Use raw_arg for CMD on Windows

CMD uses special handling for arguments to passed to /C. Unfortunately,
this causes errors with quoted program names in these arguments.

This commit implements a workaround: When CMD is requested, we build a
std::process::Command and pass the the argument to /C using the special
std::os::windows::process::CommandExt::raw_arg method. The StdCommand is
then converted to a TokioCommand and returned.

Once tokio-rs/tokio#5810 is fixed, this workaround can be removed.

Fixes watchexec#613

crates/lib/src/command.rs

@@ -99,9 +99,21 @@ impl Command {
 				args,
 				command,
 			} => {
+				if command.is_empty() {
+					return Err(RuntimeError::CommandShellEmptyCommand);
+				}
+
 				let (shcmd, shcliopt) = match shell {
 					#[cfg(windows)]
-					Shell::Cmd => ("cmd.exe", "/C"),
+					Shell::Cmd => {
+						use std::os::windows::process::CommandExt as _;
+						use std::process::Command as StdCommand;
+
+						// TODO this is a workaround until TokioCommand has a raw_arg method. See tokio-rs/tokio#5810.
+						let mut std_command = StdCommand::new("cmd.exe");
+						std_command.args(args).arg("/C").raw_arg(command);
+						return Ok(TokioCommand::from(std_command));
+					}
 
 					#[cfg(windows)]
 					Shell::Powershell => ("powershell.exe", "-Command"),
@@ -117,10 +129,6 @@ impl Command {
 					}
 				};
 
-				if command.is_empty() {
-					return Err(RuntimeError::CommandShellEmptyCommand);
-				}
-
 				let mut c = TokioCommand::new(shcmd);
 				c.args(args);
 				c.arg(shcliopt).arg(command);

crates/lib/src/command/tests.rs

@@ -85,7 +85,7 @@ async fn windows_shell_cmd() -> Result<(), std::io::Error> {
 	assert!(Command::Shell {
 		shell: Shell::Cmd,
 		args: Vec::new(),
-		command: "echo hi".into()
+		command: r#""echo" hi"#.into()
 	}
 	.to_spawnable()
 	.unwrap()