decompile: Fix bug in lookup tags

A lookup tag with no type attribute would crash the decompiler, even if
that was valid. This wasn't caught by the tests since blueprint never
generates such XML.

Also fixed a bug in the tests that caused decompiler-only tests not to
run.

blueprintcompiler/decompiler.py

@@ -255,7 +255,11 @@ def decompile_element(
 
         ctx._node_stack.append(xml)
         ctx.start_block()
+
+        try:
             gir = decompiler(*args, **kwargs)
+        except TypeError as e:
+            raise UnsupportedError(tag=xml.tag)
 
         if not decompiler._skip_children:
             for child in xml.children:
@@ -266,8 +270,6 @@ def decompile_element(
 
     except UnsupportedError as e:
         raise e
-    except TypeError as e:
-        raise UnsupportedError(tag=xml.tag)
 
 
 def decompile(data: str) -> str:

blueprintcompiler/language/expression.py

@@ -302,12 +302,18 @@ expr.children = [
 
 @decompiler("lookup", skip_children=True, cdata=True)
 def decompile_lookup(
-    ctx: DecompileCtx, gir: gir.GirContext, cdata: str, name: str, type: str
+    ctx: DecompileCtx,
+    gir: gir.GirContext,
+    cdata: str,
+    name: str,
+    type: T.Optional[str] = None,
 ):
     if ctx.parent_node is not None and ctx.parent_node.tag == "property":
         ctx.print("expr ")
 
-    if t := ctx.type_by_cname(type):
+    if type is None:
+        type = ""
+    elif t := ctx.type_by_cname(type):
         type = decompile.full_name(t)
     else:
         type = "$" + type
@@ -327,7 +333,7 @@ def decompile_lookup(
         if constant == ctx.template_class:
             ctx.print("template." + name)
         elif constant == "":
-            ctx.print("item as <" + type + ">." + name)
+            ctx.print(f"item as <{type}>.{name}")
         else:
             ctx.print(constant + "." + name)
         return

tests/samples/issue_187.ui

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <template class="GtkListItem">
+    <property name="child">
+      <object class="GtkLabel">
+        <binding name="label">
+          <lookup type="RecentObject" name="filename">
+            <lookup name="item">GtkListItem</lookup>
+          </lookup>
+        </binding>
+      </object>
+    </property>
+  </template>
+</interface>

tests/samples/issue_187_dec.blp

@@ -0,0 +1,7 @@
+using Gtk 4.0;
+
+template ListItem {
+  child: Label {
+    label: bind template.item as <$RecentObject>.filename;
+  };
+}

tests/test_samples.py

@@ -181,11 +181,7 @@ class TestSamples(unittest.TestCase):
 
     def test_samples(self):
         # list the samples directory
-        samples = [
-            f.stem
-            for f in Path(__file__).parent.glob("samples/*.blp")
-            if not f.stem.endswith("_dec")
-        ]
+        samples = [f.stem for f in Path(__file__).parent.glob("samples/*.blp")]
         samples.sort()
         for sample in samples:
             REQUIRE_ADW_1_4 = ["adw_breakpoint"]
@@ -215,7 +211,7 @@ class TestSamples(unittest.TestCase):
             ]
 
             # Decompiler-only tests
-            SKIP_COMPILE = ["issue_177", "translator_comments"]
+            SKIP_COMPILE = ["issue_177", "issue_187", "translator_comments"]
 
             SKIP_DECOMPILE = [
                 # Comments are not preserved in either direction
@@ -228,7 +224,7 @@ class TestSamples(unittest.TestCase):
                 continue
 
             with self.subTest(sample):
-                if sample not in SKIP_COMPILE:
+                if sample not in SKIP_COMPILE and not sample.endswith("_dec"):
                     self.assert_sample(sample, skip_run=sample in SKIP_RUN)
 
             with self.subTest("decompile/" + sample):