🐛(models) fix allow xapi Extensions with empty string values

When defined with a bare Dict[...] as a field in a pydantic class,
Extensions inherit from the config which disallows
empty strings in dict values.
This, however, should be allowed according to spec:
https://github.com/adlnet/xAPI-Spec/blob/master/xAPI-Data.md#requirements-18
(An LRS MUST NOT reject a Statement based on the values
of the extensions map).

We must override base the model_config for our extensions.

Author: piptouque

CHANGELOG.md

@@ -26,6 +26,11 @@ and this project adheres to
   `test-helm` CI job to fix flaky "no matching resources"/"status not found"
 - Drop the stale `add_ssh_keys` entry from the `deploy-docs` CI job so it
   pushes to `gh-pages` with the read-write checkout key
+- Fix XAPI definitions extensions not accepting empty strings as values.
+
+### Changed
+
+- Refactor statements' ExtensionMap
 
 ## [5.0.1] - 2024-07-11
 

src/ralph/models/xapi/base/common.py

@@ -1,9 +1,9 @@
 """Common for xAPI base definitions."""
 
-from typing import Dict, Type, Union
+from typing import Dict, Type, Union, Annotated
 
 from langcodes import tag_is_valid
-from pydantic import RootModel, model_validator, validate_email
+from pydantic import ConfigDict, RootModel, StringConstraints, model_validator, validate_email
 from rfc3987 import parse
 
 from ralph.conf import NonEmptyStrictStr
@@ -46,8 +46,10 @@ def validate_language_tag(cls, tag):
 
 LanguageMap = Dict[LanguageTag, NonEmptyStrictStr]
 
-ExtensionMap = Dict[IRI, Union[str, int, bool, list, dict, None]]
+ExtensionValue = Union[Annotated[str, StringConstraints(min_length=0)], bool, int, list, dict, None]
 
+class ExtensionMap(RootModel[Dict[IRI, ExtensionValue]]):
+    """Pydantic custom data type for XAPI context and object definitions extensions."""
 
 class MailtoEmail(RootModel[str]):
     """Pydantic custom data type validating `mailto:email` format."""

tests/models/xapi/base/test_common.py

@@ -143,7 +143,6 @@ class DummyLanguageTagModel(BaseModel):
     [
         ({"extensions": {}}),
         ({"extensions": {"http://localhost/foo/bar": None}}),
-        ({"extensions": {"http://localhost/foo/bar": None}}),
         ({"extensions": {"http://localhost/foo/bar": 42}}),
         ({"extensions": {"http://localhost/foo/bar": []}}),
         ({"extensions": {"http://localhost/foo/bar": {}}}),
@@ -156,6 +155,26 @@ class DummyLanguageTagModel(BaseModel):
                 }
             }
         ),
+        (
+            {
+                "extensions": {
+                    "http://localhost/foo/bar": {
+                        "http://localhost/food/bard": "An explanation",
+                        "whatever": "that_is",
+                    },
+                }
+            }
+        ),
+        (
+            {
+                "extensions": {
+                    "http://localhost/foo/bar": {
+                        "http://localhost/food/bard": "An explanation",
+                        "nope": "",
+                    },
+                }
+            }
+        ),
     ],
 )
 def test_models_xapi_base_common_field_extensions_with_valid_data(values):
@@ -181,6 +200,7 @@ class DummyExtensionsModel(BaseModel):
             "extensions\n  Input should be a valid dictionary",
         ),
         ({"extensions": {"localhost": 42}}, ValidationError, "not a valid 'IRI'"),
+        ({"extensions": {"": 43}}, ValidationError, "not a valid 'IRI'"),
     ],
 )
 def test_models_xapi_base_common_field_extensions_with_invalid_data(