Store all source languages in documentation node (#1326)

The documentation node stores the list of source languages that the node
is available in. Previously, this information was being stored in the
render node as a set containing the singular source language of the
node. This worked in the past when Swift was the only relevant language,
but `sourceLanguage` is now relegated to a backwards-compatible property
that queries `sourceLanguages` for the value it returns. This patch
updates the documentation node constructors to correctly store the set
of source languages in the node.

rdar://163034867

Author: snprajwal

Sources/SwiftDocC/Model/DocumentationNode.swift

@@ -238,7 +238,7 @@ public struct DocumentationNode {
                 Symbol.Overloads(references: [], displayIndex: overloadData.overloadGroupIndex)
             })
 
-        var languages = Set([reference.sourceLanguage])
+        var languages = reference.sourceLanguages
         var operatingSystemName = platformName.map({ Set([$0]) }) ?? []
 
         for (_, symbolAvailability) in symbolAvailabilityVariants.allValues {
@@ -776,7 +776,7 @@ public struct DocumentationNode {
 
         let symbolAvailability = symbol.mixins[SymbolGraph.Symbol.Availability.mixinKey] as? SymbolGraph.Symbol.Availability
 
-        var languages = Set([reference.sourceLanguage])
+        var languages = reference.sourceLanguages
         var operatingSystemName = platformName.map({ Set([$0]) }) ?? []
 
         let availabilityDomains = symbolAvailability?.availability.compactMap({ $0.domain?.rawValue })
@@ -859,7 +859,7 @@ public struct DocumentationNode {
         self.semantic = article
         self.sourceLanguage = reference.sourceLanguage
         self.name = .conceptual(title: article.title?.title ?? "")
-        self.availableSourceLanguages = [reference.sourceLanguage]
+        self.availableSourceLanguages = reference.sourceLanguages
         self.docChunks = [DocumentationChunk(source: .documentationExtension, markup: articleMarkup)]
         self.markup = articleMarkup
         self.isVirtual = false

Tests/SwiftDocCTests/Model/DocumentationNodeTests.swift

@@ -76,4 +76,27 @@ class DocumentationNodeTests: XCTestCase {
         XCTAssertEqual(DocumentationNode.symbolKind(for: .typeConstant), .typeProperty)
         XCTAssertEqual(DocumentationNode.symbolKind(for: .object), .dictionary)
     }
+
+    func testWithMultipleSourceLanguages() throws {
+        let sourceLanguages: Set<SourceLanguage> = [.swift, .objectiveC]
+        // Test if articles contain all available source languages
+        let article = Article(markup: Document(parsing: "# Title", options: []), metadata: nil, redirects: nil, options: [:])
+        let articleNode = try DocumentationNode(
+            reference: ResolvedTopicReference(bundleID: "org.swift.docc", path: "/blah", sourceLanguages: sourceLanguages),
+            article: article
+        )
+        XCTAssertEqual(articleNode.availableSourceLanguages, sourceLanguages)
+
+        // Test if symbols contain all available source languages
+        let symbol = makeSymbol(id: "blah", kind: .class, pathComponents: ["blah"])
+        let symbolNode = DocumentationNode(
+            reference: ResolvedTopicReference(bundleID: "org.swift.docc", path: "/blah", sourceLanguages: sourceLanguages),
+            symbol: symbol,
+            platformName: nil,
+            moduleReference: ResolvedTopicReference(bundleID: "org.swift.docc", path: "/blah", sourceLanguages: sourceLanguages),
+            article: nil,
+            engine: DiagnosticEngine()
+        )
+        XCTAssertEqual(symbolNode.availableSourceLanguages, sourceLanguages)
+    }
 }