✨ [#4980] Add schema definitions for user-defined variables

Also updated form_variables_to_json_schema

src/openforms/forms/utils.py

@@ -23,6 +23,7 @@
 from openforms.variables.registry import (
     register_static_variable as static_variable_registry,
 )
+from openforms.variables.service import get_json_schema_for_user_defined_variable
 
 from .api.datastructures import FormVariableWrapper
 from .api.serializers import (
@@ -133,9 +134,6 @@ def form_to_json(form_id: int) -> dict:
     return resources
 
 
-# TODO-4980: what should the name be? Do we need the submission, or is just the form
-#  sufficient here?
-# TODO-4980: pass form_id instead of the form?
 def form_variables_to_json_schema(
     form: Form, variables_to_include: Sequence[str]
 ) -> JSONObject:
@@ -151,37 +149,25 @@ def form_variables_to_json_schema(
     static_var_properties = {
         key: static_variable_registry[key].as_json_schema()
         for key in variables_to_include
+        # To ensure fetching form variables from static_variable_registry does not
+        # raise KeyError
         if key in static_variable_registry
     }
 
     # Handle form variables
     all_form_vars = {var.key: var for var in form.formvariable_set.all()}
-
-    # TODO-4980: add to FormVariable?
-    def get_json_schema_from_form_variable(form_variable):
-        form_def = form_variable.form_definition
-
-        component = form_def.configuration_wrapper.component_map[form_variable.key]
-        component_plugin = component_registry[component["type"]]
-
-        return component_plugin.as_json_schema(component)
-
     form_var_properties = {
         key: get_json_schema_from_form_variable(all_form_vars[key])
         for key in variables_to_include
+        # To ensure fetching static variables from all_from_vars does not raise KeyError
         if key in all_form_vars
     }
 
     # Required
-    def is_required(form_variable):
-        form_def = form_variable.form_definition
-        component = form_def.configuration_wrapper.component_map[form_variable.key]
-
-        validate = component.get("validate", {})
-        return validate.get("required", False)
-
     required_form_variables = [
-        var for var in form_var_properties.keys() if is_required(all_form_vars[var])
+        var
+        for var in form_var_properties.keys()
+        if is_form_variable_required(all_form_vars[var])
     ]
 
     required = [*static_var_properties.keys(), *required_form_variables]
@@ -199,6 +185,53 @@ def is_required(form_variable):
     return schema
 
 
+# TODO-4980: add to FormVariable?
+def get_json_schema_from_form_variable(form_variable: FormVariable) -> JSONObject:
+    """Return a JSON schema for a form variable.
+
+    :param form_variable: The form variable to generate JSON schema for.
+    :returns schema: A JSON schema representing the form variable.
+    """
+
+    match form_variable.source:
+        case FormVariableSources.component:
+            form_def = form_variable.form_definition
+            component = form_def.configuration_wrapper.component_map[form_variable.key]
+            component_plugin = component_registry[component["type"]]
+            schema = component_plugin.as_json_schema(component)
+        case FormVariableSources.user_defined:
+            schema = get_json_schema_for_user_defined_variable(form_variable.data_type)
+            schema["title"] = form_variable.name
+        case _:
+            raise NotImplementedError("Unexpected form variable source")
+
+    return schema
+
+
+# TODO-4980: add to FormVariable?
+def is_form_variable_required(form_variable: FormVariable) -> bool:
+    """Return if a form variable is required.
+
+    :param form_variable: The form variable to check.
+    :returns required: Whether the form variable is required.
+    """
+
+    match form_variable.source:
+        case FormVariableSources.component:
+            form_def = form_variable.form_definition
+            component = form_def.configuration_wrapper.component_map[form_variable.key]
+
+            validate = component.get("validate", {})
+            required = validate.get("required", False)
+        case FormVariableSources.user_defined:
+            # User defined variables have no required property
+            required = True
+        case _:
+            raise NotImplementedError("Unexpected form variable source")
+
+    return required
+
+
 def export_form(form_id, archive_name=None, response=None):
     resources = form_to_json(form_id)
 

src/openforms/variables/service.py

@@ -5,12 +5,18 @@
 from openforms.forms.models import FormVariable
 from openforms.plugins.registry import BaseRegistry
 from openforms.submissions.models import Submission
+from openforms.typing import JSONObject
 
 from .base import BaseStaticVariable
+from .constants import FormVariableDataTypes
 from .registry import register_static_variable as static_variables_registry
 from .utils import get_variables_for_context
 
-__all__ = ["get_static_variables", "get_variables_for_context"]
+__all__ = [
+    "get_json_schema_for_user_defined_variable",
+    "get_static_variables",
+    "get_variables_for_context",
+]
 
 
 type VariablesRegistry = BaseRegistry[BaseStaticVariable]
@@ -40,3 +46,36 @@ def get_static_variables(
         registered_variable.get_static_variable(submission=submission)
         for registered_variable in variables_registry
     ]
+
+
+# TODO-4980: where to add this?
+# TODO-4980: add tests
+def get_json_schema_for_user_defined_variable(
+    data_type: FormVariableDataTypes,
+) -> JSONObject:
+    """Return the JSON schema definition for a user-defined variable, depending on the
+    data type
+
+    :param data_type: The data type of the variable
+    """
+    match data_type:
+        case FormVariableDataTypes.string:
+            return {"type": "string"}
+        case FormVariableDataTypes.boolean:
+            return {"type": "boolean"}
+        case FormVariableDataTypes.object:
+            return {"type": "object"}
+        case FormVariableDataTypes.array:
+            return {"type": "array"}
+        case FormVariableDataTypes.int:
+            return {"type": "integer"}
+        case FormVariableDataTypes.float:
+            return {"type": "number"}
+        case FormVariableDataTypes.datetime:
+            return {"type": "string", "format": "date-time"}
+        case FormVariableDataTypes.date:
+            return {"type": "string", "format": "date"}
+        case FormVariableDataTypes.time:
+            return {"type": "string", "format": "time"}
+        case _:
+            raise NotImplementedError(f"Unrecognized data type: {data_type}")