From 01e1f7d49e91b6f02037997ffb465b37d2426b80 Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Fri, 30 Dec 2016 17:41:57 +0000
Subject: [PATCH 1/2] keg: fix fallback dependencies with multiple kegs

Fixes #1524.
---
 Library/Homebrew/keg.rb           | 8 +++++++-
 Library/Homebrew/test/keg_test.rb | 7 +++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/Library/Homebrew/keg.rb b/Library/Homebrew/keg.rb
index 756b272885..43e2cbc4f6 100644
--- a/Library/Homebrew/keg.rb
+++ b/Library/Homebrew/keg.rb
@@ -105,7 +105,13 @@ class Keg
     #
     # This happens after the initial dependency check because it's sloooow.
     remaining_formulae = Formula.installed.select do |f|
-      f.installed_kegs.any? { |k| Tab.for_keg(k).runtime_dependencies.nil? }
+      installed_kegs = f.installed_kegs
+
+      # All installed kegs are going to be removed anyway,
+      # so it doesn't matter what they depend on.
+      next false if (installed_kegs - kegs).empty?
+
+      installed_kegs.any? { |k| Tab.for_keg(k).runtime_dependencies.nil? }
     end
 
     keg_names = kegs.map(&:name)
diff --git a/Library/Homebrew/test/keg_test.rb b/Library/Homebrew/test/keg_test.rb
index 4fe7c6a3cf..14cdc4304a 100644
--- a/Library/Homebrew/test/keg_test.rb
+++ b/Library/Homebrew/test/keg_test.rb
@@ -382,6 +382,13 @@ class InstalledDependantsTests < LinkTestCase
     assert_equal [[@keg], ["bar"]], Keg.find_some_installed_dependents([@keg])
   end
 
+  def test_uninstalling_dependent_and_dependency
+    dependencies nil
+    Formula["bar"].class.depends_on "foo"
+    assert_empty @keg.installed_dependents
+    assert_nil Keg.find_some_installed_dependents([@keg, @dependent])
+  end
+
   def test_empty_dependencies_in_tab
     dependencies []
     assert_empty @keg.installed_dependents

From b0a38c06bfce65292dafd8e43e04d9630d236218 Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Fri, 30 Dec 2016 22:16:18 +0000
Subject: [PATCH 2/2] docs: improve Keg.find_some_installed_dependencies

See https://github.com/Homebrew/brew/pull/1752#discussion_r94257147
---
 Library/Homebrew/keg.rb | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/Library/Homebrew/keg.rb b/Library/Homebrew/keg.rb
index 43e2cbc4f6..bdb618ba2f 100644
--- a/Library/Homebrew/keg.rb
+++ b/Library/Homebrew/keg.rb
@@ -87,11 +87,23 @@ class Keg
     mime-info pixmaps sounds postgresql
   ].freeze
 
-  # Will return some kegs, and some dependencies, if they're present.
+  # Given an array of kegs, this method will try to find some other kegs
+  # that depend on them.
+  #
+  # If it does, it returns:
+  # - some kegs in the passed array that have installed dependents
+  # - some installed dependents of those kegs.
+  #
+  # If it doesn't, it returns nil.
+  #
+  # Note that nil will be returned if the only installed dependents
+  # in the passed kegs are other kegs in the array.
+  #
   # For efficiency, we don't bother trying to get complete data.
   def self.find_some_installed_dependents(kegs)
     # First, check in the tabs of installed Formulae.
     kegs.each do |keg|
+      # Don't include dependencies of kegs that were in the given array.
       dependents = keg.installed_dependents - kegs
       dependents.map! { |d| "#{d.name} #{d.version}" }
       return [keg], dependents if dependents.any?
@@ -107,8 +119,7 @@ class Keg
     remaining_formulae = Formula.installed.select do |f|
       installed_kegs = f.installed_kegs
 
-      # All installed kegs are going to be removed anyway,
-      # so it doesn't matter what they depend on.
+      # Don't include dependencies of kegs that were in the given array.
       next false if (installed_kegs - kegs).empty?
 
       installed_kegs.any? { |k| Tab.for_keg(k).runtime_dependencies.nil? }