{"record":{"id":"01525cf1c8d5ddfc","repo":"elastic/elasticsearch","slug":"error-trying-to-read-arguments","errorCode":null,"errorMessage":"Error trying to read [{}#ARGUMENTS]","messagePattern":"Error trying to read \\[(.+?)#ARGUMENTS\\]","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"modules/lang-painless/src/main/java/org/elasticsearch/painless/ScriptClassInfo.java","lineNumber":299,"sourceCode":"                \"Painless needs a constant [String[] PARAMETERS] on all interfaces it implements with the \"\n                    + \"names of the method arguments but [\"\n                    + iface.getName()\n                    + \"] doesn't have one.\",\n                e\n            );\n        }\n        if (false == argumentNamesField.getType().equals(String[].class)) {\n            throw new IllegalArgumentException(\n                \"Painless needs a constant [String[] PARAMETERS] on all interfaces it implements with the \"\n                    + \"names of the method arguments but [\"\n                    + iface.getName()\n                    + \"] doesn't have one.\"\n            );\n        }\n        try {\n            return (String[]) argumentNamesField.get(null);\n        } catch (IllegalArgumentException | IllegalAccessException e) {\n            throw new IllegalArgumentException(\"Error trying to read [\" + iface.getName() + \"#ARGUMENTS]\", e);\n        }\n    }\n}\n","sourceCodeStart":281,"sourceCodeEnd":303,"githubUrl":"https://github.com/elastic/elasticsearch/blob/db6a809a667c081ca1dc7500389d26975573215f/modules/lang-painless/src/main/java/org/elasticsearch/painless/ScriptClassInfo.java#L281-L303","documentation":"After confirming PARAMETERS exists and is of type String[], readArgumentNamesConstant calls Field.get(null) to read its value. If that reflection read throws IllegalArgumentException or IllegalAccessException (e.g. the field is not actually accessible despite being public, or security manager/module access rules block it), it is wrapped and rethrown as this IllegalArgumentException.","triggerScenarios":"A PARAMETERS field that exists and is typed String[] but cannot be reflectively read — typically due to Java module-system encapsulation, a SecurityManager denying access, or the field being declared on a class rather than an interface with non-static semantics.","commonSituations":"Running under a restrictive JPMS module that does not 'opens' the interface's package; custom security manager; field shadowing across interfaces where get(null) resolves ambiguously.","solutions":["Ensure the interface's package is open to the Painless module (add 'opens' / 'requires transitive' as appropriate) or that no SecurityManager blocks reflection.","Verify PARAMETERS is declared directly on the interface as 'public static final String[]' and is not shadowed.","Inspect the chained cause (e original) for the precise IllegalAccess/IllegalArgument reason."],"exampleFix":"// module-info.java — open the package to lang-painless\nmodule my.plugin {\n    requires elasticsearch.painless;\n    opens com.example.scripts to elasticsearch.painless;\n}","handlingStrategy":"try-catch","validationCode":"void assertParametersReadable(Class<?> iface) throws Exception {\n    Field f = iface.getField(\"PARAMETERS\");\n    if (!f.getType().equals(String[].class)) throw new IllegalStateException(\"wrong type\");\n    try { f.setAccessible(true); f.get(null); }\n    catch (IllegalAccessException e) { throw new IllegalStateException(\"open the package to lang-painless\", e); }\n}","typeGuard":null,"tryCatchPattern":"try {\n    new ScriptClassInfo(lookup, MyScript.class);\n} catch (IllegalArgumentException e) {\n    if (e.getMessage().startsWith(\"Error trying to read\")\n        && (e.getCause() instanceof IllegalAccessException || e.getCause() instanceof IllegalArgumentException)) {\n        fail(\"Module/access problem reading PARAMETERS: \" + e.getCause().getMessage());\n    }\n    throw e;\n}","preventionTips":["Under JPMS, 'opens <package> to elasticsearch.painless' (or unconditional opens).","Do not install a SecurityManager that blocks reflective reads on context interfaces.","Unit-test PARAMETERS readability in the same module layout used at runtime."],"tags":["painless","scripting","script-context","reflection","jpms","elasticsearch"],"backgroundTag":null,"analyzedSha":"db6a809a667c081ca1dc7500389d26975573215f","analyzedAt":"2026-08-12T01:39:14.192Z","schemaVersion":2},"datasetVersion":"2026-08-13T04:17:16.726Z"}