Swift: make codegen run when no registry is there

swift/codegen/lib/render.py

@@ -171,12 +171,16 @@ class RenderManager(Renderer):
         return h.hexdigest()
 
     def _load_registry(self):
-        with open(self._registry_path) as reg:
-            for line in reg:
-                filename, prehash, posthash = line.split()
-                self._hashes[pathlib.Path(filename)] = self.Hashes(prehash, posthash)
+        try:
+            with open(self._registry_path) as reg:
+                for line in reg:
+                    filename, prehash, posthash = line.split()
+                    self._hashes[pathlib.Path(filename)] = self.Hashes(prehash, posthash)
+        except FileNotFoundError:
+            pass
 
     def _dump_registry(self):
+        self._registry_path.parent.mkdir(parents=True, exist_ok=True)
         with open(self._registry_path, 'w') as out:
             for f, hashes in sorted(self._hashes.items()):
                 print(f, hashes.pre, hashes.post, file=out)

swift/codegen/test/test_render.py

@@ -75,6 +75,23 @@ def test_managed_render(pystache_renderer, sut):
         mock.call.render_name(data.template, data, generator=paths.exe_file.relative_to(paths.swift_dir)),
     ]
 
+def test_managed_render_with_no_registry(pystache_renderer, sut):
+    data = mock.Mock(spec=("template",))
+    text = "some text"
+    pystache_renderer.render_name.side_effect = (text,)
+    output = paths.swift_dir / "some/output.txt"
+    registry = paths.swift_dir / "a/registry.list"
+
+    with sut.manage(generated=(), stubs=(), registry=registry) as renderer:
+        renderer.render(data, output)
+        assert renderer.written == {output}
+        assert_file(output, text)
+
+    assert_file(registry, f"some/output.txt {hash(text)} {hash(text)}\n")
+    assert pystache_renderer.mock_calls == [
+        mock.call.render_name(data.template, data, generator=paths.exe_file.relative_to(paths.swift_dir)),
+    ]
+
 
 def test_managed_render_with_post_processing(pystache_renderer, sut):
     data = mock.Mock(spec=("template",))