Include host name in PreviewServer error messages

If there’s a problem binding to a local port, the specific host name
might be relevant.

Author: tomstuart

Sources/SwiftDocCUtilities/PreviewServer/PreviewServer.swift

@@ -45,16 +45,16 @@ final class PreviewServer {
         /// The server did not find the content directory.
         case pathNotFound(String)
         /// Cannot bind the server to the given address
-        case cannotStartServer(port: Int)
+        case cannotStartServer(host: String, port: Int)
         /// The given port is not available
-        case portNotAvailable(port: Int)
+        case portNotAvailable(host: String, port: Int)
 
         var errorDescription: String {
             switch self {
                 case .failedToStart: return "Failed to start preview server"
                 case .pathNotFound(let path): return "The preview content path '\(path)' is not found"
-                case .cannotStartServer(let port): return "Can't start the preview server on port \(port)"
-                case .portNotAvailable(let port): return "Port \(port) is not available at the moment, "
+                case .cannotStartServer(let host, let port): return "Can't start the preview server on host \(host) and port \(port)"
+                case .portNotAvailable(let host, let port): return "Port \(port) is not available on host \(host) at the moment, "
                     + "try a different port number by adding the option '--port XXXX' "
                     + "to your command invocation where XXXX is the desired (free) port."
             }
@@ -154,13 +154,13 @@ final class PreviewServer {
         } catch let error as NIO.IOError where error.errnoCode == EADDRINUSE {
             // The given port is not available.
             switch bindTo {
-                case .localhost(_, let port): throw Error.portNotAvailable(port: port)
+                case .localhost(let host, let port): throw Error.portNotAvailable(host: host, port: port)
                 default: throw error
             }
         } catch {
             // Cannot bind the given address/port.
             switch bindTo {
-                case .localhost(_, let port): throw Error.cannotStartServer(port: port)
+                case .localhost(let host, let port): throw Error.cannotStartServer(host: host, port: port)
                 default: throw error
             }
         }