refactor: Remove default model from the language model options (#498)

packages/langchain_anthropic/lib/src/chat_models/chat_anthropic.dart

@@ -154,7 +154,8 @@ class ChatAnthropic extends BaseChatModel<ChatAnthropicOptions> {
     final Map<String, dynamic>? queryParams,
     final http.Client? client,
     super.defaultOptions = const ChatAnthropicOptions(
-      model: 'claude-3-5-sonnet-20240620',
+      model: defaultModel,
+      maxTokens: defaultMaxTokens,
     ),
     this.encoding = 'cl100k_base',
   }) : _client = a.AnthropicClient(
@@ -177,6 +178,12 @@ class ChatAnthropic extends BaseChatModel<ChatAnthropicOptions> {
   @override
   String get modelType => 'anthropic-chat';
 
+  /// The default model to use unless another is specified.
+  static const defaultModel = 'claude-3-5-sonnet-20240620';
+
+  /// The default max tokens to use unless another is specified.
+  static const defaultMaxTokens = 1024;
+
   @override
   Future<ChatResult> invoke(
     final PromptValue input, {
@@ -187,7 +194,6 @@ class ChatAnthropic extends BaseChatModel<ChatAnthropicOptions> {
         input.toChatMessages(),
         options: options,
         defaultOptions: defaultOptions,
-        throwNullModelError: throwNullModelError,
       ),
     );
     return completion.toChatResult();
@@ -205,7 +211,6 @@ class ChatAnthropic extends BaseChatModel<ChatAnthropicOptions> {
             options: options,
             defaultOptions: defaultOptions,
             stream: true,
-            throwNullModelError: throwNullModelError,
           ),
         )
         .transform(MessageStreamEventTransformer());

packages/langchain_anthropic/lib/src/chat_models/mappers.dart

@@ -9,6 +9,7 @@ import 'package:langchain_core/language_models.dart';
 import 'package:langchain_core/tools.dart';
 import 'package:rxdart/rxdart.dart' show WhereNotNullExtension;
 
+import 'chat_anthropic.dart';
 import 'types.dart';
 
 /// Creates a [CreateMessageRequest] from the given input.
@@ -17,7 +18,6 @@ a.CreateMessageRequest createMessageRequest(
   required final ChatAnthropicOptions? options,
   required final ChatAnthropicOptions defaultOptions,
   final bool stream = false,
-  required Never Function() throwNullModelError,
 }) {
   final systemMsg = messages.firstOrNull is SystemChatMessage
       ? messages.firstOrNull?.contentAsString
@@ -31,10 +31,12 @@ a.CreateMessageRequest createMessageRequest(
 
   return a.CreateMessageRequest(
     model: a.Model.modelId(
-      options?.model ?? defaultOptions.model ?? throwNullModelError(),
+      options?.model ?? defaultOptions.model ?? ChatAnthropic.defaultModel,
     ),
     messages: messagesDtos,
-    maxTokens: options?.maxTokens ?? defaultOptions.maxTokens ?? 1024,
+    maxTokens: options?.maxTokens ??
+        defaultOptions.maxTokens ??
+        ChatAnthropic.defaultMaxTokens,
     stopSequences: options?.stopSequences ?? defaultOptions.stopSequences,
     system: systemMsg,
     temperature: options?.temperature ?? defaultOptions.temperature,

packages/langchain_anthropic/lib/src/chat_models/types.dart

@@ -1,14 +1,28 @@
+import 'package:collection/collection.dart';
 import 'package:langchain_core/chat_models.dart';
 import 'package:langchain_core/tools.dart';
+import 'package:meta/meta.dart';
 
 /// {@template chat_anthropic_options}
 /// Options to pass into the Anthropic Chat Model.
+///
+/// Available models:
+/// - `claude-3-5-sonnet-20240620`
+/// - `claude-3-haiku-20240307`
+/// - `claude-3-opus-20240229`
+/// - `claude-3-sonnet-20240229`
+/// - `claude-2.0`
+/// - `claude-2.1`
+///
+/// Mind that the list may be outdated.
+/// See https://docs.anthropic.com/en/docs/about-claude/models for the latest list.
 /// {@endtemplate}
+@immutable
 class ChatAnthropicOptions extends ChatModelOptions {
   /// {@macro chat_anthropic_options}
   const ChatAnthropicOptions({
-    this.model = 'claude-3-5-sonnet-20240620',
-    this.maxTokens = 1024,
+    super.model,
+    this.maxTokens,
     this.stopSequences,
     this.temperature,
     this.topK,
@@ -19,20 +33,6 @@ class ChatAnthropicOptions extends ChatModelOptions {
     super.concurrencyLimit,
   });
 
