[glib/mcatanzaro/#2597: 2/2] gproxyresolver: add asserts to ensure error is set

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 8e29865112a38dc57ce92830548c22d8dd05a2c7
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Mon Jun 27 15:10:25 2022 -0500

    gproxyresolver: add asserts to ensure error is set
    
    This will catch buggy implementations of GProxyResolver before they are
    able to return bogus results to higher level code. In particular, if
    g_proxy_resolver_lookup() returns NULL, it'd better set an error to
    explain why.

 gio/gproxyresolver.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/gio/gproxyresolver.c b/gio/gproxyresolver.c
index 1787bf81f0..7ac64df633 100644
--- a/gio/gproxyresolver.c
+++ b/gio/gproxyresolver.c
@@ -158,6 +158,7 @@ g_proxy_resolver_lookup (GProxyResolver  *resolver,
                         GError         **error)
 {
   GProxyResolverInterface *iface;
+  gchar **proxy_uris;
 
   g_return_val_if_fail (G_IS_PROXY_RESOLVER (resolver), NULL);
   g_return_val_if_fail (uri != NULL, NULL);
@@ -171,7 +172,10 @@ g_proxy_resolver_lookup (GProxyResolver  *resolver,
 
   iface = G_PROXY_RESOLVER_GET_IFACE (resolver);
 
-  return (* iface->lookup) (resolver, uri, cancellable, error);
+  proxy_uris = (* iface->lookup) (resolver, uri, cancellable, error);
+  if (proxy_uris == NULL && error != NULL)
+    g_assert (*error != NULL);
+  return proxy_uris;
 }
 
 /**
@@ -237,10 +241,14 @@ g_proxy_resolver_lookup_finish (GProxyResolver     *resolver,
                                GError            **error)
 {
   GProxyResolverInterface *iface;
+  gchar **proxy_uris;
 
   g_return_val_if_fail (G_IS_PROXY_RESOLVER (resolver), NULL);
 
   iface = G_PROXY_RESOLVER_GET_IFACE (resolver);
 
-  return (* iface->lookup_finish) (resolver, result, error);
+  proxy_uris = (* iface->lookup_finish) (resolver, result, error);
+  if (proxy_uris == NULL && error != NULL)
+    g_assert (*error != NULL);
+  return proxy_uris;
 }