Codegen for custom values in metadata (#1117)

* work in progress

* add custom types access

* nit

* custom values client

* adjust light client

* adjust doc comments

* adjust book for custom values in code gen

* format and check docs

* work in progress

* add custom types access

* nit

* custom values client

* adjust light client

* codegen and validation

* adjust docs

* use ignore in docs in book

* change iter implementation

* use validation hash and other codegen changes

* add ui test for custom values codegen

* allow 'latest' metadata to be returned from the fallback code (#1127)

* nits

* fix validation check

* fix comments

* nits

---------

Co-authored-by: James Wilson <james@jsdw.me>

testing/ui-tests/src/custom_values.rs

@@ -0,0 +1,76 @@
+// Copyright 2019-2023 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use codec::Encode;
+use frame_metadata::v15::{CustomMetadata, ExtrinsicMetadata, OuterEnums, RuntimeMetadataV15};
+use frame_metadata::RuntimeMetadataPrefixed;
+use scale_info::form::PortableForm;
+use scale_info::TypeInfo;
+use scale_info::{meta_type, IntoPortable};
+use std::collections::BTreeMap;
+
+/// Generate metadata which contains a `Foo { a: u8, b: &str }` custom value.
+pub fn metadata_custom_values_foo() -> RuntimeMetadataPrefixed {
+    let mut registry = scale_info::Registry::new();
+
+    // create foo value and type:
+
+    #[derive(TypeInfo, Encode)]
+    struct Foo {
+        a: u8,
+        b: &'static str,
+    }
+
+    let foo_value_metadata: frame_metadata::v15::CustomValueMetadata<PortableForm> = {
+        let value = Foo { a: 0, b: "Hello" };
+        let foo_ty = scale_info::MetaType::new::<Foo>();
+        let foo_ty_id = registry.register_type(&foo_ty);
+        frame_metadata::v15::CustomValueMetadata {
+            ty: foo_ty_id,
+            value: value.encode(),
+        }
+    };
+
+    // We don't care about the extrinsic type.
+    let extrinsic = ExtrinsicMetadata {
+        version: 0,
+        signed_extensions: vec![],
+        address_ty: meta_type::<()>(),
+        call_ty: meta_type::<()>(),
+        signature_ty: meta_type::<()>(),
+        extra_ty: meta_type::<()>(),
+    };
+
+    let pallets = vec![];
+    let extrinsic = extrinsic.into_portable(&mut registry);
+
+    let unit_ty = registry.register_type(&meta_type::<()>());
+
+    // Metadata needs to contain this DispatchError, since codegen looks for it.
+    registry.register_type(&meta_type::<crate::utils::dispatch_error::ArrayDispatchError>());
+
+    let metadata = RuntimeMetadataV15 {
+        types: registry.into(),
+        pallets,
+        extrinsic,
+        ty: unit_ty,
+        apis: vec![],
+        outer_enums: OuterEnums {
+            call_enum_ty: unit_ty,
+            event_enum_ty: unit_ty,
+            error_enum_ty: unit_ty,
+        },
+        custom: CustomMetadata {
+            // provide foo twice, to make sure nothing breaks in these cases:
+            map: BTreeMap::from_iter([
+                ("Foo".into(), foo_value_metadata.clone()),
+                ("foo".into(), foo_value_metadata.clone()),
+                ("12".into(), foo_value_metadata.clone()),
+                ("&Hello".into(), foo_value_metadata.clone()),
+            ]),
+        },
+    };
+
+    RuntimeMetadataPrefixed::from(metadata)
+}

testing/ui-tests/src/lib.rs

@@ -11,6 +11,7 @@
 //! Use with `TRYBUILD=overwrite` after updating codebase (see `trybuild` docs for more details on that)
 //! to automatically regenerate `stderr` files, but don't forget to check that new files make sense.
 
+mod custom_values;
 mod dispatch_errors;
 mod storage;
 mod utils;
@@ -51,6 +52,12 @@ fn ui_tests() {
             .build(dispatch_errors::metadata_array_dispatch_error()),
     );
 
+    t.pass(
+        m.new_test_case()
+            .name("custom_values_foo")
+            .build(custom_values::metadata_custom_values_foo()),
+    );
+
     // Test retaining only specific pallets and ensure that works.
     for pallet in ["Babe", "Claims", "Grandpa", "Balances"] {
         let mut metadata = MetadataTestRunner::load_metadata();