Subxt Metadata: #[no_std] compatibility

.github/workflows/rust.yml

@@ -419,3 +419,32 @@ jobs:
 
       - if: "failure()"
         uses: "andymckay/cancel-action@b9280e3f8986d7a8e91c7462efc0fa318010c8b1" # v0.3
+
+  no-std-tests:
+    name: "Test (no_std)"
+    runs-on: ubuntu-latest
+    needs: [machete, docs]
+    timeout-minutes: 30
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+
+      # Note: needs nighly toolchain because otherwise we cannot define custom lang-items.
+      - name: Install Rust nightly toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@23bce251a8cd2ffc3c1075eaa2367cf899916d84 # v2.7.3
+
+      # Note: in `no_std` no real tests are possible, we just run a binary with some tests in it which panic upon failure.
+      - name: Run no_std tests
+        run: |
+          cargo run
+        working-directory: testing/no-std-tests
+
+      - if: "failure()"
+        uses: "andymckay/cancel-action@b9280e3f8986d7a8e91c7462efc0fa318010c8b1" # v0.3

Cargo.toml

@@ -18,7 +18,7 @@ members = [
 # We exclude any crates that would depend on non mutually
 # exclusive feature flags and thus can't compile with the
 # workspace:
-exclude = ["testing/wasm-rpc-tests", "testing/wasm-lightclient-tests", "signer/wasm-tests", "examples/wasm-example", "examples/parachain-example"]
+exclude = ["testing/no-std-tests", "testing/wasm-rpc-tests", "testing/wasm-lightclient-tests", "signer/wasm-tests", "examples/wasm-example", "examples/parachain-example"]
 resolver = "2"
 
 [workspace.package]
@@ -57,16 +57,19 @@ base58 = { version = "0.2.0" }
 bitvec = { version = "1", default-features = false }
 blake2 = { version = "0.10.6", default-features = false }
 clap = { version = "4.4.18", features = ["derive", "cargo"] }
+cfg-if = "1.0.0"
 criterion = "0.4"
-codec = { package = "parity-scale-codec", version = "3.4.0", default-features = false }
+codec = { package = "parity-scale-codec", version = "3.6.9", default-features = false }
 color-eyre = "0.6.1"
 console_error_panic_hook = "0.1.7"
 darling = "0.20.3"
 derivative = "2.2.0"
+derive_more = "0.99.17"
 either = "1.9.0"
-frame-metadata = { version = "16.0.0", default-features = false, features = ["current", "std"] }
+frame-metadata = { version = "16.0.0", default-features = false }
 futures = { version = "0.3.30", default-features = false, features = ["std"] }
 getrandom = { version = "0.2", default-features = false }
+hashbrown = "0.14.3"
 hex = "0.4.3"
 heck = "0.4.1"
 impl-serde = { version = "0.4.0" }
@@ -78,7 +81,7 @@ proc-macro-error = "1.0.4"
 proc-macro2 = "1.0.78"
 quote = "1.0.35"
 regex = "1.10.3"
-scale-info = "2.10.0"
+scale-info = { version = "2.10.0", default-features = false }
 scale-value = "0.13.0"
 scale-bits = "0.4.0"
 scale-decode = "0.10.0"

metadata/Cargo.toml

@@ -13,12 +13,17 @@ documentation.workspace = true
 homepage.workspace = true
 description = "Command line utilities for checking metadata compatibility between nodes."
 
+[features]
+default = ["std"]
+std = ["scale-info/std", "frame-metadata/std"]
+
 [dependencies]
-codec = { package = "parity-scale-codec", workspace = true, features = ["derive"] }
-frame-metadata = { workspace = true }
-scale-info = { workspace = true }
+scale-info = { workspace = true, default-features = false }
+frame-metadata = { workspace = true, default-features = false, features = ["current", "decode"] }
+codec = { package = "parity-scale-codec", workspace = true, default-features = false, features = ["derive"] }
 sp-core-hashing = { workspace = true }
-thiserror = { workspace = true }
+hashbrown = { workspace = true }
+derive_more = { workspace = true }
 
 [dev-dependencies]
 bitvec = { workspace = true, features = ["alloc"] }

metadata/src/from_into/mod.rs

@@ -2,31 +2,37 @@
 // This file is dual-licensed as Apache-2.0 or GPL-3.0.
 // see LICENSE for license details.
 
+use alloc::string::String;
+use derive_more::Display;
+
 mod v14;
 mod v15;
 
 /// An error emitted if something goes wrong converting [`frame_metadata`]
 /// types into [`crate::Metadata`].
-#[derive(Debug, thiserror::Error, PartialEq, Eq)]
+#[derive(Debug, Display, PartialEq, Eq)]
 #[non_exhaustive]
 pub enum TryFromError {
     /// Type missing from type registry
-    #[error("Type id {0} is expected but not found in the type registry")]
+    #[display(fmt = "Type id {_0} is expected but not found in the type registry")]
     TypeNotFound(u32),
     /// Type was not a variant/enum type
-    #[error("Type {0} was not a variant/enum type, but is expected to be one")]
+    #[display(fmt = "Type {_0} was not a variant/enum type, but is expected to be one")]
     VariantExpected(u32),
     /// An unsupported metadata version was provided.
-    #[error("Cannot convert v{0} metadata into Metadata type")]
+    #[display(fmt = "Cannot convert v{_0} metadata into Metadata type")]
     UnsupportedMetadataVersion(u32),
     /// Type name missing from type registry
-    #[error("Type name {0} is expected but not found in the type registry")]
+    #[display(fmt = "Type name {_0} is expected but not found in the type registry")]
     TypeNameNotFound(String),
     /// Invalid type path.
-    #[error("Type has an invalid path {0}")]
+    #[display(fmt = "Type has an invalid path {_0}")]
     InvalidTypePath(String),
 }
 
+#[cfg(feature = "std")]
+impl std::error::Error for TryFromError {}
+
 impl From<crate::Metadata> for frame_metadata::RuntimeMetadataPrefixed {
     fn from(value: crate::Metadata) -> Self {
         let m: frame_metadata::v15::RuntimeMetadataV15 = value.into();

metadata/src/from_into/v14.rs

@@ -2,11 +2,15 @@
 // This file is dual-licensed as Apache-2.0 or GPL-3.0.
 // see LICENSE for license details.
 
