feat(nano): add support for json_dumps

hathor/__init__.py

@@ -39,7 +39,7 @@
     TxOutputScript,
     VertexId,
 )
-from hathor.nanocontracts.utils import sha3, verify_ecdsa
+from hathor.nanocontracts.utils import json_dumps, sha3, verify_ecdsa
 from hathor.version import __version__
 
 __all__ = [
@@ -73,5 +73,6 @@
     'VertexId',
     'sha3',
     'verify_ecdsa',
+    'json_dumps',
     '__version__',
 ]

hathor/nanocontracts/allowed_imports.py

@@ -64,5 +64,6 @@
         NCParsedArgs=hathor.NCParsedArgs,
         sha3=hathor.sha3,
         verify_ecdsa=hathor.verify_ecdsa,
+        json_dumps=hathor.json_dumps,
     ),
 }

hathor/nanocontracts/nc_exec_logs.py

@@ -233,6 +233,8 @@ def error(self, message: str, **kwargs: Any) -> None:
 
     def __emit_event__(self, data: bytes) -> None:
         """Emit a custom event from a Nano Contract."""
+        if not isinstance(data, bytes):
+            raise NCFail(f'event data must be of type `bytes`, found `{type(data).__name__}`')
         if len(data) > MAX_EVENT_SIZE:
             raise NCFail(f'event data cannot be larger than {MAX_EVENT_SIZE} bytes, is {len(data)}')
         self.__events__.append(NCEvent(nc_id=self.__nc_id__, data=data))

hathor/nanocontracts/utils.py

@@ -16,7 +16,7 @@
 
 import hashlib
 from types import ModuleType
-from typing import Callable
+from typing import Any, Callable
 
 from cryptography.exceptions import InvalidSignature
 from cryptography.hazmat.primitives import hashes
@@ -169,3 +169,32 @@ def verify_ecdsa(public_key: bytes, data: bytes, signature: bytes) -> bool:
         return True
     except InvalidSignature:
         return False
+
+
+def json_dumps(
+    obj: object,
+    *,
+    ensure_ascii: bool = True,
+    indent: int | str | None = None,
+    separators: tuple[str, str] | None = (',', ':'),
+    sort_keys: bool = False,
+) -> str:
+    """
+    Serialize obj as a JSON. Arguments are a subset of Python's `json.dumps`.
+    It automatically converts `bytes`-like values to their hex representation.
+    """
+    import json
+
+    def dump_bytes(data: Any) -> str:
+        if isinstance(data, bytes):
+            return data.hex()
+        raise TypeError(f'Object of type {type(data).__name__} is not JSON serializable')
+
+    return json.dumps(
+        obj,
+        ensure_ascii=ensure_ascii,
+        indent=indent,
+        separators=separators,
+        sort_keys=sort_keys,
+        default=dump_bytes,
+    )

hathor_tests/nanocontracts/test_exposed_properties.py

@@ -118,6 +118,7 @@
     'hathor.SignedData.some_new_attribute',
     'hathor.export.some_new_attribute',
     'hathor.fallback.some_new_attribute',
+    'hathor.json_dumps.some_new_attribute',
     'hathor.public.some_new_attribute',
     'hathor.sha3.some_new_attribute',
     'hathor.verify_ecdsa.some_new_attribute',

hathor_tests/nanocontracts/test_crypto_functions.py → hathor_tests/nanocontracts/test_utils_functions.py

@@ -19,6 +19,7 @@
 from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.primitives.asymmetric import ec
 
+from hathor import ContractId
 from hathor.crypto.util import get_public_key_bytes_compressed
 from hathor.nanocontracts import Blueprint, Context, NCFail, public, utils as nc_utils, view
 from hathor_tests.nanocontracts.blueprints.unittest import BlueprintTestCase
@@ -37,8 +38,13 @@ def test_sha3(self, data: bytes) -> bytes:
     def test_verify_ecdsa(self, public_key: bytes, data: bytes, signature: bytes) -> bool:
         return nc_utils.verify_ecdsa(public_key, data, signature)
 
+    @view
+    def test_json_dumps(self) -> str:
+        obj = dict(a=[1, 2, 3], b=123, c='abc', d=ContractId(b'\x01' * 32))
+        return nc_utils.json_dumps(obj)
+
 
-class TestCryptoFunctions(BlueprintTestCase):
+class TestUtilsFunctions(BlueprintTestCase):
     def setUp(self) -> None:
         super().setUp()
 
@@ -75,3 +81,10 @@ def test_verify_ecdsa_success(self) -> None:
         signature = private_key.sign(data, ec.ECDSA(hashes.SHA256()))
 
         assert self.runner.call_view_method(self.contract_id, 'test_verify_ecdsa', public_key, data, signature)
+
+    def test_json_dumps(self) -> None:
+        result = self.runner.call_view_method(self.contract_id, 'test_json_dumps')
+
+        assert result == (
+            '{"a":[1,2,3],"b":123,"c":"abc","d":"0101010101010101010101010101010101010101010101010101010101010101"}'
+        )