[MLA-1981] Don't allow connections to newer python trainers (#5370)

Project/Packages/manifest.json

     "com.unity.analytics": "3.2.3",
     "com.unity.collab-proxy": "1.2.15",
     "com.unity.ml-agents": "file:../../com.unity.ml-agents",
-    "com.unity.package-manager-ui": "2.0.8",
+    "com.unity.package-manager-ui": "2.0.13",
-    "com.unity.purchasing": "2.0.3",
+    "com.unity.purchasing": "2.2.1",
     "com.unity.textmeshpro": "1.4.1",
     "com.unity.modules.ai": "1.0.0",
     "com.unity.modules.animation": "1.0.0",

Project/ProjectSettings/ProjectVersion.txt

-m_EditorVersion: 2018.4.17f1
+m_EditorVersion: 2018.4.32f1

com.unity.ml-agents/CHANGELOG.md

 ### Bug Fixes
 #### com.unity.ml-agents (C#)
 - Fixed a null reference exception that occurred when loading an ONNX model file that was generated with a new
-version of the Python trainer (0.26.0 or newer).
+version of the Python trainer (0.26.0 or newer). (#5350)
+- Added checked to prevent training with incompatible versions of the python trainer (0.26.0 or newer). (#5370)
 
 ## [1.0.7] - 2021-03-04
 ### Minor Changes

com.unity.ml-agents/Documentation~/com.unity.ml-agents.md

 To install the companion Python package to enable training behaviors, follow the
 [installation instructions] on our [GitHub repository]. It is strongly recommended that you
 use the Python package that corresponds to this release (version 0.16.1) for the best experience;
-versions between 0.16.1 and 0.20.0 are supported.
+versions between 0.16.1 and 0.20.0 are supported. Versions after 0.25.1 cannot be used.
 
 ## Requirements
 

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

 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.RegularExpressions;
 using UnityEngine;
 using Unity.MLAgents.Analytics;
 using Unity.MLAgents.CommunicatorObjects;
 
         internal static bool CheckPythonPackageVersionIsCompatible(string pythonLibraryVersion)
         {
+            // Try to extract the numerical values from the pythonLibraryVersion, e.g. remove the ".dev0" suffix
+            var versionMatch = Regex.Match(pythonLibraryVersion, @"[0-9]+\.[0-9]+\.[0-9]");
+            if (versionMatch.Success)
+            {
+                pythonLibraryVersion = versionMatch.Value;
+            }
+
             Version pythonVersion;
             try
             {
             {
-                // Unparseable - this also catches things like "0.20.0-dev0" which we don't want to support
+                // Unparseable version.
+                // Anything like 0.42.0.dev0 should have been caught with the regex above, so anything here
+                // is totally bogus. For now, ignore these and let CheckPythonPackageVersionIsSupported handle it.
+                return true;
+            }
+
+            if (pythonVersion > PythonTrainerVersions.s_MaxCompatibleVersion)
+            {
+                return false;
+            }
+            return true;
+        }
+
+        /// <summary>
+        /// Check if the package is in the supported range. Note that some versions might be unsupported but
+        /// still compatible.
+        /// </summary>
+        /// <param name="pythonLibraryVersion"></param>
+        /// <returns></returns>
+        internal static bool CheckPythonPackageVersionIsSupported(string pythonLibraryVersion)
+        {
+            Version pythonVersion;
+            try
+            {
+                pythonVersion = new Version(pythonLibraryVersion);
+            }
+            catch
+            {
+                // Unparseable - this also catches things like "0.20.0.dev0" which we don't want to support
                 return false;
             }
 
                     throw new UnityAgentsException("ICommunicator.Initialize() failed.");
                 }
 
-                var packageVersionSupported = CheckPythonPackageVersionIsCompatible(pythonPackageVersion);
+                var packageVersionCompatible = CheckPythonPackageVersionIsCompatible(pythonPackageVersion);
+                if (!packageVersionCompatible)
+                {
+                    Debug.LogErrorFormat(
+                        "Python package version ({0}) will produce model files that are incompatible with this " +
+                        "version of the com.unity.ml-agents Unity package. Please downgrade to a Python package " +
+                        "between {1} and {2}, or update to a new version of com.unity.ml-agents.",
+                        pythonPackageVersion,
+                        PythonTrainerVersions.s_MinSupportedVersion,
+                        PythonTrainerVersions.s_MaxSupportedVersion
+                    );
+                    throw new UnityAgentsException("Incompatible trainer version.");
+                }
+
+                var packageVersionSupported = CheckPythonPackageVersionIsSupported(pythonPackageVersion);
                 if (!packageVersionSupported)
                 {
                     Debug.LogWarningFormat(

com.unity.ml-agents/Runtime/Constants.cs

 
     internal static class PythonTrainerVersions
     {
-        // The python package version must be >= s_MinSupportedVersion
+        // The python package version should be >= s_MinSupportedVersion
+
+        // Any version > to this is known to be incompatible and we will block training.
+        // Covers any patch to the release before the 2.0.0 package release.
+        internal static Version s_MaxCompatibleVersion = new Version("0.25.999");
     }
 
 }

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

         [Test]
         public void TestCheckPythonPackageVersionIsCompatible()
         {
-            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.13.37")); // too low
-            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.42.0")); // too high
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.13.37")); // low is OK
+            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.26.0")); // too high
-            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.20.0"));
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.25.0"));
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.25.1"));
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.25.2"));
+
+            // "dev" strings should get removed before parsing
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.17.0.dev0"));
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.25.0.dev0"));
+            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.26.0.dev0"));
+
+            // otherwise unparseable - keep support for these
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsCompatible("the airspeed velocity of an unladen swallow"));
+        }
+
+        [Test]
+        public void TestCheckPythonPackageVersionIsSupported()
+        {
+            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsSupported("0.13.37")); // too low
+            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsSupported("0.42.0")); // too high
+
+            // These are fine
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsSupported("0.16.1"));
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsSupported("0.17.17"));
+            Assert.IsTrue(RpcCommunicator.CheckPythonPackageVersionIsSupported("0.20.0"));
-            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsCompatible("0.17.0-dev0"));
-            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsCompatible("oh point seventeen point oh"));
+            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsSupported("0.17.0.dev0"));
+            Assert.IsFalse(RpcCommunicator.CheckPythonPackageVersionIsSupported("oh point seventeen point oh"));
         }
     }
 }