feat(generator): Add ParseErrorLogger

[Sadhorsephile]

Problem

Sometimes, the back-end changes the response structure unexpectedly. For example, our app expects this:

 {
    "id": "0",
    "name": "Name"
 }

but we get this instead:

{
    "id": 0,
    "name": "Name"
 }

Logging these discrepancies would be really useful. To make the logs as helpful as possible, we need to capture:

• Request details (path, URI, params, etc.);
• Parsing error details (we can use CheckedFromJsonException from json_serializable).

The most logical place for such logging is within the client.

Solution

Let's introduce a new entity - ParseErrorLogger :

import 'package:dio/dio.dart';

/// Base class for logging errors that occur during parsing of response data.
abstract class ParseErrorLogger {
  /// Logs an error that occurred during parsing of response data.
  /// 
  /// - [error] is the error that occurred.
  /// - [stackTrace] is the stack trace of the error.
  /// - [options] are the options that were used to make the request.
  void logError(Object error, StackTrace stackTrace, RequestOptions options);
}

This entity can be injected into our client:

import 'package:dio/dio.dart';
import 'package:retrofit/retrofit.dart';

part 'rest_client.g.dart';

@RestApi()
abstract class RestClient {
  /// API creation factory using [Dio].
  factory RestClient(
    Dio dio, {
    String baseUrl,
    ParseErrorLogger? errorLogger,
  }) = _RestClient;

  @GET('')
  Future<SomeDto> someRequest();
}

And this entity will be called if parsing fails.

For example, this is rest_client.g.dart. As shown in the After example, errorLogger is called if there are any issues with parsing:

Before

After

@override Future<SomeDto> someRequest() async { const _extra = <String, dynamic>{}; final queryParameters = <String, dynamic>{}; final _headers = <String, dynamic>{}; final Map<String, dynamic>? _data = null; final _result = await _dio.fetch<Map<String, dynamic>>(_setStreamType<SomeDto>(Options( method: 'GET', headers: _headers, extra: _extra, ) .compose( _dio.options, '', queryParameters: queryParameters, data: _data, ) .copyWith( baseUrl: _combineBaseUrls( _dio.options.baseUrl, baseUrl, )))); final value = SomeDto.fromJson(_result.data!); return value; }

@override Future<SomeDto> someRequest() async { final _extra = <String, dynamic>{}; final queryParameters = <String, dynamic>{}; final _headers = <String, dynamic>{}; const Map<String, dynamic>? _data = null; final options = _setStreamType<SomeDto>(Options( method: 'GET', headers: _headers, extra: _extra, ) .compose( _dio.options, '', queryParameters: queryParameters, data: _data, ) .copyWith( baseUrl: _combineBaseUrls( _dio.options.baseUrl, baseUrl, ))); final _result = await _dio.fetch<Map<String, dynamic>>(options); late SomeDto value; try { value = SomeDto.fromJson(_result.data!); } on Object catch (e, s) { errorLogger?.logError(e, s, options); rethrow; } return value; }