Allow missing functions when checking the new runtime's version (#5741)

substrate/primitives/core/src/traits.rs

@@ -262,6 +262,23 @@ impl std::fmt::Display for CodeNotFound {
 	}
 }
 
+/// `Allow` or `Disallow` missing host functions when instantiating a WASM blob.
+#[derive(Clone, Copy, Debug)]
+pub enum MissingHostFunctions {
+	/// Any missing host function will be replaced by a stub that returns an error when
+	/// being called.
+	Allow,
+	/// Any missing host function will result in an error while instantiating the WASM blob,
+	Disallow,
+}
+
+impl MissingHostFunctions {
+	/// Are missing host functions allowed?
+	pub fn allowed(self) -> bool {
+		matches!(self, Self::Allow)
+	}
+}
+
 /// Something that can call a method in a WASM blob.
 pub trait CallInWasm: Send + Sync {
 	/// Call the given `method` in the given `wasm_blob` using `call_data` (SCALE encoded arguments)
@@ -280,6 +297,7 @@ pub trait CallInWasm: Send + Sync {
 		method: &str,
 		call_data: &[u8],
 		ext: &mut dyn Externalities,
+		missing_host_functions: MissingHostFunctions,
 	) -> Result<Vec<u8>, String>;
 }
 

substrate/primitives/io/src/lib.rs

@@ -329,7 +329,18 @@ pub trait Misc {
 
 		self.extension::<CallInWasmExt>()
 			.expect("No `CallInWasmExt` associated for the current context!")
-			.call_in_wasm(wasm, None, "Core_version", &[], &mut ext)
+			.call_in_wasm(
+				wasm,
+				None,
+				"Core_version",
+				&[],
+				&mut ext,
+				// If a runtime upgrade introduces new host functions that are not provided by
+				// the node, we should not fail at instantiation. Otherwise nodes that are
+				// updated could run this successfully and it could lead to a storage root
+				// mismatch when importing this block.
+				sp_core::traits::MissingHostFunctions::Allow,
+			)
 			.ok()
 	}
 }

substrate/primitives/runtime-interface/test/Cargo.toml

@@ -18,5 +18,6 @@ sp-runtime-interface-test-wasm = { version = "2.0.0-dev", path = "../test-wasm"
 sp-runtime-interface-test-wasm-deprecated = { version = "2.0.0-dev", path = "../test-wasm-deprecated" }
 sp-state-machine = { version = "0.8.0-dev", path = "../../../primitives/state-machine" }
 sp-runtime = { version = "2.0.0-dev", path = "../../runtime" }
+sp-core = { version = "2.0.0-dev", path = "../../core" }
 sp-io = { version = "2.0.0-dev", path = "../../io" }
 tracing = "0.1.13"

substrate/primitives/runtime-interface/test/src/lib.rs

@@ -41,7 +41,6 @@ fn call_wasm_method<HF: HostFunctionsT>(binary: &[u8], method: &str) -> TestExte
 		sc_executor::WasmExecutionMethod::Interpreted,
 		Some(8),
 		host_functions,
-		false,
 		8,
 	);
 	executor.call_in_wasm(
@@ -50,6 +49,7 @@ fn call_wasm_method<HF: HostFunctionsT>(binary: &[u8], method: &str) -> TestExte
 		method,
 		&[],
 		&mut ext_ext,
+		sp_core::traits::MissingHostFunctions::Disallow,
 	).expect(&format!("Executes `{}`", method));
 
 	ext

substrate/primitives/state-machine/src/lib.rs

@@ -811,6 +811,7 @@ mod tests {
 			_: &str,
 			_: &[u8],
 			_: &mut dyn Externalities,
+			_: sp_core::traits::MissingHostFunctions,
 		) -> std::result::Result<Vec<u8>, String> {
 			unimplemented!("Not required in tests.")
 		}