Allow exporting of instances from modules and prefer real types to Any (#1153)

* Allow re-export of instances

* Add test

* Fix test

Author: Mikhail Arkhipov

src/Analysis/Ast/Impl/Analyzer/ModuleWalker.cs

@@ -19,6 +19,7 @@
 using Microsoft.Python.Analysis.Analyzer.Evaluation;
 using Microsoft.Python.Analysis.Documents;
 using Microsoft.Python.Analysis.Modules;
+using Microsoft.Python.Analysis.Specializations.Typing;
 using Microsoft.Python.Analysis.Types;
 using Microsoft.Python.Analysis.Types.Collections;
 using Microsoft.Python.Analysis.Values;
@@ -239,6 +240,11 @@ private void MergeStub() {
 
                 var sourceVar = Eval.GlobalScope.Variables[v.Name];
                 var sourceType = sourceVar?.Value.GetPythonType();
+                
+                // If stub says 'Any' but we have better type, keep the current type.
+                if (!IsStubBetterType(sourceType, stubType)) {
+                    continue;;
+                }
 
                 // If types are the classes, merge members.
                 // Otherwise, replace type from one from the stub.
@@ -250,9 +256,15 @@ private void MergeStub() {
                         var stubMember = stubType.GetMember(name);
                         var member = cls.GetMember(name);
 
+                        var memberType = member?.GetPythonType();
+                        var stubMemberType = stubMember.GetPythonType();
+                        if (!IsStubBetterType(memberType, stubMemberType)) {
+                            continue; ;
+                        }
+
                         // Get documentation from the current type, if any, since stubs
                         // typically do not contain documentation while scraped code does.
-                        member?.GetPythonType()?.TransferDocumentationAndLocation(stubMember.GetPythonType());
+                        memberType?.TransferDocumentationAndLocation(stubMemberType);
                         cls.AddMember(name, stubMember, overwrite: true);
                     }
                 } else {
@@ -268,5 +280,9 @@ private void MergeStub() {
                 }
             }
         }
+
+        private static bool IsStubBetterType(IPythonType sourceType, IPythonType stubType)
+            // If stub says 'Any' but we have better type, keep the current type.
+            => sourceType.IsUnknown() || !(stubType.DeclaringModule is TypingModule) || stubType.Name != "Any";
     }
 }

src/Analysis/Ast/Impl/Analyzer/Symbols/ClassEvaluator.cs

@@ -150,9 +150,6 @@ private void UpdateClassMembers() {
             // Add members from this file
             var members = Eval.CurrentScope.Variables.Where(v => v.Source == VariableSource.Declaration || v.Source == VariableSource.Import);
             _class.AddMembers(members, false);
-            // Add members from stub
-            var stubClass = Eval.Module.Stub?.GetMember<IPythonClassType>(_class.Name);
-            _class.AddMembers(stubClass, false);
         }
 
         // Classes and functions are walked by their respective evaluators

src/Analysis/Ast/Impl/Modules/PythonModule.cs

@@ -153,8 +153,18 @@ public virtual string Documentation {
         public virtual IEnumerable<string> GetMemberNames() {
             // drop imported modules and typing.
             return Analysis.GlobalScope.Variables
-                .Where(v => !(v.Value?.GetPythonType() is PythonModule)
-                            && !(v.Value?.GetPythonType().DeclaringModule is TypingModule && !(this is TypingModule)))
+                .Where(v => {
+                    // Instances are always fine.
+                    if (v.Value is IPythonInstance) {
+                        return true;
+                    }
+                    var valueType = v.Value?.GetPythonType();
+                    if (valueType is PythonModule) {
+                        return false; // Do not re-export modules.
+                    }
+                    // Do not re-export types from typing
+                    return !(valueType?.DeclaringModule is TypingModule) || this is TypingModule;
+                })
                 .Select(v => v.Name);
         }
         #endregion

src/Analysis/Ast/Test/ImportTests.cs

@@ -222,5 +222,14 @@ public async Task FromFuture() {
             analysis.Diagnostics.Should().BeEmpty();
             analysis.Should().HaveFunction("print");
         }
+
+        [TestMethod, Priority(0)]
+        public async Task PreferTypeToAny() {
+            var analysis = await GetAnalysisAsync(@"from TypingConstants import *", PythonVersions.LatestAvailable3X);
+            analysis.Should().HaveVariable("ONE").Which.Should().HaveType("Any");
+            analysis.Should().HaveVariable("TWO").Which.Should().HaveType(BuiltinTypeId.Str);
+            var a = analysis.Should().HaveClass("A").Which;
+            a.GetMember("x").Should().HaveType(BuiltinTypeId.Int);
+        }
     }
 }

src/UnitTests/TestData/AstAnalysis/TypingConstants.py

@@ -0,0 +1,8 @@
+from typing import Any
+
+ONE = ...  # type: Any
+TWO = 'a'
+
+class A:
+    x = 1
+

src/UnitTests/TestData/AstAnalysis/TypingConstants.pyi

@@ -0,0 +1,7 @@
+from typing import Any
+
+ONE = ...  # type: Any
+TWO = ...  # type: Any
+
+class A:
+    x: Any