Move program name from main! args to Env.program_name!

examples/command-line-args.roc

@@ -2,13 +2,16 @@
 app [main!] { pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.23.0-rc1/3hT3SoHZ6qbEsa9qVFLUW3547U5LeoNd1KbpqLpz4r1i.tar.zst" }
 
 import pf.OsStr
+import pf.Env
 import pf.Stdout
 import pf.Stderr
 
 main! : List(OsStr) => Try({}, _)
 main! = |args| {
-	# Skip first arg (executable path), get the remaining args
-	match args.drop_first(1) {
+	program_name = Env.program_name!()?
+	Stdout.line!("program name: ${OsStr.display(program_name)}")?
+
+	match args {
 		[first_arg, ..] => {
 
 			Stdout.line!("received argument: ${OsStr.display(first_arg)}")?

examples/file-accessed-modified-created-time.roc

@@ -36,7 +36,7 @@ main! = |args| {
 ## Parse the first argument into a Path
 path_argument : List(OsStr) -> Try(Path, _)
 path_argument = |args|
-	match args.drop_first(1) {
+	match args {
 		[first, ..] => Ok(Path.from_os_str(first))
 		[] => Err(MissingPathArgument)
 	}

examples/file-permissions.roc

@@ -29,7 +29,7 @@ main! = |args| {
 ## Parse the first argument into a Path
 path_argument : List(OsStr) -> Try(Path, _)
 path_argument = |args|
-	match args.drop_first(1) {
+	match args {
 		[first, ..] => Ok(Path.from_os_str(first))
 		[] => Err(MissingPathArgument)
 	}

examples/file-size.roc

@@ -21,7 +21,7 @@ main! = |args| {
 
 path_argument : List(OsStr) -> Try(Path, [MissingPathArgument, ..])
 path_argument = |args|
-	match args.drop_first(1) {
+	match args {
 		[first, ..] => Ok(Path.from_os_str(first))
 		[] => Err(MissingPathArgument)
 	}

examples/filesystem-tools.roc

@@ -9,7 +9,7 @@ import pf.Stdout
 
 main! : List(OsStr) => Try({}, _)
 main! = |args| {
-	(source_arg, destination_arg) = match args.drop_first(1) {
+	(source_arg, destination_arg) = match args {
 		[source, destination] => (source, destination)
 		_ => return Err(MissingPaths)
 	}

examples/hello.roc

@@ -17,7 +17,7 @@ main! = |args| {
 
 greeting_name : List(OsStr) -> Str
 greeting_name = |args|
-	match args.drop_first(1) {
+	match args {
 		[first, ..] => OsStr.display(first)
 		[] => "friend"
 	}

examples/path.roc

@@ -24,7 +24,7 @@ main! = |args| {
 }
 
 path_argument = |args|
-	match args.drop_first(1) {
+	match args {
 		[first, ..] => Ok(Path.from_os_str(first))
 		[] => Err(MissingPathArgument)
 	}

examples/process-control.roc

@@ -9,7 +9,7 @@ import pf.Stdout
 
 main! : List(OsStr) => Try({}, _)
 main! = |args| {
-	(program, arguments) = match args.drop_first(1) {
+	(program, arguments) = match args {
 		[command, .. as rest] => (command, rest)
 		[] => return Err(MissingCommand)
 	}

platform/Env.roc

@@ -84,6 +84,19 @@ Env :: [].{
 			Err(ExePathUnavailable) => Err(ExePathUnavailable)
 		}
 
+	## Gets the program name supplied by the process launcher as its first argument.
+	##
+	## This is conventionally the executable name or path, but launchers may supply
+	## another value. Unlike [`exe_path!`](#exe_path!), it is returned as an
+	## [`OsStr`](OsStr), preserving the value exactly without treating it as a path.
+	## Returns `Err(ProgramNameUnavailable)` if the launcher supplied no first argument.
+	program_name! : () => Try(OsStr, [ProgramNameUnavailable, ..])
+	program_name! = ||
+		match Host.env_program_name!() {
+			Ok(raw) => Ok(OsStr.from_raw(raw))
+			Err(ProgramNameUnavailable) => Err(ProgramNameUnavailable)
+		}
+
 	## Atomically create a private directory in the system temporary directory.
 	## The caller owns cleanup. Unix directories have mode 0700.
 	create_temp_dir! : () => Try(Path.Path, [TempDirErr(IOErr), ..])

platform/Host.roc

@@ -157,4 +157,6 @@ Host :: [].{
 	tcp_local_port! : TcpListener => Try(U16, Str)
 	tcp_accept! : TcpListener, U64 => Try(TcpStream, Str)
 	tcp_listener_close! : TcpListener => Try({}, Str)
+
+	env_program_name! : () => Try(NativeOsStr, [ProgramNameUnavailable])
 }

platform/main.roc

@@ -2,6 +2,8 @@
 ## SQLite, environment, random, and UTC effects.
 platform ""
 	requires {
+		## The application entry point receives command-line arguments only; the
+		## launcher-supplied program name is available from Env.program_name!.
 		main! : List([Utf8(Str), UnixBytes(List(U8)), WindowsU16s(List(U16))]) => Try({}, [Exit(I32), ..])
 	}
 	exposes [Cmd, Env, File, Http, IOErr, Locale, Monotonic, OsStr, Path, Random, Sleep, Sqlite, Stdin, Stdout, Stderr, Tcp, Tty, Url, Utc]
@@ -100,6 +102,7 @@ platform ""
 		"hosted_tcp_local_port": Host.tcp_local_port!,
 		"hosted_tcp_accept": Host.tcp_accept!,
 		"hosted_tcp_listener_close": Host.tcp_listener_close!,
+		"hosted_env_program_name": Host.env_program_name!,
 	}
 	targets: {
 		inputs_dir: "targets/",
@@ -132,6 +135,8 @@ import Tty
 import Url
 import Utc
 
+## The native host removes the invocation name (argv[0]) before calling this
+## function. Applications can read that value separately with Env.program_name!.
 main_for_host! : List(OsStr.OsStr) => I32
 main_for_host! = |args|
 	match main!(args) {

scripts/test_spec.json

@@ -39,11 +39,13 @@
           "name": "one-argument",
           "args": ["foo"],
           "contains": [
+            "program name:",
             "received argument: foo",
             "back to OsStr: OsStr.",
             "argument 1 is valid UTF-8: foo"
           ],
           "regex": [
+            "program name: .*command-line-args(?:\\.exe)?",
             "(?:Unix argument, bytes|Windows argument, UTF-16 code units): \\[102, 111, 111\\]"
           ]
         },