Stop duplicating auto-generated collections per-platform (#325)

Resolves a regression where auto-generated "Protocol Implementations"
collections were being duplicated per platform.

The immediate fix is to call the `createInheritedSymbolsAPICollection` method a
single time with all of the relevant relationships, instead of once per
platform. It tracks internal state while building up the API collections so it's
important to provide all possible relationships when calling the method.

I think there's a likely a longer-term fix we should make here in the way we're
handling multi-platform symbol graph information since currently we're handling
it similarly to multi-language symbol graph information but don't actually
emit variants for it.

Resolves rdar://95882462.

Author: ethan-kusters

Sources/SwiftDocC/Infrastructure/DocumentationContext.swift

@@ -1261,13 +1261,11 @@ public class DocumentationContext: DocumentationContextDataProviderDelegate {
             }
 
             // Create inherited API collections
-            for (_, relationships) in combinedRelationships {
-                try GeneratedDocumentationTopics.createInheritedSymbolsAPICollections(
-                    relationships: relationships,
-                    context: self,
-                    bundle: bundle
-                )
-            }
+            try GeneratedDocumentationTopics.createInheritedSymbolsAPICollections(
+                relationships: combinedRelationships.flatMap(\.value),
+                context: self,
+                bundle: bundle
+            )
 
             // Parse and prepare the nodes' content concurrently.
             let updatedNodes: [(node: DocumentationNode, matchedArticleURL: URL?)] = Array(symbolIndex.values)

Sources/SwiftDocC/Infrastructure/Symbol Graph/GeneratedDocumentationTopics.swift

@@ -224,12 +224,17 @@ enum GeneratedDocumentationTopics {
     ///   ╰ View Implementations
     ///     ╰ accessibilityValue()
     /// ```
+    ///
+    /// > Warning: This method tracks internal state via an ``InheritedSymbols`` inheritance index.
+    /// It must be called **once** per symbol by passing in _all_ of the relationships that apply
+    /// to a symbol.
+    ///
     /// - Parameters:
     ///   - relationships: A set of relationships to inspect.
     ///   - symbolsURLHierarchy: A symbol graph hierarchy as created during symbol registration.
     ///   - context: A documentation context to update.
     ///   - bundle: The current documentation bundle.
-    static func createInheritedSymbolsAPICollections(relationships: Set<SymbolGraph.Relationship>, context: DocumentationContext, bundle: DocumentationBundle) throws {
+    static func createInheritedSymbolsAPICollections(relationships: [SymbolGraph.Relationship], context: DocumentationContext, bundle: DocumentationBundle) throws {
         var inheritanceIndex = InheritedSymbols()
 
         // Walk the symbol graph relationships and look for parent <-> child links that stem in a different module.

Tests/SwiftDocCTests/Rendering/RenderNodeTranslatorTests.swift

@@ -735,6 +735,81 @@ class RenderNodeTranslatorTests: XCTestCase {
         )
     }
 
+    func testAutomaticImplementationsFromMultiPlatformSymbolGraphs() throws {
+        let inheritedDefaultImplementationsSGF = Bundle.module.url(
+            forResource: "InheritedDefaultImplementations.symbols",
+            withExtension: "json",
+            subdirectory: "Test Resources"
+        )!
+        
+        let symbolGraphWithModifiedPlatform = try String(
+            contentsOf: inheritedDefaultImplementationsSGF
+        )
+        .replacingOccurrences(
+            of: """
+                "architecture": "x86_64",
+                """,
+            with: """
+                "architecture": "arm64",
+                """
+        )
+        .replacingOccurrences(
+            of: """
+                "name": "macosx",
+                """,
+            with: """
+                "name": "ios",
+                """
+        )
+        
+        let testBundle = try Folder(
+            name: "unit-test.docc",
+            content: [
+                InfoPlist(displayName: "TestBundle", identifier: "com.test.example"),
+                Folder(
+                    name: "x86_64-apple-macos",
+                    content: [
+                        CopyOfFile(original: inheritedDefaultImplementationsSGF),
+                    ]
+                ),
+                Folder(
+                    name: "arm64-apple-ios",
+                    content: [
+                        DataFile(
+                            name: inheritedDefaultImplementationsSGF.lastPathComponent,
+                            data: Data(symbolGraphWithModifiedPlatform.utf8)
+                        ),
+                    ]
+                ),
+            ]
+        ).write(inside: createTemporaryDirectory())
+        
+        try assertDefaultImplementationCollectionTitles(
+            in: try loadRenderNode(at: "/documentation/FirstTarget/Bar", in: testBundle),
+            [
+                "Foo Implementations",
+            ]
+        )
+        
+        try assertDefaultImplementationCollectionTitles(
+            in: try loadRenderNode(at: "/documentation/FirstTarget/OtherStruct", in: testBundle),
+            [
+                "Comparable Implementations",
+                "Equatable Implementations",
+            ]
+        )
+        
+        try assertDefaultImplementationCollectionTitles(
+            in: try loadRenderNode(at: "/documentation/FirstTarget/SomeStruct", in: testBundle),
+            [
+                "Comparable Implementations",
+                "Equatable Implementations",
+                "FancyProtocol Implementations",
+                "OtherFancyProtocol Implementations",
+            ]
+        )
+    }
+    
     func assertDefaultImplementationCollectionTitles(
         in renderNode: RenderNode,
         _ expectedTitles: [String],