Add support for Doxygen abstract tag

Sources/Markdown/Base/Markup.swift

@@ -75,6 +75,8 @@ func makeMarkup(_ data: _MarkupData) -> Markup {
         return DoxygenDiscussion(data)
     case .doxygenNote:
         return DoxygenNote(data)
+    case .doxygenAbstract:
+        return DoxygenAbstract(data)
     case .doxygenParam:
         return DoxygenParameter(data)
     case .doxygenReturns:

Sources/Markdown/Base/RawMarkup.swift

@@ -54,6 +54,7 @@ enum RawMarkupData: Equatable {
 
     case doxygenDiscussion
     case doxygenNote
+    case doxygenAbstract
     case doxygenParam(name: String)
     case doxygenReturns
 }
@@ -352,6 +353,10 @@ final class RawMarkup: ManagedBuffer<RawMarkupHeader, RawMarkup> {
         return .create(data: .doxygenNote, parsedRange: parsedRange, children: children)
     }
 
+    static func doxygenAbstract(parsedRange: SourceRange?, _ children: [RawMarkup]) -> RawMarkup {
+        return .create(data: .doxygenAbstract, parsedRange: parsedRange, children: children)
+    }
+
     static func doxygenParam(name: String, parsedRange: SourceRange?, _ children: [RawMarkup]) -> RawMarkup {
         return .create(data: .doxygenParam(name: name), parsedRange: parsedRange, children: children)
     }

Sources/Markdown/Block Nodes/Block Container Blocks/Doxygen Commands/DoxygenAbstract.swift

@@ -0,0 +1,57 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2025 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+ See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+import Foundation
+
+/// A parsed Doxygen `\abstract` command.
+///
+/// The Doxygen support in Swift-Markdown parses `\abstract` commands of the form
+/// `\abstract description`, where `description` continues until the next blank
+/// line or parsed command.
+///
+/// ```markdown
+/// \abstract This object can give other objects in your program magical powers.
+/// ```
+public struct DoxygenAbstract: BlockContainer {
+    public var _data: _MarkupData
+
+    init(_ raw: RawMarkup) throws {
+        guard case .doxygenAbstract = raw.data else {
+            throw RawMarkup.Error.concreteConversionError(from: raw, to: DoxygenAbstract.self)
+        }
+        let absoluteRaw = AbsoluteRawMarkup(markup: raw, metadata: MarkupMetadata(id: .newRoot(), indexInParent: 0))
+        self.init(_MarkupData(absoluteRaw))
+    }
+
+    init(_ data: _MarkupData) {
+        self._data = data
+    }
+
+    public func accept<V: MarkupVisitor>(_ visitor: inout V) -> V.Result {
+        return visitor.visitDoxygenAbstract(self)
+    }
+}
+
+public extension DoxygenAbstract {
+    /// Create a new Doxygen abstract definition.
+    ///
+    /// - Parameter children: Block child elements.
+    init<Children: Sequence>(children: Children) where Children.Element == BlockMarkup {
+        try! self.init(.doxygenAbstract(parsedRange: nil, children.map({ $0.raw.markup })))
+    }
+
+    /// Create a new Doxygen abstract definition.
+    ///
+    /// - Parameter children: Block child elements.
+    init(children: BlockMarkup...) {
+        self.init(children: children)
+    }
+}
+

Sources/Markdown/CMakeLists.txt

@@ -19,6 +19,7 @@ add_library(Markdown
   Base/RawMarkup.swift
   "Block Nodes/Block Container Blocks/Doxygen Commands/DoxygenDiscussion.swift"
   "Block Nodes/Block Container Blocks/Doxygen Commands/DoxygenNote.swift"
+  "Block Nodes/Block Container Blocks/Doxygen Commands/DoxygenAbstract.swift"
   "Block Nodes/Block Container Blocks/Doxygen Commands/DoxygenParameter.swift"
   "Block Nodes/Block Container Blocks/Doxygen Commands/DoxygenReturns.swift"
   "Block Nodes/Block Container Blocks/BlockDirective.swift"

Sources/Markdown/Markdown.docc/Markdown/DoxygenCommands.md

@@ -44,6 +44,7 @@ Doxygen commands are not parsed within code blocks or block directive content.
 
 ### Commands
 
+- ``DoxygenAbstract``
 - ``DoxygenDiscussion``
 - ``DoxygenNote``
 - ``DoxygenParameter``

Sources/Markdown/Parser/BlockDirectiveParser.swift

@@ -226,6 +226,7 @@ struct PendingDoxygenCommand {
     enum CommandKind {
         case discussion
         case note
+        case abstract
         case param(name: Substring)
         case returns
 
