Dual execution (#311)

* Initial logic

* Remove accidental file

* Config

* Remove accidental

* Apply CLI config

* Additional work. Sadly pointless.

* Rearrange everything

* Loop into CLI param

* Implement dual execution

* typo

* fix tests.

* Better docs

* Fix bug

* Add some tests

* Report block information on consensus failure, tests

* Fix test

substrate/polkadot/cli/src/cli.yml

@@ -74,7 +74,7 @@ args:
   - pruning:
       long: pruning
       value_name: PRUNING_MODE
-      help: Specify the pruning mode. (a number of blocks to keep or "archive"). Default is 256.
+      help: Specify the pruning mode, a number of blocks to keep or "archive". Default is 256.
       takes_value: true
   - name:
       long: name
@@ -95,6 +95,10 @@ args:
       value_name: TELEMETRY_URL
       help: The URL of the telemetry server. Implies --telemetry
       takes_value: true
+  - execution:
+      long: execution
+      value_name: STRATEGY
+      help: The means of execution used when calling into the runtime. Can be either wasm, native or both.
 subcommands:
   - build-spec:
       about: Build a spec.json file, outputing to stdout

substrate/polkadot/cli/src/lib.rs

@@ -218,18 +218,32 @@ pub fn run<I, T, W>(args: I, worker: W) -> error::Result<()> where
 		if matches.is_present("collator") {
 			info!("Starting collator");
 			// TODO [rob]: collation node implementation
-			service::Role::FULL
+			// This isn't a thing. Different parachains will have their own collator executables and
+			// maybe link to libpolkadot to get a light-client. 
+			service::Role::LIGHT
 		} else if matches.is_present("light") {
 			info!("Starting (light)");
+			config.execution_strategy = service::ExecutionStrategy::NativeWhenPossible;
 			service::Role::LIGHT
 		} else if matches.is_present("validator") || matches.is_present("dev") {
 			info!("Starting validator");
+			config.execution_strategy = service::ExecutionStrategy::Both;
 			service::Role::AUTHORITY
 		} else {
 			info!("Starting (heavy)");
+			config.execution_strategy = service::ExecutionStrategy::NativeWhenPossible;
 			service::Role::FULL
 		};
 
+	if let Some(s) = matches.value_of("execution") {
+		config.execution_strategy = match s {
+			"both" => service::ExecutionStrategy::Both,
+			"native" => service::ExecutionStrategy::NativeWhenPossible,
+			"wasm" => service::ExecutionStrategy::AlwaysWasm,
+			_ => return Err(error::ErrorKind::Input("Invalid execution mode specified".to_owned()).into()),
+		};
+	}
+
 	config.roles = role;
 	{
 		config.network.boot_nodes.extend(matches