From 998d190ea06a8d539a8c4a8527905cf8758abe4a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexander=20Thei=C3=9Fen?= <alex.theissen@me.com>
Date: Sun, 21 Mar 2021 14:49:44 +0100
Subject: [PATCH] Use the log crate to output contract generated messages.
(#8403)
---
substrate/frame/contracts/README.md | 15 +++++++++++++++
substrate/frame/contracts/src/wasm/runtime.rs | 2 +-
2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/substrate/frame/contracts/README.md b/substrate/frame/contracts/README.md
index 1cb384e14c5..6c987165990 100644
--- a/substrate/frame/contracts/README.md
+++ b/substrate/frame/contracts/README.md
@@ -57,4 +57,19 @@ will make things a lot easier. One such language is [`ink`](https://github.com/p
which is an [`eDSL`](https://wiki.haskell.org/Embedded_domain_specific_language) that enables
writing WebAssembly based smart contracts in the Rust programming language.
+## Debugging
+
+Contracts can emit messages to the node console when run on a development chain through the
+`seal_println` API. This is exposed in ink! via
+[`ink_env::debug_println()`](https://docs.rs/ink_env/latest/ink_env/fn.debug_println.html).
+
+In order to see these messages the log level for the `runtime::contracts` target needs to be raised
+to at least the `info` level which is the default. However, those messages are easy to overlook
+because of the noise generated by block production. A good starting point for contract debugging
+could be:
+
+```bash
+cargo run --release -- --dev --tmp -lerror,runtime::contracts
+```
+
License: Apache-2.0
diff --git a/substrate/frame/contracts/src/wasm/runtime.rs b/substrate/frame/contracts/src/wasm/runtime.rs
index 2ceac1c5160..8e3c2244f1e 100644
--- a/substrate/frame/contracts/src/wasm/runtime.rs
+++ b/substrate/frame/contracts/src/wasm/runtime.rs
@@ -1366,7 +1366,7 @@ define_env!(Env, <E: Ext>,
seal_println(ctx, str_ptr: u32, str_len: u32) => {
let data = ctx.read_sandbox_memory(str_ptr, str_len)?;
if let Ok(utf8) = core::str::from_utf8(&data) {
- sp_runtime::print(utf8);
+ log::info!(target: "runtime::contracts", "seal_println: {}", utf8);
}
Ok(())
},
--
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