Support @Metadata and @DeprecationSummary in documentation comments

Sources/SwiftDocC/Infrastructure/Diagnostics/Diagnostic.swift

@@ -69,6 +69,12 @@ public extension Diagnostic {
     mutating func offsetWithRange(_ docRange: SymbolGraph.LineList.SourceRange) {
         // If there is no location information in the source diagnostic, the diagnostic might be removed for safety reasons.
         range?.offsetWithRange(docRange)
-
+    }
+
+    /// Returns the diagnostic with its range offset by the given documentation comment range.
+    func withRangeOffset(by docRange: SymbolGraph.LineList.SourceRange) -> Self {
+        var diagnostic = self
+        diagnostic.range?.offsetWithRange(docRange)
+        return diagnostic
     }
 }

Sources/SwiftDocC/Infrastructure/Diagnostics/Problem.swift

@@ -42,6 +42,13 @@ extension Problem {
             }
         }
     }
+
+    /// Returns the diagnostic with its range offset by the given documentation comment range.
+    func withRangeOffset(by docRange: SymbolGraph.LineList.SourceRange) -> Self {
+        var problem = self
+        problem.offsetWithRange(docRange)
+        return problem
+    }
 }
 
 extension Sequence<Problem> {

Sources/SwiftDocC/Infrastructure/DocumentationContext.swift

@@ -1048,15 +1048,21 @@ public class DocumentationContext {
     /// A lookup of resolved references based on the reference's absolute string.
     private(set) var referenceIndex = [String: ResolvedTopicReference]()
 
-    private func nodeWithInitializedContent(reference: ResolvedTopicReference, match foundDocumentationExtension: DocumentationContext.SemanticResult<Article>?) -> DocumentationNode {
+    private func nodeWithInitializedContent(
+        reference: ResolvedTopicReference,
+        match foundDocumentationExtension: DocumentationContext.SemanticResult<Article>?,
+        bundle: DocumentationBundle
+    ) -> DocumentationNode {
         guard var updatedNode = documentationCache[reference] else {
             fatalError("A topic reference that has already been resolved should always exist in the cache.")
         }
 
         // Pull a matched article out of the cache and attach content to the symbol
         updatedNode.initializeSymbolContent(
             documentationExtension: foundDocumentationExtension?.value,
-            engine: diagnosticEngine
+            engine: diagnosticEngine,
+            bundle: bundle,
+            context: self
         )
 
         // After merging the documentation extension into the symbol, warn about deprecation summary for non-deprecated symbols.
@@ -1399,7 +1405,11 @@ public class DocumentationContext {
                 Array(documentationCache.symbolReferences).concurrentMap { finalReference in
                     // Match the symbol's documentation extension and initialize the node content.
                     let match = uncuratedDocumentationExtensions[finalReference]
-                    let updatedNode = nodeWithInitializedContent(reference: finalReference, match: match)
+                    let updatedNode = nodeWithInitializedContent(
+                        reference: finalReference,
+                        match: match,
+                        bundle: bundle
+                    )
 
                     return ((
                         node: updatedNode,

Sources/SwiftDocC/Model/DocumentationNode.swift

@@ -335,12 +335,19 @@ public struct DocumentationNode {
     /// - Parameters:
     ///   - article: An optional documentation extension article.
     ///   - engine: A diagnostics engine.
-    mutating func initializeSymbolContent(documentationExtension: Article?, engine: DiagnosticEngine) {
+    mutating func initializeSymbolContent(
+        documentationExtension: Article?,
+        engine: DiagnosticEngine,
+        bundle: DocumentationBundle,
+        context: DocumentationContext
+    ) {
         precondition(unifiedSymbol != nil && symbol != nil, "You can only call initializeSymbolContent() on a symbol node.")
 
-        let (markup, docChunks) = Self.contentFrom(
+        let (markup, docChunks, metadataFromDocumentationComment) = Self.contentFrom(
             documentedSymbol: unifiedSymbol?.documentedSymbol,
             documentationExtension: documentationExtension,
+            bundle: bundle,
+            context: context,
             engine: engine
         )
 
@@ -469,7 +476,27 @@ public struct DocumentationNode {
         }
 
         options = documentationExtension?.options[.local]
-        self.metadata = documentationExtension?.metadata
+
+        if documentationExtension?.metadata != nil && metadataFromDocumentationComment != nil {
+            var problem = Problem(
+                diagnostic: Diagnostic(
+                    source: unifiedSymbol?.documentedSymbol?.docComment?.url,
+                    severity: .warning,
+                    range: metadataFromDocumentationComment?.originalMarkup.range,
+                    identifier: "org.swift.docc.DuplicateMetadata",
+                    summary: "Redeclaration of '@Metadata' for this symbol; this directive will be skipped",
+                    explanation: "A '@Metadata' directive is already declared in this symbol's documentation extension file"
+                )
+            )
+
+            if let range = unifiedSymbol?.documentedSymbol?.docComment?.lines.first?.range {
+                problem.offsetWithRange(range)
+            }
+
+            engine.emit(problem)
+        }
+
+        self.metadata = documentationExtension?.metadata ?? metadataFromDocumentationComment
 
         updateAnchorSections()
     }
@@ -483,11 +510,19 @@ public struct DocumentationNode {
     static func contentFrom(
         documentedSymbol: SymbolGraph.Symbol?,
         documentationExtension: Article?,
+        bundle: DocumentationBundle? = nil,
+        context: DocumentationContext? = nil,
         engine: DiagnosticEngine
-    ) -> (markup: Markup, docChunks: [DocumentationChunk]) {
+    ) -> (
+        markup: Markup,
+        docChunks: [DocumentationChunk],
+        metadata: Metadata?
+    ) {
         let markup: Markup
         var documentationChunks: [DocumentationChunk]
 
