[core] Add ext_println runtime call bindings

core/src/env/api.rs

@@ -56,6 +56,15 @@ where
     ContractEnv::r#return(&value.encode()[..])
 }
 
+/// Prints the given content.
+///
+/// # Note
+///
+/// Usable only in development (`--dev`) chains.
+pub fn println(content: &str) {
+    ContractEnv::println(content)
+}
+
 /// Stores the given value under the specified key in the contract storage.
 ///
 /// # Safety

core/src/env/srml/srml_only/impls.rs

@@ -119,4 +119,10 @@ where
     unsafe fn r#return(data: &[u8]) -> ! {
         sys::ext_return(data.as_ptr() as u32, data.len() as u32);
     }
+
+    fn println(content: &str) {
+        unsafe {
+            sys::ext_println(content.as_ptr() as u32, content.len() as u32)
+        }
+    }
 }

core/src/env/test_env.rs

@@ -258,6 +258,11 @@ impl TestEnvData {
         };
         std::process::exit(exit_code)
     }
+
+    /// Prints the given content.
+    pub fn println(&self, content: &str) {
+        println!("{}", content)
+    }
 }
 
 thread_local! {
@@ -375,4 +380,8 @@ where
         );
         TEST_ENV_DATA.with(|test_env| test_env.borrow().r#return(data))
     }
+
+    fn println(content: &str) {
+        TEST_ENV_DATA.with(|test_env| test_env.borrow().println(content))
+    }
 }

core/src/env/traits.rs

@@ -71,4 +71,11 @@ pub trait Env: EnvTypes + EnvStorage {
     /// returned value. This API is unsafe because it does not provide
     /// guarantees on its own to always encode the expected type.
     unsafe fn r#return(value: &[u8]) -> !;
+
+    /// Prints the given content to Substrate output.
+    ///
+    /// # Note
+    ///
+    /// Usable only in development (`--dev`) chains.
+    fn println(content: &str);
 }