Handle cls in addition to self in completions (#1794)

* Remove stale reference

* Don't suppress LHS diagnostics on augmented assign

* Revert "Don't suppress LHS diagnostics on augmented assign"

This reverts commit 6109ac7.

* Handle cls

* Remove temp test

(cherry picked from commit 398a75c)

Author: Mikhail Arkhipov

src/LanguageServer/Impl/Completion/ExpressionCompletion.cs

@@ -58,8 +58,8 @@ private static IEnumerable<CompletionItem> GetClassItems(IPythonClassType cls, E
             // See if we are completing on self. Note that we may be inside inner function
             // that does not necessarily have 'self' argument so we are looking beyond local
             // scope. We then check that variable type matches the class type, if any.
-            var selfVariable = eval.LookupNameInScopes("self");
-            var completingOnSelf = cls.Equals(selfVariable?.GetPythonType()) && e is NameExpression nex && nex.Name == "self";
+            var classVariable = eval.LookupNameInScopes("self") ?? eval.LookupNameInScopes("cls");
+            var completingOnClass = cls.Equals(classVariable?.GetPythonType()) && e is NameExpression nex && (nex.Name == "self" || nex.Name == "cls");
 
             var items = new List<CompletionItem>();
             var names = cls.GetMemberNames().ToArray();
@@ -74,7 +74,7 @@ private static IEnumerable<CompletionItem> GetClassItems(IPythonClassType cls, E
                 var unmangledName = cls.UnmangleMemberName(t);
                 if (!string.IsNullOrEmpty(unmangledName)) {
                     // Hide private variables outside of the class scope.
-                    if (!completingOnSelf && cls.IsPrivateMember(t)) {
+                    if (!completingOnClass && cls.IsPrivateMember(t)) {
                         continue;
                     }
                     items.Add(context.ItemSource.CreateCompletionItem(unmangledName, m, cls));

src/LanguageServer/Test/CompletionTests.cs

@@ -1486,5 +1486,30 @@ public async Task ImportDotMembers() {
             var result = cs.GetCompletions(analysis, new SourceLocation(1, 16));
             result.Should().OnlyHaveLabels("m1", "m2");
         }
+
+        [TestMethod, Priority(0)]
+        public async Task ClassPrivateMembers() {
+            const string code = @"
+class Op:
+    __EQ = '0'
+    __NOT_EQ = '1'
+    __OP_LIST = [__EQ]
+
+    def print_EQ1(self):
+        self.
+
+    @classmethod
+    def print_EQ2(cls):
+        cls.
+";
+            var analysis = await GetAnalysisAsync(code);
+            var cs = new CompletionSource(new PlainTextDocumentationSource(), ServerSettings.completion, Services);
+
+            var result = cs.GetCompletions(analysis, new SourceLocation(8, 14));
+            result.Should().HaveLabels("__EQ", "__NOT_EQ", "__OP_LIST");
+
+            result = cs.GetCompletions(analysis, new SourceLocation(12, 13));
+            result.Should().HaveLabels("__EQ", "__NOT_EQ", "__OP_LIST");
+        }
     }
 }