util: implement is_subpath

electrum/tests/test_util.py

@@ -1,10 +1,11 @@
 from decimal import Decimal
 
+from electrum import util
 from electrum.util import (format_satoshis, format_fee_satoshis, parse_URI,
                            is_hash256_str, chunks, is_ip_address, list_enabled_bits,
                            format_satoshis_plain, is_private_netaddress, is_hex_str,
                            is_integer, is_non_negative_integer, is_int_or_float,
-                           is_non_negative_int_or_float)
+                           is_non_negative_int_or_float, is_subpath)
 
 from . import ElectrumTestCase
 
@@ -292,3 +293,25 @@ class TestUtil(ElectrumTestCase):
         self.assertFalse(is_private_netaddress("[2a00:1450:400e:80d::200e]"))
         self.assertFalse(is_private_netaddress("8.8.8.8"))
         self.assertFalse(is_private_netaddress("example.com"))
+
+    def test_is_subpath(self):
+        self.assertTrue(util.is_subpath("/a/b/c/d/e", "/"))
+        self.assertTrue(util.is_subpath("/a/b/c/d/e", "/a"))
+        self.assertTrue(util.is_subpath("/a/b/c/d/e", "/a/"))
+        self.assertTrue(util.is_subpath("/a/b/c/d/e", "/a/b/c/"))
+        self.assertTrue(util.is_subpath("/a/b/c/d/e/", "/a/b/c/"))
+        self.assertTrue(util.is_subpath("/a/b/c/d/e/", "/a/b/c"))
+        self.assertTrue(util.is_subpath("/a/b/c/d/e/", "/a/b/c/d/e/"))
+        self.assertTrue(util.is_subpath("/", "/"))
+        self.assertTrue(util.is_subpath("a/b/c", "a"))
+        self.assertTrue(util.is_subpath("a/b/c", "a/"))
+        self.assertTrue(util.is_subpath("a/b/c", "a/b"))
+        self.assertTrue(util.is_subpath("a/b/c", "a/b/c"))
+
+        self.assertFalse(util.is_subpath("/a/b/c/d/e/", "/b"))
+        self.assertFalse(util.is_subpath("/a/b/c/d/e/", "/b/c/"))
+        self.assertFalse(util.is_subpath("/a/b/c", "/a/b/c/d/e/"))
+        self.assertFalse(util.is_subpath("/a/b/c", "a"))
+        self.assertFalse(util.is_subpath("/a/b/c", "c"))
+        self.assertFalse(util.is_subpath("a", "/a/b/c"))
+        self.assertFalse(util.is_subpath("c", "/a/b/c"))

electrum/util.py

@@ -1201,6 +1201,17 @@ def make_dir(path, allow_symlink=True):
         os.chmod(path, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR)
 
 
+def is_subpath(long_path: str, short_path: str) -> bool:
+    """Returns whether long_path is a sub-path of short_path."""
+    try:
+        common = os.path.commonpath([long_path, short_path])
+    except ValueError:
+        return False
+    short_path = standardize_path(short_path)
+    common     = standardize_path(common)
+    return short_path == common
+
+
 def log_exceptions(func):
     """Decorator to log AND re-raise exceptions."""
     assert asyncio.iscoroutinefunction(func), 'func needs to be a coroutine'