Frontend overhaul based on Tailwind CSS

crates/templates/src/functions.rs

@@ -0,0 +1,30 @@
+// Copyright 2021 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Additional functions, tests and filters used in templates
+
+use tera::{helpers::tests::number_args_allowed, Tera, Value};
+
+pub fn register(tera: &mut Tera) {
+    tera.register_tester("empty", self::tester_empty);
+}
+
+fn tester_empty(value: Option<&Value>, params: &[Value]) -> Result<bool, tera::Error> {
+    number_args_allowed("empty", 0, params.len())?;
+
+    match value.and_then(Value::as_array).map(|v| &v[..]) {
+        Some(&[]) | None => Ok(true),
+        Some(_) => Ok(false),
+    }
+}