feat: add support for date-only format (datetime.date type)

Addresses Issue #89

When an OpenAPI schema defines a string field with format='date', the
generator now produces a datetime.date type instead of falling back to str.

Changes:
- Extended _handle_format_conversions() to handle 'date' format
- Added date type conversion with proper imports (from datetime import date)
- Follows same pattern as existing date-time format handling
- Requires orjson=True (like other format conversions)
- Falls back to str when orjson is disabled

Benefits:
- Type-safe handling of date-only fields (birth_date, etc.)
- Proper Pydantic validation for date fields
- Consistent with OpenAPI 3.x date format specification
- Clean implementation in single consolidated function (PR #122 refactoring)

Tests:
- test_date_format_generates_date_type: Verifies date type generation
- test_date_format_without_orjson: Verifies str fallback behavior
- All 252 existing tests pass (including 11 xfailed)
- Coverage maintained at 95%+

Closes #89

Author: Doug Borg

src/openapi_python_generator/language_converters/python/model_generator.py

@@ -87,7 +87,7 @@ def _handle_format_conversions(
     schema: Schema, base_type: str, required: bool
 ) -> Optional[TypeConversion]:
     """
-    Handle UUID and datetime format conversions based on orjson usage.
+    Handle UUID, datetime, and date format conversions based on orjson usage.
 
     Returns TypeConversion if special format handling is needed, None otherwise.
 
@@ -126,6 +126,15 @@ def _handle_format_conversions(
             import_types=["from datetime import datetime"],
         )
 
+    # Handle date format
+    if schema.schema_format == "date" and common.get_use_orjson():
+        converted_type = "date" if required else "Optional[date]"
+        return TypeConversion(
+            original_type=base_type,
+            converted_type=converted_type,
+            import_types=["from datetime import date"],
+        )
+
     return None
 
 

tests/test_data/test_date_format.json

@@ -0,0 +1,47 @@
+{
+  "openapi": "3.0.0",
+  "info": {
+    "title": "Date Format Test API",
+    "version": "1.0.0"
+  },
+  "paths": {
+    "/person": {
+      "get": {
+        "operationId": "get_person",
+        "responses": {
+          "200": {
+            "description": "Person details",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Person"
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "Person": {
+        "type": "object",
+        "required": ["name", "birth_date", "created_at"],
+        "properties": {
+          "name": {
+            "type": "string"
+          },
+          "birth_date": {
+            "type": "string",
+            "format": "date"
+          },
+          "created_at": {
+            "type": "string",
+            "format": "date-time"
+          }
+        }
+      }
+    }
+  }
+}

tests/test_date_format.py

@@ -0,0 +1,70 @@
+"""Test support for date-only format (datetime.date type)."""
+import tempfile
+from pathlib import Path
+
+from openapi_python_generator.common import Formatter, HTTPLibrary
+from openapi_python_generator.generate_data import generate_data
+
+
+def test_date_format_generates_date_type():
+    """Test that string fields with format='date' generate datetime.date type."""
+    # OpenAPI spec with date format
+    spec_path = Path(__file__).parent / "test_data" / "test_date_format.json"
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_path = Path(tmpdir) / "generated"
+
+        # Generate code
+        generate_data(
+            spec_path,
+            output_path,
+            HTTPLibrary.httpx,
+            use_orjson=True,  # date format handling requires orjson
+        )
+
+        # Read generated Person model
+        person_model_path = output_path / "models" / "person.py"
+        assert person_model_path.exists(), "Person model should be generated"
+
+        person_model_content = person_model_path.read_text()
+
+        # Verify import from datetime
+        assert "from datetime import date, datetime" in person_model_content or (
+            "from datetime import date" in person_model_content
+            and "from datetime import datetime" in person_model_content
+        ), "Should import date from datetime"
+
+        # Verify birth_date field uses date type
+        assert "birth_date: date" in person_model_content, (
+            "birth_date with format='date' should use date type"
+        )
+
+        # Verify created_at field uses datetime type (to confirm date-time still works)
+        assert "created_at: datetime" in person_model_content, (
+            "created_at with format='date-time' should use datetime type"
+        )
+
+
+def test_date_format_without_orjson():
+    """Test that date format falls back to str when orjson is not enabled."""
+    spec_path = Path(__file__).parent / "test_data" / "test_date_format.json"
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_path = Path(tmpdir) / "generated"
+
+        # Generate code WITHOUT orjson
+        generate_data(
+            spec_path,
+            output_path,
+            HTTPLibrary.httpx,
+            use_orjson=False,  # date format handling requires orjson
+        )
+
+        # Read generated Person model
+        person_model_path = output_path / "models" / "person.py"
+        person_model_content = person_model_path.read_text()
+
+        # Without orjson, date should fall back to str
+        assert "birth_date: str" in person_model_content, (
+            "Without orjson, date format should fall back to str"
+        )