[clang-format] Add basic support for formatting C# files

Summary:

This revision adds basic support for formatting C# files with clang-format, I know the barrier to entry is high here  so I'm sending this revision in to test the water as to whether this might be something we'd consider landing.

Tracking in Bugzilla as:
https://bugs.llvm.org/show_bug.cgi?id=40850

Justification:
C# code just looks ugly in comparison to the C++ code in our source tree which is clang-formatted.

I've struggled with Visual Studio reformatting to get a clean and consistent style, I want to format our C# code on saving like I do now for C++ and i want it to have the same style as defined in our .clang-format file, so it consistent as it can be with C++.  (Braces/Breaking/Spaces/Indent etc..)

Using clang format without this patch leaves the code in a bad state, sometimes when the BreakStringLiterals is set, it  fails to compile.

Mostly the C# is similar to Java, except instead of JavaAnnotations I try to reuse the TT_AttributeSquare.

Almost the most valuable portion is to have a new Language in order to partition the configuration for C# within a common .clang-format file, with the auto detection on the .cs extension. But there are other C# specific styles that could be added later if this is accepted. in particular how  `{ set;get }` is formatted.

Reviewers: djasper, klimek, krasimir, benhamilton, JonasToth

Reviewed By: klimek

Subscribers: llvm-commits, mgorny, jdoerfert, cfe-commits

Tags: #clang, #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D58404

llvm-svn: 356662

1 files changed, 56 insertions, 1 deletions

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index eeaceb82f9f..ccf5e51576d 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -298,6 +298,8 @@ private:
           CurrentToken->Type = TT_JavaAnnotation;
         if (Left->Previous && Left->Previous->is(TT_LeadingJavaAnnotation))
           CurrentToken->Type = TT_LeadingJavaAnnotation;
+        if (Left->Previous && Left->Previous->is(TT_AttributeSquare))
+          CurrentToken->Type = TT_AttributeSquare;
 
         if (!HasMultipleLines)
           Left->PackingKind = PPK_Inconclusive;
@@ -348,6 +350,40 @@ private:
     return false;
   }
 
+  bool isCSharpAttributeSpecifier(const FormatToken &Tok) {
+    if (!Style.isCSharp())
+      return false;
+
+    const FormatToken *AttrTok = Tok.Next;
+    if (!AttrTok)
+      return false;
+
+    // Just an empty declaration e.g. string [].
+    if (AttrTok->is(tok::r_square))
+      return false;
+
+    // Move along the tokens inbetween the '[' and ']' e.g. [STAThread].
+    while (AttrTok && AttrTok->isNot(tok::r_square)) {
+      AttrTok = AttrTok->Next;
+    }
+
+    if (!AttrTok)
+      return false;
+
+    // Move past the end of ']'.
+    AttrTok = AttrTok->Next;
+    if (!AttrTok)
+      return false;
+
+    // Limit this to being an access modifier that follows.
+    if (AttrTok->isOneOf(tok::kw_public, tok::kw_private, tok::kw_protected,
+                         tok::kw_class, tok::kw_static, tok::l_square,
+                         Keywords.kw_internal)) {
+      return true;
+    }
+    return false;
+  }
+
   bool isCpp11AttributeSpecifier(const FormatToken &Tok) {
     if (!Style.isCpp() || !Tok.startsSequence(tok::l_square, tok::l_square))
       return false;
@@ -398,6 +434,11 @@ private:
     bool IsCpp11AttributeSpecifier = isCpp11AttributeSpecifier(*Left) ||
                                      Contexts.back().InCpp11AttributeSpecifier;
 
+    // Treat C# Attributes [STAThread] much like C++ attributes [[...]].
+    bool IsCSharp11AttributeSpecifier =
+        isCSharpAttributeSpecifier(*Left) ||
+        Contexts.back().InCSharpAttributeSpecifier;
+
     bool InsideInlineASM = Line.startsWith(tok::kw_asm);
     bool StartsObjCMethodExpr =
         !InsideInlineASM && !CppArrayTemplates && Style.isCpp() &&
@@ -478,6 +519,8 @@ private:
                                  // Should only be relevant to JavaScript:
                                  tok::kw_default)) {
         Left->Type = TT_ArrayInitializerLSquare;
+      } else if (IsCSharp11AttributeSpecifier) {
+        Left->Type = TT_AttributeSquare;
       } else {
         BindingIncrease = 10;
         Left->Type = TT_ArraySubscriptLSquare;
@@ -492,11 +535,14 @@ private:
 
     Contexts.back().ColonIsObjCMethodExpr = StartsObjCMethodExpr;
     Contexts.back().InCpp11AttributeSpecifier = IsCpp11AttributeSpecifier;
+    Contexts.back().InCSharpAttributeSpecifier = IsCSharp11AttributeSpecifier;
 
     while (CurrentToken) {
       if (CurrentToken->is(tok::r_square)) {
         if (IsCpp11AttributeSpecifier)
           CurrentToken->Type = TT_AttributeSquare;
+        if (IsCSharp11AttributeSpecifier)
+          CurrentToken->Type = TT_AttributeSquare;
         else if (((CurrentToken->Next &&
                    CurrentToken->Next->is(tok::l_paren)) ||
                   (CurrentToken->Previous &&
@@ -1193,6 +1239,7 @@ private:
     bool CaretFound = false;
     bool IsForEachMacro = false;
     bool InCpp11AttributeSpecifier = false;
+    bool InCSharpAttributeSpecifier = false;
   };
 
   /// Puts a new \c Context onto the stack \c Contexts for the lifetime
@@ -2630,7 +2677,7 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
     // and "%d %d"
     if (Left.is(tok::numeric_constant) && Right.is(tok::percent))
       return Right.WhitespaceRange.getEnd() != Right.WhitespaceRange.getBegin();
-  } else if (Style.Language == FormatStyle::LK_JavaScript) {
+  } else if (Style.Language == FormatStyle::LK_JavaScript || Style.isCSharp()) {
     if (Left.is(TT_JsFatArrow))
       return true;
     // for await ( ...
@@ -2977,6 +3024,14 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
   if (Left.is(TT_ObjCBlockLBrace) && !Style.AllowShortBlocksOnASingleLine)
     return true;
 
+  // Put multiple C# attributes on a new line.
+  if (Style.isCSharp() &&
+      ((Left.is(TT_AttributeSquare) && Left.is(tok::r_square)) ||
+       (Left.is(tok::r_square) && Right.is(TT_AttributeSquare) &&
+        Right.is(tok::l_square))))
+    return true;
+
+  // Put multiple Java annotation on a new line.
   if ((Style.Language == FormatStyle::LK_Java ||
        Style.Language == FormatStyle::LK_JavaScript) &&
       Left.is(TT_LeadingJavaAnnotation) &&