Adds support for 'caller_is_root' (#2332)

* Adds support for 'caller_is_root'

* Adds PR to 'CHANGELOG.md'

* Tested CI locally

* Updates Cargo nightly

* Revert "Updates Cargo nightly"

This reverts commit c70c62d.

* Revert "Tested CI locally"

This reverts commit 0e37b8e.

* Close delimiter

* Apply `cargo fmt`

* Move changelog entry to unreleased section

* Implement `caller_is_root` on-chain

* Account for `call_is_root() -> u32` return type

* Panic when `u32 -> bool` not possible

---------

Co-authored-by: Michael Mueller <[email protected]>

Author: olahfemi

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Changed
 - Restrict which `cfg` attributes can be used ‒ [#2313](https://github.com/use-ink/ink/pull/2313)
 
+## Added
+- Support for `caller_is_root` - [#2332] (https://github.com/use-ink/ink/pull/2332)
+
 ## Fixed
 - [E2E] Have port parsing handle comma-separated list ‒ [#2336](https://github.com/use-ink/ink/pull/2336)
 

crates/env/src/api.rs

@@ -729,6 +729,26 @@ where
     })
 }
 
+/// Checks whether the caller of the current contract is root.
+///
+/// Note that only the origin of the call stack can be root. Hence this function returning
+/// `true` implies that the contract is being called by the origin.
+///
+/// A return value of `true` indicates that this contract is being called by a root
+/// origin, and `false` indicates that the caller is a signed origin.
+///
+/// # Errors
+///
+/// If the returned value cannot be properly decoded.
+pub fn caller_is_root<E>() -> bool
+where
+    E: Environment,
+{
+    <EnvInstance as OnInstance>::on_instance(|instance| {
+        TypedEnvBackend::caller_is_root::<E>(instance)
+    })
+}
+
 /// Replace the contract code at the specified address with new code.
 ///
 /// # Note

crates/env/src/backend.rs

@@ -413,6 +413,15 @@ pub trait TypedEnvBackend: EnvBackend {
     where
         E: Environment;
 
+    /// Checks whether the caller of the current contract is root.
+    ///
+    /// # Note
+    ///
+    /// For more details visit: [`caller_is_root`][`crate::caller_is_root`]
+    fn caller_is_root<E>(&mut self) -> bool
+    where
+        E: Environment;
+
     /// Retrieves the code hash of the contract at the given `account` id.
     ///
     /// # Note

crates/env/src/engine/off_chain/impls.rs

@@ -567,6 +567,13 @@ impl TypedEnvBackend for EnvInstance {
         unimplemented!("off-chain environment does not support cross-contract calls")
     }
 
+    fn caller_is_root<E>(&mut self) -> bool
+    where
+        E: Environment,
+    {
+        unimplemented!("off-chain environment does not support `caller_is_root`")
+    }
+
     fn code_hash<E>(&mut self, _account: &E::AccountId) -> Result<E::Hash>
     where
         E: Environment,

crates/env/src/engine/on_chain/impls.rs

@@ -676,6 +676,20 @@ impl TypedEnvBackend for EnvInstance {
         ext::caller_is_origin()
     }
 
+    fn caller_is_root<E>(&mut self) -> bool
+    where
+        E: Environment,
+    {
+        // `ext::caller_is_root()` currently returns `u32`.
+        // See https://github.com/paritytech/polkadot-sdk/issues/6767 for more details.
+        let ret = ext::caller_is_root();
+        match ret {
+            0u32 => false,
+            1u32 => true,
+            _ => panic!("Invalid value for bool conversion: {}", ret),
+        }
+    }
+
     fn code_hash<E>(&mut self, account_id: &E::AccountId) -> Result<E::Hash>
     where
         E: Environment,

crates/ink/src/env_access.rs

@@ -1178,6 +1178,37 @@ where
         ink_env::caller_is_origin::<E>()
     }
 
+    /// Checks whether the caller of the current contract is root.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # #[ink::contract]
+    /// # pub mod my_contract {
+    /// #     #[ink(storage)]
+    /// #     pub struct MyContract { }
+    /// #
+    /// #     impl MyContract {
+    /// #         #[ink(constructor)]
+    /// #         pub fn new() -> Self {
+    /// #             Self {}
+    /// #         }
+    /// #
+    /// #[ink(message)]
+    /// pub fn caller_is_root(&mut self) -> bool {
+    ///     self.env().caller_is_root()
+    /// }
+    /// #    }
+    /// # }
+    /// ```
+    ///
+    /// # Note
+    ///
+    /// For more details visit: [`ink_env::caller_is_root`]
+    pub fn caller_is_root(self) -> bool {
+        ink_env::caller_is_root::<E>()
+    }
+
     /// Returns the code hash of the contract at the given `account` id.
     ///
     /// # Example