Overwrite broken symlinks with --overwrite

Closes Homebrew/homebrew#19480.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>

3 files changed, 25 insertions, 3 deletions

diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index ef7dcea99..25bb1e537 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -264,7 +264,20 @@ class Pathname
           raise <<-EOS.undent
             Could not symlink file: #{src.expand_path}
             Target #{self} already exists. You may need to delete it.
-            To force the link and delete this file, do:
+            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
+        # #exist? will return false for symlinks whose target doesn't exist
+        elsif self.symlink?
+          raise <<-EOS.undent
+            Could not symlink file: #{src.expand_path}
+            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:
diff --git a/Library/Homebrew/keg.rb b/Library/Homebrew/keg.rb
index 8e774ba85..a63af419d 100644
--- a/Library/Homebrew/keg.rb
+++ b/Library/Homebrew/keg.rb
@@ -194,14 +194,14 @@ class Keg < Pathname
       puts "Skipping; already exists: #{dst}" if ARGV.verbose?
     # cf. git-clean -n: list files to delete, don't really link or delete
     elsif mode.dry_run and mode.overwrite
-      puts dst if dst.exist?
+      puts dst if dst.exist? or dst.symlink?
       return
     # list all link targets
     elsif mode.dry_run
       puts dst
       return
     else
-      dst.delete if mode.overwrite && dst.exist?
+      dst.delete if mode.overwrite && (dst.exist? or dst.symlink?)
       dst.make_relative_symlink src
     end
   end
diff --git a/Library/Homebrew/test/test_keg.rb b/Library/Homebrew/test/test_keg.rb
index 3081381aa..208d62683 100644
--- a/Library/Homebrew/test/test_keg.rb
+++ b/Library/Homebrew/test/test_keg.rb
@@ -61,6 +61,15 @@ class LinkTests < Test::Unit::TestCase
     assert_equal 3, @keg.link(mode)
   end
 
+  def test_link_overwrite_broken_symlinks
+    FileUtils.cd HOMEBREW_PREFIX/"bin" do
+      FileUtils.ln_s "nowhere", "helloworld"
+    end
+    mode = OpenStruct.new
+    mode.overwrite = true
+    assert_equal 3, @keg.link(mode)
+  end
+
   def test_link_overwrite_dryrun
     FileUtils.touch HOMEBREW_PREFIX/"bin/helloworld"
     mode = OpenStruct.new