Make template parent optional

Not recommended, since you lose some type checking.

blueprintcompiler/ast.py

@@ -143,7 +143,7 @@ class Object(AstNode):
 
     @validate("class_name")
     def gir_class_exists(self):
-        if not self.tokens["ignore_gir"] and self.gir_ns is not None:
+        if self.tokens["class_name"] and not self.tokens["ignore_gir"] and self.gir_ns is not None:
             self.root.gir.validate_class(self.tokens["class_name"], self.tokens["namespace"])
 
     @property
@@ -153,7 +153,7 @@ class Object(AstNode):
 
     @property
     def gir_class(self):
-        if not self.tokens["ignore_gir"]:
+        if self.tokens["class_name"] and not self.tokens["ignore_gir"]:
             return self.root.gir.get_class(self.tokens["class_name"], self.tokens["namespace"])
 
 
@@ -181,10 +181,13 @@ class Object(AstNode):
 
 class Template(Object):
     def emit_xml(self, xml: XmlEmitter):
-        xml.start_tag("template", **{
-            "class": self.tokens["name"],
-            "parent": self.gir_class.glib_type_name if self.gir_class else self.tokens["class_name"],
-        })
+        if self.gir_class:
+            parent = self.gir_class.glib_type_name
+        elif self.tokens["class_name"]:
+            parent = self.tokens["class_name"]
+        else:
+            parent = None
+        xml.start_tag("template", **{"class": self.tokens["name"]}, parent=parent)
         for child in self.children:
             child.emit_xml(xml)
         xml.end_tag()

blueprintcompiler/parser.py

@@ -140,8 +140,12 @@ def parse(tokens) -> T.Tuple[ast.UI, T.Optional[MultipleErrors]]:
         Sequence(
             Keyword("template"),
             UseIdent("name").expected("template class name"),
-            Op(":").expected("`:`"),
-            class_name.expected("parent class"),
+            Optional(
+                Sequence(
+                    Op(":"),
+                    class_name.expected("parent class"),
+                )
+            ),
             object_content.expected("block"),
         )
     )

tests/samples/template_no_parent.blp

@@ -0,0 +1,3 @@
+using Gtk 4.0;
+
+template GtkListItem {}

tests/samples/template_no_parent.ui

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <template class="GtkListItem"></template>
+</interface>

tests/test_samples.py

@@ -131,6 +131,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample("strings")
         self.assert_sample("style")
         self.assert_sample("template")
+        self.assert_sample("template_no_parent")
         self.assert_sample("translated")
         self.assert_sample("uint")
         self.assert_sample("using")