Add command line option for running 6S binary in subprocess

src/sixs_bin/_cli.py

@@ -17,6 +17,7 @@
 
 import argparse
 import pathlib
+import subprocess
 import sys
 
 import sixs_bin
@@ -45,6 +46,13 @@ def _make_parser() -> argparse.ArgumentParser:
         choices=sixs_bin._SIXS_BINARIES.keys(),
         help="Print the path to the specified 6S executable from this package's resources.",
     )
+    command_group.add_argument(
+        "--exec",
+        choices=sixs_bin._SIXS_BINARIES.keys(),
+        help="Execute specified 6S executable in a subprocess, inheriting stdin and stdout. This option is provided"
+        " as a convenience, but its use is not recommended. Running 6S using this option is about 5%% slower than"
+        " executing the binary directly, due the overhead of starting the Python interpreter and subprocess.",
+    )
     command_group.add_argument(
         "--test-wrapper",
         action="store_true",
@@ -68,6 +76,13 @@ def main(cli_args: list[str]) -> None:
         print(_make_version())
         return
 
+    if args.exec is not None:
+        proc_args = (sixs_bin.get_path(args.exec),)
+        ret_code = subprocess.Popen(proc_args).wait()
+        if ret_code:
+            raise subprocess.CalledProcessError(ret_code, proc_args)
+        return
+
     if args.path is not None:
         print(sixs_bin.get_path(args.path))
         return

test/test_cli.py

@@ -1,9 +1,27 @@
+import subprocess
+import sys
+from typing import Any
+
 import pytest
 
 import sixs_bin
 import sixs_bin._cli as sixs_cli
 
 
+def _run_self_subprocess(
+    cli_args: list[str], **kwargs: Any
+) -> subprocess.CompletedProcess:
+    """
+    Run the command line interface in a subprocess.
+
+    Needed instead of calling the CLI entrypoint directly when more advanced control
+    over the process running the command line interface is required.
+    """
+    return subprocess.run(
+        [sys.executable, "-m", sixs_bin.__name__, *cli_args], **kwargs
+    )
+
+
 def test_version(capsys) -> None:
     sixs_cli.main(["--version"])
 
@@ -29,5 +47,31 @@ def test_bad_path() -> None:
         sixs_cli.main(["--path"])
 
 
+@pytest.mark.parametrize("version", sixs_bin._SIXS_BINARIES.keys())
+def test_exec_eof(version) -> None:
+    with pytest.raises(subprocess.CalledProcessError) as exec_info:
+        # Run in subprocess to reliably control stdin.
+        _run_self_subprocess(
+            ["--exec", version],
+            check=True,
+            capture_output=True,
+            text=True,
+            input="",  # Empty stdin
+        )
+
+    assert exec_info.value.stdout == ""
+    assert (
+        exec_info.value.stderr.splitlines()[1] == "Fortran runtime error: End of file"
+    )
+
+
+def test_exec_bad() -> None:
+    with pytest.raises(SystemExit):
+        sixs_cli.main(["--exec", "does-not-exist"])
+
+    with pytest.raises(SystemExit):
+        sixs_cli.main(["--exec"])
+
+
 def test_test_wrapper() -> None:
     sixs_cli.main(["--test-wrapper"])