Combining test flags inside [[ ]] produces unexpected results and no error message.

[Michael A. Smith]

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Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: i686-pc-linux-gnu-gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i686'
- -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu'
- -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/l$
uname output: Linux black 2.6.21-gentoo-r4 #1 PREEMPT Sun Jul 15 11:12:31 EDT
2007 i686 Intel(R) Pentium(R) 4 CPU 2.80GHz GenuineIntel GNU/Linux
Machine Type: i686-pc-linux-gnu

Bash Version: 3.2
Patch Level: 17
Release Status: release

Description:
  I set out to determine if a file was readable and not empty. To that end
  I tried combining the test flags -r and -s. I expected that syntax such as
  [[ -rs file ]] would either succeed, or fail with an error message.

  Unfortunately, while test -rs file and [ -rs file ] do error out (-rs: unary
  operator expected), [[ -rs file ]] happily ignores the 's', and returns true
  if and only if the file is readable. This is undocumented behavior.

Repeat-By:
  In an empty directory execute the following commands:
  echo abc > file1 && chmod -r file1
  > file2
  for f in *; do
    [[ -rs $f ]] &&
      echo "$f is readable and not empty" ||
      echo "$f is not readable or is empty, or there was an error"
    [[ -sr $f ]] &&
      echo "$f is not empty, and is readable" ||
      echo "$f is empty or not readable, or there was an error"
  done

  In my opinion the most intuitive result would be for [[ -rs file ]] to act
  in an equivalent manner to [[ -r file && -s file ]]; however, the most
  consistent behavior would be to see the following output:

  bash: [[: -rs: unary operator expected
  file1 is not readable or is empty, or there was an error
  bash: [[: -sr: unary operator expected
  file1 is empty or not readable, or there was an error
  bash: [[: -rs: unary operator expected
  file2 is not readable or is empty, or there was an error
  bash: [[: -sr: unary operator expected
  file2 is empty or not readable, or there was an error
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