Add availabilityAttributes property to Symbol

Sources/SwiftDoc/AvailabilityAttribute.swift

@@ -0,0 +1,65 @@
+import SwiftSemantics
+
+public enum AvailabilityAttributeType: Equatable {
+    /// all platforms (marked with *)
+    case allPlatforms
+    case platform(platform: String, version: String?)
+    case introduced(version: String?)
+    case deprecated(version: String?)
+    case obsoleted(version: String?)
+    case renamed(message: String)
+    case message(message: String)
+    case unavailable(version: String?)
+}
+
+extension AvailabilityAttributeType {
+    init?(from argument: Attribute.Argument) {
+        switch argument.value {
+        case "*":
+            self = .allPlatforms
+            return
+        case "introduced":
+            self = .introduced(version: nil)
+            return
+        case "deprecated":
+            self = .deprecated(version: nil)
+            return
+        case "obsoleted":
+            self = .obsoleted(version: nil)          
+            return
+        case "unavailable":
+            self = .unavailable(version: nil)          
+            return
+        case "iOS", "macOS", "tvOS", "watchOS", "swift":
+            self = .platform(platform: argument.value, version: nil)
+        default: 
+            guard let name = argument.name else {
+                return nil
+            }
+
+            switch name {    
+            case "iOS", "macOS", "tvOS", "watchOS", "swift":
+                self = .platform(platform: name, version: argument.value)
+            case "introduced":
+                self = .introduced(version: argument.value)
+            case "deprecated":
+                self = .deprecated(version: argument.value)
+            case "obsoleted":
+                self = .obsoleted(version: argument.value)          
+            case "renamed":
+                self = .renamed(message: argument.value)          
+            case "message":
+                self = .message(message: argument.value)               
+            default: return nil
+            }
+        }
+    }
+}
+
+public final class AvailabilityAttribute {
+    public let attributes: [AvailabilityAttributeType]
+
+    init(arguments: [Attribute.Argument]) {
+        attributes = arguments.compactMap { AvailabilityAttributeType.init(from: $0) }
+    }
+}

Sources/SwiftDoc/Symbol.swift

@@ -62,6 +62,12 @@ public final class Symbol {
     public var isDocumented: Bool {
         return documentation?.isEmpty == false
     }
+
+    public var availabilityAttributes: [AvailabilityAttribute] {
+        let availableAttributes = api.attributes.filter({ $0.name == "available" }) 
+
+        return availableAttributes.compactMap { AvailabilityAttribute(arguments: $0.arguments) }
+    }
 }
 
 // MARK: - Equatable

Tests/SwiftDocTests/AvailabilityAttributeTests.swift

@@ -0,0 +1,38 @@
+import XCTest
+
+import SwiftDoc
+import SwiftSemantics
+import struct SwiftSemantics.Protocol
+import SwiftSyntax
+
+final class AvailabilityAttributeTypesTests: XCTestCase {
+    func testBasicAvailabilityType() throws {
+        let source = #"""
+
+        @available(iOS, deprecated: 13, renamed: "NewAndImprovedViewController")
+        class OldViewController: UIViewController { }
+
+        """#
+
+        let url = try temporaryFile(contents: source)
+        let sourceFile = try SourceFile(file: url, relativeTo: url.deletingLastPathComponent())
+
+        let symbol = sourceFile.symbols[0]
+        XCTAssert(symbol.api is Class)
+
+        XCTAssertEqual(symbol.availabilityAttributes.count, 1)
+
+        let attributes = symbol.availabilityAttributes.first!.attributes
+        XCTAssertEqual(attributes.count, 3)
+
+        let iOS = attributes[0]
+        XCTAssertEqual(iOS, AvailabilityAttributeType.platform(platform: "iOS", version: nil))
+
+        let deprecation = attributes[1]
+        XCTAssertEqual(deprecation, AvailabilityAttributeType.deprecated(version: "13"))
+
+        let renamed = attributes[2]
+        XCTAssertEqual(renamed, AvailabilityAttributeType.renamed(message: "\"NewAndImprovedViewController\""))
+
+    }
+}