From 0320ae8471cbd02c04fd7c1f329cd2844bd6d545 Mon Sep 17 00:00:00 2001
From: Conrad Irwin <conrad.irwin@gmail.com>
Date: Thu, 23 Jan 2014 23:36:46 -0800
Subject: [PATCH] Make watch expressions fully global

At the moment Pry::Hooks are not local to each instance, so the hook
was only being added once. This caused problems when you opened two
binding.pry's in one program, as the second one's watch expressions
appeared to be ignored.
---
 lib/pry/commands/watch_expression.rb   | 10 +++++-----
 spec/commands/watch_expression_spec.rb | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/lib/pry/commands/watch_expression.rb b/lib/pry/commands/watch_expression.rb
index ee28a1b1..05d8e36e 100644
--- a/lib/pry/commands/watch_expression.rb
+++ b/lib/pry/commands/watch_expression.rb
@@ -38,7 +38,7 @@ class Pry
     private
 
     def expressions
-      state.expressions ||= []
+      Pry.config.watch_expressions ||= []
     end
 
     def delete(index)
@@ -66,7 +66,7 @@ class Pry
       end
     end
 
-    def eval_and_print_changed
+    def eval_and_print_changed(output)
       expressions.each do |expr|
         expr.eval!
         if expr.changed?
@@ -82,9 +82,9 @@ class Pry
 
     def add_hook
       hook = [:after_eval, :watch_expression]
-      unless Pry.config.hooks.hook_exists?(*hook)
-        _pry_.hooks.add_hook(*hook) do
-          eval_and_print_changed
+      unless Pry.hooks.hook_exists?(*hook)
+        Pry.hooks.add_hook(*hook) do |_, _pry_|
+          eval_and_print_changed _pry_.output
         end
       end
     end
diff --git a/spec/commands/watch_expression_spec.rb b/spec/commands/watch_expression_spec.rb
index 4801bdb3..e87d8be4 100644
--- a/spec/commands/watch_expression_spec.rb
+++ b/spec/commands/watch_expression_spec.rb
@@ -64,6 +64,30 @@ describe "watch expression" do
     end
   end
 
+  it "continues to work if you start a second pry instance" do
+    ReplTester.start do
+      input 'a = 1'
+      output '=> 1'
+
+      input 'watch a'
+      output "Watching a\nwatch: a => 1"
+
+      input "a = 2"
+      output "watch: a => 2\n=> 2"
+    end
+
+    ReplTester.start do
+      input 'b = 1'
+      output '=> 1'
+
+      input 'watch b'
+      output "Watching b\nwatch: b => 1"
+
+      input "b = 2"
+      output "watch: b => 2\n=> 2"
+    end
+  end
+
   describe "deleting expressions" do
     before do
       eval 'watch :keeper'