Use SemVer to check communication compatibility between C# and Python (#3760)

* [communication] Use semantic versioning to test communication compatibility between C# and Python.

- Add tests for the change.

Co-authored-by: Chris Elion <chris.elion@unity3d.com>

com.unity.ml-agents/CHANGELOG.md

  - Added ability to start training (initialize model weights) from a previous run ID. (#3710)
  - The internal event `Academy.AgentSetStatus` was renamed to `Academy.AgentPreStep` and made public.
  - The offset logic was removed from DecisionRequester.
+ - The communication API version has been bumped up to 1.0.0 and will use [Semantic Versioning](https://semver.org/) to do compatibility checks for communication between Unity and the Python process.
 
 ### Minor Changes
  - Format of console output has changed slightly and now matches the name of the model/summary directory. (#3630, #3616)

com.unity.ml-agents/Runtime/Communicator/RpcCommunicator.cs

 
         #region Initialization
 
+        internal static bool CheckCommunicationVersionsAreCompatible(
+            string unityCommunicationVersion,
+            string pythonApiVersion,
+            string pythonLibraryVersion)
+        {
+            var unityVersion = new Version(unityCommunicationVersion);
+            var pythonVersion = new Version(pythonApiVersion);
+            if (unityVersion.Major == 0)
+            {
+                if (unityVersion.Major != pythonVersion.Major || unityVersion.Minor != pythonVersion.Minor)
+                {
+                    return false;
+                }
+
+            }
+            else if (unityVersion.Major != pythonVersion.Major)
+            {
+                return false;
+            }
+            else if (unityVersion.Minor != pythonVersion.Minor)
+            {
+                // Even if we initialize, we still want to check to make sure that we inform users of minor version
+                // changes.  This will surface any features that may not work due to minor version incompatibilities.
+                Debug.LogWarningFormat(
+                    "WARNING: The communication API versions between Unity and python differ at the minor version level. " +
+                    "Python API: {0}, Unity API: {1} Python Library Version: {2} .\n" +
+                    "This means that some features may not work unless you upgrade the package with the lower version." +
+                    "Please find the versions that work best together from our release page.\n" +
+                    "https://github.com/Unity-Technologies/ml-agents/releases",
+                    pythonApiVersion, unityCommunicationVersion, pythonLibraryVersion
+                );
+            }
+            return true;
+        }
+
         /// <summary>
         /// Sends the initialization parameters through the Communicator.
         /// Is used by the academy to send initialization parameters to the communicator.
                     },
                     out input);
 
+                var pythonCommunicationVersion = initializationInput.RlInitializationInput.CommunicationVersion;
+                var pythonPackageVersion = initializationInput.RlInitializationInput.PackageVersion;
+                var unityCommunicationVersion = initParameters.unityCommunicationVersion;
+
+                var communicationIsCompatible = CheckCommunicationVersionsAreCompatible(unityCommunicationVersion,
+                    pythonCommunicationVersion,
+                    pythonPackageVersion);
+
-                    var pythonCommunicationVersion = initializationInput.RlInitializationInput.CommunicationVersion;
-                    var pythonPackageVersion = initializationInput.RlInitializationInput.PackageVersion;
-                    if (pythonCommunicationVersion != initParameters.unityCommunicationVersion)
+                    if (!communicationIsCompatible)
-                            "Communication protocol between python ({0}) and Unity ({1}) don't match. " +
-                            "Python library version: {2}.",
+                            "Communication protocol between python ({0}) and Unity ({1}) have different " +
+                            "versions which make them incompatible. Python library version: {2}.",
                             pythonCommunicationVersion, initParameters.unityCommunicationVersion,
                             pythonPackageVersion
                         );

ml-agents-envs/mlagents_envs/environment.py

 import atexit
+from distutils.version import StrictVersion
 import glob
 import uuid
 import numpy as np
 import signal
 import struct
 
-
 logger = get_logger(__name__)
 
 
     # Command line argument used to pass the port to the executable environment.
     PORT_COMMAND_LINE_ARG = "--mlagents-port"
 
+    @staticmethod
+    def _raise_version_exception(unity_com_ver: str) -> None:
+        raise UnityEnvironmentException(
+            f"The communication API version is not compatible between Unity and python. "
+            f"Python API: {UnityEnvironment.API_VERSION}, Unity API: {unity_com_ver}.\n "
+            f"Please go to https://github.com/Unity-Technologies/ml-agents/releases/tag/latest_release "
+            f"to download the latest version of ML-Agents."
+        )
+
+    @staticmethod
+    def check_communication_compatibility(
+        unity_com_ver: str, python_api_version: str, unity_package_version: str
+    ) -> bool:
+        unity_communicator_version = StrictVersion(unity_com_ver)
+        api_version = StrictVersion(python_api_version)
+        if unity_communicator_version.version[0] == 0:
+            if (
+                unity_communicator_version.version[0] != api_version.version[0]
+                or unity_communicator_version.version[1] != api_version.version[1]
+            ):
+                # Minor beta versions differ.
+                return False
+        elif unity_communicator_version.version[0] != api_version.version[0]:
+            # Major versions mismatch.
+            return False
+        elif unity_communicator_version.version[1] != api_version.version[1]:
+            # Non-beta minor versions mismatch.  Log a warning but allow execution to continue.
+            logger.warning(
+                f"WARNING: The communication API versions between Unity and python differ at the minor version level. "
+                f"Python API: {python_api_version}, Unity API: {unity_communicator_version}.\n"
+                f"This means that some features may not work unless you upgrade the package with the lower version."
+                f"Please find the versions that work best together from our release page.\n"
+                "https://github.com/Unity-Technologies/ml-agents/releases"
+            )
+        else:
+            logger.info(
+                f"Connected to Unity environment with package version {unity_package_version} "
+                f"and communication version {unity_com_ver}"
+            )
+        return True
+
     def __init__(
         self,
         file_name: Optional[str] = None,
             self._close(0)
             raise
 
