Feat: Add predicate-based Subject and sugar syntax

Package.swift

@@ -50,7 +50,7 @@ let dependencies: [Package.Dependency] = [
 
 // This adds some build settings which allow us to map "@available(gRPCSwift 2.x, *)" to
 // the appropriate OS platforms.
-let nextMinorVersion = 1
+let nextMinorVersion = 2
 let availabilitySettings: [SwiftSetting] = (0 ... nextMinorVersion).map { minor in
   let name = "gRPCSwift"
   let version = "2.\(minor)"

Sources/GRPCCore/Call/ConditionalInterceptor.swift

@@ -19,51 +19,96 @@
 /// You can configure interceptors to be applied to:
 /// - all RPCs and services;
 /// - requests directed only to specific services; or
-/// - requests directed only to specific methods (of a specific service).
+/// - requests directed only to specific methods (of a specific service); or
+/// - requests directed only to specific services or methods (of a specific service); or
+/// - all requests excluding requests directed to specific services or methods (of a specific service); or
+/// - requests whose ``MethodDescriptor`` satisfies a predicate.
 ///
 /// - SeeAlso: ``ClientInterceptor`` and ``ServerInterceptor`` for more information on client and
 ///   server interceptors, respectively.
 @available(gRPCSwift 2.0, *)
 public struct ConditionalInterceptor<Interceptor: Sendable>: Sendable {
   public struct Subject: Sendable {
-    internal enum Wrapped: Sendable {
-      case all
-      case services(Set<ServiceDescriptor>)
-      case methods(Set<MethodDescriptor>)
-    }
 
-    private let wrapped: Wrapped
+    private let predicate: @Sendable (_ descriptor: MethodDescriptor) -> Bool
 
     /// An operation subject specifying an interceptor that applies to all RPCs across all services will be registered with this client.
-    public static var all: Self { .init(wrapped: .all) }
+    public static var all: Self {
+      Self { _ in true }
+    }
 
     /// An operation subject specifying an interceptor that will be applied only to RPCs directed to the specified services.
+    ///
     /// - Parameters:
-    ///   - services: The list of service names for which this interceptor should intercept RPCs.
+    ///   - services: The list of service descriptors for which this interceptor should intercept RPCs.
     public static func services(_ services: Set<ServiceDescriptor>) -> Self {
-      Self(wrapped: .services(services))
+      Self { descriptor in
+        services.contains(descriptor.service)
+      }
     }
 
     /// An operation subject specifying an interceptor that will be applied only to RPCs directed to the specified service methods.
+    ///
     /// - Parameters:
     ///   - methods: The list of method descriptors for which this interceptor should intercept RPCs.
     public static func methods(_ methods: Set<MethodDescriptor>) -> Self {
-      Self(wrapped: .methods(methods))
+      Self { descriptor in
+        methods.contains(descriptor)
+      }
     }
 
-    @usableFromInline
-    package func applies(to descriptor: MethodDescriptor) -> Bool {
-      switch self.wrapped {
-      case .all:
-        return true
-
-      case .services(let services):
-        return services.contains(descriptor.service)
+    /// An operation subject specifying an interceptor that will be applied only to RPCs directed to the specified services or service methods.
+    ///
+    /// - Parameters:
+    ///   - services: The list of service descriptors for which this interceptor should intercept RPCs.
+    ///   - methods: The list of method descriptors for which this interceptor should intercept RPCs.
+    @available(gRPCSwift 2.2, *)
+    public static func only(
+      services: Set<ServiceDescriptor>,
+      methods: Set<MethodDescriptor>
+    ) -> Self {
+      Self { descriptor in
+        services.contains(descriptor.service) || methods.contains(descriptor)
+      }
+    }
 
