FormatStringAnnotation
Invalid format string passed to formatting method.

Category
Severity
ERROR
Maturity

The problem

Methods can be annotated with Error Prone’s @FormatMethod annotation to indicate that calls to this function should be treated similarly to String.format: One of the parameters is a ‘format string’ (the first String parameter or the only parameter annotated with @FormatString), and the subsequent parameters are used as format arguments to that format string.

For example:

@FormatMethod
void myLogMethod(@FormatString String fmt, Object... args) {}

// ERROR: 2nd format argument isn't a number
myLogMessage("My log message: %d and %d", 3, "has a message");

In order to avoid complex runtime issues when the format string part is dynamically constructed, leading to a mismatch between the arguments and format strings, we require that the ‘format string’ argument in calls to @FormatMethod-annotated methods be one of:

We will then check that the format string and format arguments match.

For more information on possible format string errors, see the documentation on the FormatString check.

Suppression

Suppress false positives by adding an @SuppressWarnings("FormatStringAnnotation") annotation to the enclosing element.