Allow using several custom template directories (#10587)

Allow using several directories in read_templates.

tests/config/test_base.py

@@ -30,7 +30,7 @@ class BaseConfigTestCase(unittest.HomeserverTestCase):
         # contain template files
         with tempfile.TemporaryDirectory() as tmp_dir:
             # Attempt to load an HTML template from our custom template directory
-            template = self.hs.config.read_templates(["sso_error.html"], tmp_dir)[0]
+            template = self.hs.config.read_templates(["sso_error.html"], (tmp_dir,))[0]
 
         # If no errors, we should've gotten the default template instead
 
@@ -60,7 +60,7 @@ class BaseConfigTestCase(unittest.HomeserverTestCase):
 
                 # Attempt to load the template from our custom template directory
                 template = (
-                    self.hs.config.read_templates([template_filename], tmp_dir)
+                    self.hs.config.read_templates([template_filename], (tmp_dir,))
                 )[0]
 
         # Render the template
@@ -74,8 +74,66 @@ class BaseConfigTestCase(unittest.HomeserverTestCase):
             "Template file did not contain our test string",
         )
 
+    def test_multiple_custom_template_directories(self):
+        """Tests that directories are searched in the right order if multiple custom
+        template directories are provided.
+        """
+        # Create two temporary directories on the filesystem.
+        tempdirs = [
+            tempfile.TemporaryDirectory(),
+            tempfile.TemporaryDirectory(),
+        ]
+
+        # Create one template in each directory, whose content is the index of the
+        # directory in the list.
+        template_filename = "my_template.html.j2"
+        for i in range(len(tempdirs)):
+            tempdir = tempdirs[i]
+            template_path = os.path.join(tempdir.name, template_filename)
+
+            with open(template_path, "w") as fp:
+                fp.write(str(i))
+                fp.flush()
+
+        # Retrieve the template.
+        template = (
+            self.hs.config.read_templates(
+                [template_filename],
+                (td.name for td in tempdirs),
+            )
+        )[0]
+
+        # Test that we got the template we dropped in the first directory in the list.
+        self.assertEqual(template.render(), "0")
+
+        # Add another template, this one only in the second directory in the list, so we
+        # can test that the second directory is still searched into when no matching file
+        # could be found in the first one.
+        other_template_name = "my_other_template.html.j2"
+        other_template_path = os.path.join(tempdirs[1].name, other_template_name)
+
+        with open(other_template_path, "w") as fp:
+            fp.write("hello world")
+            fp.flush()
+
+        # Retrieve the template.
+        template = (
+            self.hs.config.read_templates(
+                [other_template_name],
+                (td.name for td in tempdirs),
+            )
+        )[0]
+
+        # Test that the file has the expected content.
+        self.assertEqual(template.render(), "hello world")
+
+        # Cleanup the temporary directories manually since we're not using a context
+        # manager.
+        for td in tempdirs:
+            td.cleanup()
+
     def test_loading_template_from_nonexistent_custom_directory(self):
         with self.assertRaises(ConfigError):
             self.hs.config.read_templates(
-                ["some_filename.html"], "a_nonexistent_directory"
+                ["some_filename.html"], ("a_nonexistent_directory",)
             )