[lprnmns]

With lastModified: false, any request carrying If-Modified-Since is answered with 304 Not Modified, however old the date is:

$ curl -i -H 'If-Modified-Since: Thu, 01 Jan 1970 00:00:00 GMT' http://127.0.0.1:18765/   # send(req, '/name.txt', { root, lastModified: false })
HTTP/1.1 304 Not Modified

isNotModifiedFailure() treats a missing Last-Modified as "not modified":

if (!lastModified || (Date.parse(lastModified) <= Date.parse(ifModifiedSince))) {
  return true
}

With nothing to compare against, the response should be considered stale. That's what fresh does (var modifiedStale = !lastModified || !(…)), and it is what this module did before #31 replaced the fresh() call with an inlined check. In practice the 304 traps clients that still hold a Last-Modified from before lastModified was turned off (for example after switching to content hashes, or for files whose mtime is meaningless). They keep revalidating with If-Modified-Since and never receive the new content. @fastify/static passes lastModified through, so it has the same behavior.

The condition now only returns true when there is a Last-Modified to compare. An unparsable If-Modified-Since still yields a fresh 200, as before.

Test: "should respond with 200 when Last-Modified is disabled" in the If-Modified-Since block of test/send.2.test.js fails without the change. npm test passes (214 tests, 100% coverage, tstyche) and npm run lint is clean.

[gurgunday]

lgtm