Merge pull request #4 from minrk/warn-unsafe

Warn when escape character is in safe character set

.travis.yml

@@ -3,6 +3,8 @@ python:
 - 2.7
 - 3.4
 - 3.6
+- 3.7
+- 3.8
 cache:
 - pip
 install:

escapism.py

@@ -13,8 +13,9 @@
 import re
 import string
 import sys
+import warnings
 
-__version__ = '1.0.0'
+__version__ = "1.0.1"
 
 SAFE = set(string.ascii_letters + string.digits)
 ESCAPE_CHAR = '_'
@@ -67,7 +68,13 @@ def escape(to_escape, safe=SAFE, escape_char=ESCAPE_CHAR, allow_collisions=False
     if allow_collisions:
         safe.add(escape_char)
     elif escape_char in safe:
-        # escape char can't be in safe list
+        warnings.warn(
+            "Escape character %r cannot be a safe character."
+            " Set allow_collisions=True if you want to allow ambiguous escaped strings."
+            % escape_char,
+            RuntimeWarning,
+            stacklevel=2,
+        )
         safe.remove(escape_char)
 
     chars = []
@@ -81,7 +88,7 @@ def escape(to_escape, safe=SAFE, escape_char=ESCAPE_CHAR, allow_collisions=False
 
 def _unescape_char(m):
     """Unescape a single byte
-    
+
     Used as a callback in pattern.subn. `m.group(1)` must be a single byte in hex,
     e.g. `a4` or `ff`.
     """
@@ -90,7 +97,7 @@ def _unescape_char(m):
 
 def unescape(escaped, escape_char=ESCAPE_CHAR):
     """Unescape a string escaped with `escape`
-    
+
     escape_char must be the same as that used in the call to escape.
     """
     if isinstance(escaped, bytes):

tests/test_escapism.py

@@ -1,4 +1,9 @@
 # coding: utf-8
+
+import warnings
+
+import pytest
+
 from escapism import escape, unescape, SAFE
 
 text = type(u'')
@@ -11,6 +16,7 @@
     u'_\\-+',
 ]
 
+
 def test_escape_default():
     for s in test_strings:
         e = escape(s)
@@ -19,6 +25,7 @@ def test_escape_default():
         assert isinstance(u, text)
         assert u == s
 
+
 def test_escape_custom_char():
     for escape_char in r'\-%+_':
         for s in test_strings:
@@ -28,6 +35,7 @@ def test_escape_custom_char():
             assert isinstance(u, text)
             assert u == s
 
+
 def test_escape_custom_safe():
     safe = 'ABCDEFabcdef0123456789'
     escape_char = '\\'
@@ -38,14 +46,17 @@ def test_escape_custom_safe():
         u = unescape(e, escape_char=escape_char)
         assert u == s
 
+
 def test_safe_escape_char():
-    escape_char = '-'
+    escape_char = "-"
     safe = SAFE.union({escape_char})
-    e = escape(escape_char, safe=safe, escape_char=escape_char)
-    assert e == '{}{:02X}'.format(escape_char, ord(escape_char))
+    with pytest.warns(RuntimeWarning):
+        e = escape(escape_char, safe=safe, escape_char=escape_char)
+    assert e == "{}{:02X}".format(escape_char, ord(escape_char))
     u = unescape(e, escape_char=escape_char)
     assert u == escape_char
 
+
 def test_allow_collisions():
     escaped = escape('foo-bar ', escape_char='-', allow_collisions=True)
     assert escaped == 'foo-bar-20'