migrate command line example and test

lukewilliamboswell · lukewilliamboswell · commit c2b3e0500a33 · 2025-12-30T14:40:28.000+11:00
diff --git a/ci/expect_scripts/command-line-args.exp b/ci/expect_scripts/command-line-args.exp
@@ -5,18 +5,11 @@
 
 set timeout 7
 
-spawn $env(EXAMPLES_DIR)/command-line-args foo
-
 source ./ci/expect_scripts/shared-code.exp
 
+spawn $env(EXAMPLES_DIR)/command-line-args foo
 
-set expected_output [normalize_output {
-received argument: foo
-Unix argument, bytes: \[102, 111, 111\]
-back to Arg: "foo"
-}]
-
-expect $expected_output {
+expect "received argument: foo\r\n" {
     expect eof {
         check_exit_and_segfault
     }
diff --git a/examples/command-line-args.roc b/examples/command-line-args.roc
@@ -1,37 +1,18 @@
-app [main!] {
-    pf: platform "../platform/main.roc",
-}
+app [main!] { pf: platform "../platform/main.roc" }
 
 import pf.Stdout
-import pf.Arg exposing [Arg]
-
-# How to handle command line arguments in Roc.
-
-# To run this example: check the README.md in this folder
-
-main! : List Arg => Result {} _
-main! = |raw_args|
-
-    # get the second argument, the first is the executable's path
-    when List.get(raw_args, 1) |> Result.map_err(|_| ZeroArgsGiven) is
-        Err(ZeroArgsGiven) ->
-            Err(Exit(1, "Error ZeroArgsGiven:\n\tI expected one argument, but I got none.\n\tRun the app like this: `roc main.roc -- input.txt`"))
 
-        Ok(first_arg) ->
-            Stdout.line!("received argument: ${Arg.display(first_arg)}")?
-
-            # # OPTIONAL TIP:
-
-            # If you ever need to pass an arg to a Roc package, it will probably expect an argument with the type `[Unix (List U8), Windows (List U16)]`.
-            # You can convert an Arg to that with `Arg.to_os_raw`.
-            #
-            # Roc packages like to be platform agnostic so that everyone can use them, that's why they avoid platform-specific types like `pf.Arg`.
-            when Arg.to_os_raw(first_arg) is
-                Unix(bytes) ->
-                    Stdout.line!("Unix argument, bytes: ${Inspect.to_str(bytes)}")?
-
-                Windows(u16s) ->
-                    Stdout.line!("Windows argument, u16s: ${Inspect.to_str(u16s)}")?
-
-            # You can go back with Arg.from_os_raw:
-            Stdout.line!("back to Arg: ${Inspect.to_str(Arg.from_os_raw(Arg.to_os_raw(first_arg)))}")
+main! : List(Str) => Try({}, [Exit(I32)])
+main! = |args| {
+    # Skip first arg (executable path), get the remaining args
+    match args.drop_first(1) {
+        [first_arg, ..] => {
+            Stdout.line!("received argument: ${first_arg}")
+            Ok({})
+        }
+        [] => {
+            Stdout.line!("Error: I expected one argument, but got none.")
+            Err(Exit(1))
+        }
+    }
+}
