Make rusty-rlp optional

.circleci/config.yml

@@ -58,6 +58,36 @@ jobs:
       - image: circleci/python:3.7
         environment:
           TOXENV: py37-core
+  py38-core:
+    <<: *common
+    docker:
+      - image: circleci/python:3.8
+        environment:
+          TOXENV: py38-core
+  py35-rust-backend:
+    <<: *common
+    docker:
+      - image: circleci/python:3.5
+        environment:
+          TOXENV: py35-rust-backend
+  py36-rust-backend:
+    <<: *common
+    docker:
+      - image: circleci/python:3.6
+        environment:
+          TOXENV: py36-rust-backend
+  py37-rust-backend:
+    <<: *common
+    docker:
+      - image: circleci/python:3.7
+        environment:
+          TOXENV: py37-rust-backend
+  py38-rust-backend:
+    <<: *common
+    docker:
+      - image: circleci/python:3.8
+        environment:
+          TOXENV: py38-rust-backend
   py35-doctest:
     <<: *common
     docker:
@@ -76,6 +106,12 @@ jobs:
       - image: circleci/python:3.7
         environment:
           TOXENV: py37-doctest
+  py38-doctest:
+    <<: *common
+    docker:
+      - image: circleci/python:3.8
+        environment:
+          TOXENV: py38-doctest
 
   lint:
     <<: *common
@@ -91,9 +127,16 @@ workflows:
       - py35-core
       - py36-core
       - py37-core
+      - py38-core
+
+      - py35-rust-backend
+      - py36-rust-backend
+      - py37-rust-backend
+      - py38-rust-backend
 
       - py35-doctest
       - py36-doctest
       - py37-doctest
+      - py38-doctest
 
       - lint

rlp/codec.py

@@ -5,7 +5,7 @@
     int_to_big_endian,
     is_bytes,
 )
-import rusty_rlp
+
 
 from rlp.exceptions import EncodingError, DecodingError
 from rlp.sedes.binary import Binary as BinaryClass
@@ -15,20 +15,63 @@
 from rlp.utils import ALL_BYTES
 
 
-def decode_raw(item, strict, preserve_per_item_rlp):
-    try:
-        return rusty_rlp.decode_raw(item, strict, preserve_per_item_rlp)
-    except (TypeError, rusty_rlp.DecodingError) as e:
-        raise DecodingError(e, item)
-
-
-def encode_raw(obj):
-    try:
-        if isinstance(obj, bytearray):
-            obj = bytes(obj)
-        return rusty_rlp.encode_raw(obj)
-    except(rusty_rlp.EncodingError) as e:
-        raise EncodingError(e, obj)
+try:
+    import rusty_rlp
+except ImportError as e:
+    import logging
+    from rlp.atomic import (
+        Atomic,
+    )
+    logger = logging.getLogger()
+    logger.warning(
+        "Consider installing rusty-rlp to improve pyrlp performance with a rust based backend"
+    )
+
+    def encode_raw(item):
+        """RLP encode (a nested sequence of) :class:`Atomic`s."""
+        if isinstance(item, Atomic):
+            if len(item) == 1 and item[0] < 128:
+                return item
+            payload = item
+            prefix_offset = 128  # string
+        elif not isinstance(item, str) and isinstance(item, collections.abc.Sequence):
+            payload = b''.join(encode_raw(x) for x in item)
+            prefix_offset = 192  # list
+        else:
+            msg = 'Cannot encode object of type {0}'.format(type(item).__name__)
+            raise EncodingError(msg, item)
+
+        try:
+            prefix = length_prefix(len(payload), prefix_offset)
+        except ValueError:
+            raise EncodingError('Item too big to encode', item)
+
+        return prefix + payload
+
+    def decode_raw(item, strict, _):
+        try:
+            result, per_item_rlp, end = consume_item(item, 0)
+        except IndexError:
+            raise DecodingError('RLP string too short', item)
+        if end != len(item) and strict:
+            msg = 'RLP string ends with {} superfluous bytes'.format(len(item) - end)
+            raise DecodingError(msg, item)
+
+        return result, per_item_rlp
+else:
+    def decode_raw(item, strict, preserve_per_item_rlp):
+        try:
+            return rusty_rlp.decode_raw(item, strict, preserve_per_item_rlp)
+        except (TypeError, rusty_rlp.DecodingError) as e:
+            raise DecodingError(e, item)
+
+    def encode_raw(obj):
+        try:
+            if isinstance(obj, bytearray):
+                obj = bytes(obj)
+            return rusty_rlp.encode_raw(obj)
+        except(rusty_rlp.EncodingError) as e:
+            raise EncodingError(e, obj)
 
 
 def encode(obj, sedes=None, infer_serializer=True, cache=True):

setup.py

@@ -5,7 +5,6 @@
     find_packages,
 )
 
-
 extras_require = {
     'test': [
         "pytest==5.4.3",
@@ -28,6 +27,9 @@
         "ipython",
         "twine",
     ],
+    'rust-backend': [
+        "rusty-rlp>=0.1.15, <0.2"
+    ]
 }
 
 
@@ -53,7 +55,6 @@
     setup_requires=['setuptools-markdown'],
     install_requires=[
         "eth-utils>=1.0.2,<2",
-        "rusty-rlp>=0.1.15, <0.2",
     ],
     extras_require=extras_require,
     license="MIT",

tox.ini

@@ -1,7 +1,8 @@
 [tox]
 envlist =
-    py{35,36,37}-core
-    py{35,36,37}-doctest
+    py{35,36,37,38}-core
+    py{35,36,37,38}-rust-backend
+    py{35,36,37,38}-doctest
     lint
 
 [flake8]
@@ -14,12 +15,16 @@ usedevelop=True
 commands=
     core: py.test {posargs:tests/}
     doctest: py.test --doctest-glob='docs/*.rst' --doctest-modules docs rlp
+    rust-backend: py.test {posargs:tests/}
+
 basepython =
     py35: python3.5
     py36: python3.6
     py37: python3.7
+    py38: python3.8
 extras=
     test
+    rust-backend: rust-backend
 whitelist_externals=make
 
 [testenv:lint]