{"record":{"id":"dcb76052722110fa","repo":"apache/flink","slug":"fieldset-to-add-must-not-be-null","errorCode":null,"errorMessage":"FieldSet to add must not be null.","messagePattern":"FieldSet to add must not be null\\.","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"flink-core/src/main/java/org/apache/flink/api/common/operators/util/FieldList.java","lineNumber":94,"sourceCode":"            return this;\n        }\n        if (size() == 0) {\n            return new FieldList(fieldIDs);\n        } else {\n            ArrayList<Integer> list = new ArrayList<Integer>(size() + fieldIDs.length);\n            list.addAll(this.collection);\n            for (int i = 0; i < fieldIDs.length; i++) {\n                list.add(fieldIDs[i]);\n            }\n\n            return new FieldList(Collections.unmodifiableList(list));\n        }\n    }\n\n    @Override\n    public FieldList addFields(FieldSet set) {\n        if (set == null) {\n            throw new IllegalArgumentException(\"FieldSet to add must not be null.\");\n        }\n\n        if (set.size() == 0) {\n            return this;\n        } else if (size() == 0 && set instanceof FieldList) {\n            return (FieldList) set;\n        } else {\n            ArrayList<Integer> list = new ArrayList<Integer>(size() + set.size());\n            list.addAll(this.collection);\n            list.addAll(set.collection);\n            return new FieldList(Collections.unmodifiableList(list));\n        }\n    }\n\n    public Integer get(int pos) {\n        return get().get(pos);\n    }\n","sourceCodeStart":76,"sourceCodeEnd":112,"githubUrl":"https://github.com/apache/flink/blob/2f3c205e9266cb30240eb7f4fdab15cad629a70f/flink-core/src/main/java/org/apache/flink/api/common/operators/util/FieldList.java#L76-L112","documentation":"Error \"FieldSet to add must not be null.\" thrown in apache/flink.","triggerScenarios":"Triggered at runtime when the operation fails because: FieldSet to add must not be null.","commonSituations":"Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: FieldSet to add must not be null.","solutions":["Address the cause reported by the error message: FieldSet to add must not be null.","Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry."],"exampleFix":"Correct the condition described (\"FieldSet to add must not be null.\") and rerun the job or command.","handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"2f3c205e9266cb30240eb7f4fdab15cad629a70f","analyzedAt":"2026-08-14T08:48:24.518Z","schemaVersion":2},"datasetVersion":"2026-08-14T10:17:34.591Z"}