| | | 1 | | using AmbientServices.Extensions; |
| | | 2 | | using System; |
| | | 3 | | using System.Collections.Concurrent; |
| | | 4 | | using System.Collections.Generic; |
| | | 5 | | using System.Collections.Immutable; |
| | | 6 | | using System.Diagnostics; |
| | | 7 | | using System.Diagnostics.CodeAnalysis; |
| | | 8 | | using System.Linq; |
| | | 9 | | using System.Reflection; |
| | | 10 | | |
| | | 11 | | namespace AmbientServices; |
| | | 12 | | |
| | | 13 | | /// <summary> |
| | | 14 | | /// An attribute to identify classes implementing an ambient service default implementation. |
| | | 15 | | /// </summary> |
| | | 16 | | /// <remarks> |
| | | 17 | | /// <pitch>The zero-registration way to supply the fallback implementation for a service interface: mark the class and e |
| | | 18 | | /// <pledge> |
| | | 19 | | /// Applying the attribute to a class with a parameterless constructor registers that class as the default implementatio |
| | | 20 | | /// A default is only a fallback: an explicit assignment to <see cref="AmbientService{T}.Global"/> always takes preceden |
| | | 21 | | /// </pledge> |
| | | 22 | | /// When applied to a class with a parameterless constructor (public or non-public) in any assembly, causes each interfa |
| | | 23 | | /// If another implementation has already been registered, the new one will be ignored. |
| | | 24 | | /// The class instance implementing the service implementation will be constructed the first time it is requested, at mo |
| | | 25 | | /// </remarks> |
| | | 26 | | [AttributeUsage(AttributeTargets.Class)] |
| | | 27 | | public sealed class DefaultAmbientServiceAttribute : Attribute |
| | | 28 | | { |
| | | 29 | | |
| | | 30 | | /// <summary> |
| | | 31 | | /// Constructs a DefaultAmbientServiceAttribute. |
| | | 32 | | /// </summary> |
| | | 33 | | public DefaultAmbientServiceAttribute() |
| | | 34 | | { |
| | | 35 | | } |
| | | 36 | | /// <summary> |
| | | 37 | | /// Constructs a DefaultAmbientServiceAttribute that is limited to the specified interface, even if other interfaces |
| | | 38 | | /// </summary> |
| | | 39 | | /// <param name="registrationInterface">A single registration interface (for CLS compliance).</param> |
| | | 40 | | #pragma warning disable CA1019 // this constructor is only for CLS compliance--this attribute is accessible through the |
| | | 41 | | public DefaultAmbientServiceAttribute(Type registrationInterface) |
| | | 42 | | #pragma warning restore CA1019 |
| | | 43 | | { |
| | | 44 | | RegistrationInterfaces = ImmutableArray<Type>.Empty.Add(registrationInterface); |
| | | 45 | | } |
| | | 46 | | /// <summary> |
| | | 47 | | /// Constructs a DefaultAmbientServiceAttribute that is limited to the listed interfaces, even if other interfaces a |
| | | 48 | | /// </summary> |
| | | 49 | | /// <param name="registrationInterfaces">A params array of interface types to use for the registration instead of al |
| | | 50 | | public DefaultAmbientServiceAttribute(params Type[] registrationInterfaces) |
| | | 51 | | { |
| | | 52 | | RegistrationInterfaces = ImmutableArray<Type>.Empty.AddRange(registrationInterfaces); |
| | | 53 | | } |
| | | 54 | | /// <summary> |
| | | 55 | | /// Gets the interface types indicating which services are implemented by the class the attribute is applied to. |
| | | 56 | | /// If null, all interfaces that are directly implemented by the class should be used. |
| | | 57 | | /// </summary> |
| | | 58 | | public IReadOnlyList<Type>? RegistrationInterfaces { get; } |
