Merge pull request microsoft#10403 from Microsoft/completionsForNullableObjects

Fix completions for nullable objects

Author: DanielRosenwasser

src/services/services.ts

@@ -3789,7 +3789,11 @@ namespace ts {
                     // other than those within the declared type.
                     isNewIdentifierLocation = true;
 
+                    // If the object literal is being assigned to something of type 'null | { hello: string }',
+                    // it clearly isn't trying to satisfy the 'null' type. So we grab the non-nullable type if possible.
                     typeForObject = typeChecker.getContextualType(<ObjectLiteralExpression>objectLikeContainer);
+                    typeForObject = typeForObject && typeForObject.getNonNullableType();
+
                     existingMembers = (<ObjectLiteralExpression>objectLikeContainer).properties;
                 }
                 else if (objectLikeContainer.kind === SyntaxKind.ObjectBindingPattern) {
@@ -3801,7 +3805,7 @@ namespace ts {
                         // We don't want to complete using the type acquired by the shape
                         // of the binding pattern; we are only interested in types acquired
                         // through type declaration or inference.
-                        // Also proceed if rootDeclaration is parameter and if its containing function expression\arrow function is contextually typed -
+                        // Also proceed if rootDeclaration is a parameter and if its containing function expression/arrow function is contextually typed -
                         // type of parameter will flow in from the contextual type of the function
                         let canGetType = !!(rootDeclaration.initializer || rootDeclaration.type);
                         if (!canGetType && rootDeclaration.kind === SyntaxKind.Parameter) {

tests/cases/fourslash/completionListInObjectLiteral4.ts

@@ -0,0 +1,28 @@
+/// <reference path='fourslash.ts'/>
+
+// @strictNullChecks: true
+////interface Thing {
+////    hello: number;
+////    world: string;
+////}
+////
+////declare function funcA(x : Thing): void;
+////declare function funcB(x?: Thing): void;
+////declare function funcC(x : Thing | null): void;
+////declare function funcD(x : Thing | undefined): void;
+////declare function funcE(x : Thing | null | undefined): void;
+////declare function funcF(x?: Thing | null | undefined): void;
+////
+////funcA({ /*A*/ });
+////funcB({ /*B*/ });
+////funcC({ /*C*/ });
+////funcD({ /*D*/ });
+////funcE({ /*E*/ });
+////funcF({ /*F*/ });
+
+
+for (const marker of test.markers()) {
+    goTo.position(marker.position);
+    verify.completionListContains("hello");
+    verify.completionListContains("world");
+}