@@ -235,6 +236,8 @@ struct PendingDoxygenCommand {
                 return "'discussion'"
             case .note:
                 return "'note'"
+            case .abstract:
+                return "'abstract'"
             case .param(name: let name):
                 return "'param' Argument: '\(name)'"
             case .returns:
@@ -755,6 +758,8 @@ private enum ParseContainer: CustomStringConvertible {
                 return [.doxygenDiscussion(parsedRange: range, children)]
             case .note:
                 return [.doxygenNote(parsedRange: range, children)]
+            case .abstract:
+                return [.doxygenAbstract(parsedRange: range, children)]
             case .param(let name):
                 return [.doxygenParam(name: String(name), parsedRange: range, children)]
             case .returns:
@@ -887,6 +892,8 @@ struct ParseContainerStack {
             kind = .discussion
         case "note":
             kind = .note
+        case "abstract":
+            kind = .abstract
         case "param":
             guard let paramName = remainder.lex(until: { ch in
                 if ch.isWhitespace {

Sources/Markdown/Visitor/MarkupVisitor.swift

@@ -291,6 +291,14 @@ public protocol MarkupVisitor<Result> {
      */
     mutating func visitDoxygenNote(_ doxygenNote: DoxygenNote) -> Result
 
+    /**
+     Visit a `DoxygenAbstract` element and return the result.
+
+     - parameter doxygenAbstract: A `DoxygenAbstract` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitDoxygenAbstract(_ doxygenAbstract: DoxygenAbstract) -> Result
+
     /**
      Visit a `DoxygenParam` element and return the result.
 
@@ -411,6 +419,9 @@ extension MarkupVisitor {
     public mutating func visitDoxygenNote(_ doxygenNote: DoxygenNote) -> Result {
         return defaultVisit(doxygenNote)
     }
+    public mutating func visitDoxygenAbstract(_ doxygenAbstract: DoxygenAbstract) -> Result {
+            return defaultVisit(doxygenAbstract)
+    }
     public mutating func visitDoxygenParameter(_ doxygenParam: DoxygenParameter) -> Result {
         return defaultVisit(doxygenParam)
     }

Sources/Markdown/Walker/Walkers/MarkupFormatter.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021-2024 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2025 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -1178,6 +1178,11 @@ public struct MarkupFormatter: MarkupWalker {
         descendInto(doxygenDiscussion)
     }
 
+    public mutating func visitDoxygenAbstract(_ doxygenAbstract: DoxygenAbstract) {
+        printDoxygenStart("abstract", for: doxygenAbstract)
+        descendInto(doxygenAbstract)
+    }
+
     public mutating func visitDoxygenNote(_ doxygenNote: DoxygenNote) {
         printDoxygenStart("note", for: doxygenNote)
         descendInto(doxygenNote)
@@ -1194,4 +1199,5 @@ public struct MarkupFormatter: MarkupWalker {
         printDoxygenStart("returns", for: doxygenReturns)
         descendInto(doxygenReturns)
     }
+
 }

Tests/MarkdownTests/Parsing/DoxygenCommandParserTests.swift

@@ -32,6 +32,24 @@ class DoxygenCommandParserTests: XCTestCase {
         assertValidParse(source: #"\discussion The thing."#)
     }
 
+    func testParseAbstract() {
+        func assertValidParse(source: String) {
+            let document = Document(parsing: source, options: parseOptions)
+            XCTAssert(document.child(at: 0) is DoxygenAbstract)
+
+            let expectedDump = """
+            Document
+            └─ DoxygenAbstract
+               └─ Paragraph
+                  └─ Text "The thing."
+            """
+            XCTAssertEqual(document.debugDescription(), expectedDump)
+        }
+
+        assertValidParse(source: "@abstract The thing.")
+        assertValidParse(source: #"\abstract The thing."#)
+    }
+
     func testParseNote() {
         func assertValidParse(source: String) {
             let document = Document(parsing: source, options: parseOptions)
@@ -451,7 +469,9 @@ class DoxygenCommandParserTests: XCTestCase {
         let expectedDump = #"""
         Document
         ├─ BlockDirective name: "method"
-        ├─ BlockDirective name: "abstract"
+        ├─ DoxygenAbstract
+        │  └─ Paragraph
+        │     └─ Text "Some brief description of this method"
         ├─ DoxygenParameter parameter: number
         │  └─ Paragraph
         │     └─ Text "Some description of the “number” parameter"

Tests/MarkdownTests/Visitors/MarkupFormatterTests.swift

@@ -301,6 +301,26 @@ class MarkupFormatterSingleElementTests: XCTestCase {
         XCTAssertEqual(expectedAt, printedAt)
     }
 
+    func testPrintDoxygenAbstract() {
+            let expected = #"\abstract Another thing."#
+            let printed = DoxygenAbstract(children: Paragraph(Text("Another thing."))).format()
+            print (printed)
+            XCTAssertEqual(expected, printed)
+    }
+
+    func testPrintDoxygenAbstractMultiline() {
+        let expected = #"""
+        \abstract Another thing.
+        This is an extended abstract.
+        """#
+        let printed = DoxygenAbstract(children: Paragraph(
+            Text("Another thing."),
+            SoftBreak(),
+            Text("This is an extended abstract.")
+        )).format()
+        XCTAssertEqual(expected, printed)
+    }
+
     func testPrintDoxygenDiscussion() {
         let expected = #"\discussion Another thing."#
         let printed = DoxygenDiscussion(children: Paragraph(Text("Another thing."))).format()