[pve-devel] [PATCH http-server] fix generating 'extjs' response with exceptions/blessed errors

[Dominik Csapak]

when an api call with the 'extjs' formatter fails, the intention is that
the api call succeeds but contains the error in the inner structure
('error'/'status' property). When the api call fails with a raised
exception (e.g. PVE::APIClient::Exception), the '$res->{message}' field
is an object instead of a string.

Currently we directly assign the message to the resulting struct, which
we then try to convert to json. Since the message was an object,
`to_json` fails with 'encountered object` and the whole api call returns
a 501 error (since `handle_api2_request` returns that by default if
anything dies there, which is IMHO not correct but a different issue.)

By 'stringifying' the message, we avoid the error in `to_json` and the
api call can succeed.

partially fixes #6051: It improves the error message in PDM when trying
to remote migrate and the source cannot correctly resolve the target
remote. (We use PVE::APIClient there to query the remote).

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
We could of course improve the situation in other ways (too):
* handle errors of formatters better
* passing through exceptions in AnyEvent (seems weird a bit)
* passing thgough the error of the 501 in the PDM ui
  (this contains the underlying error too by accident, since `to_json`
  writes it out)

but i opted for this for now, since this is wrong either way (as in, it cannot
work as intended when we don't stringify the message) and improves the
error message on PDM side (still not optimal, but at least contains the
root cause of the error now).

 src/PVE/APIServer/Formatter/Standard.pm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/PVE/APIServer/Formatter/Standard.pm b/src/PVE/APIServer/Formatter/Standard.pm
index c4def16..5211473 100644
--- a/src/PVE/APIServer/Formatter/Standard.pm
+++ b/src/PVE/APIServer/Formatter/Standard.pm
@@ -27,7 +27,7 @@ sub prepare_response_data {
 	# HACK: extjs wants 'success' property instead of useful HTTP status codes
 	if (HTTP::Status::is_error($res->{status})) {
 	    $success = 0;
-	    $new->{message} = $res->{message} || status_message($res->{status});
+	    $new->{message} = "$res->{message}" || status_message($res->{status});
 	    $new->{status} = $res->{status} || 200;
 	    $res->{message} = undef;
 	    $res->{status} = 200;
-- 
2.39.5