Implement ResultQuery (#11257)

* Implement ResultQuery

* Fix test expectations

* Add more tests

* Fix test expectations

* Clean up some names

* Silence warnings

* Specify error type when supplying error type to ResultQuery

* cargo fmt

* Add support for type parameters in parameter_types macro

* Reduce deeply indented code

* Fixes

* Update test expectation

* Rewrite and document formula for calculating max storage size

* More docs

* cargo fmt

* formatting

Co-authored-by: parity-processbot <>

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

@@ -0,0 +1,21 @@
+#[frame_support::pallet]
+mod pallet {
+	use frame_support::pallet_prelude::*;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::error]
+	pub enum Error<T> {
+		NonExistentValue,
+	}
+
+	#[pallet::storage]
+	type Foo<T: Config> = StorageValue<_, u8, ResultQuery<Error::NonExistentValue>>;
+}
+
+fn main() {
+}

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

@@ -0,0 +1,15 @@
+error[E0107]: missing generics for enum `pallet::Error`
+  --> tests/pallet_ui/storage_result_query_missing_generics.rs:17:56
+   |
+17 |     type Foo<T: Config> = StorageValue<_, u8, ResultQuery<Error::NonExistentValue>>;
+   |                                                           ^^^^^ expected 1 generic argument
+   |
+note: enum defined here, with 1 generic parameter: `T`
+  --> tests/pallet_ui/storage_result_query_missing_generics.rs:12:11
+   |
+12 |     pub enum Error<T> {
+   |              ^^^^^ -
+help: add missing generic argument
+   |
+17 |     type Foo<T: Config> = StorageValue<_, u8, ResultQuery<Error<T>::NonExistentValue>>;
+   |                                                           ~~~~~~~~

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

@@ -0,0 +1,23 @@
+#[frame_support::pallet]
+mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::BlockNumberFor;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::error]
+	pub enum Error<T> {
+		NonExistentValue,
+		SomeOtherError,
+	}
+
+	#[pallet::storage]
+	type Foo<T: Config> = StorageValue<_, u8, ResultQuery<Error<T>::NonExistentValue, SomeOtherError>>;
+}
+
+fn main() {
+}

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

@@ -0,0 +1,5 @@
+error: Invalid pallet::storage, unexpected number of generic arguments for ResultQuery, expected 1 type argument, found 2
+  --> tests/pallet_ui/storage_result_query_multiple_type_args.rs:19:56
+   |
+19 |     type Foo<T: Config> = StorageValue<_, u8, ResultQuery<Error<T>::NonExistentValue, SomeOtherError>>;
+   |                                                           ^^^^^

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

@@ -0,0 +1,16 @@
+#[frame_support::pallet]
+mod pallet {
+	use frame_support::pallet_prelude::*;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::storage]
+	type Foo<T: Config> = StorageValue<_, u8, ResultQuery<NonExistentValue>>;
+}
+
+fn main() {
+}

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

@@ -0,0 +1,5 @@
+error: Invalid pallet::storage, unexpected number of path segments for the generics in ResultQuery, expected a path with at least 2 segments, found 1
+  --> tests/pallet_ui/storage_result_query_no_defined_pallet_error.rs:12:56
+   |
+12 |     type Foo<T: Config> = StorageValue<_, u8, ResultQuery<NonExistentValue>>;
+   |                                                           ^^^^^^^^^^^^^^^^

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

@@ -0,0 +1,22 @@
+#[frame_support::pallet]
+mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::BlockNumberFor;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::error]
+	pub enum Error<T> {
+		NonExistentValue,
+	}
+
+	#[pallet::storage]
+	type Foo<T: Config> = StorageValue<_, u8, ResultQuery(NonExistentValue)>;
+}
+
+fn main() {
+}

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

@@ -0,0 +1,5 @@
+error: Invalid pallet::storage, unexpected generic args for ResultQuery, expected angle-bracketed arguments, found `(NonExistentValue)`
+  --> tests/pallet_ui/storage_result_query_parenthesized_generics.rs:18:55
+   |
+18 |     type Foo<T: Config> = StorageValue<_, u8, ResultQuery(NonExistentValue)>;
+   |                                                          ^^^^^^^^^^^^^^^^^^

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

@@ -0,0 +1,22 @@
+#[frame_support::pallet]
+mod pallet {
+	use frame_support::pallet_prelude::*;
+	use frame_system::pallet_prelude::BlockNumberFor;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::error]
+	pub enum Error<T> {
+		NonExistentValue,
+	}
+
+	#[pallet::storage]
+	type Foo<T: Config> = StorageValue<_, u8, ResultQuery<'static>>;
+}
+
+fn main() {
+}

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

@@ -0,0 +1,5 @@
+error: Invalid pallet::storage, unexpected generic argument kind, expected a type path to a `PalletError` enum variant, found `'static`
+  --> tests/pallet_ui/storage_result_query_wrong_generic_kind.rs:18:56
+   |
+18 |     type Foo<T: Config> = StorageValue<_, u8, ResultQuery<'static>>;
+   |                                                           ^^^^^^^