feat: add Sha256Str type

pydantic_extra_types/sha256.py

@@ -0,0 +1,48 @@
+"""The `pydantic_extra_types.sha256` module provides the `Sha256Str` data type.
+
+A SHA-256 digest is 32 bytes long and is usually written as 64 hexadecimal characters,
+like the output of `hashlib.sha256(...).hexdigest()` or `sha256sum`.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import GetCoreSchemaHandler
+from pydantic_core import core_schema
+
+
+class Sha256Str(str):
+    """A hex-encoded SHA-256 digest, normalized to lowercase.
+
+    ```py
+    from pydantic import BaseModel
+
+    from pydantic_extra_types.sha256 import Sha256Str
+
+
+    class Artifact(BaseModel):
+        checksum: Sha256Str
+
+
+    artifact = Artifact(checksum='E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855')
+    print(artifact)
+    # > checksum='e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
+    ```
+    """
+
+    @classmethod
+    def __get_pydantic_core_schema__(cls, source: type[Any], handler: GetCoreSchemaHandler) -> core_schema.CoreSchema:
+        """Return a Pydantic CoreSchema with the SHA-256 digest validation.
+
+        Args:
+            source: The source type to be converted.
+            handler: The handler to get the CoreSchema.
+
+        Returns:
+            A Pydantic CoreSchema with the SHA-256 digest validation.
+        """
+        return core_schema.no_info_after_validator_function(
+            cls,
+            core_schema.str_schema(pattern=r'^[0-9a-fA-F]{64}$', strip_whitespace=True, to_lower=True),
+        )