tests: Hold each REQUIRES line to what its resource needs

A standalone program is made from an encoder by embedding the resources
its REQUIRES line names, in order, before it (the build/standalone
targets, libpostscriptbarcode's emit_required_resources), so a line that
omits a resource, or lists one before something it needs, gives a program
that fails when run, as MaxiCode's did for want of render.

tests/test_requires checks every source file: each name listed is a
resource, listed once and not itself; everything the body loads with
findresource is listed; what a listed resource requires is listed too;
and each listed resource comes after what it requires. It needs no build,
so it runs first. Against the tree before the preceding fixes it reported
the four resources those fixed, MaxiCode included.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P51a75ubvkJAfhEwpZRwcn

Author: terryburton

tests/run_tests

@@ -3,14 +3,15 @@
 # Barcode Writer in Pure PostScript
 # https://bwipp.terryburton.co.uk
 #
-# Copyright (c) 2004-2024 Terry Burton
+# Copyright (c) 2004-2026 Terry Burton
 
 set -e
 set -u
 set -o pipefail
 
 TESTDIR=$(dirname "$0")
 
+"$TESTDIR"/test_requires/run
 "$TESTDIR"/ps_tests/run
 "$TESTDIR"/test_monolithic/run
 "$TESTDIR"/test_monolithic_package/run

tests/test_requires/check_requires.pl

@@ -0,0 +1,62 @@
+#!/usr/bin/perl
+
+# Barcode Writer in Pure PostScript
+# https://bwipp.terryburton.co.uk
+#
+# Copyright (c) 2026 Terry Burton
+#
+# Hold each resource's REQUIRES line to what the resource needs. A consumer
+# makes a standalone program from an encoder by embedding the resources its
+# REQUIRES line names, in that order, followed by the encoder (the
+# build/standalone targets, libpostscriptbarcode's emit_required_resources),
+# so the line must name every resource needed, however indirectly, and each
+# before the resources that need it.
+#
+# For every source file:
+#   - each name listed is a resource, listed once, and not the resource itself
+#   - each resource the body loads with findresource is listed
+#   - the list is closed: what a listed resource requires is listed too
+#   - a listed resource comes after everything it requires
+
+use strict;
+use warnings;
+use lib 'build';
+use BWIPP qw(parse_source);
+
+my (%requires, %loads);
+for my $file (sort glob 'src/*.ps.src') {
+    open(my $fh, '<', $file) || die "Unable to open $file";
+    my $src = join('', <$fh>);
+    close($fh);
+    my $res = parse_source($src);
+    $requires{$res->{name}} = [ split ' ', $res->{requires} ];
+    $loads{$res->{name}} = [ $res->{body} =~ m{/([\w-]+) dup /uk\.co\.terryburton\.bwipp findresource}g ];
+}
+
+my @problems;
+for my $name (sort keys %requires) {
+    my @req = @{ $requires{$name} };
+    my %pos;
+    for my $i (0 .. $#req) {
+        my $r = $req[$i];
+        push @problems, "$name: lists $r, which is not a resource" unless exists $requires{$r};
+        push @problems, "$name: lists $r more than once" if exists $pos{$r};
+        push @problems, "$name: lists itself" if $r eq $name;
+        $pos{$r} //= $i;
+    }
+    for my $l (@{ $loads{$name} }) {
+        push @problems, "$name: loads $l but does not list it" unless exists $pos{$l};
+    }
+    for my $r (grep { exists $requires{$_} } @req) {
+        for my $rr (@{ $requires{$r} }) {
+            if (!exists $pos{$rr}) {
+                push @problems, "$name: lists $r, which requires $rr, but does not list $rr";
+            } elsif ($pos{$rr} > $pos{$r}) {
+                push @problems, "$name: lists $rr after $r, which requires it";
+            }
+        }
+    }
+}
+
+print "$_\n" for @problems;
+exit(@problems ? 1 : 0);

tests/test_requires/run

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+# Barcode Writer in Pure PostScript
+# https://bwipp.terryburton.co.uk
+#
+# Copyright (c) 2026 Terry Burton
+
+set -e
+set -u
+set -o pipefail
+
+TEST=$(dirname "$0")
+
+echo -n "Running $TEST: "
+
+if problems=$(perl "$TEST/check_requires.pl"); then
+	echo "PASS"
+	exit 0
+else
+	echo "FAIL"
+	echo "$problems"
+	exit 1
+fi