Split out parsing method from initializer (#61)

---------

Co-authored-by: LeaveMyYard <[email protected]>
Co-authored-by: Pavel Zhukov <[email protected]>

README.md

@@ -18,22 +18,22 @@ SIWE provides a `SiweMessage` class which implements EIP-4361.
 
 Parsing is done by initializing a `SiweMessage` object with an EIP-4361 formatted string:
 
-``` python
+```python
 from siwe import SiweMessage
-message: SiweMessage = SiweMessage(message=eip_4361_string)
+message = SiweMessage.from_message(message=eip_4361_string)
 ```
 
-Alternatively, initialization of a `SiweMessage` object can be done with a dictionary containing expected attributes:
+Or to initialize a `SiweMessage` as a `pydantic.BaseModel` right away:
 
-``` python
-message: SiweMessage = SiweMessage(message={"domain": "login.xyz", "address": "0x1234...", ...})
+```python
+message = SiweMessage(domain="login.xyz", address="0x1234...", ...)
 ```
 
 ### Verifying and Authenticating a SIWE Message
 
 Verification and authentication is performed via EIP-191, using the `address` field of the `SiweMessage` as the expected signer. The validate method checks message structural integrity, signature address validity, and time-based validity attributes.
 
-``` python
+```python
 try:
     message.verify(signature="0x...")
     # You can also specify other checks (e.g. the nonce or domain expected).
@@ -45,15 +45,15 @@ except siwe.ValidationError:
 
 `SiweMessage` instances can also be serialized as their EIP-4361 string representations via the `prepare_message` method:
 
-``` python
+```python
 print(message.prepare_message())
 ```
 
 ## Example
 
 Parsing and verifying a `SiweMessage` is easy:
 
-``` python
+```python
 try:
     message: SiweMessage = SiweMessage(message=eip_4361_string)
     message.verify(signature, nonce="abcdef", domain="example.com"):

siwe/siwe.py

@@ -4,7 +4,7 @@
 import string
 from datetime import datetime, timezone
 from enum import Enum
-from typing import Any, Dict, Iterable, List, Optional, Union
+from typing import Iterable, List, Optional
 
 import eth_utils
 from eth_account.messages import SignableMessage, _hash_eip191_message, encode_defunct
@@ -216,23 +216,16 @@ def address_is_checksum_address(cls, v: str) -> str:
             raise ValueError("Message `address` must be in EIP-55 format")
         return v
 
-    def __init__(self, message: Union[str, Dict[str, Any]], abnf: bool = True):
-        """Construct or parse a message."""
-        if isinstance(message, str):
-            if abnf:
-                parsed_message = ABNFParsedMessage(message=message)
-            else:
-                parsed_message = RegExpParsedMessage(message=message)
-            message_dict = parsed_message.__dict__
-
-        elif isinstance(message, dict):
-            message_dict = message
-
+    @classmethod
+    def from_message(cls, message: str, abnf: bool = True) -> "SiweMessage":
+        """Parse a message in its EIP-4361 format."""
+        if abnf:
+            parsed_message = ABNFParsedMessage(message=message)
         else:
-            raise TypeError(f"Unhandable message type: '{type(message)}'.")
+            parsed_message = RegExpParsedMessage(message=message)
 
         # TODO There is some redundancy in the checks when deserialising a message.
-        super().__init__(**message_dict)
+        return cls(**parsed_message.__dict__)
 
     def prepare_message(self) -> str:
         """Serialize to the EIP-4361 format for signing.

tests/test_siwe.py

@@ -30,7 +30,7 @@ class TestMessageParsing:
         [(test_name, test) for test_name, test in parsing_positive.items()],
     )
     def test_valid_message(self, abnf, test_name, test):
-        siwe_message = SiweMessage(message=test["message"], abnf=abnf)
+        siwe_message = SiweMessage.from_message(message=test["message"], abnf=abnf)
         for key, value in test["fields"].items():
             v = getattr(siwe_message, key)
             if not (isinstance(v, int) or isinstance(v, list) or v is None):
@@ -44,15 +44,15 @@ def test_valid_message(self, abnf, test_name, test):
     )
     def test_invalid_message(self, abnf, test_name, test):
         with pytest.raises(ValueError):
-            SiweMessage(message=test, abnf=abnf)
+            SiweMessage.from_message(message=test, abnf=abnf)
 
     @pytest.mark.parametrize(
         "test_name,test",
         [(test_name, test) for test_name, test in parsing_negative_objects.items()],
     )
     def test_invalid_object_message(self, test_name, test):
         with pytest.raises(ValidationError):
-            SiweMessage(message=test)
+            SiweMessage(**test)
 
 
 class TestMessageGeneration:
@@ -61,7 +61,7 @@ class TestMessageGeneration:
         [(test_name, test) for test_name, test in parsing_positive.items()],
     )
     def test_valid_message(self, test_name, test):
-        siwe_message = SiweMessage(message=test["fields"])
+        siwe_message = SiweMessage(**test["fields"])
         assert siwe_message.prepare_message() == test["message"]
 
 
@@ -71,7 +71,7 @@ class TestMessageVerification:
         [(test_name, test) for test_name, test in verification_positive.items()],
     )
     def test_valid_message(self, test_name, test):
-        siwe_message = SiweMessage(message=test)
+        siwe_message = SiweMessage(**test)
         timestamp = datetime_from_iso8601_string(test["time"]) if "time" in test else None
         siwe_message.verify(test["signature"], timestamp=timestamp)
 
@@ -81,7 +81,7 @@ def test_valid_message(self, test_name, test):
     )
     def test_eip1271_message(self, test_name, test):
         provider = HTTPProvider(endpoint_uri="https://cloudflare-eth.com")
-        siwe_message = SiweMessage(message=test["message"])
+        siwe_message = SiweMessage.from_message(message=test["message"])
         siwe_message.verify(test["signature"], provider=provider)
 
     @pytest.mark.parametrize(
@@ -98,9 +98,9 @@ def test_invalid_message(self, provider, test_name, test):
             "invalidissued_at",
         ]:
             with pytest.raises(ValidationError):
-                siwe_message = SiweMessage(message=test)
+                siwe_message = SiweMessage(**test)
             return
-        siwe_message = SiweMessage(message=test)
+        siwe_message = SiweMessage(**test)
         domain_binding = test.get("domain_binding")
         match_nonce = test.get("match_nonce")
         timestamp = datetime_from_iso8601_string(test["time"]) if "time" in test else None
@@ -122,7 +122,7 @@ class TestMessageRoundTrip:
         [(test_name, test) for test_name, test in parsing_positive.items()],
     )
     def test_message_round_trip(self, test_name, test):
-        message = SiweMessage(test["fields"])
+        message = SiweMessage(**test["fields"])
         message.address = self.account.address
         signature = self.account.sign_message(
             messages.encode_defunct(text=message.prepare_message())