[clang] 06763ea - [clang-format] Ignore first token when finding MustBreak

[Emilia Kond via cfe-commits]

Author: Emilia Kond
Date: 2023-05-18T05:50:26+03:00
New Revision: 06763ea5d8f96625545bb2c2445363aca9922bf1

URL: https://github.com/llvm/llvm-project/commit/06763ea5d8f96625545bb2c2445363aca9922bf1
DIFF: https://github.com/llvm/llvm-project/commit/06763ea5d8f96625545bb2c2445363aca9922bf1.diff

LOG: [clang-format] Ignore first token when finding MustBreak

When in ColumnLimit 0, the formatter looks for MustBreakBefore in the
line in order to check if a line is allowed to be merged onto one line.

However, since MustBreakBefore is really a property of the gap between
the token and the one previously, I belive the check is erroneous in
checking all the tokens in a line, since whether the previous line ended
with a forced line break should have no effect on whether the current
line is allowed to merge with the next one.

This patch changes the check to skip the first token in
`LineJoiner.containsMustBreak`.

This patch also changes a test, which is not ideal, but I believe the
test also suffered from this bug. The test case in question sets
AllowShortFunctionsOnASingleLine to "Empty", but the empty function in
said test case isn't merged to a single line, because of the very same
bug this patch fixes.

Fixes https://github.com/llvm/llvm-project/issues/62721

Reviewed By: HazardyKnusperkeks, owenpan, MyDeveloperDay

Differential Revision: https://reviews.llvm.org/D150614

Added: 
    

Modified: 
    clang/lib/Format/UnwrappedLineFormatter.cpp
    clang/unittests/Format/FormatTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index ee0de2c8e20da..33be74dfe1b9f 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -888,7 +888,10 @@ class LineJoiner {
   }
 
   bool containsMustBreak(const AnnotatedLine *Line) {
-    for (const FormatToken *Tok = Line->First; Tok; Tok = Tok->Next)
+    assert(Line->First);
+    // Ignore the first token, because in this situation, it applies more to the
+    // last token of the previous line.
+    for (const FormatToken *Tok = Line->First->Next; Tok; Tok = Tok->Next)
       if (Tok->MustBreakBefore)
         return true;
     return false;

diff  --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index dec0ea72b58ab..942c6259015e9 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -13832,6 +13832,20 @@ TEST_F(FormatTest, PullTrivialFunctionDefinitionsIntoSingleLine) {
             "}",
             format("A()\n:b(0)\n{\n}", NoColumnLimit));
 
+  FormatStyle NoColumnLimitWrapAfterFunction = NoColumnLimit;
+  NoColumnLimitWrapAfterFunction.BreakBeforeBraces = FormatStyle::BS_Custom;
+  NoColumnLimitWrapAfterFunction.BraceWrapping.AfterFunction = true;
+  verifyFormat("class C {\n"
+               "#pragma foo\n"
+               "  int foo { return 0; }\n"
+               "};",
+               NoColumnLimitWrapAfterFunction);
+  verifyFormat("class C {\n"
+               "#pragma foo\n"
+               "  void foo {}\n"
+               "};",
+               NoColumnLimitWrapAfterFunction);
+
   FormatStyle DoNotMergeNoColumnLimit = NoColumnLimit;
   DoNotMergeNoColumnLimit.AllowShortFunctionsOnASingleLine =
       FormatStyle::SFS_None;
@@ -20120,9 +20134,7 @@ TEST_F(FormatTest, WhitesmithsBraceBreaking) {
                "  int i = 5;\n"
                "  }\n"
                "#ifdef _DEBUG\n"
-               "void bar()\n"
-               "  {\n"
-               "  }\n"
+               "void bar() {}\n"
                "#else\n"
                "void bar()\n"
                "  {\n"