Implements require_transactional (#7261)

* Implements require_transactional

* support wasm

* only enable for debug build

* remove wasm support and add feature flag

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* only use check for debug_assertions

* update per review

* update docs

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* remove duplicated tests

* fix test

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/frame/support/src/lib.rs

@@ -267,7 +267,40 @@ macro_rules! ord_parameter_types {
 }
 
 #[doc(inline)]
-pub use frame_support_procedural::{decl_storage, construct_runtime, transactional};
+pub use frame_support_procedural::{
+	decl_storage, construct_runtime, transactional
+};
+
+/// Assert the annotated function is executed within a storage transaction.
+///
+/// The assertion is enabled for native execution and when `debug_assertions` are enabled.
+///
+/// # Example
+///
+/// ```
+/// # use frame_support::{
+/// # 	require_transactional, transactional, dispatch::DispatchResult
+/// # };
+///
+/// #[require_transactional]
+/// fn update_all(value: u32) -> DispatchResult {
+/// 	// Update multiple storages.
+/// 	// Return `Err` to indicate should revert.
+/// 	Ok(())
+/// }
+///
+/// #[transactional]
+/// fn safe_update(value: u32) -> DispatchResult {
+/// 	// This is safe
+/// 	update_all(value)
+/// }
+///
+/// fn unsafe_update(value: u32) -> DispatchResult {
+/// 	// this may panic if unsafe_update is not called within a storage transaction
+/// 	update_all(value)
+/// }
+/// ```
+pub use frame_support_procedural::require_transactional;
 
 /// Return Err of the expression: `return Err($expression);`.
 ///