Implement dynamic prerequisites

dist.ini

@@ -59,3 +59,4 @@ check_dual_life_versions = 0
 skip = ExtUtils::Config
 skip = ExtUtils::Helpers
 skip = ExtUtils::InstallPaths
+skip = CPAN::Requirements::Dynamic

lib/Module/Build/Tiny.pm

@@ -188,6 +188,15 @@ sub Build_PL {
 	make_executable('Build');
 	my @env = defined $ENV{PERL_MB_OPT} ? split_like_shell($ENV{PERL_MB_OPT}) : ();
 	write_file('_build_params', encode_json([ \@env, \@ARGV ]));
+	if (-e 'dynamic-prereqs.json') {
+		my %meta = (%{ $meta->as_struct }, dynamic_config => 0);
+		my %opt = get_arguments(\@env, \@ARGV);
+		require CPAN::Requirements::Dynamic;
+		my $dynamic_parser = CPAN::Requirements::Dynamic->new(%opt);
+		my $prereq = $dynamic_parser->evaluate_file('dynamic-prereqs.json');
+		$meta{prereqs} = $meta->effective_prereqs->with_merged_prereqs($prereq)->as_string_hash;
+		$meta = CPAN::Meta->new(\%meta);
+	}
 	$meta->save(@$_) for ['MYMETA.json'], [ 'MYMETA.yml' => { version => 1.4 } ];
 }
 
@@ -228,14 +237,14 @@ than 200, yet supports the features needed by most distributions.
 
 =item * Module sharedirs
 
+=item * Dynamic prerequisites
+
 =back
 
 =head2 Not Supported
 
 =over 4
 
-=item * Dynamic prerequisites
-
 =item * HTML documentation generation
 
 =item * Extending Module::Build::Tiny

t/simple.t

@@ -55,6 +55,13 @@ if ($has_compiler) {
 		---
 }
 
+$dist->add_file('dynamic-prereqs.json', undent(<<"	---"));
+	{
+		"version": 1,
+		"expressions": [ { "condition": [ "has_perl", "$]"], "prereqs": { "Bar": 1 } } ]
+	}
+	---
+
 $dist->regen;
 
 my $interpreter = ($Config{startperl} eq $^X )
@@ -136,6 +143,13 @@ sub _slurp { do { local (@ARGV,$/)=$_[0]; <> } }
   ok( -d catdir(qw/blib lib auto share module Foo-Bar/), 'moduole sharedir has been made');
   ok( -f catfile(qw/blib lib auto share module Foo-Bar file.txt/), 'module sharedir file has been made');
 
+  require CPAN::Meta;
+  my $meta = CPAN::Meta->load_file("MYMETA.json");
+  my $req = $meta->effective_prereqs->requirements_for('runtime', 'requires');
+  my $dynamic_dependency = join ',', sort $req->required_modules;
+
+  is($dynamic_dependency, 'Bar,perl', 'Dependency on Foo has been inserted');
+
   if ($has_compiler) {
     XSLoader::load('Foo::Bar');
     is(Foo::Bar::foo(), "Hello World!\n", 'Can run XSub Foo::Bar::foo');