Add async overload for search API

This acts as an example for the conversation being held in issue meilisearch#332.

Async/await continues to grow in popularity and all modern codebases are moving towards its usage. This commit demonstrates how we can add support for Swift Concurrency without breaking existing compatibility with older operating systems.

For a test I have taken an existing test, copied it, and converted it for async/await. In this instance, removing the XCTestExpectation and simply using an async test available since Xcode 13 back in September 2021.

Sources/MeiliSearch/Indexes.swift

@@ -26,7 +26,7 @@ public struct Indexes {
   private let documents: Documents
 
   // Search methods
-  private let search: Search
+  fileprivate let search: Search
 
   // Settings methods
   private let settings: Settings
@@ -1101,3 +1101,23 @@ public struct Indexes {
     }
   }
 }
+
+// MARK: Swift Concurrency (Async/Await)
+
+@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
+extension Indexes {
+  /**
+   Search in the index.
+
+   - Parameter searchParameters: Options on search.
+   - Throws: Error if a failure occurred.
+   - Returns: On completion if the request was successful a `Searchable<T>` instance is returned containing the values.
+   */
+  public func search<T: Codable & Equatable>(_ searchParameters: SearchParameters) async throws -> Searchable<T> {
+    try await withCheckedThrowingContinuation { continuation in
+      self.search.search(self.uid, searchParameters) { result in
+        continuation.resume(with: result)
+      }
+    }
+  }
+}

Tests/MeiliSearchUnitTests/SearchTests.swift

@@ -80,6 +80,46 @@ class SearchTests: XCTestCase {
 
     self.wait(for: [expectation], timeout: TESTS_TIME_OUT)
   }
+
+  @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
+  func testSearchForBotmanMovieAsync() async throws {
+    let jsonString = """
+      {
+        "hits": [
+          {
+            "id": 29751,
+            "title": "Batman Unmasked: The Psychology of the Dark Knight",
+            "poster": "https://image.tmdb.org/t/p/w1280/jjHu128XLARc2k4cJrblAvZe0HE.jpg",
+            "overview": "Delve into the world of Batman and the vigilante justice tha",
+            "release_date": "2020-04-04T19:59:49.259572Z"
+          },
+          {
+            "id": 471474,
+            "title": "Batman: Gotham by Gaslight",
+            "poster": "https://image.tmdb.org/t/p/w1280/7souLi5zqQCnpZVghaXv0Wowi0y.jpg",
+            "overview": "ve Victorian Age Gotham City, Batman begins his war on crime",
+            "release_date": "2020-04-04T19:59:49.259572Z"
+          }
+        ],
+        "offset": 0,
+        "limit": 20,
+        "processingTimeMs": 2,
+        "estimatedTotalHits": 2,
+        "query": "botman"
+      }
+      """
+
+    // Prepare the mock server
+    let data = jsonString.data(using: .utf8)!
+    let stubSearchResult: Searchable<Movie> = try! Constants.customJSONDecoder.decode(Searchable<Movie>.self, from: data)
+    session.pushData(jsonString)
+
+    // Start the test with the mocked server
+    let searchParameters = SearchParameters.query("botman")
+
+    let searchResult: Searchable<Movie> = try await self.index.search(searchParameters)
+    XCTAssertEqual(stubSearchResult, searchResult)
+  }
 
   func testSearchForBotmanMovieFacets() {
     let jsonString = """