Add Children section to SyntaxCollection nodes

Author: ahoppen

CodeGeneration/Sources/SyntaxSupport/Node.swift

@@ -270,4 +270,21 @@ public struct CollectionNode {
       return choices
     }
   }
+
+  public var grammar: SwiftSyntax.Trivia {
+    let grammar: String
+    if let onlyElement = elementChoices.only {
+      grammar = "``\(onlyElement.syntaxType)``*"
+    } else {
+      grammar = "(\(elementChoices.map { "``\($0.syntaxType)``" }.joined(separator: " | "))) `*`"
+    }
+
+    return docCommentTrivia(
+      from: """
+        ### Children
+
+        \(grammar)
+        """
+    )
+  }
 }

CodeGeneration/Sources/SyntaxSupport/Utils.swift

@@ -54,3 +54,14 @@ public func docCommentTrivia(from string: String?) -> SwiftSyntax.Trivia {
   }
   return SwiftSyntax.Trivia(pieces: pieces)
 }
+
+public extension Collection {
+  /// If the collection contains a single element, return it, otherwise `nil`.
+  var only: Element? {
+    if !isEmpty && index(after: startIndex) == endIndex {
+      return self.first!
+    } else {
+      return nil
+    }
+  }
+}

CodeGeneration/Sources/Utils/Utils.swift

@@ -35,14 +35,3 @@ public func removedEmptyLines(string: String) -> String {
     .filter { !$0.allSatisfy(\.isWhitespace) }
     .joined(separator: "\n")
 }
-
-public extension Collection {
-  /// If the collection contains a single element, return it, otherwise `nil`.
-  var only: Element? {
-    if !isEmpty && index(after: startIndex) == endIndex {
-      return self.first!
-    } else {
-      return nil
-    }
-  }
-}

CodeGeneration/Sources/generate-swiftsyntax/templates/swiftsyntax/SyntaxCollectionsFile.swift

@@ -20,7 +20,9 @@ let syntaxCollectionsFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
     try! StructDeclSyntax(
       """
       \(raw: node.documentation)
-      public struct \(raw: node.kind.syntaxType): SyntaxCollection, SyntaxHashable
+      \(raw: node.documentation.isEmpty ? "" : "///")
+      \(raw: node.grammar)
+      public struct \(node.kind.syntaxType): SyntaxCollection, SyntaxHashable
       """
     ) {
       if let onlyElement = node.elementChoices.only {