ctx.output_format for map is wrong and fix type validation for map params

engine/baml-lib/baml-core/src/ir/ir_helpers/to_baml_arg.rs

@@ -269,15 +269,21 @@ impl ArgCoercer {
             }
             FieldType::Map(k, v) => {
                 if let BamlValue::Map(kv) = value {
+                    let mut map = BamlMap::new();
                     for (key, value) in kv {
-                        let mut key_scope = ScopeStack::new();
-                        let _ =
-                            self.coerce_arg(ir, k, &BamlValue::String(key.clone()), &mut key_scope);
+                        scope.push("<key>".to_string());
+                        let k = self.coerce_arg(ir, k, &BamlValue::String(key.clone()), scope);
+                        scope.pop(false);
 
-                        let mut value_scope = ScopeStack::new();
-                        let _ = self.coerce_arg(ir, v, value, &mut value_scope);
+                        if k.is_ok() {
+                            scope.push(key.to_string());
+                            if let Ok(v) = self.coerce_arg(ir, v, value, scope) {
+                                map.insert(key.clone(), v);
+                            }
+                            scope.pop(false);
+                        }
                     }
-                    Ok(value.clone())
+                    Ok(BamlValue::Map(map))
                 } else {
                     scope.push_error(format!("Expected map, got `{}`", value));
                     Err(())

engine/baml-lib/jinja/src/output_format/types.rs

@@ -238,7 +238,7 @@ impl OutputFormatContent {
                 FieldType::List(_) => Some("Answer with a JSON Array using this schema:\n"),
                 FieldType::Union(_) => Some("Answer in JSON using any of these schemas:\n"),
                 FieldType::Optional(_) => Some("Answer in JSON using this schema:\n"),
-                FieldType::Map(_, _) => None,
+                FieldType::Map(_, _) => Some("Answer in JSON using this schema:\n"),
                 FieldType::Tuple(_) => None,
             },
         }

integ-tests/python/tests/test_functions.py

@@ -1020,4 +1020,9 @@ async def test_arg_exceptions():
         )
 
     with pytest.raises(errors.BamlValidationError):
-        await b.DummyOutputFunction("dummy input")
+        await b.DummyOutputFunction("dummy input")
+
+@pytest.mark.asyncio
+async def test_map_as_param():
+    with pytest.raises(errors.BamlInvalidArgumentError):
+        _ = await b.TestFnNamedArgsSingleMapStringToMap({ "a" : "b"}) # intentionally passing the wrong type