Fix wxXmlResource::Load() with HTTP URLs

Make the code in this function work even with wxFileSystemHandlers that
don't implement FindFirst() at all: we can, and should, still try
loading the passed in path with them, rather than not doing anything at
all.

This makes Load() works with HTTP URLs again, as it apparently used to
do a long time ago, but didn't do any more.

Add a unit test, even if only a semi-manual one, to try to help with
this not getting broken again (ideal would be to launch our own HTTP
server inside the test, but this is a bit more complicated).

Closes #19109.

src/xrc/xmlres.cpp

@@ -343,7 +343,8 @@ bool wxXmlResource::Load(const wxString& filemask_)
 {
     wxString filemask = ConvertFileNameToURL(filemask_);
 
-    bool allOK = true;
+    bool allOK = true,
+         anyOK = false;
 
 #if wxUSE_FILESYSTEM
     wxFileSystem fsys;
@@ -356,33 +357,47 @@ bool wxXmlResource::Load(const wxString& filemask_)
     wxString fnd = wxXmlFindFirst;
     if ( fnd.empty() )
     {
-        wxLogError(_("Cannot load resources from '%s'."), filemask);
+        // Some file system handlers (e.g. wxInternetFSHandler) just don't
-        return false;
+        // implement FindFirst() at all, try using the original path as is.
+        fnd = filemask;
     }
 
     while (!fnd.empty())
     {
+        bool thisOK = true;
+
 #if wxUSE_FILESYSTEM
         if ( IsArchive(fnd) )
         {
             if ( !Load(fnd + wxT("#zip:*.xrc")) )
-                allOK = false;
+                thisOK = false;
         }
         else // a single resource URL
 #endif // wxUSE_FILESYSTEM
         {
             wxXmlDocument * const doc = DoLoadFile(fnd);
             if ( !doc )
-                allOK = false;
+                thisOK = false;
             else
                 Data().push_back(new wxXmlResourceDataRecord(fnd, doc));
         }
 
+        if ( thisOK )
+            anyOK = true;
+        else
+            allOK = false;
+
         fnd = wxXmlFindNext;
     }
 #   undef wxXmlFindFirst
 #   undef wxXmlFindNext
 
+    if ( !anyOK )
+    {
+        wxLogError(_("Cannot load resources from '%s'."), filemask);
+        return false;
+    }
+
     return allOK;
 }
 

tests/xml/xrctest.cpp

@@ -19,6 +19,7 @@
 
 #if wxUSE_XRC
 
+#include "wx/fs_inet.h"
 #include "wx/xml/xml.h"
 #include "wx/sstream.h"
 #include "wx/wfstream.h"
@@ -204,4 +205,31 @@ TEST_CASE_METHOD(XrcTestCase, "XRC::IDRanges", "[xrc]")
     }
 }
 
+// This test is disabled by default as it requires the environment variable
+// below to be defined to point to a HTTP URL with the file to load.
+//
+// Use something like "python3 -m http.server samples/xrc/rc" and set
+// WX_TEST_XRC_URL to http://localhost/menu.xrc to run this test.
+TEST_CASE_METHOD(XrcTestCase, "XRC::LoadURL", "[xrc][.]")
+{
+    wxString url;
+    REQUIRE( wxGetEnv("WX_TEST_XRC_URL", &url) );
+
+    // Ensure that loading from HTTP URLs is supported.
+    struct InetHandler : wxInternetFSHandler
+    {
+        InetHandler()
+        {
+            wxFileSystem::AddHandler(this);
+        }
+
+        ~InetHandler()
+        {
+            wxFileSystem::RemoveHandler(this);
+        }
+    } inetHandler;
+
+    CHECK( wxXmlResource::Get()->Load(url) );
+}
+
 #endif // wxUSE_XRC