From a7638d384983e8e3eb44a2d8c757238efc7096dc Mon Sep 17 00:00:00 2001
From: Martin Probst <martin@probst.io>
Date: Thu, 7 Nov 2019 23:39:03 +0100
Subject: [PATCH] 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
---
 clang/lib/Format/FormatToken.h          |  2 ++
 clang/lib/Format/FormatTokenLexer.cpp   | 12 ++++++++++++
 clang/unittests/Format/FormatTestJS.cpp | 10 ++++++++++
 3 files changed, 24 insertions(+)

diff --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
index b11f3655..3949828 100644
--- a/clang/lib/Format/FormatToken.h
+++ b/clang/lib/Format/FormatToken.h
@@ -60,6 +60,8 @@ namespace format {
   TYPE(JsExponentiationEqual)                                                  \
   TYPE(JsFatArrow)                                                             \
   TYPE(JsNonNullAssertion)                                                     \
+  TYPE(JsNullishCoalescingOperator)                                            \
+  TYPE(JsNullPropagatingOperator)                                              \
   TYPE(JsPrivateIdentifier)                                                    \
   TYPE(JsTypeColon)                                                            \
   TYPE(JsTypeOperator)                                                         \
diff --git a/clang/lib/Format/FormatTokenLexer.cpp b/clang/lib/Format/FormatTokenLexer.cpp
index 5d8a775..ef20ba8 100644
--- a/clang/lib/Format/FormatTokenLexer.cpp
+++ b/clang/lib/Format/FormatTokenLexer.cpp
@@ -100,6 +100,10 @@ void FormatTokenLexer::tryMergePreviousTokens() {
     static const tok::TokenKind JSExponentiation[] = {tok::star, tok::star};
     static const tok::TokenKind JSExponentiationEqual[] = {tok::star,
                                                            tok::starequal};
+    static const tok::TokenKind JSNullPropagatingOperator[] = {tok::question,
+                                                               tok::period};
+    static const tok::TokenKind JSNullishOperator[] = {tok::question,
+                                                       tok::question};
 
     // FIXME: Investigate what token type gives the correct operator priority.
     if (tryMergeTokens(JSIdentity, TT_BinaryOperator))
@@ -116,6 +120,14 @@ void FormatTokenLexer::tryMergePreviousTokens() {
       Tokens.back()->Tok.setKind(tok::starequal);
       return;
     }
+    if (tryMergeTokens(JSNullishOperator, TT_JsNullishCoalescingOperator))
+      return;
+    if (tryMergeTokens(JSNullPropagatingOperator,
+                       TT_JsNullPropagatingOperator)) {
+      // Treat like a regular "." access.
+      Tokens.back()->Tok.setKind(tok::period);
+      return;
+    }
     if (tryMergeJSPrivateIdentifier())
       return;
   }
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index ca2093a..30a0b37 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;");
-- 
2.7.4