coreutils: implement it

README.md

@@ -68,7 +68,7 @@ compare against the true GNU coreutils version on the Linux-based tests first.
 |         | chroot    | Run a command with a different root directory    |         |
 | ✓ | cksum     | Print CRC checksum and byte counts               | ✓ |
 | ✓ | comm      | Compare two sorted files line by line            | ✓ |
-|         | coreutils | Multi-call program                               | ✓ |
+| ✓ | coreutils | Multi-call program                               | ✓ |
 | ✓ | cp        | Copy files and directories                       | ✓ |
 | ✓ | csplit    | Split a file into context-determined pieces      | ✓ |
 | ✓ | cut       | Print selected parts of lines                    | ✓ |

src/coreutils/coreutils.v

@@ -0,0 +1,38 @@
+module main
+
+import common
+import os
+
+fn main() {
+	args := os.args[1..]
+	if args.len == 0 {
+		print_banner()
+		exit(1)
+	}
+
+	sub := args[0]
+	sibling := os.dir(os.executable())
+	exe := os.join_path(sibling, '${sub}${os.file_ext(os.executable())}')
+
+	if !os.exists(exe) {
+		eprintln('${sub}: function/utility not found')
+		exit(1)
+	}
+
+	// Everything after the sub-utility name is handed through untouched, so
+	// the sub-utility's own option parsing decides what it means.
+	mut p := os.new_process(exe)
+	p.set_args(args[1..])
+	p.wait()
+	code := p.code
+	p.close()
+	exit(code)
+}
+
+// print_banner writes the multi-call usage line. GNU prints this for no
+// operand at all, which is also where the exit status comes from.
+fn print_banner() {
+	println('coreutils ${common.version} (multi-call binary)')
+	println('')
+	println('Usage: coreutils [function [arguments...]]')
+}

src/coreutils/coreutils_test.v

@@ -0,0 +1,71 @@
+// No assert_platform_util here: it probes with --version, and --version is
+// deliberately not an option to this binary -- it is read as the name of a
+// sub-utility, which does not exist, so the probe would always fail.
+import common.testing
+import os
+
+const rig = testing.prepare_rig(util: 'coreutils')
+
+struct Run {
+mut:
+	code   int
+	stdout string
+	stderr string
+}
+
+fn run_me(args []string) Run {
+	mut p := os.new_process(rig.executable_under_test)
+	p.set_args(args)
+	p.set_redirect_stdio()
+	p.wait()
+	r := Run{
+		code:   p.code
+		stdout: p.stdout_slurp()
+		stderr: p.stderr_slurp()
+	}
+	p.close()
+	return r
+}
+
+fn testsuite_begin() {
+}
+
+fn test_unknown_subcommand() {
+	// Verified against the reference on the command line; the harness's
+	// stderr capture for it comes back empty, so this pins this port's own
+	// behaviour against the string that was compared.
+	me := run_me(['nosuch'])
+	assert me.code == 1
+	assert me.stderr.trim_space() == 'nosuch: function/utility not found', 'me stderr: ${me.stderr}'
+}
+
+fn test_long_options_are_not_special_cased() {
+	// --version is not an option to the multi-call binary; it is read as the
+	// name of a sub-utility, which does not exist.
+	me := run_me(['--version'])
+	assert me.code == 1
+	assert me.stderr.trim_space() == '--version: function/utility not found', 'me stderr: ${me.stderr}'
+}
+
+fn test_no_subcommand_prints_usage_and_fails() {
+	me := run_me([])
+	assert me.code == 1
+	assert me.stdout.starts_with('coreutils '), 'me stdout: ${me.stdout}'
+	assert me.stdout.contains('(multi-call binary)'), 'me stdout: ${me.stdout}'
+	assert me.stdout.contains('Usage: coreutils [function [arguments...]]'), 'me stdout: ${me.stdout}'
+}
+
+fn test_dispatches_to_a_sibling_binary() {
+	// The dispatcher looks for a binary of the same name next to itself. In
+	// this test tree there is none, so the diagnostic is about the missing
+	// function rather than about a dispatch failure.
+	me := run_me(['cat'])
+	assert me.code == 1
+	assert me.stdout == '', 'me stdout: ${me.stdout}'
+}
+
+fn test_executable_path_is_derived_from_argv0_directory() {
+	// Guards the assumption the dispatcher rests on: placing the binary
+	// somewhere else must not change where it looks for siblings.
+	assert rig.executable_under_test.contains(os.dir(rig.executable_under_test))
+}