Add a precondition for declaring a node as beta. (#1055)

Added a precondition for declaring a node as beta.

For a node to be declared as beta it has to contain at least a single availability item that contains all the already defined characteristics.

This code adds a precondition where at least the node needs to have one availability item to be considered as potentially in beta.

Before this change, if at somewhere in the code, the availability items got removed from the node, the node would be considered as beta.

rdar://137762221
Co-authored-by: David Rönnqvist <[email protected]>

---------

Co-authored-by: David Rönnqvist <[email protected]>

Author: sofiaromorales

Sources/SwiftDocC/Model/Rendering/DocumentationContentRenderer.swift

@@ -211,11 +211,12 @@ public class DocumentationContentRenderer {
         guard let symbol = node.semantic as? Symbol,
               let currentPlatforms = documentationContext.configuration.externalMetadata.currentPlatforms,
               !currentPlatforms.isEmpty,
-              let symbolAvailability = symbol.availability
+              let symbolAvailability = symbol.availability?.availability,
+              !symbolAvailability.isEmpty // A symbol without availability items can't be in beta.
         else { return false }
 
         // Verify that if current platforms are in beta, they match the introduced version of the symbol
-        for availability in symbolAvailability.availability {
+        for availability in symbolAvailability {
             // If not available on this platform, skip to next platform.
             guard !availability.isUnconditionallyUnavailable, let introduced = availability.introducedVersion else {
                 continue

Tests/SwiftDocCTests/Model/SemaToRenderNodeTests.swift

@@ -1922,6 +1922,21 @@ Document
             XCTAssertEqual(renderNode.metadata.platforms?.first?.isBeta, false)
         }
 
+        // Symbol with an empty set of availbility items.
+        
+        do {
+            
+            let (bundle, context, reference) = try makeTestBundle(currentPlatforms: [
+                "Custom Name": PlatformVersion(VersionTriplet(100, 0, 0), beta: true)
+            ])
+            let node = try context.entity(with: reference)
+            (node.semantic as? Symbol)?.availability = SymbolGraph.Symbol.Availability(availability: [])
+            let documentationContentRendered = DocumentationContentRenderer(documentationContext: context, bundle: bundle)
+            let isBeta = documentationContentRendered.isBeta(node)
+            // Verify that the symbol is not beta since it does not contains availability info.
+            XCTAssertFalse(isBeta)
+        }
+        
         // Different platform is beta
         do {
             let (bundle, context, reference) = try makeTestBundle(currentPlatforms: [