Apply fallback availability logic to the CLI platform version parameter. (#910)

For platforms that have a fallback platform, copy the platform availability information passed through the CLI, including the `isBeta` value.

rdar://127227456

Author: sofiaromorales

Sources/SwiftDocC/Infrastructure/DocumentationConverter.swift

@@ -166,7 +166,11 @@ public struct DocumentationConverter: DocumentationConverterProtocol {
         self.experimentalModifyCatalogWithGeneratedCuration = experimentalModifyCatalogWithGeneratedCuration
 
         // Inject current platform versions if provided
-        if let currentPlatforms {
+        if var currentPlatforms {
+            // Add missing platforms if their fallback platform is present.
+            for (platform, fallbackPlatform) in DefaultAvailability.fallbackPlatforms where currentPlatforms[platform.displayName] == nil {
+                currentPlatforms[platform.displayName] = currentPlatforms[fallbackPlatform.displayName]
+            }
             self.context.externalMetadata.currentPlatforms = currentPlatforms
         }
     }

Tests/SwiftDocCUtilitiesTests/ConvertActionTests.swift

@@ -1818,6 +1818,71 @@ class ConvertActionTests: XCTestCase {
         ])
     }
 
+    func testBetaInAvailabilityFallbackPlatforms() throws {
+        
+        func generateConvertAction(currentPlatforms: [String : PlatformVersion]) throws -> ConvertAction {
+            try ConvertAction(
+                documentationBundleURL: bundle.absoluteURL,
+                outOfProcessResolver: nil,
+                analyze: false,
+                targetDirectory: targetDirectory,
+                htmlTemplateDirectory: Folder.emptyHTMLTemplateDirectory.absoluteURL,
+                emitDigest: false,
+                currentPlatforms: currentPlatforms,
+                dataProvider: testDataProvider,
+                fileManager: testDataProvider,
+                temporaryDirectory: testDataProvider.uniqueTemporaryDirectory()
+            )
+        }
+        let bundle = Folder(name: "nested", content: [
+            Folder(name: "folders", content: [
+                Folder(name: "unit-test.docc", content: [
+                    InfoPlist(displayName: "TestBundle", identifier: "com.test.example"),
+                ]),
+            ])
+        ])
+        let testDataProvider = try TestFileSystem(folders: [bundle, Folder.emptyHTMLTemplateDirectory])
+        let targetDirectory = URL(fileURLWithPath: testDataProvider.currentDirectoryPath)
+            .appendingPathComponent("target", isDirectory: true)
+        
+        // Test whether the missing platforms copy the availability information from the fallback platform.
+        var action = try generateConvertAction(currentPlatforms: ["iOS": PlatformVersion(.init(10, 0, 0), beta: true)])
+        XCTAssertEqual(action.context.externalMetadata.currentPlatforms, [
+            "iOS" : PlatformVersion(.init(10, 0, 0), beta: true),
+            "Mac Catalyst" : PlatformVersion(.init(10, 0, 0), beta: true),
+            "iPadOS" : PlatformVersion(.init(10, 0, 0), beta: true),
+        ])
+        // Test whether the non-missing platforms don't copy the availability information from the fallback platform.
+        action = try generateConvertAction(currentPlatforms: [
+            "iOS": PlatformVersion(.init(10, 0, 0), beta: true),
+            "Mac Catalyst": PlatformVersion(.init(11, 0, 0), beta: false)
+        ])
+        XCTAssertEqual(action.context.externalMetadata.currentPlatforms, [
+            "iOS" : PlatformVersion(.init(10, 0, 0), beta: true),
+            "Mac Catalyst" : PlatformVersion(.init(11, 0, 0), beta: false),
+            "iPadOS" : PlatformVersion(.init(10, 0, 0), beta: true)
+        ])
+        action = try generateConvertAction(currentPlatforms: [
+            "iOS": PlatformVersion(.init(10, 0, 0), beta: true),
+            "Mac Catalyst" : PlatformVersion(.init(11, 0, 0), beta: true),
+            "iPadOS": PlatformVersion(.init(12, 0, 0), beta: false),
+            
+        ])
+        XCTAssertEqual(action.context.externalMetadata.currentPlatforms, [
+            "iOS" : PlatformVersion(.init(10, 0, 0), beta: true),
+            "Mac Catalyst" : PlatformVersion(.init(11, 0, 0), beta: true),
+            "iPadOS" : PlatformVersion(.init(12, 0, 0), beta: false),
+        ])
+        // Test whether the non-missing platforms don't copy the availability information from the non-fallback platform.
+        action = try generateConvertAction(currentPlatforms: [
+            "tvOS": PlatformVersion(.init(13, 0, 0), beta: true)
+            
+        ])
+        XCTAssertEqual(action.context.externalMetadata.currentPlatforms, [
+            "tvOS": PlatformVersion(.init(13, 0, 0), beta: true)
+        ])
+    }
+    
     func testResolvedTopicReferencesAreCachedByDefaultWhenConverting() throws {
         let bundle = Folder(
             name: "unit-test.docc",