tests: fix spurious failure when zip is present but unzip is not

Fixes automake bug#15181.

* t/dist-formats.tap (have_compressor): When checking that zip(1), also
check for unzip(1), otherwise "make distcheck" will be unable to extract
the zip tarball it creates, which will cause spurious failures.  While
at it, reorganize the existing code a bit.
* THANKS, NEWS: Update.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

1 files changed, 29 insertions, 25 deletions

diff --git a/t/dist-formats.tap b/t/dist-formats.tap
index 49281d92d..3c9e6210f 100644
--- a/t/dist-formats.tap
+++ b/t/dist-formats.tap
@@ -67,34 +67,38 @@ setup_vars_for_compression_format ()
 have_compressor ()
 {
   test $# -eq 1 || fatal_ "have_compressor(): bad usage"
-  case $1 in
+  if test $1 = gzip; then
     # Assume gzip(1) is available on every reasonable portability target.
-    gzip)
-      return 0;;
-    *)
-      case $1 in
-        # Do not use --version, or older versions bzip2 would try to
-        # compress stdin.  This would cause binary output in the test
-        # logs, with potential breakage of our testsuite harness.
-        bzip2) o=--help;;
-        # OpenSolaris zip do not support the '--version' option, but
-        # accepts the '-v' one with a similar meaning (if no further
-        # arguments are given).
-        zip) o=-v;;
-        # Assume the other compressors we care about support the
-        # '--version' option.
-        *) o=--version;;
-      esac
-      # Redirect to stderr to avoid polluting the output, in case this
-      # function is used in a command substitution (as it is, below).
-      if $1 $o </dev/null >&2; then
-        return 0
-      else
-        return 1
-      fi
+    return 0
+  fi
+  needed_programs=$1
+  # Assume by default the other compressors we care about support the
+  # '--version' option.  We'll special-case the one which don't.
+  checker_option=--version
+  case $1 in
+    bzip2)
+      # Do not use --version, or older versions bzip2 would try to
+      # compress stdin.  This would cause binary output in the test
+      # logs, with potential breakage of our testsuite harness.
+      checker_option=--help
+      ;;
+    zip)
+      # OpenSolaris zip do not support the '--version' option, but
+      # accepts the '-v' one with a similar meaning (if no further
+      # arguments are given).
+      checker_option=-v
+      # Also, we need 'unzip' to decompress the created zipped archives
+      # (bug#15181).
+      needed_programs='zip unzip'
       ;;
   esac
-  fatal_ "have_compressor(): dead code reached"
+  # Redirect to stderr to avoid polluting the output, in case this
+  # function is used in a command substitution (as it is, later in
+  # this script).
+  for p in $needed_programs; do
+    $p $checker_option </dev/null >&2 || return 1
+  done
+  return 0
 }
 
 all_compression_formats='gzip lzip xz bzip2 zip'