Improve build system auto-selection process

[debhelper.git] / Debian / Debhelper / Dh_Buildsystems.pm

diff --git a/Debian/Debhelper/Dh_Buildsystems.pm b/Debian/Debhelper/Dh_Buildsystems.pm
index a9a13a29d98e287b93732116c74728220073a1f1..2893c1a4c626dea352708e3c38cbb47f615cf6dd 100644 (file)
--- a/Debian/Debhelper/Dh_Buildsystems.pm
+++ b/Debian/Debhelper/Dh_Buildsystems.pm
@@ -14,6 +14,8 @@ use File::Spec;
 use base 'Exporter';
 our @EXPORT=qw(&buildsystems_init &buildsystems_do &load_buildsystem &load_all_buildsystems);
 
+use constant BUILD_STEPS => qw(configure build test install clean);
+
 # Historical order must be kept for backwards compatibility. New
 # build systems MUST be added to the END of the list.
 our @BUILDSYSTEMS = (
@@ -66,14 +68,26 @@ sub load_buildsystem {
        }
        else {
                # Try to determine build system automatically
+               my $selected;
+               my $selected_level = 0;
                for $system (@BUILDSYSTEMS) {
                        my $inst = create_buildsystem_instance($system, @_);
-                       if ($inst->check_auto_buildable($step)) {
-                               return $inst;
+
+                       # Only derived (i.e. more specific) build system can be
+                       # considered beyond the currently selected one.
+                       next if defined $selected && !$inst->isa(ref $selected);
+
+                       # If the build system says it is auto-buildable at the current
+                       # step and it can provide more specific information about its
+                       # status than its parent (if any), auto-select it.
+                       my $level = $inst->check_auto_buildable($step);
+                       if ($level > $selected_level) {
+                               $selected = $inst;
+                               $selected_level = $level;
                        }
                }
+               return $selected;
        }
-       return;
 }
 
 sub load_all_buildsystems {
@@ -189,7 +203,7 @@ sub buildsystems_do {
                $step =~ s/^dh_auto_//;
        }
 
-       if (grep(/^\Q$step\E$/, qw{configure build test install clean}) == 0) {
+       if (grep(/^\Q$step\E$/, BUILD_STEPS) == 0) {
                error("unrecognized build step: " . $step);
        }