Add failing spec for mocked component without template

docs/CHANGELOG.md

@@ -10,6 +10,10 @@ nav_order: 5
 
 ## main
 
+* Improve error messaging for malformed components.
+
+    *Martin Meyerhoff*, *Joel Hawksley*
+
 * Do not prefix release tags with `v`, per recommendation from @bkuhlmann.
 
     *Joel Hawksley*

lib/view_component/compiler.rb

@@ -93,11 +93,15 @@ def define_render_template_for
         end
 
       @component.silence_redefinition_of_method(:render_template_for)
-      @component.class_eval <<-RUBY, __FILE__, __LINE__ + 1
-      def render_template_for(variant = nil, format = nil)
-        #{method_body}
+      begin
+        @component.class_eval <<-RUBY, __FILE__, __LINE__ + 1
+        def render_template_for(variant = nil, format = nil)
+          #{method_body}
+        end
+        RUBY
+      rescue SyntaxError
+        raise ViewComponent::CompilerMethodBodySyntaxError.new(@component.name, method_body)
       end
-      RUBY
     end
 
     def template_errors

lib/view_component/errors.rb

@@ -237,4 +237,12 @@ def initialize(setter_method_name, setter_name)
       super(MESSAGE.gsub("SETTER_METHOD_NAME", setter_method_name.to_s).gsub("SETTER_NAME", setter_name.to_s))
     end
   end
+
+  class CompilerMethodBodySyntaxError < StandardError
+    MESSAGE = "Could not compile COMPONENT_NAME due to SyntaxError in method body: METHOD_BODY"
+
+    def initialize(component_name, method_body)
+      super(MESSAGE.gsub("COMPONENT_NAME", component_name.to_s).gsub("METHOD_BODY", method_body.to_s))
+    end
+  end
 end

test/sandbox/test/rendering_test.rb

@@ -17,7 +17,7 @@ def test_render_inline_allocations
 
     allocations = (Rails.version.to_f >= 8.0) ?
       {"3.5.0" => 117, "3.4.1" => 117, "3.3.6" => 129} :
-      {"3.3.6" => 120, "3.3.0" => 120, "3.2.6" => 118, "3.1.6" => 118, "3.0.7" => 127}
+      {"3.3.6" => 120, "3.3.0" => 132, "3.2.6" => 118, "3.1.6" => 118, "3.0.7" => 127}
 
     assert_allocations(**allocations) do
       render_inline(MyComponent.new)
@@ -1236,4 +1236,19 @@ def test_request_param
 
     assert_text("foo")
   end
+
+  # In https://github.com/ViewComponent/view_component/issues/2187,
+  # the Solidus test suite built mocked components by hand, resulting
+  # in a difficult-to-debug error. While this test case is quite narrow,
+  # it isolates the unintentional error masking we were doing.
+  def test_render_anonymous_component_without_template
+    location = caller(1, 1).first
+    mock_component = Class.new(MyComponent)
+    mock_component.define_singleton_method(:name) { "Foo" }
+    mock_component.define_singleton_method(:to_s) { "#{name} (#{location})" }
+
+    assert_raises(ViewComponent::CompilerMethodBodySyntaxError) do
+      render_inline(mock_component.new)
+    end
+  end
 end