From b9979088ec7a642a0620f46d970249798e3f035a Mon Sep 17 00:00:00 2001
From: Thierry Joyal <thierry.joyal@gmail.com>
Date: Thu, 21 May 2020 12:31:32 -0400
Subject: [PATCH] [StaticRegisters] Fetch raise on missing

Co-authored-by: Dylan Thacker-Smith <dylan.smith@shopify.com>
---
 History.md                              |  1 +
 lib/liquid/static_registers.rb          | 12 ++++++++++--
 test/unit/static_registers_unit_test.rb | 10 +++++++++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/History.md b/History.md
index 4781b23..c4b6d0f 100644
--- a/History.md
+++ b/History.md
@@ -4,6 +4,7 @@
 
 * Split Strainer class as a factory and a template (#1208) [Thierry Joyal]
 * Remove handling of a nil context in the Strainer class (#1218) [Thierry Joyal]
+* StaticRegisters#fetch to raise on missing key (#1250) [Thierry Joyal]
 
 ## 4.0.3 / 2019-03-12
 
diff --git a/lib/liquid/static_registers.rb b/lib/liquid/static_registers.rb
index da2c2c3..e8fdd9b 100644
--- a/lib/liquid/static_registers.rb
+++ b/lib/liquid/static_registers.rb
@@ -25,8 +25,16 @@ module Liquid
       @registers.delete(key)
     end
 
-    def fetch(key, default = nil)
-      key?(key) ? self[key] : default
+    UNDEFINED = Object.new
+
+    def fetch(key, default = UNDEFINED, &block)
+      if @registers.key?(key)
+        @registers.fetch(key)
+      elsif default != UNDEFINED
+        @static.fetch(key, default, &block)
+      else
+        @static.fetch(key, &block)
+      end
     end
 
     def key?(key)
diff --git a/test/unit/static_registers_unit_test.rb b/test/unit/static_registers_unit_test.rb
index 37a2c28..80bbf39 100644
--- a/test/unit/static_registers_unit_test.rb
+++ b/test/unit/static_registers_unit_test.rb
@@ -51,7 +51,15 @@ class StaticRegistersUnitTest < Minitest::Test
     assert_equal("one", static_register.fetch(:one))
     assert_equal(3, static_register.fetch("two"))
     assert_nil(static_register.fetch(false))
-    assert_nil(static_register.fetch("unknown"))
+
+    assert_raises(KeyError) do
+      static_register.fetch(:unknown)
+    end
+    assert_equal("default", static_register.fetch(:unknown, "default"))
+
+    static_register[:unknown] = "known"
+    assert_equal("known", static_register.fetch(:unknown))
+    assert_equal("known", static_register.fetch(:unknown, "default"))
   end
 
   def test_fetch_default