-      case .methods(let methods):
-        return methods.contains(descriptor)
+    /// An operation subject specifying an interceptor that will be applied to all RPCs across all services for this client excluding the specified services or service methods.
+    ///
+    /// - Parameters:
+    ///   - services: The list of service descriptors for which this interceptor should **not** intercept RPCs.
+    ///   - methods: The list of method descriptors for which this interceptor should **not** intercept RPCs.
+    @available(gRPCSwift 2.2, *)
+    public static func allExcluding(
+      services: Set<ServiceDescriptor>,
+      methods: Set<MethodDescriptor>
+    ) -> Self {
+      Self { descriptor in
+        !(services.contains(descriptor.service) || methods.contains(descriptor))
       }
     }
+
+    /// An operation subject specifying an interceptor that will be applied to RPCs whose ``MethodDescriptor`` satisfies a `predicate`.
+    ///
+    /// - Important: The result of `predicate` is **cached per `MethodDescriptor`** by the client.
+    ///   The predicate is evaluated the first time a given method is encountered, and that result
+    ///   is reused for subsequent RPCs of the same method for the lifetime of the client.
+    ///   As a consequence, the `predicate` closure should be **deterministic**.
+    ///   Do **not** base it on dynamic state (time, session, feature flags, etc.).
+    ///   If you need per-call decisions, put that logic inside the interceptor itself.
+    ///
+    /// - Parameters:
+    ///   - predicate: A `@Sendable` closure evaluated per RPC. Return `true` to intercept.
+    @available(gRPCSwift 2.2, *)
+    public static func allMatching(
+      _ predicate: @Sendable @escaping (_ descriptor: MethodDescriptor) -> Bool
+    ) -> Self {
+      Self(predicate: predicate)
+    }
+
+    @usableFromInline
+    package func applies(to descriptor: MethodDescriptor) -> Bool {
+      self.predicate(descriptor)
+    }
   }
 
   /// The interceptor.

Tests/GRPCCoreTests/Call/ConditionalInterceptorTests.swift

@@ -20,7 +20,7 @@ import Testing
 @Suite("ConditionalInterceptor")
 struct ConditionalInterceptorTests {
   @Test(
-    "Applies to",
+    "Applies to all, services and methods",
     arguments: [
       (
         .all,
@@ -53,12 +53,66 @@ struct ConditionalInterceptorTests {
       #expect(!target.applies(to: notApplicableMethod))
     }
   }
+
+  @Test(
+    "Applies to only and allExcluding",
+    arguments: [
+      (
+        .only(services: [.foo], methods: [.barFoo]),
+        [.fooBar, .fooBaz, .barFoo],
+        [.barBaz]
+      ),
+      (
+        .allExcluding(services: [.foo], methods: [.barFoo]),
+        [.barBaz],
+        [.fooBar, .fooBaz, .barFoo]
+      ),
+    ] as [(ConditionalInterceptor<any Sendable>.Subject, [MethodDescriptor], [MethodDescriptor])]
+  )
+  @available(gRPCSwift 2.2, *)
+  func appliesToOnlyAndAllExcluding(
+    target: ConditionalInterceptor<any Sendable>.Subject,
+    applicableMethods: [MethodDescriptor],
+    notApplicableMethods: [MethodDescriptor]
+  ) {
+    for applicableMethod in applicableMethods {
+      #expect(target.applies(to: applicableMethod))
+    }
+
+    for notApplicableMethod in notApplicableMethods {
+      #expect(!target.applies(to: notApplicableMethod))
+    }
+  }
+
+  @Test("Applies to all matching")
+  @available(gRPCSwift 2.2, *)
+  func appliesToAllMatching() {
+    let target = ConditionalInterceptor<any Sendable>.Subject.allMatching { descriptor in
+      descriptor.method == "baz"
+    }
+    let applicableMethods: [MethodDescriptor] = [.fooBaz, .barBaz]
+    let notApplicableMethods: [MethodDescriptor] = [.fooBar, .barFoo]
+
+    for applicableMethod in applicableMethods {
+      #expect(target.applies(to: applicableMethod))
+    }
+
+    for notApplicableMethod in notApplicableMethods {
+      #expect(!target.applies(to: notApplicableMethod))
+    }
+  }
+}
+
+@available(gRPCSwift 2.2, *)
+extension ServiceDescriptor {
+  fileprivate static let foo = Self(fullyQualifiedService: "pkg.foo")
+  fileprivate static let bar = Self(fullyQualifiedService: "pkg.bar")
 }
 
 @available(gRPCSwift 2.0, *)
 extension MethodDescriptor {
   fileprivate static let fooBar = Self(fullyQualifiedService: "pkg.foo", method: "bar")
   fileprivate static let fooBaz = Self(fullyQualifiedService: "pkg.foo", method: "baz")
   fileprivate static let barFoo = Self(fullyQualifiedService: "pkg.bar", method: "foo")
-  fileprivate static let barBaz = Self(fullyQualifiedService: "pkg.bar", method: "Baz")
+  fileprivate static let barBaz = Self(fullyQualifiedService: "pkg.bar", method: "baz")
 }