slither-doctor: fix `is_relative_to` on Python 3.8

slither/tools/doctor/checks/paths.py

@@ -1,12 +1,41 @@
 from pathlib import Path
 from typing import List, Optional, Tuple
 import shutil
+import sys
 import sysconfig
 
 from slither.utils.colors import yellow, green, red
 
 
+def path_is_relative_to(path: Path, relative_to: Path) -> bool:
+    """
+    Check if a path is relative to another one.
+
+    Compatibility wrapper for Path.is_relative_to
+    """
+    if sys.version_info >= (3, 9, 0):
+        return path.is_relative_to(relative_to)
+
+    path_parts = path.resolve().parts
+    relative_to_parts = relative_to.resolve().parts
+
+    if len(path_parts) < len(relative_to_parts):
+        return False
+
+    for (a, b) in zip(path_parts, relative_to_parts):
+        if a != b:
+            return False
+
+    return True
+
+
 def check_path_config(name: str) -> Tuple[bool, Optional[Path], List[Path]]:
+    """
+    Check if a given Python binary/script is in PATH.
+    :return: Returns if the binary on PATH corresponds to this installation,
+             its path (if present), and a list of possible paths where this
+             binary might be found.
+    """
     binary_path = shutil.which(name)
     possible_paths = []
 
@@ -21,9 +50,9 @@ def check_path_config(name: str) -> Tuple[bool, Optional[Path], List[Path]]:
     if binary_path is not None:
         binary_path = Path(binary_path)
         this_code = Path(__file__)
-        this_binary = list(filter(lambda x: this_code.is_relative_to(x[1]), possible_paths))
+        this_binary = list(filter(lambda x: path_is_relative_to(this_code, x[1]), possible_paths))
         binary_here = len(this_binary) > 0 and all(
-            binary_path.is_relative_to(script) for script, _ in this_binary
+            path_is_relative_to(binary_path, script) for script, _ in this_binary
         )
 
     return binary_here, binary_path, list(set(script for script, _ in possible_paths))