Construct Runtime v2 (#1378)

Moved from https://github.com/paritytech/substrate/pull/14788

----

Fixes https://github.com/paritytech/polkadot-sdk/issues/232

This PR introduces outer-macro approach for `construct_runtime` as
discussed in the linked issue. It looks like the following:
```rust
#[frame_support::runtime]
mod runtime {
	#[runtime::runtime]
        #[runtime::derive(
		RuntimeCall,
		RuntimeEvent,
		RuntimeError,
		RuntimeOrigin,
		RuntimeFreezeReason,
		RuntimeHoldReason,
		RuntimeSlashReason,
		RuntimeLockId,
                RuntimeTask,
	)]
	pub struct Runtime;

	#[runtime::pallet_index(0)]
	pub type System = frame_system;

	#[runtime::pallet_index(1)]
	pub type Timestamp = pallet_timestamp;

	#[runtime::pallet_index(2)]
	pub type Aura = pallet_aura;

	#[runtime::pallet_index(3)]
	pub type Grandpa = pallet_grandpa;

	#[runtime::pallet_index(4)]
	pub type Balances = pallet_balances;

	#[runtime::pallet_index(5)]
	pub type TransactionPayment = pallet_transaction_payment;

	#[runtime::pallet_index(6)]
	pub type Sudo = pallet_sudo;

	// Include the custom logic from the pallet-template in the runtime.
	#[runtime::pallet_index(7)]
	pub type TemplateModule = pallet_template;
}
```

## Features
- `#[runtime::runtime]` attached to a struct defines the main runtime
- `#[runtime::derive]` attached to this struct defines the types
generated by runtime
- `#[runtime::pallet_index]` must be attached to a pallet to define its
index
- `#[runtime::disable_call]` can be optionally attached to a pallet to
disable its calls
- `#[runtime::disable_unsigned]` can be optionally attached to a pallet
to disable unsigned calls
- A pallet instance can be defined as `TemplateModule:
pallet_template<Instance>`
- An optional attribute can be defined as
`#[frame_support::runtime(legacy_ordering)]` to ensure that the order of
hooks is same as the order of pallets (and not based on the
pallet_index). This is to support legacy runtimes and should be avoided
for new ones.

## Todo
- [x] Update the latest syntax in kitchensink and tests
- [x] Update UI tests
- [x] Docs

## Extension
- Abstract away the Executive similar to
https://github.com/paritytech/substrate/pull/14742
- Optionally avoid the need to specify all runtime types (TBD)

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Nikhil Gupta <>

substrate/frame/support/procedural/src/lib.rs

@@ -31,6 +31,7 @@ mod match_and_insert;
 mod no_bound;
 mod pallet;
 mod pallet_error;
+mod runtime;
 mod storage_alias;
 mod transactional;
 mod tt_macro;
@@ -1220,6 +1221,73 @@ pub fn import_section(attr: TokenStream, tokens: TokenStream) -> TokenStream {
 	.into()
 }
 
+/// Construct a runtime, with the given name and the given pallets.
+///
+/// # Example:
+///
+/// ```ignore
+/// #[frame_support::runtime]
+/// mod runtime {
+///   // The main runtime
+///   #[runtime::runtime]
+///   // Runtime Types to be generated
+///   #[runtime::derive(
+///       RuntimeCall,
+/// 	  RuntimeEvent,
+/// 	  RuntimeError,
+/// 	  RuntimeOrigin,
+/// 	  RuntimeFreezeReason,
+/// 	  RuntimeHoldReason,
+/// 	  RuntimeSlashReason,
+/// 	  RuntimeLockId,
+/// 	  RuntimeTask,
+///   )]
+///   pub struct Runtime;
+///
+///   #[runtime::pallet_index(0)]
+///   pub type System = frame_system;
+///
+///   #[runtime::pallet_index(1)]
+///   pub type Test = path::to::test;
+///
+///   // Pallet with instance.
+///   #[runtime::pallet_index(2)]
+///   pub type Test2_Instance1 = test2<Instance1>;
+///
+///   // Pallet with calls disabled.
+///   #[runtime::pallet_index(3)]
+///   #[runtime::disable_call]
+///   pub type Test3 = test3;
+///
+///   // Pallet with unsigned extrinsics disabled.
+///   #[runtime::pallet_index(4)]
+///   #[runtime::disable_unsigned]
+///   pub type Test4 = test4;
+/// }
+/// ```
+///
+/// # Legacy Ordering
+///
+/// An optional attribute can be defined as #[frame_support::runtime(legacy_ordering)] to
+/// ensure that the order of hooks is same as the order of pallets (and not based on the
+/// pallet_index). This is to support legacy runtimes and should be avoided for new ones.
+///
+/// # Note
+///
+/// The population of the genesis storage depends on the order of pallets. So, if one of your
+/// pallets depends on another pallet, the pallet that is depended upon needs to come before
+/// the pallet depending on it.
+///
+/// # Type definitions
+///
+/// * The macro generates a type alias for each pallet to their `Pallet`. E.g. `type System =
+///   frame_system::Pallet<Runtime>`
+#[cfg(feature = "experimental")]
+#[proc_macro_attribute]
+pub fn runtime(attr: TokenStream, item: TokenStream) -> TokenStream {
+	runtime::runtime(attr, item)
+}
+
 /// Mark a module that contains dynamic parameters.
 ///
 /// See the `pallet_parameters` for a full example.