From 5e2ea072ca5d4eff66e7a419249e95fb67b9e3d0 Mon Sep 17 00:00:00 2001
From: Tim Woodbury <tim@midpackrunner.com>
Date: Thu, 13 Oct 2016 15:42:39 -0400
Subject: [PATCH] Raise exception for unrecognized join styles

---
 lib/prawn/errors.rb              | 3 +++
 lib/prawn/graphics/join_style.rb | 5 +++++
 spec/stroke_styles_spec.rb       | 6 ++++++
 3 files changed, 14 insertions(+)

diff --git a/lib/prawn/errors.rb b/lib/prawn/errors.rb
index aafff5e52..8e8aed5c5 100644
--- a/lib/prawn/errors.rb
+++ b/lib/prawn/errors.rb
@@ -75,5 +75,8 @@ module Errors
     # Raised when unrecognized content is provided for a table cell.
     #
     UnrecognizedTableContent = Class.new(StandardError)
+
+    # This error is raised when an incompatible join style is specified
+    InvalidJoinStyle = Class.new(StandardError)
   end
 end
diff --git a/lib/prawn/graphics/join_style.rb b/lib/prawn/graphics/join_style.rb
index a5d098c24..467a4bbd7 100644
--- a/lib/prawn/graphics/join_style.rb
+++ b/lib/prawn/graphics/join_style.rb
@@ -25,6 +25,11 @@ def join_style(style = nil)
 
         self.current_join_style = style
 
+        unless JOIN_STYLES.has_key?(current_join_style)
+          raise Prawn::Errors::InvalidJoinStyle,
+            "#{style} is not a recognized join style. Valid styles are #{JOIN_STYLES.keys.join(", ")}"
+        end
+
         write_stroke_join_style
       end
 
diff --git a/spec/stroke_styles_spec.rb b/spec/stroke_styles_spec.rb
index c2c54ed98..079ab5239 100644
--- a/spec/stroke_styles_spec.rb
+++ b/spec/stroke_styles_spec.rb
@@ -97,6 +97,12 @@
     expect(join_styles.join_style_count).to eq(2)
     expect(join_styles.join_style).to eq(1)
   end
+
+  context "with invalid arguments" do
+    it "should raise an exception" do
+      expect{ @pdf.join_style(:mitre) }.to raise_error(Prawn::Errors::InvalidJoinStyle)
+    end
+  end
 end
 
 describe "Dashes" do