util.stanza: Add method for extracting a single attribute value
Sometimes you only care about a single attribute, but the child tag
itself may be optional, leading to needing `tag and tag.attr.foo` or
`stanza:find("tag@foo")`.
The `:find()` method is fairly complex, so avoiding it for this kind of
simpler use case is a win.
--- a/plugins/mod_pubsub/pubsub.lib.lua Mon Aug 15 16:35:14 2022 +0200
+++ b/plugins/mod_pubsub/pubsub.lib.lua Wed Aug 17 19:04:30 2022 +0200
@@ -678,8 +678,7 @@
function handlers.set_retract(origin, stanza, retract, service)
local node, notify = retract.attr.node, retract.attr.notify;
notify = (notify == "1") or (notify == "true");
- local item = retract:get_child("item");
- local id = item and item.attr.id
+ local id = retract:get_child_attr("item", nil, "id");
if not (node and id) then
origin.send(pubsub_error_reply(stanza, node and "item-not-found" or "nodeid-required"));
return true;
--- a/spec/util_dataforms_spec.lua Mon Aug 15 16:35:14 2022 +0200
+++ b/spec/util_dataforms_spec.lua Wed Aug 17 19:04:30 2022 +0200
@@ -130,7 +130,7 @@
assert.truthy(st.is_stanza(xform));
assert.equal("x", xform.name);
assert.equal("jabber:x:data", xform.attr.xmlns);
- assert.equal("FORM_TYPE", xform:find("field@var"));
+ assert.equal("FORM_TYPE", xform:get_child_attr("field", nil, "var"));
assert.equal("xmpp:prosody.im/spec/util.dataforms#1", xform:find("field/value#"));
local allowed_direct_children = {
title = true,
--- a/util/stanza.lua Mon Aug 15 16:35:14 2022 +0200
+++ b/util/stanza.lua Wed Aug 17 19:04:30 2022 +0200
@@ -176,6 +176,14 @@
return nil;
end
+function stanza_mt:get_child_attr(name, xmlns, attr)
+ local tag = self:get_child(name, xmlns);
+ if tag then
+ return tag.attr[attr];
+ end
+ return nil;
+end
+
function stanza_mt:child_with_name(name)
for _, child in ipairs(self.tags) do
if child.name == name then return child; end