[Diagnostics] Provide category name + documentation path

Bridge the category name and educational note computed for the Swift
compiler's diagnostics to the newly-introduced category field for
the swift-syntax diagnostics. This lets the swift-syntax renderer
introduce the category name and (optionally) link to the
documentation.

Author: DougGregor

include/swift/Bridging/ASTGen.h

@@ -28,6 +28,9 @@ void swift_ASTGen_addQueuedSourceFile(
 void swift_ASTGen_addQueuedDiagnostic(
     void *_Nonnull queued, const char *_Nonnull text, ptrdiff_t textLength,
     BridgedDiagnosticSeverity severity, const void *_Nullable sourceLoc,
+    const char *_Nullable categoryName, ptrdiff_t categoryNameLength,
+    const char *_Nullable documentationPath,
+    ptrdiff_t documentationPathLength,
     const void *_Nullable *_Nullable highlightRanges,
     ptrdiff_t numHighlightRanges);
 void swift_ASTGen_renderQueuedDiagnostics(

lib/AST/DiagnosticBridge.cpp

@@ -64,9 +64,17 @@ static void addQueueDiagnostic(void *queuedDiagnostics,
     highlightRanges.push_back(range.getEnd().getOpaquePointerValue());
   }
 
+  StringRef documentationPath;
+  if (info.EducationalNotePaths.size() > 0)
+    documentationPath = info.EducationalNotePaths[0];
+
   // FIXME: Translate Fix-Its.
   swift_ASTGen_addQueuedDiagnostic(queuedDiagnostics, text.data(), text.size(),
                                    severity, info.Loc.getOpaquePointerValue(),
+                                   info.Category.data(),
+                                   info.Category.size(),
+                                   documentationPath.data(),
+                                   documentationPath.size(),
                                    highlightRanges.data(),
                                    highlightRanges.size() / 2);
 }

lib/ASTGen/Sources/ASTGen/DiagnosticsBridge.swift

@@ -165,6 +165,8 @@ fileprivate struct SimpleDiagnostic: DiagnosticMessage {
 
   let severity: DiagnosticSeverity
 
+  let category: DiagnosticCategory?
+
   var diagnosticID: MessageID {
     .init(domain: "SwiftCompiler", id: "SimpleDiagnostic")
   }
@@ -237,6 +239,10 @@ public func addQueuedDiagnostic(
   textLength: Int,
   severity: BridgedDiagnosticSeverity,
   cLoc: BridgedSourceLoc,
+  categoryName: UnsafePointer<UInt8>?,
+  categoryLength: Int,
+  documentationPath: UnsafePointer<UInt8>?,
+  documentationPathLength: Int,
   highlightRangesPtr: UnsafePointer<BridgedSourceLoc>?,
   numHighlightRanges: Int
 ) {
@@ -333,13 +339,35 @@ public func addQueuedDiagnostic(
     }
   }
 
+  let category: DiagnosticCategory? = categoryName.map { categoryNamePtr in
+    let categoryNameBuffer = UnsafeBufferPointer(
+      start: categoryNamePtr,
+      count: categoryLength
+    )
+    let categoryName = String(decoding: categoryNameBuffer, as: UTF8.self)
+
+    let documentationPath = documentationPath.map { documentationPathPtr in
+      let documentationPathBuffer = UnsafeBufferPointer(
+        start: documentationPathPtr,
+        count: documentationPathLength
+      )
+      return String(decoding: documentationPathBuffer, as: UTF8.self)
+    }
+
+    return DiagnosticCategory(
+      name: categoryName,
+      documentationPath: documentationPath
+    )
+  }
+
   let textBuffer = UnsafeBufferPointer(start: text, count: textLength)
   let diagnostic = Diagnostic(
     node: node,
     position: position,
     message: SimpleDiagnostic(
       message: String(decoding: textBuffer, as: UTF8.self),
-      severity: severity.asSeverity
+      severity: severity.asSeverity,
+      category: category
     ),
     highlights: highlights
   )