add more validations

Sources/XMTPiOS/Conversations.swift

@@ -6,7 +6,7 @@ public enum ConversationError: Error {
 }
 
 public enum GroupError: Error {
-	case emptyCreation
+	case emptyCreation, memberCannotBeSelf, memberNotRegistered([String])
 }
 
 /// Handles listing and creating Conversations.
@@ -45,6 +45,35 @@ public actor Conversations {
 			throw GroupError.emptyCreation
 		}
 
+		if addresses.first(where: { $0.lowercased() == client.address.lowercased() }) != nil {
+			throw GroupError.memberCannotBeSelf
+		}
+
+		let erroredAddresses = try await withThrowingTaskGroup(of: (String?).self) { group in
+			for address in addresses {
+				group.addTask {
+					if try await self.client.canMessageV3(address: address) {
+						return nil
+					} else {
+						return address
+					}
+				}
+			}
+
+			var results: [String] = []
+			for try await result in group {
+				if let result {
+					results.append(result)
+				}
+			}
+
+			return results
+		}
+
+		if !erroredAddresses.isEmpty {
+			throw GroupError.memberNotRegistered(erroredAddresses)
+		}
+
 		return try await client.v3Client.conversations().createGroup(accountAddresses: addresses).fromFFI(client: client)
 	}
 

Tests/XMTPTests/GroupTests.swift

@@ -154,6 +154,24 @@ class GroupTests: XCTestCase {
 		)
 	}
 
+	func testCannotStartGroupWithNonRegisteredIdentity() async throws {
+		let fixtures = try await localFixtures()
+
+		let nonRegistered = try PrivateKey.generate()
+
+		do {
+			_ = try await fixtures.aliceClient.conversations.newGroup(with: [nonRegistered.address])
+
+			XCTFail("did not throw error")
+		} catch {
+			if case let GroupError.memberNotRegistered(addresses) = error {
+				XCTAssertEqual([nonRegistered.address.lowercased()], addresses.map { $0.lowercased() })
+			} else {
+				XCTFail("did not throw correct error")
+			}
+		}
+	}
+
 	func testCanSendMessagesToGroup() async throws {
 		let fixtures = try await localFixtures()
 		let aliceGroup = try await fixtures.aliceClient.conversations.newGroup(with: [fixtures.bob.address])