[clang-format] [C++20] [Module] clang-format couldn't recognize partitions

https://bugs.llvm.org/show_bug.cgi?id=52517

clang-format is butchering modules, this could easily become a barrier to entry for modules given clang-formats wide spread use.

Prevent the following from adding spaces around the  `:`  (cf was considering the ':' as an InheritanceColon)

Reviewed By: HazardyKnusperkeks, owenpan, ChuanqiXu

Differential Revision: https://reviews.llvm.org/D114151

clang/docs/ReleaseNotes.rst

@@ -265,6 +265,8 @@ clang-format
   space before parentheses. The custom options can be set using
   ``SpaceBeforeParensOptions``.
 
+- Improved Cpp20 Modules support.
+
 libclang
 --------
 

clang/lib/Format/FormatToken.h

@@ -76,6 +76,7 @@ namespace format {
   TYPE(LineComment)                                                            \
   TYPE(MacroBlockBegin)                                                        \
   TYPE(MacroBlockEnd)                                                          \
+  TYPE(ModulePartitionColon)                                                   \
   TYPE(NamespaceMacro)                                                         \
   TYPE(NonNullAssertion)                                                       \
   TYPE(NullCoalescingEqual)                                                    \

clang/lib/Format/TokenAnnotator.cpp

@@ -903,9 +903,13 @@ private:
           break;
         }
       }
-      if (Contexts.back().ColonIsDictLiteral ||
-          Style.Language == FormatStyle::LK_Proto ||
-          Style.Language == FormatStyle::LK_TextProto) {
+      if (Line.First->isOneOf(Keywords.kw_module, Keywords.kw_import) ||
+          Line.First->startsSequence(tok::kw_export, Keywords.kw_module) ||
+          Line.First->startsSequence(tok::kw_export, Keywords.kw_import)) {
+        Tok->setType(TT_ModulePartitionColon);
+      } else if (Contexts.back().ColonIsDictLiteral ||
+                 Style.Language == FormatStyle::LK_Proto ||
+                 Style.Language == FormatStyle::LK_TextProto) {
         Tok->setType(TT_DictLiteral);
         if (Style.Language == FormatStyle::LK_TextProto) {
           if (FormatToken *Previous = Tok->getPreviousNonComment())
@@ -3244,6 +3248,7 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
   auto HasExistingWhitespace = [&Right]() {
     return Right.WhitespaceRange.getBegin() != Right.WhitespaceRange.getEnd();
   };
+
   if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
     return true; // Never ever merge two identifiers.
 
@@ -3253,6 +3258,25 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
     return true;
 
   if (Style.isCpp()) {
+    // Space between import <iostream>.
+    // or import .....;
+    if (Left.is(Keywords.kw_import) && Right.isOneOf(tok::less, tok::ellipsis))
+      return true;
+    // No space between module :.
+    if (Left.isOneOf(Keywords.kw_module, Keywords.kw_import) &&
+        Right.is(TT_ModulePartitionColon))
+      return true;
+    // No space between import foo:bar but keep a space between import :bar;
+    if (Left.is(tok::identifier) && Right.is(TT_ModulePartitionColon))
+      return false;
+    // No space between :bar;
+    if (Left.is(TT_ModulePartitionColon) &&
+        Right.isOneOf(tok::identifier, tok::kw_private))
+      return false;
+    if (Left.is(tok::ellipsis) && Right.is(tok::identifier) &&
+        Line.First->is(Keywords.kw_import))
+      return false;
+
     if (Left.is(tok::kw_operator))
       return Right.is(tok::coloncolon);
     if (Right.is(tok::l_brace) && Right.is(BK_BracedInit) &&

clang/lib/Format/UnwrappedLineParser.cpp

@@ -1114,6 +1114,35 @@ static bool isC78ParameterDecl(const FormatToken *Tok, const FormatToken *Next,
   return Tok->Previous && Tok->Previous->isOneOf(tok::l_paren, tok::comma);
 }
 
