From e0b53b23d46f8467884c5c387a9081d98cb7cca7 Mon Sep 17 00:00:00 2001
From: Kevin Gilpin <kgilpin@gmail.com>
Date: Tue, 25 Jul 2023 15:19:49 -0400
Subject: [PATCH] fix: Guard access to the :size method

Fixes #341
---
 lib/appmap/value_inspector.rb |  2 +-
 spec/value_inspector_spec.rb  | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/appmap/value_inspector.rb b/lib/appmap/value_inspector.rb
index 6fd67045..15a7cdde 100644
--- a/lib/appmap/value_inspector.rb
+++ b/lib/appmap/value_inspector.rb
@@ -7,7 +7,7 @@ module ValueInspector
 
     def detect_size(value)
       # Don't risk calling #size on things like data-access objects, which can and will issue queries for this information.
-      if value.is_a?(Array) || value.is_a?(Hash)
+      if (value.is_a?(Array) || value.is_a?(Hash)) && value.respond_to?(:size)
         value.size
       end
     end
diff --git a/spec/value_inspector_spec.rb b/spec/value_inspector_spec.rb
index d5b3d8c2..89fa08db 100644
--- a/spec/value_inspector_spec.rb
+++ b/spec/value_inspector_spec.rb
@@ -289,4 +289,22 @@
       )
     end
   end
+
+  describe "Array that doesn't implement :size" do
+    it 'does not try and invoke :size' do
+      ary = []
+      class << ary
+        def respond_to?(method)
+          return false if method.to_sym == :size
+
+          super
+        end
+      end
+
+      inspector = Struct.new(:id) do
+        include AppMap::ValueInspector
+      end.new
+      expect(inspector.detect_size(ary)).to be_nil
+    end
+  end
 end