stop trying to handle substvars idempotently

In the beginning, I tried to be careful to have commands that added a
substvar remove it when ran again with different options that caused it
to not be needed. However, now when I look over the code, I see 3 places
that got it right, 1 that was right but I just broke, and a dozen that
don't even try to handle this case.

Also, handling the case is hard; code that adds substvars may be complex
and calculate versioned dependencies. The removal code then has to somehow
also come up with those same exact dependency strings. It's a recipe for
nasty code and maintenance headache even if I went and fixed everything
right now.

Instead, I dropped the whole thing. Many debhelper commands make no
pretense of being idempotent anyway; it's easy and normal to call dh_prep
when starting a binary package build, with the exact purpose of not needing
to worry about idempotency.

I did leave in the delsubstvar function, as well as the option to
addsubstvar that, confusingly, causes an item to be removed. Just for
library compatability reasons.

5 files changed, 4 insertions, 14 deletions

diff --git a/dh_installdebconf b/dh_installdebconf
index ff49f8ea..3e51f8ee 100755
--- a/dh_installdebconf
+++ b/dh_installdebconf
@@ -117,9 +117,6 @@ foreach my $package (@{$dh{DOPACKAGES}}) {
 	if ($config ne '' || $templates ne '') {
 		addsubstvar($package, "misc:Depends", $debconfdep);
 	}
-	else {
-		addsubstvar($package, "misc:Depends", $debconfdep, undef, 1); # remove
-	}
 	
 	if (($config ne '' || $templates ne '') && ! $dh{NOSCRIPTS}) {
 		autoscript($package,"postrm","postrm-debconf");
diff --git a/dh_installxfonts b/dh_installxfonts
index 21e7fcec..25e073bc 100755
--- a/dh_installxfonts
+++ b/dh_installxfonts
@@ -82,10 +82,6 @@ foreach my $package (@{$dh{DOPACKAGES}}) {
 
 		addsubstvar($package, "misc:Depends", "xfonts-utils");
 	}
-	else {
-		# remove
-		addsubstvar($package, "misc:Depends", "xfonts-utils", "", 1);
-	}
 }
 
 =head1 SEE ALSO
diff --git a/dh_perl b/dh_perl
index eaa08fa8..d43043fa 100755
--- a/dh_perl
+++ b/dh_perl
@@ -90,8 +90,6 @@ use constant XS_MODULE => 4;
 foreach my $package (@{$dh{DOPACKAGES}}) {
 	my $tmp=tmpdir($package);
 
-	delsubstvar($package, "perl:Depends"); # for idempotency
-	
 	# Check also for alternate locations given on the command line
 	my @dirs = grep -d, map "$tmp/$_", $vendorlib, $vendorarch, @ARGV;
 
diff --git a/dh_python b/dh_python
index 8f8c3788..d7a4bed7 100755
--- a/dh_python
+++ b/dh_python
@@ -135,8 +135,6 @@ use constant SO_MODULE_NONSTANDARD => 16;
 foreach my $package (@{$dh{DOPACKAGES}}) {
 	my $tmp = tmpdir($package);
 
-	delsubstvar($package, "python:Depends");
-
 	my @dirs = ("usr/lib/site-python", "usr/lib/$package", "usr/share/$package", "usr/lib/games/$package", "usr/share/games/$package", @ARGV );
 	my @dirs_so = ("usr/lib/site-python", @ARGV );
 
diff --git a/doc/PROGRAMMING b/doc/PROGRAMMING
index 0fca4722..ca76b9c9 100644
--- a/doc/PROGRAMMING
+++ b/doc/PROGRAMMING
@@ -216,9 +216,10 @@ addsubstvar($package, $substvar, $deppackage, $verinfo, $remove)
 	- version info for the package (optional) (ie: ">= 1.1")
 	- if this last parameter is passed, the thing that would be added
 	  is removed instead. This can be useful to ensure that a debhelper
-	  command is idempotent. Note that without this parameter, if you
-	  call the function twice with the same values it will only add one
-	  item to the substvars file.
+	  command is idempotent. (However, we generally don't bother,
+	  and rely on the user calling dh_prep.) Note that without this
+	  parameter, if you call the function twice with the same values it
+	  will only add one item to the substvars file.
 delsubstvar($package, $substvar)
 	This function removes the entire line for the substvar from the
 	package's shlibs file.