fix: read the invoked model path once for staleness checks

pytm/tm.py

@@ -461,7 +461,7 @@ def _stale(self, days: int) -> str:
         """Report source files whose age diverges from the model script."""
         base_path = os.path.dirname(sys.argv[0])
         try:
-            tm_path = os.path.join(base_path, sys.argv[0])
+            tm_path = sys.argv[0]
             tm_mtime = datetime.fromtimestamp(os.stat(tm_path).st_mtime)
         except OSError as err:
             sys.stderr.write(f"{sys.argv[0]} - {err}\n")

tests/test_stale_paths.py

@@ -0,0 +1,47 @@
+"""CLI staleness checks use the path of the invoked model once."""
+
+import os
+import subprocess
+import sys
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    "model_name,absolute",
+    [
+        ("models/model.py", False),
+        ("./models/model.py", False),
+        ("nested/models/model.py", False),
+        ("model directory/model.py", False),
+        ("model.py", False),
+        ("models/model.py", True),
+    ],
+)
+def test_stale_days_reads_invoked_model(tmp_path, model_name, absolute):
+    model = tmp_path / model_name
+    model.parent.mkdir(parents=True, exist_ok=True)
+    model.write_text(
+        "from pytm import TM, Server\n"
+        "tm = TM('Staleness')\n"
+        "Server('API', sourceFiles=['source.py'])\n"
+        "tm.process()\n"
+    )
+    source = model.parent / "source.py"
+    source.write_text("# Source newer than its model\n")
+    os.utime(model, (1_700_000_000, 1_700_000_000))
+    os.utime(source, (1_700_259_200, 1_700_259_200))
+    invocation = str(model) if absolute else model_name
+
+    result = subprocess.run(
+        [sys.executable, invocation, "--stale_days", "2"],
+        cwd=tmp_path,
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+
+    assert result.stderr == ""
+    assert "[ERROR]" not in result.stdout
+    assert "This model is 3 days older than" in result.stdout
+    assert "source.py" in result.stdout