Add support for python 3.6

Changes:
- Update config and docs to reference 3.6
- Add backports of dataclasses and datetime.fromisoformat
- Support both 3.7 and 3.6 usages of undocumented __origin__ attribute on typing objects
- Make github ci run tests for python 3.6 as well

Author: nat-n

.github/workflows/ci.yml

@@ -3,7 +3,28 @@ name: CI
 on: [push, pull_request]
 
 jobs:
-  build:
+
+  build-p36:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-python@v1
+        with:
+          python-version: 3.6
+      - uses: dschep/install-pipenv-action@v1
+      - name: Install dependencies
+        run: |
+          sudo apt install protobuf-compiler libprotobuf-dev
+          pipenv install --dev
+      - name: Run tests
+        run: |
+          cp .env.default .env
+          pipenv run pip install -e .
+          pipenv run generate
+          pipenv run test
+
+  build-p37:
     runs-on: ubuntu-latest
 
     steps:

.gitignore

@@ -2,6 +2,7 @@
 .vscode/settings.json
 .mypy_cache
 .pytest_cache
+.python-version
 betterproto/tests/*.bin
 betterproto/tests/*_pb2.py
 betterproto/tests/*.py

Pipfile

@@ -9,16 +9,19 @@ mypy = "*"
 isort = "*"
 pytest = "*"
 rope = "*"
+v = {editable = true,version = "*"}
 
 [packages]
 protobuf = "*"
 jinja2 = "*"
 grpclib = "*"
 stringcase = "*"
 black = "*"
+backports-datetime-fromisoformat = "*"
+dataclasses = "*"
 
 [requires]
-python_version = "3.7"
+python_version = "3.6"
 
 [scripts]
 plugin = "protoc --plugin=protoc-gen-custom=betterproto/plugin.py --custom_out=output"

Pipfile.lock

@@ -6,7 +6,7 @@ This project aims to provide an improved experience when using Protobuf / gRPC i
 
 - Protobuf 3 & gRPC code generation
   - Both binary & JSON serialization is built-in
-- Python 3.7+ making use of:
+- Python 3.6+ making use of:
   - Enums
   - Dataclasses
   - `async`/`await`
@@ -296,7 +296,7 @@ datetime.datetime(2019, 1, 1, 11, 59, 58, 800000, tzinfo=datetime.timezone.utc)
 
 ## Development
 
-First, make sure you have Python 3.7+ and `pipenv` installed, along with the official [Protobuf Compiler](https://github.com/protocolbuffers/protobuf/releases) for your platform. Then:
+First, make sure you have Python 3.6+ and `pipenv` installed, along with the official [Protobuf Compiler](https://github.com/protocolbuffers/protobuf/releases) for your platform. Then:
 
 ```sh
 # Get set up with the virtual env & dependencies

README.md

@@ -3,6 +3,7 @@
 import inspect
 import json
 import struct
+import sys
 from abc import ABC
 from base64 import b64encode, b64decode
 from datetime import datetime, timedelta, timezone
@@ -33,6 +34,13 @@
 if TYPE_CHECKING:
     from grpclib._protocols import IProtoMessage
 
+if not (sys.version_info.major == 3 and sys.version_info.minor >= 7):
+    # Apply backport of datetime.fromisoformat from 3.7
+    from backports.datetime_fromisoformat import MonkeyPatch
+
+    MonkeyPatch.patch_fromisoformat()
+
+
 # Proto 3 data types
 TYPE_ENUM = "enum"
 TYPE_BOOL = "bool"
@@ -569,10 +577,10 @@ def _get_field_default(self, field: dataclasses.Field, meta: FieldMetadata) -> A
 
         value: Any = 0
         if hasattr(t, "__origin__"):
-            if t.__origin__ == dict:
+            if t.__origin__ in (dict, Dict):
                 # This is some kind of map (dict in Python).
                 value = {}
-            elif t.__origin__ == list:
+            elif t.__origin__ in (list, List):
                 # This is some kind of list (repeated) field.
                 value = []
             elif t.__origin__ == Union and t.__args__[1] == type(None):

betterproto/__init__.py

@@ -1,5 +1,5 @@
 [tool.black]
-target-version = ['py37']
+target-version = ['py36']
 
 [tool.isort]
 multi_line_output = 3

betterproto/__pycache__/__init__.cpython-37.pyc

@@ -17,7 +17,7 @@
         exclude=["tests", "*.tests", "*.tests.*", "output", "output.*"]
     ),
     package_data={"betterproto": ["py.typed", "templates/template.py"]},
-    python_requires=">=3.7",
+    python_requires=">=3.6",
     install_requires=["grpclib", "stringcase"],
     extras_require={"compiler": ["black", "jinja2", "protobuf"]},
     zip_safe=False,