Filter @INC hook refs from yath startup and process_includes

lib/App/Yath/Script/V1.pm

@@ -21,7 +21,8 @@ sub do_begin {
     my $ORIG_TMP_PERMS;
     my %ORIG_SIG = map { defined($SIG{$_}) ? ($_ => "$SIG{$_}") : () } keys %SIG;
     my @ORIG_ARGV = @$argv;
-    my @ORIG_INC = @INC;
+    # Skip @INC hook refs (coderef / arrayref / blessed); they can't cross exec via -I nor round-trip JSON.
+    my @ORIG_INC = grep { ref $_ eq '' } @INC;
     my %CONFIG;
 
     @ARGV = @$argv;

lib/Test2/Harness/Util.pm

@@ -104,7 +104,8 @@ sub process_includes {
         @list = @start;
     }
 
-    push @list => @INC if delete $params{include_current};
+    # Skip @INC hook refs; clean_path would stringify them to bogus paths.
+    push @list => grep { ref $_ eq '' } @INC if delete $params{include_current};
 
     @list = map { $_ eq '.' ? $_ : clean_path($_) || $_ } @list if delete $params{clean};
 

t/integration/inc_hook.t

@@ -0,0 +1,63 @@
+use Test2::V0;
+
+use File::Spec;
+
+use App::Yath::Tester qw/yath/;
+
+use App::Yath::Util qw/find_yath/;
+find_yath();
+
+my $dir = __FILE__;
+$dir =~ s{\.t$}{}g;
+
+my $hook_dir = File::Spec->rel2abs($dir);
+my $target   = File::Spec->catfile($hook_dir, 'simple.tx');
+
+# Each fixture injects one of the three @INC hook forms documented in
+# perlvar "@INC": blessed object, coderef, arrayref. Without filtering,
+# the ref would be snapshotted into settings->harness->orig_inc, crash
+# JSON encoding in write_settings_to, and inject "HASH(0x...)" /
+# "CODE(0x...)" / "ARRAY(0x...)" garbage paths into child -I flags.
+my @cases = (
+    {
+        name   => 'blessed object hook',
+        module => 'FakeHook',
+        ref_re => qr/FakeHook=HASH\(/,
+    },
+    {
+        name   => 'coderef hook',
+        module => 'CoderefHook',
+        ref_re => qr{/CODE\(0x},
+    },
+    {
+        name   => 'arrayref hook',
+        module => 'ArrayrefHook',
+        ref_re => qr{/ARRAY\(0x},
+    },
+);
+
+for my $case (@cases) {
+    yath(
+        command => 'test',
+        args    => [$target],
+        env     => {
+            PERL5OPT => "-I$hook_dir -M$case->{module}",
+        },
+        exit    => 0,
+        test    => sub {
+            my $out = shift;
+            unlike(
+                $out->{output},
+                qr/encountered object/,
+                "$case->{name}: no JSON encode error",
+            );
+            unlike(
+                $out->{output},
+                $case->{ref_re},
+                "$case->{name}: no stringified ref leaked into output",
+            );
+        },
+    );
+}
+
+done_testing;

t/integration/inc_hook/ArrayrefHook.pm

@@ -0,0 +1,7 @@
+package ArrayrefHook;
+use strict;
+use warnings;
+
+unshift @INC, [sub { return }];
+
+1;

t/integration/inc_hook/CoderefHook.pm

@@ -0,0 +1,7 @@
+package CoderefHook;
+use strict;
+use warnings;
+
+unshift @INC, sub { return };
+
+1;

t/integration/inc_hook/FakeHook.pm

@@ -0,0 +1,10 @@
+package FakeHook;
+use strict;
+use warnings;
+
+# INC is a special identifier that lives in main::, hence the FQN.
+sub FakeHook::INC { return }
+
+unshift @INC, bless({}, __PACKAGE__);
+
+1;

t/integration/inc_hook/simple.tx

@@ -0,0 +1,5 @@
+use Test2::V0;
+
+ok(1, 'basic test runs under @INC hook');
+
+done_testing;