fix(resolve_exe): allow shutil.which() to find exe without suffix in Windows (#2408)

martclanor · web-flow · commit 4deabe1d34b3 · 2025-01-09T21:22:08.000-05:00
This PR aims to address a behavior change in shutil.which (in Windows) introduced in python/cpython#127035. For more context, in test_run_model_exe_rel_path, the mf6 executable is copied to a relative path, ../bin/mf6 (without extension). Within the test, shutil.which is used to locate the executable path. However, with the new changes in shutil.which, by default, it would only search for the path with an extension in PATHEXT, excluding paths without extension.
diff --git a/autotest/test_mbase.py b/autotest/test_mbase.py
@@ -135,10 +135,8 @@ def test_run_model_exe_rel_path(mf6_model_path, function_tmpdir, use_ext):
 
     bin_dir = function_tmpdir / "bin"
     bin_dir.mkdir()
-    inner_dir = function_tmpdir / "inner"
-    inner_dir.mkdir()
 
-    with set_dir(inner_dir):
+    with set_dir(ws):
         # copy exe to relative dir
         copy(mf6, bin_dir / "mf6")
         assert (bin_dir / "mf6").is_file()
diff --git a/flopy/mbase.py b/flopy/mbase.py
@@ -64,31 +64,31 @@ def resolve_exe(exe_name: Union[str, os.PathLike], forgive: bool = False) -> str
         str: absolute path to the executable
     """
 
-    def _resolve(exe_name):
-        exe = which(exe_name)
-        if exe is not None:
-            # if which() returned a relative path, resolve it
-            exe = which(str(Path(exe).resolve()))
-        else:
-            if exe_name.lower().endswith(".exe"):
-                # try removing .exe suffix
-                exe = which(exe_name[:-4])
-            if exe is not None:
-                # in case which() returned a relative path, resolve it
-                exe = which(str(Path(exe).resolve()))
-            else:
-                # try tilde-expanded abspath
-                exe = which(Path(exe_name).expanduser().absolute())
-            if exe is None and exe_name.lower().endswith(".exe"):
-                # try tilde-expanded abspath without .exe suffix
-                exe = which(Path(exe_name[:-4]).expanduser().absolute())
-        return exe
-
-    name = str(exe_name)
-    exe_path = _resolve(name)
-    if exe_path is None and on_windows and Path(name).suffix == "":
-        # try adding .exe suffix on windows (for portability from other OS)
-        exe_path = _resolve(f"{name}.exe")
+    def _resolve(exe_name, checked=set()):
+        # Prevent infinite recursion by checking if exe_name has been checked
+        if exe_name in checked:
+            return None
+        checked.add(exe_name)
+
+        # exe_name is found (not None), ensure absolute path is returned
+        if exe := which(str(exe_name)):
+            return which(str(Path(exe).resolve()))
+
+        # exe_name is relative path
+        if not Path(exe_name).is_absolute() and (
+            exe := which(str(Path(exe_name).expanduser().resolve()), mode=0)
+        ):
+            # expanduser() in case of ~ in path
+            # mode=0 effectively allows which() to find exe without suffix in windows
+            return exe
+
+        # try adding/removing .exe suffix
+        if exe_name.lower().endswith(".exe"):
+            return _resolve(exe_name[:-4], checked)
+        elif on_windows and "." not in Path(exe_name).stem:
+            return _resolve(f"{exe_name}.exe", checked)
+
+    exe_path = _resolve(exe_name)
 
     # raise if we are unforgiving, otherwise return None
     if exe_path is None:
@@ -103,7 +103,7 @@ def _resolve(exe_name):
             f"The program {exe_name} does not exist or is not executable."
         )
 
-    return exe_path
+    return str(exe_path)
 
 
 # external exceptions for users
