clang-format: [JS] support null operators.

Summary:
JavaScript / TypeScript is adding two new operators: the null
propagating operator `?.` and the nullish coalescing operator `??`.

    const x = foo ?? 'default';
    const z = foo?.bar?.baz;

This change adds support to lex and format both.

Reviewers: krasimir

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69971

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index ca2093a05cc..30a0b37ef69 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -2222,6 +2222,16 @@ TEST_F(FormatTestJS, NonNullAssertionOperator) {
   verifyFormat("return !!x;\n");
 }
 
+TEST_F(FormatTestJS, NullPropagatingOperator) {
+  verifyFormat("let x = foo?.bar?.baz();\n");
+  verifyFormat("let x = foo?.(foo);\n");
+  verifyFormat("let x = foo?.['arr'];\n");
+}
+
+TEST_F(FormatTestJS, NullishCoalescingOperator) {
+  verifyFormat("const val = something ?? 'some other default';\n");
+}
+
 TEST_F(FormatTestJS, Conditional) {
   verifyFormat("y = x ? 1 : 2;");
   verifyFormat("x ? 1 : 2;");