piecrust: allow passing no argument when constructor exist

contracts/Cargo.toml

@@ -7,6 +7,7 @@ members = [
     "counter",
     "debugger",
     "double_counter",
+    "empty_constructor",
     "eventer",
     "everest",
     "fallible_counter",

contracts/empty_constructor/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "empty_constructor"
+version = "0.1.0"
+authors = [
+    "Eduardo Leegwater Simões <[email protected]>",
+]
+edition = "2021"
+
+license = "MPL-2.0"
+
+[dependencies]
+piecrust-uplink = { path = "../../piecrust-uplink", features = ["abi", "dlmalloc"] }
+
+[lib]
+crate-type = ["cdylib", "rlib"]

contracts/empty_constructor/src/lib.rs

@@ -0,0 +1,56 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+// Copyright (c) DUSK NETWORK. All rights reserved.
+
+//! Contract that provides and example use of the constructor.
+
+#![no_std]
+
+use piecrust_uplink as uplink;
+
+/// Struct that describes the state of the Constructor contract
+pub struct EmptyConstructor {
+    value: u8,
+}
+
+impl EmptyConstructor {
+    pub fn init(&mut self) {
+        self.value = 0x10;
+    }
+}
+
+/// State of the EmptyConstructor contract
+static mut STATE: EmptyConstructor = EmptyConstructor { value: 0x00 };
+
+impl EmptyConstructor {
+    /// Read the value of the constructor contract state
+    pub fn read_value(&self) -> u8 {
+        self.value
+    }
+
+    /// Increment the value  by 1
+    pub fn increment(&mut self) {
+        let value = self.value + 1;
+        self.value = value;
+    }
+}
+
+/// Expose `EmptyConstructor::read_value()` to the host
+#[no_mangle]
+unsafe fn read_value(arg_len: u32) -> u32 {
+    uplink::wrap_call(arg_len, |_: ()| STATE.read_value())
+}
+
+/// Expose `EmptyConstructor::increment()` to the host
+#[no_mangle]
+unsafe fn increment(arg_len: u32) -> u32 {
+    uplink::wrap_call(arg_len, |_: ()| STATE.increment())
+}
+
+/// Expose `EmptyConstructor::init()` to the host
+#[no_mangle]
+unsafe fn init(arg_len: u32) -> u32 {
+    uplink::wrap_call(arg_len, |()| STATE.init())
+}

piecrust/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Use empty constructor arguments by default [#316]
 - Upgrade `dusk-wasmtime` to version `18`
 
 ## [0.16.0] - 2024-02-14
@@ -366,6 +367,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 <!-- ISSUES -->
 [#325]: https://github.com/dusk-network/piecrust/issues/325
 [#324]: https://github.com/dusk-network/piecrust/issues/324
+[#316]: https://github.com/dusk-network/piecrust/issues/316
 [#301]: https://github.com/dusk-network/piecrust/issues/313
 [#301]: https://github.com/dusk-network/piecrust/issues/301
 [#296]: https://github.com/dusk-network/piecrust/issues/296

piecrust/src/session.rs

@@ -289,22 +289,13 @@ impl Session {
             let instance =
                 self.instance(&contract_id).expect("instance should exist");
 
-            let has_init = instance.is_function_exported(INIT_METHOD);
-            if has_init && arg.is_none() {
-                return Err(InitalizationError(
-                    "Contract has constructor but no argument was provided"
-                        .into(),
-                ));
-            }
-
-            if let Some(arg) = arg {
-                if !has_init {
-                    return Err(InitalizationError(
-                        "Argument was provided but contract has no constructor"
-                            .into(),
-                    ));
-                }
-
+            if instance.is_function_exported(INIT_METHOD) {
+                // If no argument was provided, we call the constructor anyway,
+                // but with an empty argument. The alternative is to panic, but
+                // that assumes that the caller of `deploy` knows that the
+                // contract has a constructor in the first place, which might
+                // not be the case, such as when ingesting untrusted bytecode.
+                let arg = arg.unwrap_or_default();
                 self.call_inner(contract_id, INIT_METHOD, arg, gas_limit)?;
             }
 

piecrust/tests/constructor.rs

@@ -73,20 +73,20 @@ fn constructor() -> Result<(), Error> {
 }
 
 #[test]
-fn missing_init() -> Result<(), Error> {
+fn empty_constructor_argument() -> Result<(), Error> {
     let vm = VM::ephemeral()?;
 
     let mut session = vm.session(SessionData::builder())?;
 
-    let result = session.deploy(
-        contract_bytecode!("counter"),
-        ContractData::builder(OWNER).constructor_arg(&0xabu8),
+    let id = session.deploy(
+        contract_bytecode!("empty_constructor"),
+        ContractData::builder(OWNER),
         LIMIT,
-    );
+    )?;
 
-    assert!(
-        result.is_err(),
-        "deploy with data when the 'init' method is not exported should fail with an error"
+    assert_eq!(
+        session.call::<_, u8>(id, "read_value", &(), LIMIT)?.data,
+        0x10
     );
 
     Ok(())