{"record":{"id":"f60970a889c870b7","repo":"nautechsystems/nautilus_trader","slug":"missing-event-signature-in-topic0","errorCode":null,"errorMessage":"Missing event signature in topic0","messagePattern":"Missing event signature in topic0","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"crates/adapters/blockchain/src/hypersync/log.rs","lineNumber":106,"sourceCode":"/// Extracts the event signature from a log entry and returns it as a hex string\n///\n/// # Errors\n///\n/// Returns an error if the event signature (topic0) is not present in the log.\npub fn extract_event_signature(log: &HypersyncLog) -> anyhow::Result<String> {\n    extract_event_signature_bytes(log).map(hex::encode)\n}\n\n/// Extracts the event signature from a log entry and returns it as raw bytes\n///\n/// # Errors\n///\n/// Returns an error if the event signature (topic0) is not present in the log.\npub fn extract_event_signature_bytes(log: &HypersyncLog) -> anyhow::Result<&[u8]> {\n    if let Some(topic) = log.topics.first().and_then(|t| t.as_ref()) {\n        Ok(topic.as_ref())\n    } else {\n        anyhow::bail!(\"Missing event signature in topic0\");\n    }\n}\n\n/// Validates that a log entry corresponds to the expected event by comparing its topic0 with the provided event signature hash.\n///\n/// # Errors\n///\n/// Returns an error if the event signature doesn't match or if topic0 is missing.\npub fn validate_event_signature_hash(\n    event_name: &str,\n    target_event_signature_hash: &str,\n    log: &HypersyncLog,\n) -> anyhow::Result<()> {\n    let sig_bytes = extract_event_signature_bytes(log)?;\n    core::validate_signature_bytes(sig_bytes, target_event_signature_hash, event_name)\n}\n\n#[cfg(test)]","sourceCodeStart":88,"sourceCodeEnd":124,"githubUrl":"https://github.com/nautechsystems/nautilus_trader/blob/18893faf8b356be3320add8de2f861b0b647cf06/crates/adapters/blockchain/src/hypersync/log.rs#L88-L124","documentation":"This error means a log entry had no topic0 value, so the event signature bytes cannot be extracted. The library requires topic0 because it is the keccak-256 hash of the event signature used to identify which event the log belongs to. It is thrown whenever `log.topics` is empty or the first element is null, rather than silently returning empty bytes that could cause false event matches.","triggerScenarios":"Calling `extract_event_signature_bytes`, `extract_event_signature`, or `validate_event_signature_hash` with a `HypersyncLog` whose `topics` array is empty, or whose first entry is `None`/null (e.g. anonymous events or malformed log data).","commonSituations":"Querying logs for contracts that emit anonymous events (no topic0); fetching logs with a topic filter that does not constrain topic0; decoding raw logs from chain reorgs or partial data where the topics array was truncated; passing an artificially constructed log in tests.","solutions":["Check `log.topics.first()` is `Some` before calling, and skip anonymous logs (events declared with `anonymous` in Solidity have no topic0)","Filter your Hypersync query on topic0 so returned logs always carry an event signature","When decoding arbitrary logs, treat absence of topic0 as 'undecodable' and skip the log instead of erroring","If the log should always have topic0, verify the query/table mapping isn't dropping the topics column"],"exampleFix":"// before\nlet sig = extract_event_signature_bytes(&log)?;\n// after\nlet sig = log.topics.first().and_then(|t| t.as_ref()).map(|t| t.as_ref());\nmatch sig {\n    Some(sig) => { /* use signature */ }\n    None => { /* skip anonymous/unmatched log */ }\n}","handlingStrategy":"validation","validationCode":"fn log_has_topic0(log: &HypersyncLog) -> bool {\n    matches!(log.topics.first(), Some(Some(_)))\n}\n// call only if log_has_topic0(&log)","typeGuard":"fn has_signature(log: &HypersyncLog) -> Option<&[u8]> {\n    log.topics.first().and_then(|t| t.as_ref()).map(|t| t.as_ref())\n}","tryCatchPattern":"match extract_event_signature_bytes(&log) {\n    Ok(sig) => decode_with(sig),\n    Err(_) => skip_log(), // anonymous or malformed log\n}","preventionTips":["Filter Hypersync queries on topic0 so only signature-bearing logs are returned","Skip logs with empty topics arrays — anonymous events legitimately have none","Never assume log shape from query parameters alone; re-check the topics array"],"tags":["blockchain","hypersync","event-logs","missing-topic0"],"backgroundTag":"missing-required-argument","analyzedSha":"18893faf8b356be3320add8de2f861b0b647cf06","analyzedAt":"2026-09-08T20:49:34.690Z","contentChangedAt":"2026-09-08T20:49:34.690Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}