Make export blocks default to json on stdout (paritytech#5090)

* Make export blocks default to json on stdout

* Multiline instead of single line to stay under 100 cols

* Change --json flag to --binary, defaulting to json

client/cli/src/commands/export_blocks_cmd.rs

@@ -50,9 +50,9 @@ pub struct ExportBlocksCmd {
 	#[structopt(long = "to", value_name = "BLOCK")]
 	pub to: Option<BlockNumber>,
 
-	/// Use JSON output rather than binary.
-	#[structopt(long = "json")]
-	pub json: bool,
+	/// Use binary output rather than JSON.
+	#[structopt(long = "binary", value_name = "BOOL", parse(try_from_str), default_value("false"))]
+	pub binary: bool,
 
 	#[allow(missing_docs)]
 	#[structopt(flatten)]
@@ -85,15 +85,15 @@ impl ExportBlocksCmd {
 		let from = self.from.as_ref().and_then(|f| f.parse().ok()).unwrap_or(1);
 		let to = self.to.as_ref().and_then(|t| t.parse().ok());
 
-		let json = self.json;
+		let binary = self.binary;
 
 		let file: Box<dyn io::Write> = match &self.output {
 			Some(filename) => Box::new(fs::File::create(filename)?),
 			None => Box::new(io::stdout()),
 		};
 
 		run_until_exit(config, |config| {
-			Ok(builder(config)?.export_blocks(file, from.into(), to, json))
+			Ok(builder(config)?.export_blocks(file, from.into(), to, binary))
 		})
 	}
 

client/service/src/builder.rs

@@ -742,7 +742,7 @@ pub trait ServiceBuilderCommand {
 		output: impl Write + 'static,
 		from: NumberFor<Self::Block>,
 		to: Option<NumberFor<Self::Block>>,
-		json: bool
+		binary: bool
 	) -> Pin<Box<dyn Future<Output = Result<(), Error>>>>;
 
 	/// Performs a revert of `blocks` blocks.

client/service/src/chain_ops.rs

@@ -203,7 +203,7 @@ impl<
 		mut output: impl Write + 'static,
 		from: NumberFor<TBl>,
 		to: Option<NumberFor<TBl>>,
-		json: bool
+		binary: bool
 	) -> Pin<Box<dyn Future<Output = Result<(), Error>>>> {
 		let client = self.client;
 		let mut block = from;
@@ -230,7 +230,7 @@ impl<
 
 			if !wrote_header {
 				info!("Exporting blocks from #{} to #{}", block, last);
-				if !json {
+				if binary {
 					let last_: u64 = last.saturated_into::<u64>();
 					let block_: u64 = block.saturated_into::<u64>();
 					let len: u64 = last_ - block_ + 1;
@@ -241,13 +241,13 @@ impl<
 
 			match client.block(&BlockId::number(block))? {
 				Some(block) => {
-					if json {
+					if binary {
+						output.write_all(&block.encode())?;
+					} else {
 						serde_json::to_writer(&mut output, &block)
 							.map_err(|e| format!("Error writing JSON: {}", e))?;
-						} else {
-							output.write_all(&block.encode())?;
 					}
-				},
+			},
 				// Reached end of the chain.
 				None => return std::task::Poll::Ready(Ok(())),
 			}