[PATCH] D119649: [clang-format] Correctly format loops even if preceded with comments.

[Marek Kurdej via Phabricator via cfe-commits]

curdeius created this revision.
curdeius added reviewers: MyDeveloperDay, HazardyKnusperkeks, owenpan.
curdeius requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Fixes https://github.com/llvm/llvm-project/issues/53758.

Braces in loops with leading (block) comments were formatted according to BraceWrapping.AfterFunction and not AllowShortBlocksOnASingleLine/AllowShortLoopsOnASingleLine.

Previously, the code:

  while (true) {
    f();
  }
  /*comment*/ while (true) {
    f();
  }

was incorrectly formatted to:

  while (true) {
    f();
  }
  /*comment*/ while (true) { f(); }

when using config:

  BasedOnStyle: LLVM
  BreakBeforeBraces: Custom
  BraceWrapping:
    AfterFunction: false
  AllowShortBlocksOnASingleLine: false
  AllowShortLoopsOnASingleLine: false

and it was (correctly but by chance) formatted to:

  while (true) {
    f();
  }
  /*comment*/ while (true) {
    f();
  }

when using enabling brace wrapping after functions:

  BasedOnStyle: LLVM
  BreakBeforeBraces: Custom
  BraceWrapping:
    AfterFunction: true
  AllowShortBlocksOnASingleLine: false
  AllowShortLoopsOnASingleLine: false


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119649

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


Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -1520,6 +1520,22 @@
 
 TEST_F(FormatTest, FormatShortBracedStatements) {
   FormatStyle AllowSimpleBracedStatements = getLLVMStyle();
+  EXPECT_EQ(AllowSimpleBracedStatements.AllowShortBlocksOnASingleLine, false);
+  EXPECT_EQ(AllowSimpleBracedStatements.AllowShortLoopsOnASingleLine, false);
+  EXPECT_EQ(AllowSimpleBracedStatements.BraceWrapping.AfterFunction, false);
+  verifyFormat("for (;;) {\n"
+               "  f();\n"
+               "}");
+  verifyFormat("/*comment*/ for (;;) {\n"
+               "  f();\n"
+               "}");
+  verifyFormat("while (true) {\n"
+               "  f();\n"
+               "}");
+  verifyFormat("/*comment*/ while (true) {\n"
+               "  f();\n"
+               "}");
+
   AllowSimpleBracedStatements.IfMacros.push_back("MYIF");
   // Where line-lengths matter, a 2-letter synonym that maintains line length.
   // Not IF to avoid any confusion that IF is somehow special.
Index: clang/lib/Format/UnwrappedLineFormatter.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineFormatter.cpp
+++ clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -319,6 +319,15 @@
 
     bool MergeShortFunctions = ShouldMergeShortFunctions();
 
+    const FormatToken *FirstNonComment = TheLine->First;
+    if (FirstNonComment->is(tok::comment)) {
+      FirstNonComment = FirstNonComment->getNextNonComment();
+      if (!FirstNonComment)
+        return 0;
+    }
+    // FIXME: There are probably cases where we should use FirstNonComment
+    // instead of TheLine->First.
+
     if (Style.CompactNamespaces) {
       if (auto nsToken = TheLine->First->getNamespaceToken()) {
         int i = 0;
@@ -358,9 +367,9 @@
     if (TheLine->Last->is(TT_FunctionLBrace) && TheLine->First != TheLine->Last)
       return MergeShortFunctions ? tryMergeSimpleBlock(I, E, Limit) : 0;
     // Try to merge a control statement block with left brace unwrapped.
-    if (TheLine->Last->is(tok::l_brace) && TheLine->First != TheLine->Last &&
-        TheLine->First->isOneOf(tok::kw_if, tok::kw_while, tok::kw_for,
-                                TT_ForEachMacro)) {
+    if (TheLine->Last->is(tok::l_brace) && FirstNonComment != TheLine->Last &&
+        FirstNonComment->isOneOf(tok::kw_if, tok::kw_while, tok::kw_for,
+                                 TT_ForEachMacro)) {
       return Style.AllowShortBlocksOnASingleLine != FormatStyle::SBS_Never
                  ? tryMergeSimpleBlock(I, E, Limit)
                  : 0;


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