+        var metadata: Metadata?
+
         // We should ignore the symbol's documentation comment if it wasn't provided
         // or if the documentation extension was set to override.
         let ignoreDocComment = documentedSymbol?.docComment == nil
@@ -512,7 +547,36 @@ public struct DocumentationNode {
             let docCommentMarkup = Document(parsing: docCommentString, source: docCommentLocation?.url, options: documentOptions)
             let offset = symbol.docComment?.lines.first?.range
 
-            let docCommentDirectives = docCommentMarkup.children.compactMap({ $0 as? BlockDirective })
+            var docCommentMarkupElements = Array(docCommentMarkup.children)
+
+            var problems = [Problem]()
+
+            if let bundle, let context {
+                metadata = DirectiveParser()
+                    .parseSingleDirective(
+                        Metadata.self,
+                        from: &docCommentMarkupElements,
+                        parentType: Symbol.self,
+                        source: docCommentLocation?.url,
+                        bundle: bundle,
+                        context: context,
+                        problems: &problems
+                    )
+
+                metadata?.validateForUseInDocumentationComment(
+                    symbolSource: symbol.docComment?.url,
+                    problems: &problems
+                )
+            }
+
+            if let offset {
+                problems = problems.map { $0.withRangeOffset(by: offset) }
+            }
+
+            engine.emit(problems)
+
+            let docCommentDirectives = docCommentMarkupElements.compactMap { $0 as? BlockDirective }
+
             if !docCommentDirectives.isEmpty {
                 let location = symbol.mixins.getValueIfPresent(
                     for: SymbolGraph.Symbol.Location.self
@@ -529,9 +593,7 @@ public struct DocumentationNode {
                         continue
                     }
 
-                    // Renderable directives are processed like any other piece of structured markdown (tables, lists, etc.)
-                    // and so are inherently supported in doc comments.
-                    guard DirectiveIndex.shared.renderableDirectives[directive.name] == nil else {
+                    guard !directive.isSupportedInDocumentationComment else {
                         continue
                     }
 
@@ -579,7 +641,7 @@ public struct DocumentationNode {
             documentationChunks = [DocumentationChunk(source: .sourceCode(location: nil, offset: nil), markup: markup)]
         }
 
-        return (markup: markup, docChunks: documentationChunks)
+        return (markup: markup, docChunks: documentationChunks, metadata: metadata)
     }
 
     /// Returns a documentation node kind for the given symbol kind.
@@ -667,7 +729,7 @@ public struct DocumentationNode {
         // Prefer content sections coming from an article (documentation extension file)
         var deprecated: DeprecatedSection?
 
-        let (markup, docChunks) = Self.contentFrom(documentedSymbol: symbol, documentationExtension: article, engine: engine)
+        let (markup, docChunks, _) = Self.contentFrom(documentedSymbol: symbol, documentationExtension: article, engine: engine)
         self.markup = markup
         self.docChunks = docChunks
 
@@ -784,3 +846,18 @@ public struct DocumentationNode {
     /// These tags contain information about the symbol's return values, potential errors, and parameters.
     public var tags: Tags = (returns: [], throws: [], parameters: [])
 }
+
+private let directivesSupportedInDocumentationComments = [
+        Comment.directiveName,
+        Metadata.directiveName,
+        DeprecationSummary.directiveName,
+    ]
+    // Renderable directives are processed like any other piece of structured markdown (tables, lists, etc.)
+    // and so are inherently supported in doc comments.
+    + DirectiveIndex.shared.renderableDirectives.keys
+
+private extension BlockDirective {
+    var isSupportedInDocumentationComment: Bool {
+        directivesSupportedInDocumentationComments.contains(name)
+    }
+}

Sources/SwiftDocC/Semantics/Article/Article.swift

@@ -129,19 +129,16 @@ public final class Article: Semantic, MarkupConvertible, Abstracted, Redirected,
             return Redirect(from: childDirective, source: source, for: bundle, in: context, problems: &problems)
         }
 
-        let metadata: [Metadata]
-        (metadata, remainder) = remainder.categorize { child -> Metadata? in
-            guard let childDirective = child as? BlockDirective, childDirective.name == Metadata.directiveName else {
-                return nil
-            }
-            return Metadata(from: childDirective, source: source, for: bundle, in: context)
-        }
-
-        for extraMetadata in metadata.dropFirst() {
-            problems.append(Problem(diagnostic: Diagnostic(source: source, severity: .warning, range: extraMetadata.originalMarkup.range, identifier: "org.swift.docc.HasAtMostOne<\(Article.self), \(Metadata.self)>.DuplicateChildren", summary: "Duplicate \(Metadata.directiveName.singleQuoted) child directive", explanation: nil, notes: []), possibleSolutions: []))
-        }
-
-        var optionalMetadata = metadata.first
+        var optionalMetadata = DirectiveParser()
+            .parseSingleDirective(
+                Metadata.self,
+                from: &remainder,
+                parentType: Article.self,
+                source: source,
+                bundle: bundle,
+                context: context,
+                problems: &problems
+            )
 
         // Append any redirects found in the metadata to the redirects
         // found in the main content.

