no-unawaited-log

Require await on LogTape log calls that use async lazy callbacks.

Severity	Fixable	Category
error	yes (when enclosing function is async)	no-unawaited-log

Rationale

LogTape log methods accept a lazy callback as the second argument. When that callback is async, the log method returns a Promise<void>. If the promise is not awaited, LogTape cannot guarantee that the log record is fully processed before execution moves on.

// Incorrect — the async callback's result is silently dropped
logger.debug("Data: {d}.", async () => ({ d: await fetchData() }));

// Correct — awaiting ensures the log is flushed before continuing
await logger.debug("Data: {d}.", async () => ({ d: await fetchData() }));

The rule is silent for:

• Synchronous callbacks (not async)
• Calls directly preceded by await
• Calls used as the return value of a function (promise is propagated)
• Calls chained with .then(), .catch(), or .finally()
• Calls that form the concise body of an arrow function (promise is propagated to the caller)

The auto-fix inserts await before the log call. It is only applied when the enclosing function is itself async; otherwise the fix would introduce a syntax error.

Examples

Incorrect

import { getLogger } from "@logtape/logtape";
const logger = getLogger(["my-app"]);

async function handler() {
  logger.debug("Data: {d}.", async () => ({  // ← error
    d: await fetchData(),
  }));
}

Correct

import { getLogger } from "@logtape/logtape";
const logger = getLogger(["my-app"]);

async function handler() {
  // Awaited:
  await logger.debug("Data: {d}.", async () => ({ d: await fetchData() }));

  // Returned (caller is responsible for awaiting):
  return logger.debug("Data: {d}.", async () => ({ d: await fetchData() }));
}

// Concise arrow body propagates the promise:
const logData = async () =>
  logger.debug("Data: {d}.", async () => ({ d: await fetchData() }));

Configuration

ESLint v9 flat config:

import logtape from "@logtape/lint/eslint";

export default [
  {
    plugins: { "@logtape": logtape },
    rules: {
      "@logtape/no-unawaited-log": "error",
    },
  },
];

Deno Lint (deno.json):

{
  "unstable": ["lint"],
  "lint": {
    "plugins": ["jsr:@logtape/lint/deno"],
    "rules": {
      "include": ["logtape/no-unawaited-log"]
    }
  }
}