Improvements to 31c9a3 - CPAN code did depend on the previous behaviour of blessing filehandles into FileHandle

It turns out that it's not quite as simple as blessing into IO::File.
If you do (just) that, then it breaks any existing code that does
C<require IO::Handle;> to allow it to call methods on file handles,
because they're blessed into IO::File, which isn't loaded. (Note this code
doesn't assume that methods in IO::Seekable are there to be called)

So, it all should work if you also set @IO::File:::ISA correctly?
That way, code that assumes that methods from IO::Handle can be called will
work. However, gv.c now starts complaining (but not failing) if IO::Handle,
IO::Seekable and Exporter aren't present, because it goes looking for
methods in them.

So the solution seems to be to set @IO::File::ISA *and* create (empty)
stashes for the other 3 packages. Patch appended, but not applied.

1 files changed, 25 insertions, 0 deletions

diff --git a/t/op/filehandle.t b/t/op/filehandle.t
new file mode 100644
index 0000000000..408c6701c1
--- /dev/null
+++ b/t/op/filehandle.t
@@ -0,0 +1,25 @@
+#!./perl
+
+# There are few filetest operators that are portable enough to test.
+# See pod/perlport.pod for details.
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require './test.pl';
+}
+
+plan 4;
+use FileHandle;
+
+my $str = "foo";
+open my $fh, "<", \$str;
+is <$fh>, "foo";
+
+eval {
+   $fh->seek(0, 0);
+   is $fh->tell, 0;
+   is <$fh>, "foo";
+};
+
+is $@, '';