Be a bit more defensive and don't throw errors for unexpected values.

expression-ruby/ext/lago_expression/src/lib.rs

@@ -28,10 +28,7 @@ impl EventWrapper {
             } else if value.is_kind_of(ruby.class_string()) {
                 PropertyValue::String(String::try_convert(value)?)
             } else {
-                return Err(magnus::Error::new(
-                    ruby.exception_runtime_error(),
-                    "Expected string or number".to_owned(),
-                ));
+                PropertyValue::String(value.to_string())
             };
             properties.insert(key, property_value);
             Ok(ForEach::Continue)

expression-ruby/spec/lago-expression/expression_spec.rb

@@ -2,7 +2,14 @@
 
 
 RSpec.describe Lago::Expression do
-  let(:event) { Lago::Event.new("code", 1234, {"property_1" => 1.23, "property_2" => "test", "property_3" => "12.34"}) }
+
+  class Dummy < Struct.new(:v)
+    def to_s
+      v
+    end
+  end
+
+  let(:event) { Lago::Event.new("code", 1234, {"property_1" => 1.23, "dummy" => Dummy.new(1), "decimal_property" => BigDecimal("2.3"), "property_2" => "test", "property_3" => "12.34"}) }
 
   describe '#evaluate' do
     context "with a simple math expression" do
@@ -47,6 +54,22 @@
       end
     end
 
+    context "with a decimal expression with a decimal value from the event" do
+      let(:expression) { Lago::ExpressionParser.parse("event.properties.property_1 + event.properties.decimal_property") }
+
+      it "returns the calculated value" do
+        expect(expression.evaluate(event)).to eq(3.53)
+      end
+    end
+
+    context "with a non-number / string value in the event payload" do
+      let(:expression) { Lago::ExpressionParser.parse("event.properties.dummy") }
+
+      it "returns the calculated value" do
+        expect(expression.evaluate(event)).not_to be(nil)
+      end
+    end
+
     context "with a concat function" do
       let(:expression) { Lago::ExpressionParser.parse("concat(event.properties.property_2, '-', 'suffix')") }