Convert StrippedConstraint to PatternConstraint subclass

StrippedConstraint now extends PatternConstraint, using the same
constructor as every other concrete constraint. Custom validate()
and __get_pydantic_json_schema__() eliminated.

Uses \Z (absolute end-of-string) instead of $ because Python's $
matches before a trailing \n. JSON schema emission swaps \Z back
to $ since ECMA regex treats $ as absolute end-of-string.

Signed-off-by: Seth Fitzsimmons <sethfitz@amazon.com>

Author: sethfitz

packages/overture-schema-system/src/overture/schema/system/field_constraint/string.py

@@ -208,23 +208,27 @@ def __init__(self) -> None:
         )
 
 
-class StrippedConstraint(StringConstraint):
-    """Allows only strings that have no leading/trailing whitespace."""
+class StrippedConstraint(PatternConstraint):
+    r"""Allows only strings that have no leading/trailing whitespace.
 
-    def validate(self, value: str, info: ValidationInfo) -> None:
-        if value != value.strip():
-            self._raise_validation_error(
-                value,
-                info,
-                f"String cannot have leading or trailing whitespace: {repr(value)}",
-            )
+    Uses ``\Z`` (absolute end-of-string) instead of ``$`` because
+    Python's ``$`` matches before a trailing ``\n``. ECMA regex (used by
+    JSON Schema) treats ``$`` as absolute end-of-string, so the JSON
+    schema output swaps ``\Z`` back to ``$``.
+    """
+
+    def __init__(self) -> None:
+        super().__init__(
+            pattern=r"^(\S(.*\S)?)?\Z",
+            error_message="String cannot have leading or trailing whitespace: {value}",
+            description="String with no leading/trailing whitespace",
+        )
 
     def __get_pydantic_json_schema__(
         self, core_schema: core_schema.CoreSchema, handler: GetJsonSchemaHandler
     ) -> dict[str, Any]:
-        json_schema = handler(core_schema)
-        json_schema["pattern"] = r"^(\S(.*\S)?)?$"
-        json_schema["description"] = "String with no leading/trailing whitespace"
+        json_schema = super().__get_pydantic_json_schema__(core_schema, handler)
+        json_schema["pattern"] = self.pattern.pattern.replace(r"\Z", "$")
         return json_schema
 
 

packages/overture-schema-system/tests/field_constraint/test_string_constraints.py

@@ -72,6 +72,12 @@
         ["Restaurant", "gas-station", "shopping mall", "category!"],
         "Invalid category format",
     ),
+    (
+        StrippedConstraint,
+        ["hello", "hello world", "text with internal spaces", ""],
+        [" hello", "hello ", "\thello", "hello\n", " hello world "],
+        "leading or trailing whitespace",
+    ),
 ]
 
 
@@ -174,22 +180,9 @@ class TestModel(BaseModel):
                 TestModel(pointer=ptr)
             assert "JSON Pointer must start" in str(exc_info.value)
 
-    def test_whitespace_constraint_valid(self) -> None:
-        class TestModel(BaseModel):
-            text: Annotated[str, StrippedConstraint()]
-
-        for text in ["hello", "hello world", "text with internal spaces", ""]:
-            model = TestModel(text=text)
-            assert model.text == text
-
-    def test_whitespace_constraint_invalid(self) -> None:
-        class TestModel(BaseModel):
-            text: Annotated[str, StrippedConstraint()]
-
-        for text in [" hello", "hello ", "\thello", "hello\n", " hello world "]:
-            with pytest.raises(ValidationError) as exc_info:
-                TestModel(text=text)
-            assert "cannot have leading or trailing whitespace" in str(exc_info.value)
+    def test_stripped_constraint_pattern_string(self) -> None:
+        """Codegen extracts the regex via constraint.pattern.pattern."""
+        assert StrippedConstraint().pattern.pattern == r"^(\S(.*\S)?)?\Z"
 
 
 class TestJsonSchemaGeneration:
@@ -294,6 +287,7 @@ class TestPatternConstraintHierarchy:
             SnakeCaseConstraint,
             PhoneNumberConstraint,
             RegionCodeConstraint,
+            StrippedConstraint,
             WikidataIdConstraint,
         ],
     )