Sources/SwiftDocC/Semantics/DirectiveParser.swift

@@ -0,0 +1,68 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2024 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
+import Markdown
+
+/// A utlity type for parsing directives from markup.
+struct DirectiveParser<Directive: AutomaticDirectiveConvertible> {
+
+    /// Returns a directive of the given type if found in the given sequence of markup elements and the remaining markup.
+    ///
+    /// If there are multiple instances of the same directive type, this functions returns the first instance
+    /// and diagnoses subsequent instances.
+    func parseSingleDirective(
+        _ directiveType: Directive.Type,
+        from markupElements: inout [any Markup],
+        parentType: Semantic.Type,
+        source: URL?,
+        bundle: DocumentationBundle,
+        context: DocumentationContext,
+        problems: inout [Problem]
+    ) -> Directive? {
+        let (directiveElements, remainder) = markupElements.categorize { markup -> Directive? in
+            guard let childDirective = markup as? BlockDirective,
+                  childDirective.name == Directive.directiveName
+            else {
+                return nil
+            }
+            return Directive(
+                from: childDirective,
+                source: source,
+                for: bundle,
+                in: context,
+                problems: &problems
+            )
+        }
+
+        let directive = directiveElements.first
+
+        for extraDirective in directiveElements.dropFirst() {
+            problems.append(
+                Problem(
+                    diagnostic: Diagnostic(
+                        source: source,
+                        severity: .warning,
+                        range: extraDirective.originalMarkup.range,
+                        identifier: "org.swift.docc.HasAtMostOne<\(parentType), \(Directive.self)>.DuplicateChildren",
+                        summary: "Duplicate \(Metadata.directiveName.singleQuoted) child directive",
+                        explanation: nil,
+                        notes: []
+                    ),
+                    possibleSolutions: []
+                )
+            )
+        }
+
+        markupElements = remainder
+
+        return directive
+    }
+}

Sources/SwiftDocC/Semantics/Metadata/Metadata.swift

@@ -192,5 +192,52 @@ public final class Metadata: Semantic, AutomaticDirectiveConvertible {
 
         return true
     }
+
+    /// Validates the use of this Metadata directive in a documentation comment.
+    ///
+    /// Some configuration options of Metadata are invalid in documentation comments. This function
+    /// emits warnings for illegal uses and sets their values to `nil`.
+    func validateForUseInDocumentationComment(
+        symbolSource: URL?,
+        problems: inout [Problem]
+    ) {
+        let invalidDirectives: [(any AutomaticDirectiveConvertible)?] = [
+            documentationOptions,
+            technologyRoot,
+            displayName,
+            callToAction,
+            pageKind,
+            _pageColor,
+            titleHeading,
+        ] + (redirects ?? [])
+          + supportedLanguages
+          + pageImages
+
+        let namesAndRanges = invalidDirectives
+            .compactMap { $0 }
+            .map { (type(of: $0).directiveName, $0.originalMarkup.range) }
+
+        problems.append(
+            contentsOf: namesAndRanges.map { (name, range) in
+                Problem(
+                    diagnostic: Diagnostic(
+                        source: symbolSource,
+                        severity: .warning,
+                        range: range,
+                        identifier: "org.swift.docc.\(Metadata.directiveName).Invalid\(name)InDocumentationComment",
+                        summary: "Invalid use of \(name.singleQuoted) directive in documentation comment; configuration will be ignored",
+                        explanation: "Specify this configuration in a documentation extension file"
+
+                        // TODO: It would be nice to offer a solution here that removes the directive for you (#1111, rdar://140846407)
+                    )
+                )
+            }
+        )
+
+        documentationOptions = nil
+        technologyRoot = nil
+        displayName = nil
+        pageKind = nil
+        _pageColor = nil
+    }
 }
-

Sources/SwiftDocC/Semantics/Symbol/DeprecationSummary.swift

@@ -24,7 +24,9 @@ import Markdown
 /// }
 /// ```
 ///
-/// You can use the `@DeprecationSummary` directive top-level in both articles and documentation extension files.
+/// You can use the `@DeprecationSummary` directive top-level in articles, documentation extension files, or documentation comments.
+///
+/// > Earlier versions: Before Swift-DocC 6.1, `@DeprecationSummary` was not supported in documentation comments.
 ///
 /// > Tip:
 /// > If you are writing a custom deprecation summary message for an API or documentation page that isn't already deprecated,