pallet_macro: Generate default documentation for well known types (#8276)

substrate/frame/support/procedural/src/pallet/expand/config.rs

@@ -0,0 +1,43 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020-2021 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// 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.
+
+use crate::pallet::{Def, parse::helper::get_doc_literals};
+
+/// * Generate default rust doc
+pub fn expand_config(def: &mut Def) -> proc_macro2::TokenStream {
+	let config = &def.config;
+	let config_item = {
+		let item = &mut def.item.content.as_mut().expect("Checked by def parser").1[config.index];
+		if let syn::Item::Trait(item) = item {
+			item
+		} else {
+			unreachable!("Checked by config parser")
+		}
+	};
+
+	if get_doc_literals(&config_item.attrs).is_empty() {
+		config_item.attrs.push(syn::parse_quote!(
+			#[doc = r"
+			Configuration trait of this pallet.
+
+			Implement this type for a runtime in order to customize this pallet.
+			"]
+		));
+	}
+
+	Default::default()
+}