avoid-not-encodable-in-to-json

v1.14.0

warning

effort: 2m

recommended

configurable

starter+

Warns when a toJson method references a non-encodable object.

Passing results of such toJson methods to jsonEncode will result in a runtime exception.

⚙️ Config

Set methods (default is empty) to configure the list of additional methods that should be checked (example).

analysis_options.yaml

dcm:
  rules:
    - avoid-not-encodable-in-to-json:
        methods:
          - customToJson

Example

❌ Bad:

class SomeClass {
  final String value;

  const SomeClass(this.value);
}

class WithJson {
  Map<String, Object?> toJson(Set<String> values) => {
    // LINT: This expression is not encodable and will lead to an error when passed to 'jsonEncode'.
    //  Try converting it to 'List'.
    'key': values,
    // LINT: This expression is not encodable and will lead to an error when passed to 'jsonEncode'.
    //  Ensure it implements 'toJson' or try replacing it with a different expression.
    'function': () => null,
    // LINT: This expression is not encodable and will lead to an error when passed to 'jsonEncode'.
    //  Ensure it implements 'toJson' or try replacing it with a different expression.
    'instance': SomeClass(''),
  };
}

✅ Good:

class SomeClass {
  final String value;

  const SomeClass(this.value);

  Map<String, Object?> toJson() => {'some': 'class'};
}

class WithJson {
  Map<String, Object?> toJson(Set<String> values) => {
    'key': values.toList(), // Correct, converted to List
    'instance': SomeClass(''), // Correct, has custom 'toJson'
  };
}

Example with "methods"

Config

analysis_options.yaml

dcm:
  rules:
    - avoid-not-encodable-in-to-json:
        methods:
          - customToJson

❌ Bad:

class WithJson {
  // Also checked
  Map<String, Object?> customToJson(Set<String> values) => {
    // LINT: This expression is not encodable and will lead to an error when passed to 'jsonEncode'.
    //  Try converting it to 'List'.
    'key': values,
    // LINT: This expression is not encodable and will lead to an error when passed to 'jsonEncode'.
    //  Ensure it implements 'toJson' or try replacing it with a different expression.
    'function': () => null,
  };
}

Additional Resources

• CWE-1070: Serializable Data Element Containing non-Serializable Item Elements