-        unity_communicator_version = aca_params.communication_version
-        if unity_communicator_version != UnityEnvironment.API_VERSION:
+        if not UnityEnvironment.check_communication_compatibility(
+            aca_params.communication_version,
+            UnityEnvironment.API_VERSION,
+            aca_params.package_version,
+        ):
-            raise UnityEnvironmentException(
-                f"The communication API version is not compatible between Unity and python. "
-                f"Python API: {UnityEnvironment.API_VERSION}, Unity API: {unity_communicator_version}.\n "
-                f"Please go to https://github.com/Unity-Technologies/ml-agents/releases/tag/latest_release "
-                f"to download the latest version of ML-Agents."
-            )
-        else:
-            logger.info(
-                f"Connected to Unity environment with package version {aca_params.package_version} "
-                f"and communication version {aca_params.communication_version}"
-            )
+            UnityEnvironment._raise_version_exception(aca_params.communication_version)
+
         self._env_state: Dict[str, Tuple[DecisionSteps, TerminalSteps]] = {}
         self._env_specs: Dict[str, BehaviorSpec] = {}
         self._env_actions: Dict[str, np.ndarray] = {}

ml-agents-envs/mlagents_envs/tests/test_envs.py

     assert comm.has_been_closed
 
 
+def test_check_communication_compatibility():
+    unity_ver = "1.0.0"
+    python_ver = "1.0.0"
+    unity_package_version = "0.15.0"
+    assert UnityEnvironment.check_communication_compatibility(
+        unity_ver, python_ver, unity_package_version
+    )
+    unity_ver = "1.1.0"
+    assert UnityEnvironment.check_communication_compatibility(
+        unity_ver, python_ver, unity_package_version
+    )
+    unity_ver = "2.0.0"
+    assert not UnityEnvironment.check_communication_compatibility(
+        unity_ver, python_ver, unity_package_version
+    )
+
+    unity_ver = "0.16.0"
+    python_ver = "0.16.0"
+    assert UnityEnvironment.check_communication_compatibility(
+        unity_ver, python_ver, unity_package_version
+    )
+    unity_ver = "0.17.0"
+    assert not UnityEnvironment.check_communication_compatibility(
+        unity_ver, python_ver, unity_package_version
+    )
+    unity_ver = "1.16.0"
+    assert not UnityEnvironment.check_communication_compatibility(
+        unity_ver, python_ver, unity_package_version
+    )
+
+
 def test_returncode_to_signal_name():
     assert UnityEnvironment.returncode_to_signal_name(-2) == "SIGINT"
     assert UnityEnvironment.returncode_to_signal_name(42) is None

com.unity.ml-agents/Tests/Editor/Communicator.meta

+fileFormatVersion: 2
+guid: da8f640243c749388a0329393c8fce64
+timeCreated: 1586386315

com.unity.ml-agents/Tests/Editor/Communicator/RpcCommunicatorTests.cs

+using System;
+using System.Collections;
+using System.Text.RegularExpressions;
+using NUnit.Framework;
+using UnityEngine;
+using UnityEngine.TestTools;
+
+namespace MLAgents.Tests.Communicator
+{
+    [TestFixture]
+    public class RpcCommunicatorTests
+    {
+
+        [Test]
+        public void TestCheckCommunicationVersionsAreCompatible()
+        {
+            var unityVerStr = "1.0.0";
+            var pythonVerStr = "1.0.0";
+            var pythonPackageVerStr = "0.16.0";
+
+            Assert.IsTrue(RpcCommunicator.CheckCommunicationVersionsAreCompatible(unityVerStr,
+                pythonVerStr,
+                pythonPackageVerStr));
+            LogAssert.NoUnexpectedReceived();
+
+            pythonVerStr = "1.1.0";
+            Assert.IsTrue(RpcCommunicator.CheckCommunicationVersionsAreCompatible(unityVerStr,
+                pythonVerStr,
+                pythonPackageVerStr));
+
+            // Ensure that a warning was printed.
+            LogAssert.Expect(LogType.Warning, new Regex("(.\\s)+"));
+
+            unityVerStr = "2.0.0";
+            Assert.IsFalse(RpcCommunicator.CheckCommunicationVersionsAreCompatible(unityVerStr,
+                pythonVerStr,
+                pythonPackageVerStr));
+
+            unityVerStr = "0.15.0";
+            pythonVerStr = "0.15.0";
+            Assert.IsTrue(RpcCommunicator.CheckCommunicationVersionsAreCompatible(unityVerStr,
+                pythonVerStr,
+                pythonPackageVerStr));
+            unityVerStr = "0.16.0";
+            Assert.IsFalse(RpcCommunicator.CheckCommunicationVersionsAreCompatible(unityVerStr,
+                pythonVerStr,
+                pythonPackageVerStr));
+            unityVerStr = "1.15.0";
+            Assert.IsFalse(RpcCommunicator.CheckCommunicationVersionsAreCompatible(unityVerStr,
+                pythonVerStr,
+                pythonPackageVerStr));
+
+        }
+    }
+}

com.unity.ml-agents/Tests/Editor/Communicator/RpcCommunicatorTests.cs.meta

+fileFormatVersion: 2
+guid: 251fab8dff424abb95b2b381c7c924c3
+timeCreated: 1586386329