[Diagnostics] Record diagnostic groups in serialized diagnostics

The serialized diagnostic format has some extra fields that we can
adopt for diagnostic groups. Specifically:
* Category: store the diagnostic group name here
* Flags: extend the hack used by educational notes of placing Markdown file paths here

Author: DougGregor

include/swift/AST/DiagnosticGroups.h

@@ -41,7 +41,7 @@ constexpr const auto DiagGroupsCount = [] {
 struct DiagGroupInfo {
   DiagGroupID id;
   std::string_view name;
-  std::string_view version;
+  std::string_view documentationFile;
   llvm::ArrayRef<DiagGroupID> supergroups;
   llvm::ArrayRef<DiagGroupID> subgroups;
   llvm::ArrayRef<DiagID> diagnostics;

lib/AST/DiagnosticEngine.cpp

@@ -1330,13 +1330,16 @@ DiagnosticEngine::diagnosticInfoForDiagnostic(const Diagnostic &diagnostic,
     }
   }
 
+  auto groupID = diagnostic.getGroupID();
   StringRef Category;
   if (isAPIDigesterBreakageDiagnostic(diagnostic.getID()))
     Category = "api-digester-breaking-change";
   else if (isDeprecationDiagnostic(diagnostic.getID()))
     Category = "deprecation";
   else if (isNoUsageDiagnostic(diagnostic.getID()))
     Category = "no-usage";
+  else if (groupID != DiagGroupID::no_group)
+    Category = getDiagGroupInfoByID(groupID).name;
 
   auto fixIts = diagnostic.getFixIts();
   if (loc.isValid()) {
@@ -1362,12 +1365,13 @@ DiagnosticEngine::diagnosticInfoForDiagnostic(const Diagnostic &diagnostic,
   }
 
   llvm::StringRef format;
-  if (includeDiagnosticName)
+  if (includeDiagnosticName) {
     format =
-        diagnosticStringWithNameFor(diagnostic.getID(), diagnostic.getGroupID(),
+        diagnosticStringWithNameFor(diagnostic.getID(), groupID,
                                     getPrintDiagnosticNamesMode());
-  else
+  } else {
     format = diagnosticStringFor(diagnostic.getID());
+  }
 
   return DiagnosticInfo(diagnostic.getID(), loc, toDiagnosticKind(behavior),
                         format, diagnostic.getArgs(), Category,
@@ -1523,6 +1527,18 @@ void DiagnosticEngine::emitDiagnostic(const Diagnostic &diagnostic) {
       educationalNotePaths.push_back(notePath.str().str());
       ++associatedNotes;
     }
+
+    // Capture information about the diagnostic group along with the remaining
+    // educational notes.
+    auto groupID = diagnostic.getGroupID();
+    if (groupID != DiagGroupID::no_group) {
+      const auto &diagGroup = getDiagGroupInfoByID(groupID);
+
+      SmallString<128> docPath(getDiagnosticDocumentationPath());
+      llvm::sys::path::append(docPath, diagGroup.documentationFile);
+      educationalNotePaths.push_back(docPath.str().str());
+    }
+
     info->EducationalNotePaths = educationalNotePaths;
 
     for (auto &consumer : Consumers) {

lib/AST/DiagnosticGroups.cpp

@@ -68,7 +68,7 @@ constexpr const auto diagnosticGroupConnections = [] {
   constexpr auto diagnosticsCount = std::get<2>(sizes);
 
   // Declare all edges
-#define GROUP(Name, Version)                                              \
+#define GROUP(Name, DocsFile)                                                  \
   std::array<DiagGroupID, supergroupsCount[(size_t)DiagGroupID::Name]>         \
       Name##_supergroups{};                                                    \
   std::array<DiagGroupID, subgroupsCount[(size_t)DiagGroupID::Name]>           \
@@ -92,15 +92,15 @@ constexpr const auto diagnosticGroupConnections = [] {
 #include "swift/AST/DiagnosticsAll.def"
 
   // Produce the resulting structure with all the edges
-#define GROUP(Name, Version)                                              \
+#define GROUP(Name, DocsFile)                                              \
   GroupConnections(Name##_supergroups, Name##_subgroups, Name##_diagnostics),
   return std::tuple{
 #include "swift/AST/DiagnosticGroups.def"
   };
 }();
 
 std::unordered_map<std::string_view, DiagGroupID> nameToIDMap{
-#define GROUP(Name, Version) {#Name, DiagGroupID::Name},
+#define GROUP(Name, DocsFile) {#Name, DiagGroupID::Name},
 #include "swift/AST/DiagnosticGroups.def"
 };
 
@@ -119,11 +119,11 @@ void traverseDepthFirst(DiagGroupID id,
 } // end anonymous namespace
 
 constexpr const std::array<DiagGroupInfo, DiagGroupsCount> diagnosticGroupsInfo{
-#define GROUP(Name, Version)                                              \
+#define GROUP(Name, DocsFile)                                              \
   DiagGroupInfo{                                                               \
       DiagGroupID::Name,                                                       \
       #Name,                                                                   \
-      #Version,                                                                \
+      DocsFile,                                                                \
       llvm::ArrayRef<DiagGroupID>(                                             \
           std::get<(size_t)DiagGroupID::Name>(diagnosticGroupConnections)      \
               .supergroups),                                                   \

test/diagnostics/diagnostic-group-serialization.swift

@@ -0,0 +1,23 @@
+// %target-swift-frontend -no-color-diagnostics -print-diagnostic-groups -diagnostic-documentation-path %S/test-docs/ -typecheck %s -strict-memory-safety
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -no-color-diagnostics -print-diagnostic-groups -diagnostic-documentation-path %S/test-docs/ -serialize-diagnostics-path %t/serialized.dia %s -strict-memory-safety
+// RUN: c-index-test -read-diagnostics %t/serialized.dia > %t/serialized.txt 2>&1
+// RUN: %FileCheck %s < %t/serialized.txt
+
+@available(*, deprecated, message: "please do not use")
+func f() { }
+
+func g() {
+  f()
+// CHECK: [[@LINE-1]]:3: warning: 'f()' is deprecated: please do not use [DeprecatedDeclaration] [-W{{.*}}deprecated-declaration.md] [deprecation]
+}
+
+
+@unsafe
+func beCareful() { }
+
+func test() {
+  beCareful()
+// CHECK: [[@LINE-1]]:3: warning: expression uses unsafe constructs but is not marked with 'unsafe' [StrictMemorySafety] [-W{{.*}}strict-memory-safety.md] [StrictMemorySafety]
+}