| | | 59 | | } |
| | | 60 | | |
| | | 61 | | /// <summary> |
| | | 62 | | /// An internal static class that collects default ambient service implementations in every currently and subsequently l |
| | | 63 | | /// </summary> |
| | | 64 | | /// <remarks> |
| | | 65 | | /// <pitch>The discovery registry behind <see cref="DefaultAmbientServiceAttribute"/>: the one place that answers "which |
| | | 66 | | /// <pledge><see cref="TryFind"/> maps an interface type to its default implementation type or null, is thread-safe, and |
| | | 67 | | /// <plan>A static <see cref="ConcurrentDictionary{TKey, TValue}"/> from interface type to implementation type, seeded b |
| | | 68 | | /// </remarks> |
| | | 69 | | internal static class DefaultAmbientServices |
| | | 70 | | { |
| | | 71 | | private static readonly Assembly _ThisAssembly; |
| | | 72 | | private static readonly ConcurrentDictionary<Type, Type> _DefaultImplementations; |
| | | 73 | | |
| | | 74 | | static DefaultAmbientServices() |
| | | 75 | | { |
| | 3 | 76 | | _ThisAssembly = Assembly.GetExecutingAssembly(); |
| | 3 | 77 | | _DefaultImplementations = InitializeAlreadyLoadedDefaultAmbientServices(); |
| | | 78 | | // start hooking into assembly loading now, but only do this ONCE |
| | 3 | 79 | | AppDomain.CurrentDomain.AssemblyLoad += CurrentDomain_AssemblyLoad; |
| | 3 | 80 | | } |
| | | 81 | | private static void CurrentDomain_AssemblyLoad(object? sender, AssemblyLoadEventArgs args) |
| | | 82 | | { |
| | 3 | 83 | | Assembly assembly = args.LoadedAssembly; |
| | 3 | 84 | | OnAssemblyLoad(assembly); |
| | 3 | 85 | | } |
| | | 86 | | |
| | | 87 | | private static ConcurrentDictionary<Type, Type> InitializeAlreadyLoadedDefaultAmbientServices() |
| | | 88 | | { |
| | 3 | 89 | | ConcurrentDictionary<Type, Type> dictionary = new(); |
| | 3 | 90 | | foreach (Type type in AllLoadedReferringTypes()) |
| | | 91 | | { |
| | 3 | 92 | | AddDefaultImplementation(dictionary, type); |
| | | 93 | | } |
| | 3 | 94 | | return dictionary; |
| | | 95 | | } |
| | | 96 | | /// <summary> |
| | | 97 | | /// Enumerates all the types in all currently loaded assemblies that refer to this assembly (they can't possibly hav |
| | | 98 | | /// </summary> |
| | | 99 | | /// <returns>An enumeration of <see cref="Type"/>s.</returns> |
| | | 100 | | private static IEnumerable<Type> AllLoadedReferringTypes() |
| | | 101 | | { |
| | 3 | 102 | | List<Assembly> checkedAssemblies = new(); |
| | | 103 | | // loop through all the assemblies loaded in our AppDomain |
| | 3 | 104 | | foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies()) |
| | | 105 | | { |
| | | 106 | | // is this assembly us or does it reference us? |
| | 3 | 107 | | if (assembly == _ThisAssembly || assembly.DoesAssemblyReferDirectlyToAssembly(_ThisAssembly)) |
| | | 108 | | { |
| | 3 | 109 | | checkedAssemblies.Add(assembly); |
| | 3 | 110 | | foreach (Type type in assembly.GetLoadableTypes()) |
| | | 111 | | { |
| | 3 | 112 | | yield return type; |
| | | 113 | | } |
| | | 114 | | } |
| | | 115 | | } |
| | 3 | 116 | | System.Diagnostics.Trace.WriteLine($"Loading Ambient Types From {string.Join(",", checkedAssemblies.Select(a => |
| | 3 | 117 | | } |
| | | 118 | | /// <summary> |
| | | 119 | | /// Adds the default implementation for the specified interface type. |
| | | 120 | | /// </summary> |
| | | 121 | | /// <param name="dictionary">The dictionary to add to (usually <see cref="_DefaultImplementations"/>).</param> |
