Dropped Exception

ID

kotlin.dropped_exception

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Kotlin

Tags

CWE:391, error-handling, exception

Description

Reports catch blocks whose body never references the caught exception variable.

The catch block may contain code, but if the exception variable itself is never used — not logged, not re-thrown, not inspected — the exception information is effectively discarded. Use _ as the parameter name to document that the suppression is intentional.

Rationale

// Bad — exception e is caught but ignored; retry() loses the root cause
try {
    connect()
} catch (e: IOException) {  // FLAW
    retry()
}

// Good — exception logged before retry
try {
    connect()
} catch (e: IOException) {
    logger.warn("Connection failed, retrying", e)
    retry()
}

// OK — intentional ignore with _ convention
try {
    connect()
} catch (_: IOException) {
    retry()
}

Remediation

  • Log the exception before taking alternative action.

  • Re-throw it if the caller needs to handle it.

  • If suppression is intentional, use _ as the catch parameter name.

References