-  /// ID of the model to use (e.g. 'claude-3-5-sonnet-20240620').
-  ///
-  /// Available models:
-  /// - `claude-3-5-sonnet-20240620`
-  /// - `claude-3-haiku-20240307`
-  /// - `claude-3-opus-20240229`
-  /// - `claude-3-sonnet-20240229`
-  /// - `claude-2.0`
-  /// - `claude-2.1`
-  ///
-  /// Mind that the list may be outdated.
-  /// See https://docs.anthropic.com/en/docs/about-claude/models for the latest list.
-  final String? model;
-
   /// The maximum number of tokens to generate before stopping.
   ///
   /// Note that our models may stop _before_ reaching this maximum. This parameter
@@ -113,4 +113,33 @@ class ChatAnthropicOptions extends ChatModelOptions {
       concurrencyLimit: concurrencyLimit ?? this.concurrencyLimit,
     );
   }
+
+  @override
+  bool operator ==(covariant final ChatAnthropicOptions other) {
+    return model == other.model &&
+        maxTokens == other.maxTokens &&
+        const ListEquality<String>()
+            .equals(stopSequences, other.stopSequences) &&
+        temperature == other.temperature &&
+        topK == other.topK &&
+        topP == other.topP &&
+        userId == other.userId &&
+        const ListEquality<ToolSpec>().equals(tools, other.tools) &&
+        toolChoice == other.toolChoice &&
+        concurrencyLimit == other.concurrencyLimit;
+  }
+
+  @override
+  int get hashCode {
+    return model.hashCode ^
+        maxTokens.hashCode ^
+        const ListEquality<String>().hash(stopSequences) ^
+        temperature.hashCode ^
+        topK.hashCode ^
+        topP.hashCode ^
+        userId.hashCode ^
+        const ListEquality<ToolSpec>().hash(tools) ^
+        toolChoice.hashCode ^
+        concurrencyLimit.hashCode;
+  }
 }

packages/langchain_anthropic/pubspec.yaml

@@ -21,6 +21,7 @@ dependencies:
   http: ^1.1.0
   langchain_core: 0.3.3
   langchain_tiktoken: ^1.0.1
+  meta: ^1.11.0
   rxdart: ^0.27.7
 
 dev_dependencies:

packages/langchain_core/lib/src/chat_models/types.dart

@@ -10,9 +10,10 @@ import '../tools/base.dart';
 class ChatModelOptions extends LanguageModelOptions {
   /// {@macro chat_model_options}
   const ChatModelOptions({
-    super.concurrencyLimit,
+    super.model,
     this.tools,
     this.toolChoice,
+    super.concurrencyLimit,
   });
 
   /// A list of tools the model may call.

packages/langchain_core/lib/src/language_models/base.dart

@@ -1,5 +1,3 @@
-import 'package:meta/meta.dart';
-
 import '../langchain/base.dart';
 import '../prompts/types.dart';
 import 'types.dart';
@@ -58,33 +56,4 @@ abstract class BaseLanguageModel<
 
   @override
   String toString() => modelType;
-
-  /// Throws an error if the model id is not specified.
-  @protected
-  Never throwNullModelError() {
-    throw ArgumentError('''
-Null model in $runtimeType.
-        
-You need to specify the id of model to use either in `$runtimeType.defaultOptions` 
-or in the options passed when invoking the model.
-
-Example:
-```
-// In defaultOptions
-final model = $runtimeType(
-  defaultOptions: ${runtimeType}Options(
-    model: 'model-id',
-  ),
-);
-
-// Or when invoking the model
-final res = await model.invoke(
-  prompt,
-  options: ${runtimeType}Options(
-    model: 'model-id',
-  ),
-);
-```
-''');
-  }
 }

packages/langchain_core/lib/src/language_models/types.dart

@@ -10,8 +10,13 @@ import '../langchain/types.dart';
 abstract class LanguageModelOptions extends BaseLangChainOptions {
   /// {@macro language_model_options}
   const LanguageModelOptions({
+    this.model,
     super.concurrencyLimit,
   });
+
+  /// ID of the language model to use.
+  /// Check the provider's documentation for available models.
+  final String? model;
 }
 
 /// {@template language_model}

packages/langchain_core/lib/src/llms/types.dart

@@ -9,6 +9,7 @@ import '../language_models/types.dart';
 class LLMOptions extends LanguageModelOptions {
   /// {@macro llm_options}
   const LLMOptions({
+    super.model,
     super.concurrencyLimit,
   });
 }

packages/langchain_firebase/lib/src/chat_models/vertex_ai/chat_firebase_vertex_ai.dart

@@ -154,7 +154,7 @@ class ChatFirebaseVertexAI extends BaseChatModel<ChatFirebaseVertexAIOptions> {
   /// - [ChatFirebaseVertexAI.location]
   ChatFirebaseVertexAI({
     super.defaultOptions = const ChatFirebaseVertexAIOptions(
-      model: 'gemini-1.5-flash',
+      model: defaultModel,
     ),
     this.app,
     this.appCheck,
@@ -188,15 +188,18 @@ class ChatFirebaseVertexAI extends BaseChatModel<ChatFirebaseVertexAIOptions> {
   /// A UUID generator.
   late final Uuid _uuid = const Uuid();
 
-  @override
-  String get modelType => 'chat-firebase-vertex-ai';
-
   /// The current model set in [_firebaseClient];
   String _currentModel;
 
   /// The current system instruction set in [_firebaseClient];
   String? _currentSystemInstruction;
 
+  @override
+  String get modelType => 'chat-firebase-vertex-ai';
+
+  /// The default model to use unless another is specified.
+  static const defaultModel = 'gemini-1.5-flash';
+
   @override
   Future<ChatResult> invoke(
     final PromptValue input, {
@@ -329,8 +332,7 @@ class ChatFirebaseVertexAI extends BaseChatModel<ChatFirebaseVertexAIOptions> {
     final List<ChatMessage> messages,
     final ChatFirebaseVertexAIOptions? options,
   ) {
-    final model =
-        options?.model ?? defaultOptions.model ?? throwNullModelError();
+    final model = options?.model ?? defaultOptions.model ?? defaultModel;
 
     final systemInstruction = messages.firstOrNull is SystemChatMessage
         ? messages.firstOrNull?.contentAsString