Add output positional arg to undying-collator cli (#2375)

Follow up from https://github.com/paritytech/polkadot-sdk/pull/2370 to
add `output` positional argument to undying-collator.

cc @JoshOrndorff

---------

Co-authored-by: Bastian Köcher <git@kchr.de>

polkadot/parachain/test-parachains/undying/collator/src/cli.rs

@@ -18,6 +18,7 @@
 
 use clap::Parser;
 use sc_cli::SubstrateCli;
+use std::path::PathBuf;
 
 /// Sub-commands supported by the collator.
 #[derive(Debug, Parser)]
@@ -34,6 +35,10 @@ pub enum Subcommand {
 /// Command for exporting the genesis state of the parachain
 #[derive(Debug, Parser)]
 pub struct ExportGenesisStateCommand {
+	/// Output file name or stdout if unspecified.
+	#[arg()]
+	pub output: Option<PathBuf>,
+
 	/// Id of the parachain this collator collates for.
 	#[arg(long, default_value_t = 100)]
 	pub parachain_id: u32,
@@ -50,7 +55,11 @@ pub struct ExportGenesisStateCommand {
 
 /// Command for exporting the genesis wasm file.
 #[derive(Debug, Parser)]
-pub struct ExportGenesisWasmCommand {}
+pub struct ExportGenesisWasmCommand {
+	/// Output file name or stdout if unspecified.
+	#[arg()]
+	pub output: Option<PathBuf>,
+}
 
 #[allow(missing_docs)]
 #[derive(Debug, Parser)]

polkadot/parachain/test-parachains/undying/collator/src/main.rs

@@ -22,6 +22,10 @@ use polkadot_node_subsystem::messages::{CollationGenerationMessage, CollatorProt
 use polkadot_primitives::Id as ParaId;
 use sc_cli::{Error as SubstrateCliError, SubstrateCli};
 use sp_core::hexdisplay::HexDisplay;
+use std::{
+	fs,
+	io::{self, Write},
+};
 use test_parachain_undying_collator::Collator;
 
 mod cli;
@@ -35,14 +39,30 @@ fn main() -> Result<()> {
 			// `pov_size` and `pvf_complexity` need to match the ones that we start the collator
 			// with.
 			let collator = Collator::new(params.pov_size, params.pvf_complexity);
-			println!("0x{:?}", HexDisplay::from(&collator.genesis_head()));
+
+			let output_buf =
+				format!("0x{:?}", HexDisplay::from(&collator.genesis_head())).into_bytes();
+
+			if let Some(output) = params.output {
+				std::fs::write(output, output_buf)?;
+			} else {
+				std::io::stdout().write_all(&output_buf)?;
+			}
 
 			Ok::<_, Error>(())
 		},
-		Some(cli::Subcommand::ExportGenesisWasm(_params)) => {
+		Some(cli::Subcommand::ExportGenesisWasm(params)) => {
 			// We pass some dummy values for `pov_size` and `pvf_complexity` as these don't
 			// matter for `wasm` export.
-			println!("0x{:?}", HexDisplay::from(&Collator::default().validation_code()));
+			let output_buf =
+				format!("0x{:?}", HexDisplay::from(&Collator::default().validation_code()))
+					.into_bytes();
+
+			if let Some(output) = params.output {
+				fs::write(output, output_buf)?;
+			} else {
+				io::stdout().write_all(&output_buf)?;
+			}
 
 			Ok(())
 		},