gproxyresolver: lookup_finish() should better parallel lookup_async()

In g_proxy_resolver_lookup_async() we have some error validation that
detects invalid URIs and directly returns an error, bypassing the
interface's lookup_async() function. This is great, but when the
interface's lookup_finish() function gets called later, it may assert
that the source tag of the GTask matches the interface's lookup_async()
function, which will not be the case.

As suggested by Philip, we need to check for this situation in
g_proxy_resolver_lookup_finish() and avoid calling into the interface
here if we did the same in g_proxy_resolver_lookup_async(). This can be
done by checking the source tag.

I added a few new tests to check the invalid URI "asdf" used in the
issue report. The final case, using async GProxyResolver directly,
checks for this bug.

Fixes #2799

1 files changed, 3 insertions, 0 deletions

diff --git a/gio/gproxyresolver.c b/gio/gproxyresolver.c
index 7ac64df63..61f61a797 100644
--- a/gio/gproxyresolver.c
+++ b/gio/gproxyresolver.c
@@ -245,6 +245,9 @@ g_proxy_resolver_lookup_finish (GProxyResolver     *resolver,
 
   g_return_val_if_fail (G_IS_PROXY_RESOLVER (resolver), NULL);
 
+  if (g_async_result_is_tagged (result, g_proxy_resolver_lookup_async))
+    return g_task_propagate_pointer (G_TASK (result), error);
+
   iface = G_PROXY_RESOLVER_GET_IFACE (resolver);
 
   proxy_uris = (* iface->lookup_finish) (resolver, result, error);