+void UnwrappedLineParser::parseModuleImport() {
+  nextToken();
+  while (!eof()) {
+    if (FormatTok->is(tok::colon)) {
+      FormatTok->setType(TT_ModulePartitionColon);
+    }
+    // Handle import <foo/bar.h> as we would an include statement.
+    else if (FormatTok->is(tok::less)) {
+      nextToken();
+      while (!FormatTok->isOneOf(tok::semi, tok::greater, tok::eof)) {
+        // Mark tokens up to the trailing line comments as implicit string
+        // literals.
+        if (FormatTok->isNot(tok::comment) &&
+            !FormatTok->TokenText.startswith("//"))
+          FormatTok->setType(TT_ImplicitStringLiteral);
+        nextToken();
+      }
+    }
+    if (FormatTok->is(tok::semi)) {
+      nextToken();
+      break;
+    }
+    nextToken();
+  }
+
+  addUnwrappedLine();
+  return;
+}
+
 // readTokenWithJavaScriptASI reads the next token and terminates the current
 // line if JavaScript Automatic Semicolon Insertion must
 // happen between the current token and the next token.
@@ -1312,6 +1341,10 @@ void UnwrappedLineParser::parseStructuralElement(bool IsTopLevel) {
         addUnwrappedLine();
         return;
       }
+      if (Style.isCpp()) {
+        parseModuleImport();
+        return;
+      }
     }
     if (Style.isCpp() &&
         FormatTok->isOneOf(Keywords.kw_signals, Keywords.kw_qsignals,

clang/lib/Format/UnwrappedLineParser.h

@@ -110,6 +110,7 @@ private:
   void parseCaseLabel();
   void parseSwitch();
   void parseNamespace();
+  void parseModuleImport();
   void parseNew();
   void parseAccessSpecifier();
   bool parseEnum();

clang/unittests/Format/FormatTest.cpp

@@ -22616,6 +22616,71 @@ TEST_F(FormatTest, FormatDecayCopy) {
   verifyFormat("auto(*p)() = f;");       // actually a declaration; TODO FIXME
 }
 
+TEST_F(FormatTest, Cpp20ModulesSupport) {
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Never;
+  Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_None;
+
+  verifyFormat("export import foo;", Style);
+  verifyFormat("export import foo:bar;", Style);
+  verifyFormat("export import foo.bar;", Style);
+  verifyFormat("export import foo.bar:baz;", Style);
+  verifyFormat("export import :bar;", Style);
+  verifyFormat("export module foo:bar;", Style);
+  verifyFormat("export module foo;", Style);
+  verifyFormat("export module foo.bar;", Style);
+  verifyFormat("export module foo.bar:baz;", Style);
+  verifyFormat("export import <string_view>;", Style);
+
+  verifyFormat("export type_name var;", Style);
+  verifyFormat("template <class T> export using A = B<T>;", Style);
+  verifyFormat("export using A = B;", Style);
+  verifyFormat("export int func() {\n"
+               "  foo();\n"
+               "}",
+               Style);
+  verifyFormat("export struct {\n"
+               "  int foo;\n"
+               "};",
+               Style);
+  verifyFormat("export {\n"
+               "  int foo;\n"
+               "};",
+               Style);
+  verifyFormat("export export char const *hello() { return \"hello\"; }");
+
+  verifyFormat("import bar;", Style);
+  verifyFormat("import foo.bar;", Style);
+  verifyFormat("import foo:bar;", Style);
+  verifyFormat("import :bar;", Style);
+  verifyFormat("import <ctime>;", Style);
+  verifyFormat("import \"header\";", Style);
+
+  verifyFormat("module foo;", Style);
+  verifyFormat("module foo:bar;", Style);
+  verifyFormat("module foo.bar;", Style);
+  verifyFormat("module;", Style);
+
+  verifyFormat("export namespace hi {\n"
+               "const char *sayhi();\n"
+               "}",
+               Style);
+
+  verifyFormat("module :private;", Style);
+  verifyFormat("import <foo/bar.h>;", Style);
+  verifyFormat("import foo...bar;", Style);
+  verifyFormat("import ..........;", Style);
+  verifyFormat("module foo:private;", Style);
+  verifyFormat("import a", Style);
+  verifyFormat("module a", Style);
+  verifyFormat("export import a", Style);
+  verifyFormat("export module a", Style);
+
+  verifyFormat("import", Style);
+  verifyFormat("module", Style);
+  verifyFormat("export", Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang