Fixed extracting charset from response. (OpenFeign#2545)

While building FeignException, ignore quotes in regexp, ignore case and catch IllegalCharsetNameException to be sure it does not raise in other cases.

These content types are all valid and results in utf-8:
text/html;charset=utf-8
text/html;charset=UTF-8
Text/HTML;Charset="utf-8"
text/html; charset="utf-8"

Fixes OpenFeign#2540

Co-authored-by: Jakub Venglar <venglar@rixo.cz>

core/src/main/java/feign/FeignException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 The Feign Authors
+ * Copyright 2012-2024 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -21,6 +21,7 @@
 import java.nio.ByteBuffer;
 import java.nio.CharBuffer;
 import java.nio.charset.Charset;
+import java.nio.charset.IllegalCharsetNameException;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
@@ -29,6 +30,7 @@
 import java.util.regex.Pattern;
 import static feign.Util.*;
 import static java.lang.String.format;
+import static java.util.regex.Pattern.CASE_INSENSITIVE;
 
 /**
  * Origin exception type for all Http Apis.
@@ -519,14 +521,18 @@ private static Charset getResponseCharset(Map<String, Collection<String>> header
         return null;
       }
 
-      Pattern pattern = Pattern.compile(".*charset=([^\\s|^;]+).*");
+      Pattern pattern = Pattern.compile(".*charset=\"?([^\\s|^;|^\"]+).*", CASE_INSENSITIVE);
       Matcher matcher = pattern.matcher(strings.iterator().next());
       if (!matcher.lookingAt()) {
         return null;
       }
 
       String group = matcher.group(1);
-      if (!Charset.isSupported(group)) {
+      try {
+        if (!Charset.isSupported(group)) {
+          return null;
+        }
+      } catch (IllegalCharsetNameException ex) {
         return null;
       }
       return Charset.forName(group);

core/src/test/java/feign/FeignExceptionTest.java

@@ -24,6 +24,8 @@
 import java.util.HashMap;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 class FeignExceptionTest {
 
@@ -76,6 +78,32 @@ void createFeignExceptionWithCorrectCharsetResponse() {
         .isEqualTo("[400] during [GET] to [/home] [methodKey]: [response]");
   }
 
+  @ParameterizedTest
+  @ValueSource(strings = {
+      "application/json;charset=\"UTF-16BE\"",
+      "application/json; charset=UTF-16BE",
+      "application/json; charset=\"UTF-16BE\"",
+      "application/json;charset=UTF-16BE"
+  })
+  void createFeignExceptionWithCorrectCharsetResponseButDifferentContentTypeFormats(String contentType) {
+    Map<String, Collection<String>> map = new HashMap<>();
+    map.put("connection", new ArrayList<>(Collections.singletonList("keep-alive")));
+    map.put("content-length", new ArrayList<>(Collections.singletonList("100")));
+    map.put("content-type",
+        new ArrayList<>(Collections.singletonList(contentType)));
+
+    Request request = Request.create(Request.HttpMethod.GET, "/home", Collections.emptyMap(),
+        "data".getBytes(StandardCharsets.UTF_16BE), StandardCharsets.UTF_16BE, null);
+
+    Response response =
+        Response.builder().status(400).body("response".getBytes(StandardCharsets.UTF_16BE))
+            .headers(map).request(request).build();
+
+    FeignException exception = FeignException.errorStatus("methodKey", response);
+    assertThat(exception.getMessage())
+        .isEqualTo("[400] during [GET] to [/home] [methodKey]: [response]");
+  }
+
   @Test
   void createFeignExceptionWithErrorCharsetResponse() {
     Map<String, Collection<String>> map = new HashMap<>();