ipc: improve exception handling

When an exception triggers a teardown of the worker process
(ipc_worker_stop), we need to combine subsequent exceptions and
show the original one, first.  In other words, we must not lose
the original exception if new exceptions are thrown during
teardown.

So rely on `wantarray' to grab caller contexts to allow
returning exceptions as a list rather than throwing them
immediately.

diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index 257c78677bc0ed48a4034914c51aae08573cb0ec..6f380d4c888e64c5a7ee650e0562afa7326c8075 100644 (file)
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -66,8 +66,8 @@ sub _get_rec ($) {
 
 sub ipc_fail ($@) {
        my ($self, @msg) = @_;
-       eval { ipc_worker_stop($self) };
-       unshift @msg, " (stop: $@)" if $@;
+       my @err = eval { ipc_worker_stop($self) };
+       unshift @msg, @err;
        eval { delete $self->{-ipc_res} };
        unshift @msg, " (delete -ipc_res: $@)" if $@;
        croak @msg;
@@ -91,6 +91,7 @@ sub ipc_read_step ($$) {
        my $ret = ipc_get_res $self;
        splice @$inflight, 0, 4;
        eval { $acb->($self, $sub, $sub_arg, $acb_arg, $ret) };
+       return ($@ ? ($@) : ()) if wantarray;
        ipc_fail $self, "E: $sub $@" if $@;
 }
 
@@ -236,9 +237,13 @@ sub ipc_worker_stop {
        my ($self) = @_;
        if (my $w_req = delete $self->{-ipc_req}) {
                close $w_req; # invalidate if referenced upstack
-               ipc_wait_all $self;
-               delete $self->{-ipc_res}; # ipc_worker_reap will fire
+               my @exc = ipc_wait_all $self;
+               my $res = delete $self->{-ipc_res};
+               return @exc if wantarray;
+               die @exc if @exc;
+               # ipc_worker_reap will fire for $res going out-of-scope
        }
+       ();
 }
 
 sub _wait_return ($$) {
@@ -251,15 +256,22 @@ sub _wait_return ($$) {
 my $ipc_die = sub { # default ipc_async acb
        my ($self, undef, undef, undef, $ret) = @_;
        if (ref($ret) eq 'PublicInbox::IPC::Die') {
-               ipc_worker_stop $self;
-               croak $$ret;
+               my @err = ("$$ret");
+               push @err, (eval { ipc_worker_stop $self });
+               push @err, $@ if $@;
+               die @err;
        }
 };
 
 sub ipc_wait_all ($) {
        my ($self) = @_;
-       my $inflight = $self->{-ipc_inflight} // return;
-       ipc_read_step($self, $inflight) while @$inflight;
+       my @exc;
+       my $inflight = $self->{-ipc_inflight} // return @exc;
+       while (@$inflight) {
+               push @exc, ipc_read_step($self, $inflight);
+       }
+       croak(@exc) if @exc && !wantarray;
+       @exc;
 }
 
 # call $self->$sub(@args), on a worker if ipc_worker_spawn was used