From 184ac9d463f371671e6c5d9eac99b552a2b75072 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fe=CC=81lix=20Saparelli?= <felix@passcod.name>
Date: Sat, 20 Apr 2024 22:15:56 +1200
Subject: [PATCH] Breaking changes for --shell

---
 crates/cli/src/args.rs   | 25 ++++----------
 crates/cli/src/config.rs | 71 +++++++++++++++++++++++++---------------
 2 files changed, 51 insertions(+), 45 deletions(-)

diff --git a/crates/cli/src/args.rs b/crates/cli/src/args.rs
index a11b971..143996d 100644
--- a/crates/cli/src/args.rs
+++ b/crates/cli/src/args.rs
@@ -434,18 +434,18 @@ pub struct Args {
 
 	/// Use a different shell
 	///
-	/// By default, Watchexec will use 'sh' on unix and 'cmd' (CMD.EXE) on Windows. With this, you
-	/// can override that and use a different shell, for example one with more features or one which
-	/// has your custom aliases and functions.
+	/// By default, Watchexec will use '$SHELL' if it's defined or a default of 'sh' on Unix-likes,
+	/// and either 'pwsh', 'powershell', or 'cmd' (CMD.EXE) on Windows, depending on what Watchexec
+	/// detects is the running shell.
+	///
+	/// With this option, you can override that and use a different shell, for example one with more
+	/// features or one which has your custom aliases and functions.
 	///
 	/// If the value has spaces, it is parsed as a command line, and the first word used as the
 	/// shell program, with the rest as arguments to the shell.
 	///
 	/// The command is run with the '-c' flag (except for 'cmd' on Windows, where it's '/C').
 	///
-	/// Note that the default shell will change at the next major release: the value of '$SHELL'
-	/// will be respected, falling back to 'sh' on unix and to PowerShell on Windows.
-	///
 	/// The special value 'none' can be used to disable shell use entirely. In that case, the
 	/// command provided to Watchexec will be parsed, with the first word being the executable and
 	/// the rest being the arguments, and executed directly. Note that this parsing is rudimentary,
@@ -465,7 +465,7 @@ pub struct Args {
 	///
 	///   $ watchexec --shell=pwsh -- Test-Connection localhost
 	///
-	/// Use with cmd (default on Windows):
+	/// Use with CMD.exe:
 	///
 	///   $ watchexec --shell=cmd -- dir
 	///
@@ -492,17 +492,6 @@ pub struct Args {
 	)]
 	pub no_shell: bool,
 
-	/// Don't use a shell
-	///
-	/// This is a deprecated alias for '--shell=none'.
-	#[arg(
-		long,
-		hide = true,
-		help_heading = OPTSET_COMMAND,
-		alias = "no-shell", // deprecated
-	)]
-	pub no_shell_long: bool,
-
 	/// Shorthand for '--emit-events=none'
 	///
 	/// This is the old way to disable event emission into the environment. See '--emit-events' for
diff --git a/crates/cli/src/config.rs b/crates/cli/src/config.rs
index 87aaf15..a018b53 100644
--- a/crates/cli/src/config.rs
+++ b/crates/cli/src/config.rs
@@ -1,7 +1,7 @@
 use std::{
 	borrow::Cow,
 	collections::HashMap,
-	env::current_dir,
+	env::{current_dir, var},
 	ffi::{OsStr, OsString},
 	fs::File,
 	io::{IsTerminal, Write},
@@ -469,35 +469,52 @@ fn interpret_command_args(args: &Args) -> Result<Arc<Command>> {
 		panic!("(clap) Bug: command is not present");
 	}
 
-	let shell = match if args.no_shell || args.no_shell_long {
+	let shell = if args.no_shell {
 		None
 	} else {
-		args.shell.as_deref().or(Some("default"))
-	} {
-		Some("") => return Err(RuntimeError::CommandShellEmptyShell).into_diagnostic(),
-
-		Some("none") | None => None,
-
-		#[cfg(windows)]
-		Some("default") | Some("cmd") | Some("cmd.exe") | Some("CMD") | Some("CMD.EXE") => {
-			Some(Shell::cmd())
-		}
-
-		#[cfg(not(windows))]
-		Some("default") => Some(Shell::new("sh")),
-
-		Some(other) => {
-			let sh = other.split_ascii_whitespace().collect::<Vec<_>>();
-
-			// UNWRAP: checked by Some("")
-			#[allow(clippy::unwrap_used)]
-			let (shprog, shopts) = sh.split_first().unwrap();
-
-			Some(Shell {
-				prog: shprog.into(),
-				options: shopts.iter().map(|s| (*s).to_string()).collect(),
-				program_option: Some(Cow::Borrowed(OsStr::new("-c"))),
+		let shell = args.shell.clone().or_else(|| var("SHELL").ok());
+		match shell
+			.as_deref()
+			.or_else(|| {
+				if cfg!(not(windows)) {
+					Some("sh")
+				} else if var("POWERSHELL_DISTRIBUTION_CHANNEL").is_ok()
+					&& (which::which("pwsh").is_ok() || which::which("pwsh.exe").is_ok())
+				{
+					trace!("detected pwsh");
+					Some("pwsh")
+				} else if var("PSModulePath").is_ok()
+					&& (which::which("powershell").is_ok()
+						|| which::which("powershell.exe").is_ok())
+				{
+					trace!("detected powershell");
+					Some("powershell")
+				} else {
+					Some("cmd")
+				}
 			})
+			.or(Some("default"))
+		{
+			Some("") => return Err(RuntimeError::CommandShellEmptyShell).into_diagnostic(),
+
+			Some("none") | None => None,
+
+			#[cfg(windows)]
+			Some("cmd") | Some("cmd.exe") | Some("CMD") | Some("CMD.EXE") => Some(Shell::cmd()),
+
+			Some(other) => {
+				let sh = other.split_ascii_whitespace().collect::<Vec<_>>();
+
+				// UNWRAP: checked by Some("")
+				#[allow(clippy::unwrap_used)]
+				let (shprog, shopts) = sh.split_first().unwrap();
+
+				Some(Shell {
+					prog: shprog.into(),
+					options: shopts.iter().map(|s| (*s).to_string()).collect(),
+					program_option: Some(Cow::Borrowed(OsStr::new("-c"))),
+				})
+			}
 		}
 	};