Reconstructable deterministic constrids (#272)

* Change the constructor id computation to be reproducible by third
parties

* Add test to check that id_map supports complex types

* dict -> map and support indefinitelist, Datum

* QA

* Fix hash of unit

* Add support for ByteString type and fix constructor id for test

* Add support for ByteString type in PlutusData

Author: nielstron

pycardano/plutus.py

@@ -4,6 +4,7 @@
 
 import inspect
 import json
+import typing
 from dataclasses import dataclass, field, fields
 from enum import Enum
 from hashlib import sha256
@@ -448,6 +449,45 @@ def get_tag(constr_id: int) -> Optional[int]:
         return None
 
 
+def id_map(cls, skip_constructor=False):
+    """
+    Constructs a unique representation of a PlutusData type definition.
+    Intended for automatic constructor generation.
+    """
+    if cls == bytes or cls == ByteString:
+        return "bytes"
+    if cls == int:
+        return "int"
+    if cls == RawCBOR or cls == RawPlutusData or cls == Datum:
+        return "any"
+    if cls == IndefiniteList:
+        return "list"
+    if hasattr(cls, "__origin__"):
+        origin = getattr(cls, "__origin__")
+        if origin == list:
+            prefix = "list"
+        elif origin == dict:
+            prefix = "map"
+        elif origin == typing.Union:
+            prefix = "union"
+        else:
+            raise TypeError(
+                f"Unexpected parameterized type for automatic constructor generation: {cls}"
+            )
+        return prefix + "<" + ",".join(id_map(a) for a in cls.__args__) + ">"
+    if issubclass(cls, PlutusData):
+        return (
+            "cons["
+            + cls.__name__
+            + "]("
+            + (str(cls.CONSTR_ID) if not skip_constructor else "_")
+            + ";"
+            + ",".join(f.name + ":" + id_map(f.type) for f in fields(cls))
+            + ")"
+        )
+    raise TypeError(f"Unexpected type for automatic constructor generation: {cls}")
+
+
 @dataclass(repr=False)
 class PlutusData(ArrayCBORSerializable):
     """
@@ -481,11 +521,7 @@ def CONSTR_ID(cls):
         """
         k = f"_CONSTR_ID_{cls.__name__}"
         if not hasattr(cls, k):
-            det_string = (
-                cls.__name__
-                + "*"
-                + "*".join([f"{f.name}~{f.type}" for f in fields(cls)])
-            )
+            det_string = id_map(cls, skip_constructor=True)
             det_hash = sha256(det_string.encode("utf8")).hexdigest()
             setattr(cls, k, int(det_hash, 16) % 2**32)
 

test/pycardano/test_plutus.py

@@ -18,8 +18,11 @@
     Redeemer,
     RedeemerTag,
     plutus_script_hash,
+    id_map,
+    Datum,
+    Unit,
 )
-from pycardano.serialization import ByteString, IndefiniteList
+from pycardano.serialization import IndefiniteList, RawCBOR, ByteString
 
 
 @dataclass
@@ -206,10 +209,8 @@ def test_plutus_data_from_json_wrong_data_structure_type():
 
 def test_plutus_data_hash():
     assert (
-        bytes.fromhex(
-            "19d31e4f3aa9b03ad93b64c8dd2cc822d247c21e2c22762b7b08e6cadfeddb47"
-        )
-        == PlutusData().hash().payload
+        "923918e403bf43c34b4ef6b48eb2ee04babed17320d8d1b9ff9ad086e86f44ec"
+        == Unit().hash().payload.hex()
     )
 
 
@@ -398,20 +399,47 @@ class A(PlutusData):
     ), "Same class has different default constructor id in two consecutive runs"
 
 
+def test_id_map_supports_all():
+    @dataclass
+    class A(PlutusData):
+        CONSTR_ID = 0
+        a: int
+        b: bytes
+        c: ByteString
+        d: List[int]
+
+    @dataclass
+    class C(PlutusData):
+        x: RawPlutusData
+        y: RawCBOR
+        z: Datum
+        w: IndefiniteList
+
+    @dataclass
+    class B(PlutusData):
+        a: int
+        c: A
+        d: Dict[bytes, C]
+        e: Union[A, C]
+
+    s = id_map(B)
+    assert (
+        s
+        == "cons[B](3809077817;a:int,c:cons[A](0;a:int,b:bytes,c:bytes,d:list<int>),d:map<bytes,cons[C](892310804;x:any,y:any,z:any,w:list)>,e:union<cons[A](0;a:int,b:bytes,c:bytes,d:list<int>),cons[C](892310804;x:any,y:any,z:any,w:list)>)"
+    )
+
+
 def test_plutus_data_long_bytes():
     @dataclass
     class A(PlutusData):
+        CONSTR_ID = 0
         a: ByteString
 
     quote = (
         "The line separating good and evil passes ... right through every human heart."
     )
 
-    quote_hex = (
-        "d866821a8e5890cf9f5f5840546865206c696e652073657061726174696e6720676f6f6420616"
-        "e64206576696c20706173736573202e2e2e207269676874207468726f7567682065766572794d"
-        "2068756d616e2068656172742effff"
-    )
+    quote_hex = "d8799f5f5840546865206c696e652073657061726174696e6720676f6f6420616e64206576696c20706173736573202e2e2e207269676874207468726f7567682065766572794d2068756d616e2068656172742effff"
 
     A_tmp = A(ByteString(quote.encode()))