Merge branch '1880-fix-when_empty-must-be-the-same-type-error-when-working-with-url-and-email-fields-2' into 'develop'

Resolve "Fix when_empty must be the same type error when working with url and email fields"

Closes #1880

See merge request baserow/baserow!1682

backend/src/baserow/contrib/database/formula/ast/function_defs.py

@@ -127,6 +127,7 @@ def register_formula_functions(registry):
     registry.register(BaserowLower())
     registry.register(BaserowConcat())
     registry.register(BaserowToText())
+    registry.register(BaserowToVarchar())
     registry.register(BaserowT())
     registry.register(BaserowReplace())
     registry.register(BaserowSearch())
@@ -378,6 +379,30 @@ class BaserowToText(OneArgumentBaserowFunction):
         )
 
 
+class BaserowToVarchar(OneArgumentBaserowFunction):
+    """
+    Internal function not registered in the frontend intentionally as we don't want
+    users making char types. Used purely for working with our BaserowFormulaCharType
+    on internal operations.
+    """
+
+    type = "tovarchar"
+    arg_type = [BaserowFormulaTextType]
+    try_coerce_nullable_args_to_not_null = False
+
+    def type_function(
+        self,
+        func_call: BaserowFunctionCall[UnTyped],
+        arg: BaserowExpression[BaserowFormulaValidType],
+    ) -> BaserowExpression[BaserowFormulaType]:
+        return arg.with_valid_type(
+            BaserowFormulaCharType(nullable=arg.expression_type.nullable)
+        )
+
+    def to_django_expression(self, arg: Expression) -> Expression:
+        return Cast(arg, output_field=fields.CharField())
+
+
 class BaserowT(OneArgumentBaserowFunction):
     type = "t"
     arg_type = [BaserowFormulaValidType]

backend/src/baserow/contrib/database/formula/types/formula_types.py

@@ -106,7 +106,7 @@ class BaserowFormulaTextType(
         )
 
 
-class BaserowFormulaCharType(BaserowFormulaBaseTextType, BaserowFormulaValidType):
+class BaserowFormulaCharType(BaserowFormulaTextType, BaserowFormulaValidType):
     type = "char"
     baserow_field_type = "text"
     can_order_by_in_array = True
@@ -116,8 +116,13 @@ class BaserowFormulaCharType(BaserowFormulaBaseTextType, BaserowFormulaValidType
             field_name, "value", "text", output_field=models.TextField()
         )
 
+    def placeholder_empty_baserow_expression(
+        self,
+    ) -> "BaserowExpression[BaserowFormulaValidType]":
+        return formula_function_registry.get("tovarchar")(literal(""))
 
-class BaserowFormulaLinkType(BaserowFormulaTextType):
+
+class BaserowFormulaLinkType(BaserowFormulaValidType):
     type = "link"
     baserow_field_type = None
     can_order_by = False

backend/tests/baserow/contrib/database/formula/test_baserow_formula_results.py

@@ -354,6 +354,7 @@ VALID_FORMULA_TESTS = [
     ("get_link_url(link('https://www.google.com'))", "https://www.google.com"),
     ("get_link_label(button('1', 'l'))", "l"),
     ("get_link_url(button('a' + 'b', 'l' + 'a'))", "ab"),
+    ("lower(tovarchar('AB'))", "ab"),
     (
         "encode_uri('http://example.com/wiki/Señor')",
         "http://example.com/wiki/Se%c3%b1or",
@@ -487,6 +488,17 @@ def test_can_compare_a_datetime_field_and_text_with_eu_formatting(data_fixture):
     )
 
 
+@pytest.mark.django_db
+def test_can_upper_an_email_field(data_fixture):
+    assert_formula_results_are_case(
+        data_fixture,
+        given_field_in_table=data_fixture.create_email_field(name="email"),
+        given_field_has_rows=["test@test.com", "other@das.c", None],
+        when_created_formula_is="upper(field('email'))",
+        then_formula_values_are=["TEST@TEST.COM", "OTHER@DAS.C", ""],
+    )
+
+
 @pytest.mark.django_db
 def test_todate_handles_empty_values(data_fixture):
     assert_formula_results_are_case(

changelog/entries/unreleased/bug/1880_fix_when_empty_must_be_the_same_type_error_when_working_with.json

@@ -0,0 +1,7 @@
+{
+    "type": "bug",
+    "message": "fix when_empty must be the same type error when working with url and email fields",
+    "issue_number": 1880,
+    "bullet_points": [],
+    "created_at": "2023-09-19"
+}