Support loading tokenizer from local folder #76 (#81)

* Support loading tokenizer from local folder #76

* PR feedback & minor optimisations

Sources/Hub/Hub.swift

@@ -120,6 +120,15 @@ public class LanguageModelConfigurationFromHub {
             return try await self.loadConfig(modelName: modelName, hubApi: hubApi)
         }
     }
+
+    public init(
+        modelFolder: URL,
+        hubApi: HubApi = .shared
+    ) {
+        self.configPromise = Task {
+            return try await self.loadConfig(modelFolder: modelFolder, hubApi: hubApi)
+        }
+    }
 
     public var modelConfig: Config {
         get async throws {
@@ -170,12 +179,19 @@ public class LanguageModelConfigurationFromHub {
     ) async throws -> Configurations {
         let filesToDownload = ["config.json", "tokenizer_config.json", "tokenizer.json"]
         let repo = Hub.Repo(id: modelName)
-        try await hubApi.snapshot(from: repo, matching: filesToDownload)
+        let downloadedModelFolder = try await hubApi.snapshot(from: repo, matching: filesToDownload)
 
+        return try await loadConfig(modelFolder: downloadedModelFolder, hubApi: hubApi)
+    }
+
+    func loadConfig(
+        modelFolder: URL,
+        hubApi: HubApi = .shared
+    ) async throws -> Configurations {
         // Note tokenizerConfig may be nil (does not exist in all models)
-        let modelConfig = try hubApi.configuration(from: "config.json", in: repo)
-        let tokenizerConfig = try? hubApi.configuration(from: "tokenizer_config.json", in: repo)
-        let tokenizerVocab = try hubApi.configuration(from: "tokenizer.json", in: repo)
+        let modelConfig = try hubApi.configuration(fileURL: modelFolder.appending(path: "config.json"))
+        let tokenizerConfig = try? hubApi.configuration(fileURL: modelFolder.appending(path: "tokenizer_config.json"))
+        let tokenizerVocab = try hubApi.configuration(fileURL: modelFolder.appending(path: "tokenizer.json"))
 
         let configs = Configurations(
             modelConfig: modelConfig,

Sources/Hub/HubApi.swift

@@ -93,8 +93,14 @@ public extension HubApi {
     /// Assumes the file has already been downloaded.
     /// `filename` is relative to the download base.
     func configuration(from filename: String, in repo: Repo) throws -> Config {
-        let url = localRepoLocation(repo).appending(path: filename)
-        let data = try Data(contentsOf: url)
+        let fileURL = localRepoLocation(repo).appending(path: filename)
+        return try configuration(fileURL: fileURL)
+    }
+
+    /// Assumes the file is already present at local url.
+    /// `fileURL` is a complete local file path for the given model
+    func configuration(fileURL: URL) throws -> Config {
+        let data = try Data(contentsOf: fileURL)
         let parsed = try JSONSerialization.jsonObject(with: data, options: [])
         guard let dictionary = parsed as? [String: Any] else { throw Hub.HubClientError.parse }
         return Config(dictionary)

Sources/Tokenizers/Tokenizer.swift

@@ -256,6 +256,17 @@ extension AutoTokenizer {
 
         return try PreTrainedTokenizer(tokenizerConfig: tokenizerConfig, tokenizerData: tokenizerData)
     }
+
+    public static func from(
+        modelFolder: URL,
+        hubApi: HubApi = .shared
+    ) async throws -> Tokenizer {
+        let config = LanguageModelConfigurationFromHub(modelFolder: modelFolder, hubApi: hubApi)
+        guard let tokenizerConfig = try await config.tokenizerConfig else { throw TokenizerError.missingConfig }
+        let tokenizerData = try await config.tokenizerData
+
+        return try PreTrainedTokenizer(tokenizerConfig: tokenizerConfig, tokenizerData: tokenizerData)
+    }
 }
 
 // MARK: - Tokenizer model classes

Tests/TokenizersTests/FactoryTests.swift

@@ -42,4 +42,24 @@ class FactoryTests: TestWithCustomHubDownloadLocation {
         let inputIds = tokenizer("Today she took a train to the West")
         XCTAssertEqual(inputIds, [50258, 50363, 27676, 750, 1890, 257, 3847, 281, 264, 4055, 50257])
     }
+
+    func testFromModelFolder() async throws {
+        let filesToDownload = ["config.json", "tokenizer_config.json", "tokenizer.json"]
+        let repo = Hub.Repo(id: "coreml-projects/Llama-2-7b-chat-coreml")
+        let localModelFolder = try await hubApi.snapshot(from: repo, matching: filesToDownload)
+
+        let tokenizer = try await AutoTokenizer.from(modelFolder: localModelFolder, hubApi: hubApi)
+        let inputIds = tokenizer("Today she took a train to the West")
+        XCTAssertEqual(inputIds, [1, 20628, 1183, 3614, 263, 7945, 304, 278, 3122])
+    }
+
+    func testWhisperFromModelFolder() async throws {
+        let filesToDownload = ["config.json", "tokenizer_config.json", "tokenizer.json"]
+        let repo = Hub.Repo(id: "openai/whisper-large-v2")
+        let localModelFolder = try await hubApi.snapshot(from: repo, matching: filesToDownload)
+
+        let tokenizer = try await AutoTokenizer.from(modelFolder: localModelFolder, hubApi: hubApi)
+        let inputIds = tokenizer("Today she took a train to the West")
+        XCTAssertEqual(inputIds, [50258, 50363, 27676, 750, 1890, 257, 3847, 281, 264, 4055, 50257])
+    }
 }