[clang] [clang-format] add option to control bin-packing keyworded parameters (PR #131605)

[via cfe-commits]

owenca wrote:

> As to the implementation, it can be simplified and probably made less brittle. I would do something like the following instead:
> 
> * Name the option as `AllowBreakBeforeQtProperty`.
> * Use `Q_PROPERTY` for a new context `Context::QtProperty`. (See `_Generic` and `Context::C11GenericSelection`.)
> * Either use all-uppercase identifiers as the criterion or binary-search in a sorted table of all Qt property keywords (`READ`, `WRITE`, etc.) similar to `CppNonKeywordTypes` in FormatToken.cpp.
> * Set the token type of those keywords to `TT_QtProperty`.

When I said the above in https://github.com/llvm/llvm-project/pull/131605#issuecomment-2774441914, I had the following in mind:
```diff
diff --git a/clang/lib/Format/FormatToken.cpp b/clang/lib/Format/FormatToken.cpp
@@ -34,6 +34,17 @@ const char *getTokenTypeName(TokenType Type) {
   return nullptr;
 }
 
+static SmallVector<StringRef> QtPropertyKeywords = {
+    "BINDABLE",   "CONSTANT", "DESIGNABLE", "FINAL", "MEMBER",
+    "NOTIFY",     "READ",     "REQUIRED",   "RESET", "REVISION",
+    "SCRIPTABLE", "STORED",   "USER",       "WRITE",
+};
+
+bool FormatToken::isQtProperty() const {
+  return std::binary_search(QtPropertyKeywords.begin(),
+                            QtPropertyKeywords.end(), TokenText);
+}
+
 // Sorted common C++ non-keyword types.
 static SmallVector<StringRef> CppNonKeywordTypes = {
     "clock_t",  "int16_t",   "int32_t", "int64_t",   "int8_t",
@@ -331,6 +342,8 @@ bool startsNextParameter(const FormatToken &Current, const FormatStyle &Style) {
   }
   if (Style.Language == FormatStyle::LK_Proto && Current.is(TT_SelectorName))
     return true;
+  if (Current.is(TT_QtProperty))
+    return true;
   return Previous.is(tok::comma) && !Current.isTrailingComment() &&
          ((Previous.isNot(TT_CtorInitializerComma) ||
            Style.BreakConstructorInitializers !=
diff --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
@@ -135,6 +135,7 @@ namespace format {
   TYPE(PointerOrReference)                                                     \
   TYPE(ProtoExtensionLSquare)                                                  \
   TYPE(PureVirtualSpecifier)                                                   \
+  TYPE(QtProperty)                                                             \
   TYPE(RangeBasedForLoopColon)                                                 \
   TYPE(RecordLBrace)                                                           \
   TYPE(RecordRBrace)                                                           \
@@ -703,6 +704,7 @@ public:
            isAttribute();
   }
 
+  [[nodiscard]] bool isQtProperty() const;
   [[nodiscard]] bool isTypeName(const LangOptions &LangOpts) const;
   [[nodiscard]] bool isTypeOrIdentifier(const LangOptions &LangOpts) const;
 
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
@@ -390,6 +390,10 @@ private:
                OpeningParen.Previous->is(tok::kw__Generic)) {
       Contexts.back().ContextType = Context::C11GenericSelection;
       Contexts.back().IsExpression = true;
+    } else if (OpeningParen.Previous &&
+               OpeningParen.Previous->TokenText == "Q_PROPERTY") {
+      Contexts.back().ContextType = Context::QtProperty;
+      Contexts.back().IsExpression = false;
     } else if (Line.InPPDirective &&
                (!OpeningParen.Previous ||
                 OpeningParen.Previous->isNot(tok::identifier))) {
@@ -1811,6 +1815,11 @@ private:
             return false;
         }
       }
+      if (Style.AllowBreakBeforeQtProperty &&
+          Contexts.back().ContextType == Context::QtProperty &&
+          Tok->isQtProperty()) {
+        Tok->setFinalizedType(TT_QtProperty);
+      }
       break;
     case tok::arrow:
       if (Tok->isNot(TT_LambdaArrow) && Tok->Previous &&
@@ -2179,6 +2188,7 @@ private:
       TemplateArgument,
       // C11 _Generic selection.
       C11GenericSelection,
+      QtProperty,
       // Like in the outer parentheses in `ffnand ff1(.q());`.
       VerilogInstancePortList,
     } ContextType = Unknown;
@@ -6235,7 +6245,7 @@ bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
               Right.Next->isOneOf(TT_FunctionDeclarationName, tok::kw_const)));
   }
   if (Right.isOneOf(TT_StartOfName, TT_FunctionDeclarationName,
-                    TT_ClassHeadName, tok::kw_operator)) {
+                    TT_ClassHeadName, TT_QtProperty, tok::kw_operator)) {
     return true;
   }
   if (Right.isAttribute())
```

https://github.com/llvm/llvm-project/pull/131605