# Description
This PR introduces two changes:
- the previous `Tracing` trait has been modified to accept contract
address instead of code hash (seems to be way more convenient)
- a new trait `CallInterceptor` that allows intercepting contract calls;
in particular the default implementation for `()` will just proceed in a
standard way (after compilation optimizations, there will be no
footprint of that); however, implementing type might decide to mock
invocation and return `ExecResult` instead
Note: one might try merging `before_call` and `intercept_call`. However,
IMHO this would be bad, since it would mix two completely different
abstractions - tracing without any effects and actual intervention into
execution process.
This will unblock working on mocking contracts utility in drink and
similar tools (https://github.com/Cardinal-Cryptography/drink/issues/33)
# Checklist
- [x] My PR includes a detailed description as outlined in the
"Description" section above
- [ ] My PR follows the [labeling
requirements](https://github.com/paritytech/polkadot-sdk/blob/master/docs/CONTRIBUTING.md#process)
of this project (at minimum one label for `T` required)
- [x] I have made corresponding changes to the documentation (if
applicable)
- [x] I have added tests that prove my fix is effective or that my
feature works (if applicable)
* Provide basic breakpoints
* Rename to Observer
* Rename feature. Single trait. Borrow-checker
* : frame_system::Config
* Confused type name
* Minor bugs
* pub trait
* No unnecessary cloning
* Make node compile with all features
* Move everything debug-related to a single module
* Add docs and implementation for ()
* fmt
* Make it feature-gated or for tests
* Prepare testing kit
* Testcase
* Fmt
* Use feature in dev-deps
* ?
* feature propagation
* AAAA
* lol, that doesn't make much sense to me
* Turn on
* clippy
* Remove self dep
* fmt, feature-gating test
* Noop to trigger CI
* idk
* add feature to pipeline
* Corrupt test to see if it is actually being run
* Revert change
* Doc for conf type
* Review
* Imports
* ...
* Remove debug for kitchen-sink
* Move test
* Fix imports
* I must have already tried this one...
* Adjust to the new API
* Remove mutability
* Async constructor
* unwrap result
* do not panic
* suggestion
* leftover
* update lockfile for {"substrate"}
Co-authored-by: parity-processbot <>
Piotr Mikołajczyk