Fix httpx is not encoding with symbol '%s' (#3140)

Add parsing symbol '%s' test

httpx/_urlparse.py

@@ -424,13 +424,23 @@ def is_safe(string: str, safe: str = "/") -> bool:
     """
     Determine if a given string is already quote-safe.
     """
-    NON_ESCAPED_CHARS = UNRESERVED_CHARACTERS + safe + "%"
-
-    # All characters must already be non-escaping or '%'
-    for char in string:
-        if char not in NON_ESCAPED_CHARS:
+    NON_ESCAPED_CHARS = UNRESERVED_CHARACTERS + safe
+    i = 0
+    while i < len(string):
+        char = string[i]
+        if char in NON_ESCAPED_CHARS:
+            i += 1
+            continue
+        # Check if the character is a start of a valid percent-encoded sequence
+        elif (
+            char == "%"
+            and i + 2 < len(string)
+            and string[i + 1 : i + 3].isalnum()
+            and len(string[i + 1 : i + 3]) == 2
+        ):
+            i += 3
+        else:
             return False
-
     return True
 
 

tests/models/test_url.py

@@ -284,6 +284,8 @@ def test_url_leading_dot_prefix_on_relative_url():
 def test_param_requires_encoding():
     url = httpx.URL("http://webservice", params={"u": "with spaces"})
     assert str(url) == "http://webservice?u=with%20spaces"
+    url = httpx.URL("http://webservice", params={"u": "%"})
+    assert str(url) == "http://webservice?u=%25"
 
 
 def test_param_does_not_require_encoding():