| | | 122 | | /// <param name="type">The interface type whose default implementation type is to be added.</param> |
| | | 123 | | private static void AddDefaultImplementation(ConcurrentDictionary<Type, Type> dictionary, Type type) |
| | | 124 | | { |
| | 3 | 125 | | DefaultAmbientServiceAttribute? attribute = type.GetCustomAttribute<DefaultAmbientServiceAttribute>(); |
| | 3 | 126 | | if (attribute != null) |
| | | 127 | | { |
| | 3 | 128 | | IReadOnlyList<Type>? registrationInterfaces = attribute.RegistrationInterfaces; |
| | 3 | 129 | | if ((registrationInterfaces?.Count ?? 0) == 0) |
| | | 130 | | { |
| | 3 | 131 | | registrationInterfaces = type.GetInterfaces(); // this could be null if the specified type doesn't sup |
| | | 132 | | } |
| | 3 | 133 | | if (registrationInterfaces != null) |
| | | 134 | | { |
| | 3 | 135 | | foreach (Type iface in registrationInterfaces) |
| | | 136 | | { |
| | 3 | 137 | | dictionary.TryAdd(iface, type); |
| | | 138 | | } |
| | | 139 | | } |
| | | 140 | | } |
| | 3 | 141 | | } |
| | | 142 | | /// <summary> |
| | | 143 | | /// Loads the default implementations in the specified assembly and notifies subscribers that the assembly has been |
| | | 144 | | /// </summary> |
| | | 145 | | /// <param name="assembly">The <see cref="Assembly"/> whose default implementations are to be found and registered.< |
| | | 146 | | internal static void OnAssemblyLoad(Assembly assembly) |
| | | 147 | | { |
| | | 148 | | // does the being-loaded assembly reference THIS assembly? |
| | 3 | 149 | | if (assembly.DoesAssemblyReferDirectlyToAssembly(_ThisAssembly)) |
| | | 150 | | { |
| | 2 | 151 | | System.Diagnostics.Trace.WriteLine($"Late Loading Ambient Types From {assembly.FullName}"); |
| | | 152 | | // check every type in the being-loaded assembly to see if the type indicates a default service implementati |
| | 2 | 153 | | foreach (Type type in assembly.GetLoadableTypes()) |
| | | 154 | | { |
| | 2 | 155 | | AddDefaultImplementation(_DefaultImplementations, type); |
| | | 156 | | } |
| | | 157 | | } |
| | 3 | 158 | | } |
| | | 159 | | |
| | | 160 | | /// <summary> |
| | | 161 | | /// Tries to find the default implementation of the specified interface, if one exists. |
| | | 162 | | /// Thread-safe. |
| | | 163 | | /// </summary> |
| | | 164 | | /// <param name="iface">The <see cref="Type"/> of interface whose implementation is wanted.</param> |
| | | 165 | | /// <returns>The <see cref="Type"/> that implements that interface, or null if no implementation could be found.</re |
| | | 166 | | public static Type? TryFind( |
| | | 167 | | #if NETCOREAPP3_0_OR_GREATER |
| | | 168 | | [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.N |
| | | 169 | | #endif |
| | | 170 | | Type iface) |
| | | 171 | | { |
| | 3 | 172 | | if (!iface.IsInterface) throw new ArgumentException("The specified type is not an interface type!", nameof(iface |
| | | 173 | | Type? impType; |
| | 3 | 174 | | if (_DefaultImplementations.TryGetValue(iface, out impType)) |
| | | 175 | | { |
| | | 176 | | Debug.Assert(iface.IsAssignableFrom(impType)); |
| | 3 | 177 | | return impType; |
| | | 178 | | } |
| | 3 | 179 | | return null; |
| | | 180 | | } |
| | | 181 | | } |
| | | 182 | | /// <summary> |
| | | 183 | | /// An empty interface that needs to be in this assembly in order to get tested properly because the interface will be r |
| | | 184 | | /// </summary> |
| | | 185 | | internal interface ILateAssignmentTest |
| | | 186 | | { } |