commit 36605ea2f0d0cfd40fbdfa90ab7083c0b4bc4b4b
author Manuel Klimek <klimek@google.com> Wed Dec 01 11:19:19 2021 +0100
committer Copybara-Service <copybara-worker@google.com> Wed Dec 01 02:27:09 2021 -0800
tree 883154e7c96706c460c34f9ea5719dec4f36ddf4
parent 1d8845ce47f54b53110cf5b655ef9a28f96222ef

Fix clang-format bug when handling conflict markers.

Previously, clang-format would not correctly identify preprocessor
directives directly following a conflict marker, which would result in
violating the formatter's invariants.

The provided test fails in assert mode before this change.

GitOrigin-RevId: 59788422609433c50c3d3c16ca531fa56b9acb4f

lib/Format/UnwrappedLineParser.cpp

diff --git a/lib/Format/UnwrappedLineParser.cpp b/lib/Format/UnwrappedLineParser.cpp
index da35648..a7e0422 100644
--- a/lib/Format/UnwrappedLineParser.cpp
+++ b/lib/Format/UnwrappedLineParser.cpp
@@ -3388,6 +3388,20 @@
   do {
     FormatTok = Tokens->getNextToken();
     assert(FormatTok);
+    while (FormatTok->getType() == TT_ConflictStart ||
+           FormatTok->getType() == TT_ConflictEnd ||
+           FormatTok->getType() == TT_ConflictAlternative) {
+      if (FormatTok->getType() == TT_ConflictStart) {
+        conditionalCompilationStart(/*Unreachable=*/false);
+      } else if (FormatTok->getType() == TT_ConflictAlternative) {
+        conditionalCompilationAlternative();
+      } else if (FormatTok->getType() == TT_ConflictEnd) {
+        conditionalCompilationEnd();
+      }
+      FormatTok = Tokens->getNextToken();
+      FormatTok->MustBreakBefore = true;
+    }
+
     while (!Line->InPPDirective && FormatTok->Tok.is(tok::hash) &&
            (FormatTok->HasUnescapedNewline || FormatTok->IsFirst)) {
       distributeComments(Comments, FormatTok);
@@ -3409,19 +3423,6 @@
       flushComments(isOnNewLine(*FormatTok));
       parsePPDirective();
     }
-    while (FormatTok->getType() == TT_ConflictStart ||
-           FormatTok->getType() == TT_ConflictEnd ||
-           FormatTok->getType() == TT_ConflictAlternative) {
-      if (FormatTok->getType() == TT_ConflictStart) {
-        conditionalCompilationStart(/*Unreachable=*/false);
-      } else if (FormatTok->getType() == TT_ConflictAlternative) {
-        conditionalCompilationAlternative();
-      } else if (FormatTok->getType() == TT_ConflictEnd) {
-        conditionalCompilationEnd();
-      }
-      FormatTok = Tokens->getNextToken();
-      FormatTok->MustBreakBefore = true;
-    }
 
     if (!PPStack.empty() && (PPStack.back().Kind == PP_Unreachable) &&
         !Line->InPPDirective) {

unittests/Format/FormatTest.cpp

diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 39f1b83..65809ab 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -21117,6 +21117,14 @@
                    ">>>>>>>\n"
                    "  End\n"
                    "int i;\n"));
+
+  verifyFormat(R"(====
+#ifdef A
+a
+#else
+b
+#endif
+)");
 }
 
 TEST_F(FormatTest, DisableRegions) {