[clang-format] Special handling of spaces for C# code

[jbcoe]

Summary

Ensure that there are spaces around braces '{', '}'.

Ensure that there is a space before and after '=>'.

Ensure that 'async' and 'when' are considered as keywords when inserting spaces.

[krasimir]

As a general comment, we should consider which of these special cases can already be simulated by a combination of existing style options:
https://clang.llvm.org/docs/ClangFormatStyleOptions.html
There are several Spaces* options there that can be used to independently control various spacing around parenthesis.

[krasimir]

clang/lib/Format/TokenAnnotator.cpp

2839

Move this to the already existing } else if (Style.isCSharp()) { on line 2902 below.

[jbcoe]

Treat async and when as keywords.

Consolidate C# space insertion logic.

[jbcoe]

remove commented out code

[krasimir]

clang/unittests/Format/FormatTestCSharp.cpp

584

If these values for these options make sense for Google style in general, consider updating the getGoogleStyle default style with a C#-specific section here:
https://github.com/llvm/llvm-project/blob/master/clang/lib/Format/Format.cpp#L992
I'd recommend doing this in a separate patch based on top of this one.

clang/lib/Format/TokenAnnotator.cpp

if (Right.Type == TT_TrailingAnnotation &&
     // void Fn() const &;
     return Style.PointerAlignment != FormatStyle::PAS_Left;
   return true;
 }
 
 bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
                                          const FormatToken &Right) {
   const FormatToken &Left = *Right.Previous;
+  if (Style.isCSharp()) {
+    // Require spaces around '{' and  before '}' unless they appear in
+    // interpolated strings. Interpolated strings are merged into a single token
+    // so cannot have spaces inserted by this function.
+
+    // Space before {
+    if (Left.isOneOf(tok::identifier, tok::r_paren, tok::r_square,
+                     tok::greater) &&
+        Right.is(tok::l_brace))
+      return true;
+
+    // Spaces inside braces.
+    if (Left.is(tok::l_brace) &&
+        Right.isOneOf(tok::kw_new, tok::identifier, tok::string_literal,
+                      tok::r_paren, tok::l_square, tok::numeric_constant,
+                      tok::kw_true, tok::kw_false, tok::kw_typeof))
+      return true;
+    if (Left.isOneOf(tok::identifier, tok::string_literal, tok::r_paren,
+                     tok::r_square, tok::numeric_constant, tok::kw_true,
+                     tok::kw_false) &&
+        Right.is(tok::r_brace))
+      return true;
+
+    // Spaces around '=>'.
+    if (Left.is(TT_JsFatArrow) || Right.is(TT_JsFatArrow))
+      return true;
+    // No space between identifier and '['.
+    if (Left.is(tok::identifier) && Right.is(tok::l_square))
+      return false;
+  }
   if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
     return true; // Never ever merge two identifiers.
   if (Style.isCpp()) {
     if (Left.is(tok::kw_operator))
       return Right.is(tok::coloncolon);
     if (Right.is(tok::l_brace) && Right.BlockKind == BK_BracedInit &&
         !Left.opensScope() && Style.SpaceBeforeCpp11BracedList)
       return true;

clang/unittests/Format/FormatTestCSharp.cpp

new Square {
         Side = 101.1,
         Colour = Colours.Yellow,
     },
 };)",
                Style);
 
   // Omitted final `,`s will change the formatting.
   verifyFormat(R"(//
-Shape[] shapes = new[] {new Circle {Radius = 2.7281, Colour = Colours.Red},
+Shape[] shapes = new[] { new Circle { Radius = 2.7281, Colour = Colours.Red },
                          new Square {
                              Side = 101.1,
                              Colour = Colours.Yellow,
                          }};)",
                Style);
 }
 
 TEST_F(FormatTestCSharp, CSharpNamedArguments) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
 
   verifyFormat(R"(//
 PrintOrderDetails(orderNum: 31, productName: "Red Mug",
TEST_F(FormatTestCSharp, CSharpPropertyAccessors) {
   verifyFormat(R"(//
 public string Name {
   get => _name;
   set => _name = value;
 })",
                Style);
 }
 
+TEST_F(FormatTestCSharp, CSharpSpaces) {
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
+
+  verifyFormat(R"(new Car { "Door", 0.1 })", Style);
+  verifyFormat(R"(new Car { 0.1, "Door" })", Style);
+  verifyFormat(R"(new string[] { "A" })", Style);
+  verifyFormat(R"(new string[] {})", Style);
+  verifyFormat(R"(new Car { someVariableName })", Style);
+  verifyFormat(R"(new Car { someVariableName })", Style);
+  verifyFormat(R"(new Dictionary<string, string> { ["Key"] = "Value" };)",
+               Style);
+  verifyFormat(R"(Apply(x => x.Name, x => () => x.ID);)", Style);
+  verifyFormat(R"(bool[] xs = { true, true };)", Style);
+}
+
 } // namespace format
 } // end namespace clang