if-clause garbles variable content

[marius]

I'd like to use a map in order to prevent various spiders from indexing documents, but I'm running into strange issues, which I can't explain (nginx 0.7.62 or 0.7.64):


root /tmp/test;

map $lookup $test_blacklist {
  default "";
  /aabbccddeeff/aabbccddeeff/2009/A/Pdf/20090101.pdf 1;
}

location ~* ^/aabbccddeeff(/.*) {
  set $lookup "";
  if ($http_user_agent ~ "Googlebot|Slurp|msnbot") {
    # force lowercase "aabbccddeeff"
    set $lookup /aabbccddeeff$1;
  }

  if ($test_blacklist != "") {
    return 410;
  }

  charset iso-8859-1;
  alias  /tmp/test/aabbccddeeff$1;
}


When requesting a file from that map, the open() log points to a garbled path "/aabbccddeeffcddeeff" rather than the requested "/aabbccddeeff/aabbccddeeff":


 31998#0: *1 "Googlebot|Slurp|msnbot" matches "Googlebot", client: 127.0.0.1, server: test, request: "HEAD /aabbccddeeff/aabbccddeeff/2009/A/Pdf/20090101.pdf HTTP/1.1", host: "test"
 31998#0: *1 open() "/tmp/test/aabbccddeeffcddeeff/2009/A/Pdf/20090101.pdf" failed (2: No such file or directory), client: 127.0.0.1, server: test, request: "HEAD /aabbccddeeff/aabbccddeeff/2009/A/Pdf/20090101.pdf HTTP/1.1", host: "test"


What's more, if the user-agent isn't matched, the server sends a 301 redirect with an appended "/" rather than delivering the file:

HTTP/1.1 301 Moved Permanently
Location: http://test/aabbccddeeff/aabbccddeeff/2009/A/Pdf/20090101.pdf/


On the other hand, if I omit the $http_user_agent test, the server behaves as expected, by either delivering the file or returning a 410 status, dependning of the content of $lookup.

Am I doing something wrong?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,31950,31950#msg-31950