Fix dh_bash-completion for debhelper 13

As reported in bug #965225, dh_bash-completion fails with debhelper 13.
Patch submitted via BTS [2].

[1] https://bugs.debian.org/965225
[2] https://bugs.debian.org/965225#19

2 files changed, 66 insertions, 0 deletions

diff --git a/debian/changelog b/debian/changelog
index eb65c105..546eedd7 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,5 +1,8 @@
 bash-completion (1:2.10-2) UNRELEASED; urgency=medium
 
+  [ Sergio Durigan Junior ]
+  * Fix dh_bash-completion for debhelper 13 (Closes: #965225).
+
   [ Gabriel F. T. Gomes ]
   * Update standards version to 4.5.0, no changes needed.
   * Bump debhelper from 12 to 13.
diff --git a/debian/extra/debhelper/dh_bash-completion b/debian/extra/debhelper/dh_bash-completion
index f96704b0..d1d9bf2e 100755
--- a/debian/extra/debhelper/dh_bash-completion
+++ b/debian/extra/debhelper/dh_bash-completion
@@ -33,6 +33,60 @@ completion snippet after. The file format is as follows:
 
 =cut
 
+# This helper function tries to determine (using some poor man's
+# heuristics) whether $file (its first and only argument) is a
+# filelist containing a list of files to be installed by us, or a
+# bash-completion script, which should itself be installed.
+#
+# If we're dealing with a filelist, return 1.  Otherwise, return 0.
+sub is_filelist {
+	# The file to be checked.
+	my ($file) = @_;
+
+	open (DH_FILE, '<', $file) || error("cannot read $file: $!");
+
+	while (<DH_FILE>) {
+		# Get rid of lines containing just spaces or comments.
+		chomp;
+		s/^\s++//;
+		next if /^#/;
+		s/\s++$//;
+
+		# We always ignore/permit empty lines
+		next if $_ eq '';
+
+		# This is the heart of the script.  Here, we check for some
+		# well-known idioms on bash scripts, and try to determine if
+		# they're present in the file we're examining.  We assume that
+		# if they are, then this means the file is a bash-completion
+		# script.
+		#
+		# The regexes check:
+		#
+		# - If we're calling the bash function "complete", which is a
+		#   pretty common thing to do in bash-completion scripts, or
+		#
+		# - If we're using the $(program) way of executing a program.
+		#   We don't take into account multi-line statements.  Or
+		#
+		# - If we're calling the bash function "compgen", which is
+		#   also a pretty common thing that bash-completion scripts
+		#   do.  Or
+		#
+		# - If we see an "if...then" construction in the file.  We
+		#   take into account multi-line statements.
+		if (/\s*complete.*-[A-Za-z].*/
+			|| /\$\(.*\)/
+			|| /\s*compgen.*-[A-Za-z].*/
+			|| /\s*if.*;.*then/s) {
+			return 0;
+		}
+	}
+
+	# If we reached the end, this is not a bash-completion script.
+	return 1;
+}
+
 init();
 
 my $srcdir = '.';
@@ -53,6 +107,15 @@ PKG: foreach my $package (@{$dh{DOPACKAGES}}) {
 	if ($completions) {
 		install_dir($bc_dir);
 
+		# Invoke our heuristic function to try and determine
+		# if we're dealing with a filelist or with a
+		# bash-completion script.
+		if (!is_filelist($completions)) {
+			verbose_print "detected $completions as a bash-completion script";
+			install_file($completions, "$bc_dir/$package");
+			next PKG
+		}
+
 		# try parsing a list of files
 		@install = filedoublearray($completions);
 		foreach my $set (@install) {