Metadata V16: Implement support for Pallet View Functions (#1981)

* Support Pallet View Functions in Subxt * fmt * clippy * Move a little view function logic to subxt_core * clippy * Add back check that prob isnt needed * avoid vec macro in core * Add view funciton test and apply various fixes to get it working * Add test for dynamic view fn call and fix issues * clippy * fix test-runtime * fmt * remove export * avoid vec for nostd core * use const instead of fn for view fn call name * Update to support latest unstable metadata * Update metadata stripping tests for new v16 version
2026-06-13 19:51:05 +00:00 · 2025-04-24 14:42:07 +01:00
parent 21b3f52191
commit 4524590821
28 changed files with 875 additions and 108 deletions
@@ -0,0 +1,153 @@
+// Copyright 2019-2024 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! This module contains the trait and types used to represent
+//! View Function calls that can be made.
+
+use alloc::vec::Vec;
+use core::marker::PhantomData;
+use derive_where::derive_where;
+use scale_encode::EncodeAsFields;
+use scale_value::Composite;
+
+use crate::dynamic::DecodedValueThunk;
+use crate::error::MetadataError;
+use crate::Error;
+
+use crate::metadata::{DecodeWithMetadata, Metadata};
+
+/// This represents a View Function payload that can call into the runtime of node.
+///
+/// # Components
+///
+/// - associated return type
+///
+/// Resulting bytes of the call are interpreted into this type.
+///
+/// - query ID
+///
+/// The ID used to identify in the runtime which view function to call.
+///
+/// - encoded arguments
+///
+/// Each argument of the View Function must be scale-encoded.
+pub trait Payload {
+    /// The return type of the function call.
+    // Note: `DecodeWithMetadata` is needed to decode the function call result
+    // with the `subxt::Metadata.
+    type ReturnType: DecodeWithMetadata;
+
+    /// The payload target.
+    fn query_id(&self) -> &[u8; 32];
+
+    /// Scale encode the arguments data.
+    fn encode_args_to(&self, metadata: &Metadata, out: &mut Vec<u8>) -> Result<(), Error>;
+
+    /// Encode arguments data and return the output. This is a convenience
+    /// wrapper around [`Payload::encode_args_to`].
+    fn encode_args(&self, metadata: &Metadata) -> Result<Vec<u8>, Error> {
+        let mut v = Vec::new();
+        self.encode_args_to(metadata, &mut v)?;
+        Ok(v)
+    }
+
+    /// Returns the statically generated validation hash.
+    fn validation_hash(&self) -> Option<[u8; 32]> {
+        None
+    }
+}
+
+/// A View Function payload containing the generic argument data
+/// and interpreting the result of the call as `ReturnTy`.
+///
+/// This can be created from static values (ie those generated
+/// via the `subxt` macro) or dynamic values via [`dynamic`].
+#[derive_where(Clone, Debug, Eq, Ord, PartialEq, PartialOrd; ArgsData)]
+pub struct DefaultPayload<ArgsData, ReturnTy> {
+    query_id: [u8; 32],
+    args_data: ArgsData,
+    validation_hash: Option<[u8; 32]>,
+    _marker: PhantomData<ReturnTy>,
+}
+
+/// A statically generated View Function payload.
+pub type StaticPayload<ArgsData, ReturnTy> = DefaultPayload<ArgsData, ReturnTy>;
+/// A dynamic View Function payload.
+pub type DynamicPayload = DefaultPayload<Composite<()>, DecodedValueThunk>;
+
+impl<ArgsData: EncodeAsFields, ReturnTy: DecodeWithMetadata> Payload
+    for DefaultPayload<ArgsData, ReturnTy>
+{
+    type ReturnType = ReturnTy;
+
+    fn query_id(&self) -> &[u8; 32] {
+        &self.query_id
+    }
+
+    fn encode_args_to(&self, metadata: &Metadata, out: &mut Vec<u8>) -> Result<(), Error> {
+        let view_function = metadata
+            .view_function_by_query_id(&self.query_id)
+            .ok_or(MetadataError::ViewFunctionNotFound(self.query_id))?;
+        let mut fields = view_function
+            .inputs()
+            .map(|input| scale_encode::Field::named(input.ty, &input.name));
+
+        self.args_data
+            .encode_as_fields_to(&mut fields, metadata.types(), out)?;
+
+        Ok(())
+    }
+
+    fn validation_hash(&self) -> Option<[u8; 32]> {
+        self.validation_hash
+    }
+}
+
+impl<ReturnTy, ArgsData> DefaultPayload<ArgsData, ReturnTy> {
+    /// Create a new [`DefaultPayload`] for a View Function call.
+    pub fn new(query_id: [u8; 32], args_data: ArgsData) -> Self {
+        DefaultPayload {
+            query_id,
+            args_data,
+            validation_hash: None,
+            _marker: PhantomData,
+        }
+    }
+
+    /// Create a new static [`DefaultPayload`] for a View Function call
+    /// using static function name and scale-encoded argument data.
+    ///
+    /// This is only expected to be used from codegen.
+    #[doc(hidden)]
+    pub fn new_static(
+        query_id: [u8; 32],
+        args_data: ArgsData,
+        hash: [u8; 32],
+    ) -> DefaultPayload<ArgsData, ReturnTy> {
+        DefaultPayload {
+            query_id,
+            args_data,
+            validation_hash: Some(hash),
+            _marker: core::marker::PhantomData,
+        }
+    }
+
+    /// Do not validate this call prior to submitting it.
+    pub fn unvalidated(self) -> Self {
+        Self {
+            validation_hash: None,
+            ..self
+        }
+    }
+
+    /// Returns the arguments data.
+    pub fn args_data(&self) -> &ArgsData {
+        &self.args_data
+    }
+}
+
+/// Create a new [`DynamicPayload`] to call a View Function.
+pub fn dynamic(query_id: [u8; 32], args_data: impl Into<Composite<()>>) -> DynamicPayload {
+    DefaultPayload::new(query_id, args_data.into())
+}