Add pallet dev mode (#12536)

* stub for construct_dev_runtime!

* revert

* stub for dev_mode proc macro

* preliminary docs for pallet::dev_mode (attribute) proc macro

* add dev_mode to pallet_macros module

* add docs item for dev_mode to frame_support

* parsing of #[pallet(dev_mode)]

* strip out dev_mode stub since it will be an arg for pallet instead

* make pallet Def struct aware of dev mode

* WIP

* revert changes to call.rs

* pass dev_mode to pallet parsing code

* auto-specify default weights when in dev mode if not specified

* add proof / expect for syn::parse in dev mode weight processing

* set all storages to unbounded when in dev mode

* just use 0

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

* add invalid pallet arg test

* add passing dev mode pallet test

* add test confirming that dev mode features only work in dev mode

* cargo fmt + clean up

* bump CI

* fix pallet ui test

* add docs for dev mode

* add warning about using dev mode in production circumstances

* remove comment about no other attributes being supported

* fix unneeded assignment

* make warning more explicit

* more explicit warning about using dev mode in production

* simpler assignment for dev_mode boolean

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* add note about MEL requirement

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* add comment specifying why weights can be omitted in example

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* tweak wording of comments

* bump ci

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

substrate/frame/support/test/tests/pallet_ui/attr_non_empty.stderr

@@ -1,5 +1,5 @@
-error: Invalid pallet macro call: expected no attributes, e.g. macro call must be just `#[frame_support::pallet]` or `#[pallet]`
- --> $DIR/attr_non_empty.rs:1:26
+error: Invalid pallet macro call: unexpected attribute. Macro call must be bare, such as `#[frame_support::pallet]` or `#[pallet]`, or must specify the `dev_mode` attribute, such as `#[frame_support::pallet(dev_mode)]` or #[pallet(dev_mode)].
+ --> tests/pallet_ui/attr_non_empty.rs:1:26
   |
 1 | #[frame_support::pallet [foo]]
   |                          ^^^

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg.rs

@@ -0,0 +1,33 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub use pallet::*;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+
+	// The struct on which we build all of our Pallet logic.
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	// Your Pallet's configuration trait, representing custom external types and interfaces.
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::storage]
+	type MyStorage<T: Config> = StorageValue<_, Vec<u8>>;
+
+	// Your Pallet's callable functions.
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		pub fn my_call(_origin: OriginFor<T>) -> DispatchResult {
+			Ok(())
+		}
+	}
+
+	// Your Pallet's internal functions.
+	impl<T: Config> Pallet<T> {}
+}
+
+fn main() {}

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg.stderr

@@ -0,0 +1,11 @@
+error: Invalid pallet::call, requires weight attribute i.e. `#[pallet::weight($expr)]`
+  --> tests/pallet_ui/dev_mode_without_arg.rs:24:7
+   |
+24 |         pub fn my_call(_origin: OriginFor<T>) -> DispatchResult {
+   |             ^^
+
+error[E0432]: unresolved import `pallet`
+ --> tests/pallet_ui/dev_mode_without_arg.rs:3:9
+  |
+3 | pub use pallet::*;
+  |         ^^^^^^ help: a similar path exists: `test_pallet::pallet`

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg_max_encoded_len.rs

@@ -0,0 +1,34 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub use pallet::*;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+
+	// The struct on which we build all of our Pallet logic.
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	// Your Pallet's configuration trait, representing custom external types and interfaces.
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::storage]
+	type MyStorage<T: Config> = StorageValue<_, Vec<u8>>;
+
+	// Your Pallet's callable functions.
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		#[pallet::weight(0)]
+		pub fn my_call(_origin: OriginFor<T>) -> DispatchResult {
+			Ok(())
+		}
+	}
+
+	// Your Pallet's internal functions.
+	impl<T: Config> Pallet<T> {}
+}
+
+fn main() {}

substrate/frame/support/test/tests/pallet_ui/dev_mode_without_arg_max_encoded_len.stderr

@@ -0,0 +1,17 @@
+error[E0277]: the trait bound `Vec<u8>: MaxEncodedLen` is not satisfied
+  --> tests/pallet_ui/dev_mode_without_arg_max_encoded_len.rs:11:12
+   |
+11 |     #[pallet::pallet]
+   |               ^^^^^^ the trait `MaxEncodedLen` is not implemented for `Vec<u8>`
+   |
+   = help: the following other types implement trait `MaxEncodedLen`:
+             ()
+             (TupleElement0, TupleElement1)
+             (TupleElement0, TupleElement1, TupleElement2)
+             (TupleElement0, TupleElement1, TupleElement2, TupleElement3)
+             (TupleElement0, TupleElement1, TupleElement2, TupleElement3, TupleElement4)
+             (TupleElement0, TupleElement1, TupleElement2, TupleElement3, TupleElement4, TupleElement5)
+             (TupleElement0, TupleElement1, TupleElement2, TupleElement3, TupleElement4, TupleElement5, TupleElement6)
+             (TupleElement0, TupleElement1, TupleElement2, TupleElement3, TupleElement4, TupleElement5, TupleElement6, TupleElement7)
+           and 78 others
+   = note: required because of the requirements on the impl of `StorageInfoTrait` for `frame_support::pallet_prelude::StorageValue<_GeneratedPrefixForStorageMyStorage<T>, Vec<u8>>`

substrate/frame/support/test/tests/pallet_ui/pallet_invalid_arg.rs

@@ -0,0 +1,4 @@
+#[frame_support::pallet(foo)]
+pub mod pallet {}
+
+fn main() {}

substrate/frame/support/test/tests/pallet_ui/pallet_invalid_arg.stderr

@@ -0,0 +1,5 @@
+error: Invalid pallet macro call: unexpected attribute. Macro call must be bare, such as `#[frame_support::pallet]` or `#[pallet]`, or must specify the `dev_mode` attribute, such as `#[frame_support::pallet(dev_mode)]` or #[pallet(dev_mode)].
+ --> tests/pallet_ui/pallet_invalid_arg.rs:1:25
+  |
+1 | #[frame_support::pallet(foo)]
+  |                         ^^^

substrate/frame/support/test/tests/pallet_ui/pass/dev_mode_valid.rs

@@ -0,0 +1,35 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub use pallet::*;
+
+#[frame_support::pallet(dev_mode)]
+pub mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::*;
+
+	// The struct on which we build all of our Pallet logic.
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	// Your Pallet's configuration trait, representing custom external types and interfaces.
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	// The MEL requirement for bounded pallets is skipped by `dev_mode`.
+	#[pallet::storage]
+	type MyStorage<T: Config> = StorageValue<_, Vec<u8>>;
+
+	// Your Pallet's callable functions.
+	#[pallet::call]
+	impl<T: Config> Pallet<T> {
+		// No need to define a `weight` attribute here because of `dev_mode`.
+		pub fn my_call(_origin: OriginFor<T>) -> DispatchResult {
+			Ok(())
+		}
+	}
+
+	// Your Pallet's internal functions.
+	impl<T: Config> Pallet<T> {}
+}
+
+fn main() {}