Added some comments

.gitlab-ci.yml

@@ -123,6 +123,8 @@ examples-fmt:
         cargo fmt --verbose --manifest-path ./examples/upgradeable-contracts/${contract}/Cargo.toml -- --check;
       done
     - cargo fmt --verbose --manifest-path ./examples/upgradeable-contracts/delegate-calls/upgradeable-flipper/Cargo.toml -- --check
+    # This file is not a part of the cargo project, so it wouldn't be formatted the usual way
+    - rustfmt --verbose --check ./examples/psp22-extension/runtime/psp22-extension-example.rs
   allow_failure:                   true
 
 clippy-std:

examples/psp22-extension/README.md

@@ -24,10 +24,10 @@ To integrate this example into Substrate you need to do two things:
 * In your runtime, use the code in
   [`psp22-extension-example.rs`](runtime/psp22-extension-example.rs)
   as an implementation for the trait `ChainExtension` in Substrate.
-  You can just copy/paste the content of that file into e.g. your `runtime/src/lib.rs`.
+  You can just copy/paste that file as a new module, e.g. `runtime/src/chain_extension.rs`.
 
-* Use the implementation as the associated type `ChainExtension` of the trait
-  `pallet_contracts::Config`:
+* In your runtime, use the implementation as the associated type `ChainExtension` of the
+  trait `pallet_contracts::Config`:
   ```rust
   impl pallet_contracts::Config for Runtime {
     …
@@ -42,6 +42,9 @@ See the example contract in [`lib.rs`](lib.rs).
 
 ## Disclaimer
 
-This is not a feature-complete or production-ready PSP22 implementation. This example
-currently lacks proper error management, precise weight accounting, tests (these all
-might be added at a later point).
+:warning: This is not a feature-complete or production-ready PSP22 implementation. This
+example currently lacks proper error management, precise weight accounting, tests (these
+all  might be added at a later point).
+
+:warning: `decrease_allowance` function is currently not implemented due to limitations
+of the `assets` pallet.

examples/psp22-extension/lib.rs

@@ -113,6 +113,7 @@ impl ink_env::chain_extension::FromStatusCode for Psp22ErrorCode {
     }
 }
 
+/// An environment using default ink env types, with Psp22Extension included
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "std", derive(scale_info::TypeInfo))]
 pub enum CustomEnvironment {}

examples/psp22-extension/runtime/psp22-extension-example.rs

@@ -163,6 +163,8 @@ where
 {
     let mut env = env.buf_in_buf_out();
     let base_weight = <T as pallet_assets::Config>::WeightInfo::transfer();
+    // debug_message weight is a good approximation of the additional overhead of going from
+    // contract layer to substrate layer.
     let overhead = <T as pallet_contracts::Config>::Schedule::get()
         .host_fn_weights
         .debug_message;
@@ -197,9 +199,6 @@ where
         DispatchError::Other("ChainExtension failed to call transfer")
     })?;
     Ok(())
-
-    // TODO: adjust weight
-    // env.adjust_weight(charged, actual_weight)
 }
 
 fn transfer_from<T, E>(env: Environment<E, InitState>) -> Result<(), DispatchError>
@@ -210,6 +209,8 @@ where
 {
     let mut env = env.buf_in_buf_out();
     let base_weight = <T as pallet_assets::Config>::WeightInfo::transfer();
+    // debug_message weight is a good approximation of the additional overhead of going from
+    // contract layer to substrate layer.
     let overhead = <T as pallet_contracts::Config>::Schedule::get()
         .host_fn_weights
         .debug_message;
@@ -244,9 +245,6 @@ where
         );
         DispatchError::Other("ChainExtension failed to call transfer_from")
     })
-
-    // TODO: adjust weight
-    // env.adjust_weight(charged, actual_weight)
 }
 
 fn approve<T, E>(env: Environment<E, InitState>) -> Result<(), DispatchError>
@@ -257,6 +255,8 @@ where
 {
     let mut env = env.buf_in_buf_out();
     let base_weight = <T as pallet_assets::Config>::WeightInfo::approve_transfer();
+    // debug_message weight is a good approximation of the additional overhead of going from
+    // contract layer to substrate layer.
     let overhead = <T as pallet_contracts::Config>::Schedule::get()
         .host_fn_weights
         .debug_message;
@@ -288,9 +288,6 @@ where
         );
         DispatchError::Other("ChainExtension failed to call approve")
     })
-
-    // TODO: adjust weight
-    // env.adjust_weight(charged, actual_weight)
 }
 
 fn decrease_allowance<T, E>(_env: Environment<E, InitState>) -> Result<(), DispatchError>