Load ~dev files as well as main provider files for new v2 protocol, fixes #6415

src/Composer/Repository/ComposerRepository.php

@@ -581,6 +581,13 @@ class ComposerRepository extends ArrayRepository implements ConfigurableReposito
             throw new \LogicException('loadAsyncPackages only supports v2 protocol composer repos with a metadata-url');
         }
 
+        // load ~dev variants as well if present
+        // TODO ideally there should be a flag set from the repositoryset/poolbuilder to know which packages should have the dev packages loaded
+        // so we can optimize away some requests entirely
+        foreach ($packageNames as $name => $constraint) {
+            $packageNames[$name.'~dev'] = $constraint;
+        }
+
         foreach ($packageNames as $name => $constraint) {
             $name = strtolower($name);