Règle un problème de compat 7.1.

JSON_THROW_ON_ERROR: PHP ^7.3.

src/Composer/ComposerPackage.php

@@ -109,6 +109,9 @@ final class ComposerPackage implements ComposerPackageInterface
         $content = file_get_contents($composerPath);
         Assertion::string($content, "could not read `$composerPath`");
 
-        return $this->composerJson = json_decode($content, true, 512, \JSON_THROW_ON_ERROR);
+        $this->composerJson = json_decode($content, true);
+        Assertion::isArray($this->composerJson);
+
+        return $this->composerJson;
     }
 }