Also check Python scripts with a valid shebang

prospector/identify.py

@@ -0,0 +1,90 @@
+# Largely inspied by https://github.com/pre-commit/identify/blob/main/identify/identify.py#L178
+
+import errno
+import os
+import shlex
+import string
+from pathlib import Path
+from typing import IO
+
+printable = frozenset(string.printable)
+
+
+def _shebang_split(line: str) -> tuple[str, ...]:
+    try:
+        # shebangs aren't supposed to be quoted, though some tools such as
+        # setuptools will write them with quotes so we'll best-guess parse
+        # with shlex first
+        return tuple(shlex.split(line))
+    except ValueError:
+        # failing that, we'll do a more "traditional" shebang parsing which
+        # just involves splitting by whitespace
+        return tuple(line.split())
+
+
+def _parse_nix_shebang(
+    bytes_io: IO[bytes],
+    cmd: tuple[str, ...],
+) -> tuple[str, ...]:
+    while bytes_io.read(2) == b"#!":
+        next_line_b = bytes_io.readline()
+        try:
+            next_line = next_line_b.decode("UTF-8")
+        except UnicodeDecodeError:
+            return cmd
+
+        for c in next_line:
+            if c not in printable:
+                return cmd
+
+        line_tokens = _shebang_split(next_line.strip())
+        for i, token in enumerate(line_tokens[:-1]):
+            if token != "-i":  # noqa: S105
+                continue
+            # The argument to -i flag
+            cmd = (line_tokens[i + 1],)
+    return cmd
+
+
+def _parse_shebang(bytes_io: IO[bytes]) -> tuple[str, ...]:
+    """Parse the shebang from a file opened for reading binary."""
+    if bytes_io.read(2) != b"#!":
+        return ()
+    first_line_b = bytes_io.readline()
+    try:
+        first_line = first_line_b.decode("UTF-8")
+    except UnicodeDecodeError:
+        return ()
+
+    # Require only printable ascii
+    for c in first_line:
+        if c not in printable:
+            return ()
+
+    cmd = _shebang_split(first_line.strip())
+    if cmd[:2] == ("/usr/bin/env", "-S"):
+        cmd = cmd[2:]
+    elif cmd[:1] == ("/usr/bin/env",):
+        cmd = cmd[1:]
+
+    if cmd == ("nix-shell",):
+        return _parse_nix_shebang(bytes_io, cmd)
+
+    return cmd
+
+
+def parse_shebang_from_file(path: Path) -> tuple[str, ...]:
+    """Parse the shebang given a file path."""
+    if not path.exists():
+        raise ValueError(f"{path} does not exist.")
+    if not os.access(path, os.X_OK):
+        return ()
+
+    try:
+        with path.open("rb") as f:
+            return _parse_shebang(f)
+    except OSError as e:
+        if e.errno == errno.EINVAL:
+            return ()
+        else:
+            raise

prospector/pathutils.py

@@ -1,14 +1,28 @@
+import mimetypes
 import os
+import re
 from pathlib import Path
 
+from prospector import identify
+
+_PYTHON_COMMAND_RE = re.compile(r"^python[0-9]?$")
+
 
 def is_python_package(path: Path) -> bool:
     return path.is_dir() and (path / "__init__.py").exists()
 
 
 def is_python_module(path: Path) -> bool:
-    # TODO: is this too simple?
-    return path.suffix == ".py"
+    mimetype, encoding = mimetypes.guess_type(path)
+    del encoding
+    if mimetype == "text/x-python":
+        return True
+
+    executor = identify.parse_shebang_from_file(path)
+    if executor is not None and len(executor) > 0:
+        return _PYTHON_COMMAND_RE.match(Path(executor[0]).name) is not None
+
+    return False
 
 
 def is_virtualenv(path: Path) -> bool: