", "-s", src.relative_path_from(dirname), basename)
-    end
-
-    if symlink? && exist?
-      raise <<-EOS.undent
-        Could not symlink file: #{src}
-        Target #{self} already exists as a symlink to #{readlink}.
-        If this file is from another formula, you may need to
-        `brew unlink` it. Otherwise, you may want to delete it.
-        To force the link and overwrite all other conflicting files, do:
-          brew link --overwrite formula_name
-
-        To list all files that would be deleted:
-          brew link --overwrite --dry-run formula_name
-        EOS
-    elsif exist?
-      raise <<-EOS.undent
-        Could not symlink file: #{src}
-        Target #{self} already exists. You may need to delete it.
-        To force the link and overwrite all other conflicting files, do:
-          brew link --overwrite formula_name
-
-        To list all files that would be deleted:
-          brew link --overwrite --dry-run formula_name
-        EOS
-    elsif symlink?
-      unlink
-      make_relative_symlink(src)
-    elsif !dirname.writable_real?
-      raise <<-EOS.undent
-        Could not symlink file: #{src}
-        #{dirname} is not writable. You should change its permissions.
-        EOS
-    else
-      raise <<-EOS.undent
-        Could not symlink file: #{src}
-        #{self} may already exist.
-        #{dirname} may not be writable.
-        EOS
-    end
+    File.symlink(src.relative_path_from(dirname), self)
   end
 
   def / that
@@ -503,6 +459,7 @@ module ObserverPathnameExtension
   end
   def make_relative_symlink src
     super
+    puts "ln -s #{src.relative_path_from(dirname)} #{basename}" if ARGV.verbose?
     ObserverPathnameExtension.n += 1
   end
   def install_info

Library/Homebrew/keg.rb

@@ -183,7 +183,7 @@ class Keg < Pathname
     end
 
     unless mode.dry_run
-      linked_keg_record.make_relative_symlink(self)
+      make_relative_symlink(linked_keg_record, self, mode)
       optlink
     end
 
@@ -203,7 +203,7 @@ class Keg < Pathname
     elsif from.exist?
       from.delete
     end
-    from.make_relative_symlink(self)
+    make_relative_symlink(from, self)
   end
 
   def delete_pyc_files!
@@ -250,7 +250,45 @@ class Keg < Pathname
     end
 
     dst.delete if mode.overwrite && (dst.exist? || dst.symlink?)
-    dst.make_relative_symlink src
+    dst.make_relative_symlink(src)
+  rescue Errno::EEXIST
+    if dst.symlink? && dst.exist?
+      raise <<-EOS.undent
+        Could not symlink file: #{src}
+        Target #{dst} already exists as a symlink to #{dst.readlink}.
+        If this file is from another formula, you may need to
+        `brew unlink` it. Otherwise, you may want to delete it.
+        To force the link and overwrite all other conflicting files, do:
+          brew link --overwrite formula_name
+
+        To list all files that would be deleted:
+          brew link --overwrite --dry-run formula_name
+        EOS
+    elsif dst.exist?
+      raise <<-EOS.undent
+        Could not symlink file: #{src}
+        Target #{dst} already exists. You may need to delete it.
+        To force the link and overwrite all other conflicting files, do:
+          brew link --overwrite formula_name
+
+        To list all files that would be deleted:
+          brew link --overwrite --dry-run formula_name
+        EOS
+    elsif dst.symlink?
+      dst.unlink
+      retry
+    end
+  rescue Errno::EACCES
+    raise <<-EOS.undent
+      Could not symlink file: #{src}
+      #{dst.dirname} is not writable. You should change its permissions.
+      EOS
+  rescue SystemCallError
+    raise <<-EOS.undent
+      Could not symlink file: #{src}
+      #{dst} may already exist.
+      #{dst.dirname} may not be writable.
+      EOS
   end
 
   # symlinks the contents of self+foo recursively into #{HOMEBREW_PREFIX}/foo