Fix IOHttpClientAdapter.onHttpClientCreate Repeated calls (cfug#1810)

Fix cfug#1809

### New Pull Request Checklist

- [x] I have read the
[Documentation](https://pub.dev/documentation/dio/latest/)
- [x] I have searched for a similar pull request in the
[project](https://github.com/cfug/dio/pulls) and found none
- [x] I have updated this branch with the latest `main` branch to avoid
conflicts (via merge from master or rebase)
- [x] I have added the required tests to prove the fix/feature I'm
adding
- [x] I have updated the documentation (if necessary)
- [x] I have run the tests without failures
- [x] I have updated the `CHANGELOG.md` in the corresponding package

---------

Signed-off-by: 友人A <[email protected]>
Co-authored-by: Peter Leibiger <[email protected]>
Co-authored-by: Alex Li <[email protected]>

dio/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Make `LogInterceptor` prints in DEBUG mode (when the assertion is enabled) by default.
+- Fix `IOHttpClientAdapter.onHttpClientCreate` Repeated calls
 
 ## 5.1.2
 

dio/lib/src/adapters/io_adapter.dart

@@ -35,7 +35,7 @@ class IOHttpClientAdapter implements HttpClientAdapter {
   /// [validateCertificate] evaluates the leaf certificate.
   ValidateCertificate? validateCertificate;
 
-  HttpClient? _defaultHttpClient;
+  HttpClient? _cachedHttpClient;
 
   bool _closed = false;
 
@@ -187,27 +187,26 @@ class IOHttpClientAdapter implements HttpClientAdapter {
     Future<void>? cancelFuture,
     Duration? connectionTimeout,
   ) {
-    HttpClient client = onHttpClientCreate?.call(HttpClient()) ?? HttpClient();
     if (cancelFuture != null) {
+      final HttpClient client =
+          onHttpClientCreate?.call(HttpClient()) ?? HttpClient();
       client.userAgent = null;
       client.idleTimeout = Duration(seconds: 0);
       cancelFuture.whenComplete(() => client.close(force: true));
       return client..connectionTimeout = connectionTimeout;
     }
-    if (_defaultHttpClient == null) {
-      client.idleTimeout = Duration(seconds: 3);
-      if (onHttpClientCreate?.call(client) != null) {
-        client = onHttpClientCreate!(client)!;
-      }
-      client.connectionTimeout = connectionTimeout;
-      _defaultHttpClient = client;
+
+    if (_cachedHttpClient == null) {
+      final HttpClient client = HttpClient()
+        ..idleTimeout = Duration(seconds: 3);
+      _cachedHttpClient = onHttpClientCreate?.call(client) ?? client;
     }
-    return _defaultHttpClient!..connectionTimeout = connectionTimeout;
+    return _cachedHttpClient!..connectionTimeout = connectionTimeout;
   }
 
   @override
   void close({bool force = false}) {
     _closed = true;
-    _defaultHttpClient?.close(force: force);
+    _cachedHttpClient?.close(force: force);
   }
 }

dio/test/adapters_test.dart

@@ -0,0 +1,20 @@
+import 'package:dio/dio.dart';
+import 'package:dio/io.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(HttpClientAdapter, () {
+    test(
+        'IOHttpClientAdapter.onHttpClientCreate is only executed once per request',
+        () async {
+      int onHttpClientCreateInvokeCount = 0;
+      final dio = Dio();
+      dio.httpClientAdapter = IOHttpClientAdapter(onHttpClientCreate: (client) {
+        onHttpClientCreateInvokeCount++;
+        return client;
+      });
+      await dio.get('https://pub.dev');
+      expect(onHttpClientCreateInvokeCount, 1);
+    });
+  });
+}