Add new clang-format alignment option

[philbert]

Summary

I work on a code base that aligns all declarations execpt parameters to
functions. This patch adds a new option to AlignConsecutiveDeclarations.

TODO I need to add unit-tests for this option but this would be really useful for me
but given its a new option I have not done this yet just to get feedback whether this
option would get accepted or not.

[MyDeveloperDay]

Please add the unit tests

[MyDeveloperDay]

Can you please do a full context diff see (https://llvm.org/docs/Contributing.html)

clang/include/clang/Format/Format.h

225

Ok you have to give us the example at least

[MyDeveloperDay]

please point to a github issue which outlines what you are fixing and why

clang/lib/Format/Format.cpp

35

why moving?

[MyDeveloperDay]

" just to get feedback whether this
option would get accepted or not."

Honestly I can't tell from the code what problem you are trying to fix. The github issue and unit tests are vital for us to understand what you are trying to achieve (and to ensure you are not breaking anything)

clang/include/clang/Format/Format.h

     ///   bbb = 2;
     /// \endcode
     bool AlignCompound;
+    // TODO
+    bool AcrossParameterDeclarations;
     /// Only for ``AlignConsecutiveAssignments``.  Whether short assignment
     /// operators are left-padded to the same length as long ones in order to
     /// put all assignment operators to the right of the left hand side.

clang/lib/Format/Format.cpp

 ///
 //===----------------------------------------------------------------------===//
 
-#include "clang/Format/Format.h"
 #include "AffectedRangeManager.h"
 #include "BreakableToken.h"
 #include "ContinuationIndenter.h"

 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Basic/SourceManager.h"
+#include "clang/Format/Format.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Tooling/Inclusions/HeaderIncludes.h"
 #include "llvm/ADT/STLExtras.h"

                 FormatStyle::AlignConsecutiveStyle(
                     {/*Enabled=*/false, /*AcrossEmptyLines=*/false,
                      /*AcrossComments=*/false, /*AlignCompound=*/false,
+                     /*AcrossParameterDeclarations*/ true,
                      /*PadOperators=*/true}));
     IO.enumCase(Value, "Consecutive",
                 FormatStyle::AlignConsecutiveStyle(
                     {/*Enabled=*/true, /*AcrossEmptyLines=*/false,
                      /*AcrossComments=*/false, /*AlignCompound=*/false,
+                     /*AcrossParameterDeclarations*/ true,
                      /*PadOperators=*/true}));
     IO.enumCase(Value, "AcrossEmptyLines",
                 FormatStyle::AlignConsecutiveStyle(
                     {/*Enabled=*/true, /*AcrossEmptyLines=*/true,
                      /*AcrossComments=*/false, /*AlignCompound=*/false,
+                     /*AcrossParameterDeclarations*/ true,
                      /*PadOperators=*/true}));
     IO.enumCase(Value, "AcrossComments",
-                FormatStyle::AlignConsecutiveStyle({/*Enabled=*/true,
-                                                    /*AcrossEmptyLines=*/false,
-                                                    /*AcrossComments=*/true,
-                                                    /*AlignCompound=*/false,
-                                                    /*PadOperators=*/true}));
+                FormatStyle::AlignConsecutiveStyle(
+                    {/*Enabled=*/true,
+                     /*AcrossEmptyLines=*/false,
+                     /*AcrossComments=*/true,
+                     /*AlignCompound=*/false,
+                     /*AcrossParameterDeclarations*/ true,
+                     /*PadOperators=*/true}));
     IO.enumCase(Value, "AcrossEmptyLinesAndComments",
-                FormatStyle::AlignConsecutiveStyle({/*Enabled=*/true,
-                                                    /*AcrossEmptyLines=*/true,
-                                                    /*AcrossComments=*/true,
-                                                    /*AlignCompound=*/false,
-                                                    /*PadOperators=*/true}));
+                FormatStyle::AlignConsecutiveStyle(
+                    {/*Enabled=*/true,
+                     /*AcrossEmptyLines=*/true,
+                     /*AcrossComments=*/true,
+                     /*AlignCompound=*/false,
+                     /*AcrossParameterDeclarations*/ true,
+                     /*PadOperators=*/true}));
+    IO.enumCase(Value, "ConsecutiveMinusParameterDeclarations",
+                FormatStyle::AlignConsecutiveStyle(
+                    {/*Enabled=*/true,
+                     /*AcrossEmptyLines=*/false,
+                     /*AcrossComments=*/false,
+                     /*AlignCompound=*/false,
+                     /*AcrossParameterDeclarations*/ false,
+                     /*PadOperators=*/true}));
 
     // For backward compatibility.
     IO.enumCase(Value, "true",

clang/lib/Format/WhitespaceManager.cpp

 
   AlignTokens(
       Style,
-      [](Change const &C) {
+      [&](Change const &C) {
         if (C.Tok->is(TT_FunctionDeclarationName))
           return true;
         if (C.Tok->isNot(TT_StartOfName))

         if (C.Tok->Previous &&
             C.Tok->Previous->is(TT_StatementAttributeLikeMacro))
           return false;
+
+        if (C.Tok->is(TT_StartOfName)) {
+          bool isParam = C.Tok->Next && C.Tok->Next->is(clang::tok::comma);
+          bool shouldAlignParams =
+              Style.AlignConsecutiveDeclarations.AcrossParameterDeclarations;
+          if (isParam && !shouldAlignParams)
+            return false;
+        }
+
         // Check if there is a subsequent name that starts the same declaration.
         for (FormatToken *Next = C.Tok->Next; Next; Next = Next->Next) {
           if (Next->is(tok::comment))