-use std::collections::HashMap;
-
 use super::TryFromError;
 use crate::Metadata;
+use alloc::borrow::ToOwned;
+use alloc::string::String;
+use alloc::vec;
+use alloc::vec::Vec;
+use core::fmt::Write;
 use frame_metadata::{v14, v15};
+use hashbrown::HashMap;
 use scale_info::TypeDef;
 
 impl TryFrom<v14::RuntimeMetadataV14> for Metadata {
@@ -31,27 +35,27 @@ fn v15_to_v14(mut metadata: v15::RuntimeMetadataV15) -> v14::RuntimeMetadataV14
     let extrinsic_type = scale_info::Type {
         path: scale_info::Path {
             segments: vec![
-                "primitives".to_string(),
-                "runtime".to_string(),
-                "generic".to_string(),
-                "UncheckedExtrinsic".to_string(),
+                "primitives".to_owned(),
+                "runtime".to_owned(),
+                "generic".to_owned(),
+                "UncheckedExtrinsic".to_owned(),
             ],
         },
         type_params: vec![
             scale_info::TypeParameter::<scale_info::form::PortableForm> {
-                name: "Address".to_string(),
+                name: "Address".to_owned(),
                 ty: Some(metadata.extrinsic.address_ty),
             },
             scale_info::TypeParameter::<scale_info::form::PortableForm> {
-                name: "Call".to_string(),
+                name: "Call".to_owned(),
                 ty: Some(metadata.extrinsic.call_ty),
             },
             scale_info::TypeParameter::<scale_info::form::PortableForm> {
-                name: "Signature".to_string(),
+                name: "Signature".to_owned(),
                 ty: Some(metadata.extrinsic.signature_ty),
             },
             scale_info::TypeParameter::<scale_info::form::PortableForm> {
-                name: "Extra".to_string(),
+                name: "Extra".to_owned(),
                 ty: Some(metadata.extrinsic.extra_ty),
             },
         ],
@@ -342,7 +346,7 @@ fn generate_outer_enums(
         let Some(last) = call_path.last_mut() else {
             return Err(TryFromError::InvalidTypePath("RuntimeCall".into()));
         };
-        *last = "RuntimeError".to_string();
+        *last = "RuntimeError".to_owned();
         generate_outer_error_enum_type(metadata, call_path)
     };
 
@@ -368,7 +372,10 @@ fn generate_outer_error_enum_type(
                 return None;
             };
 
-            let path = format!("{}Error", pallet.name);
+            // Note:  using the `alloc::format!` macro like in `let path = format!("{}Error", pallet.name);`
+            // leads to linker errors about extern function `_Unwind_Resume` not being defined.
+            let mut path = String::new();
+            write!(path, "{}Error", pallet.name).expect("Cannot panic, qed;");
             let ty = error.ty.id.into();
 
             Some(scale_info::Variant {

metadata/src/from_into/v15.rs

@@ -3,16 +3,18 @@
 // see LICENSE for license details.
 
 use super::TryFromError;
+
 use crate::utils::variant_index::VariantIndex;
 use crate::{
     utils::ordered_map::OrderedMap, ArcStr, ConstantMetadata, ExtrinsicMetadata, Metadata,
     OuterEnumsMetadata, PalletMetadataInner, RuntimeApiMetadataInner, RuntimeApiMethodMetadata,
     RuntimeApiMethodParamMetadata, SignedExtensionMetadata, StorageEntryMetadata,
     StorageEntryModifier, StorageEntryType, StorageHasher, StorageMetadata,
 };
+use alloc::borrow::ToOwned;
 use frame_metadata::v15;
+use hashbrown::HashMap;
 use scale_info::form::PortableForm;
-use std::collections::HashMap;
 
 // Converting from V15 metadata into our Subxt repr.
 mod from_v15 {

metadata/src/lib.rs

@@ -14,14 +14,19 @@
 //! 2. Obtaining [`frame_metadata::RuntimeMetadataPrefixed`], and then
 //!    using `.try_into()` to convert it into [`Metadata`].
 
+#![cfg_attr(not(feature = "std"), no_std)]
 #![deny(missing_docs)]
 
+extern crate alloc;
+
 mod from_into;
 mod utils;
 
+use alloc::string::String;
+use alloc::sync::Arc;
+use alloc::vec::Vec;
+use hashbrown::HashMap;
 use scale_info::{form::PortableForm, PortableRegistry, Variant};
-use std::collections::HashMap;
-use std::sync::Arc;
 use utils::variant_index::VariantIndex;
 use utils::{ordered_map::OrderedMap, validation::outer_enum_hashes::OuterEnumHashes};
 
@@ -200,7 +205,7 @@ impl Metadata {
             // its name to ensure that every unique type has a unique path, too.
             if *visited_count > 1 {
                 if let Some(name) = ty.ty.path.segments.last_mut() {
-                    *name = format!("{name}{visited_count}");
+                    *name = alloc::format!("{name}{visited_count}");
                 }
             }
         }