Making sure contain and matching clashes are always resolved, fixes #5584

Author: lorenzo

src/ORM/EagerLoader.php

@@ -465,10 +465,15 @@ protected function _resolveJoins($associations, $matching = [])
                     $options->associations(),
                     $inMatching ? $mathching[$table] : []
                 );
-            } else {
-                $options->canBeJoined(false);
-                $this->_loadExternal[] = $options;
+                continue;
+            }
+
+            if ($inMatching) {
+                $this->_correctStrategy($options, $table);
             }
+
+            $options->canBeJoined(false);
+            $this->_loadExternal[] = $options;
         }
         return $result;
     }

tests/TestCase/ORM/QueryRegressionTest.php

@@ -670,4 +670,30 @@ public function testFindMatchingOverwrite()
         $this->assertNotNull($result->article);
         $this->assertEquals($result->article, $result->_matchingData['Articles']);
     }
+
+    /**
+     * Tests that matching does not overwrite associations in contain
+     *
+     * @see https://github.com/cakephp/cakephp/issues/5584
+     * @return void
+     */
+    public function testFindMatchingOverwrite2()
+    {
+        $comments = TableRegistry::get('Comments');
+        $comments->belongsTo('Articles');
+
+        $articles = TableRegistry::get('Articles');
+        $articles->belongsTo('Authors');
+        $articles->belongsToMany('Tags');
+
+        $result = $comments
+            ->find()
+            ->matching('Articles.Tags', function($q) {
+                return $q->where(['Tags.id' => 2]);
+            })
+                ->contain('Articles.Authors')
+                ->first();
+
+        $this->assertNotNull($result->article->author);
+    }
 }