Arguments silently ignored in filter mode

[rdpate]

Ack silently ignores given filenames in filter mode. Expected behavior is to either ignore stdin (this is what grep does), search the specified arguments in addition to stdin, or warn/error. Actual behavior is to silently ignore the arguments. Examples:

$ cat file
xbyz
$ ack b. file  # as expected
xbyz
$ echo abcd | ack b. file  # bug-1
abcd
$ ack b. file --filter  # bug-2
$ echo abcd | ack b. file --filter  # bug-3
$ echo abcd | ack b. file /dev/stdin --nofilter  # as expected
file
1:xbyz

/dev/stdin
1:abcd
$

Tested against http://beyondgrep.com/ack-2.14-single-file on Ubuntu 14.04.

The last example, with /dev/stdin, doesn't make sense in isolation. I started with "-" instead, then found out ack doesn't treat "-" to mean "read stdin". I didn't think that warranted a separate issue, but any fix to this bug could address that too. (edit: it was a deeper problem than I expected, see #269)

$ ack b. - <file
ack: -: No such file or directory

[hoelzro]

@rdpate Thanks for all of the time and effort you've spent investigating this! I think @petdance and I are going to have a discussion involving the community on what the right way to handle these sorts of things is.

[rdpate]

Another option to the three for expected behavior I listed above: use the presence/absence of --[no]filter to determine what to do. Specifically:

• echo abcd | ack b. file
  • bug-1 above
  • I would ignore stdin, similar to grep
• ack b. file --filter
  • bug-2 above
  • I would read stdin and file, in that order, even if stdin is a tty
    • which adds using arguments to current behavior, instead of ignoring them
• echo abcd | ack b. file --filter
  • bug-3 above
  • I would read stdin and file, in that order
• echo abcd | ack b. file --nofilter
  • existing behavior is ignore stdin and read file
  • I would keep existing

In fact, if my suggested behavior was adopted, then the --filter option can be removed. Instead of using --nofilter, you would instead redirect stdin from </dev/null. Instead of --filter, you would use "-" or "/dev/stdin". (Whenever I say /dev/stdin, I really mean to say also allow "-" if ack is changed to interpret it as stdin, since I know /dev/stdin isn't universal.)

The quick "type tool | ack pat in a terminal" behavior is preserved -- though a typo of "pat" being more than one word would not be a warning/error, it should be quickly identified by the user because the second half of a pattern is unlikely to be a file ack can open. In a script, you would be required to either redirect stdin or specify "." -- but no warning could be given if you didn't.

This has breaking changes per-project/user .ackrc using --[no]filter, but I think such would be acceptable as I don't imagine this option is ever used in .ackrc.

Do you have a system in place for deprecating --[no]filter? Or should it just be removed, giving an error if specified? I'd like to try my hand at implementing this.

[rdpate]

I'd like to try my hand at implementing this.

Twelve hours later... at least I know some perl now. :) Please let me know if I wrote non-idiomatic code, I tried to follow project conventions. In particular, using scalar @a == 1 to test array length seemed weird, but I couldn't find anything better.