percent-encode pipe character in URL paths

the | character was not being percent-encoded in path segments,
even though it's not a valid pchar per RFC 3986. this caused
issues with servers that reject or redirect URLs with unencoded
pipes. now | gets encoded as %7C in paths, matching the behavior
of Python's urllib and the requests library.

httpx/_urlparse.py

@@ -51,12 +51,15 @@ QUERY_SAFE = "".join(
 )
 
 # The path percent-encode set is the query percent-encode set
-# and U+003F (?), U+0060 (`), U+007B ({), and U+007D (}).
+# and U+003F (?), U+0060 (`), U+007B ({), U+007C (|), and U+007D (}).
+# We include U+007C (|) in the encode set to align with RFC 3986 and
+# Python's stdlib, since | is not a valid pchar and can cause servers
+# to issue redirects or reject requests when left unencoded.
 PATH_SAFE = "".join(
     [
         chr(i)
         for i in range(0x20, 0x7F)
-        if i not in (0x20, 0x22, 0x23, 0x3C, 0x3E) + (0x3F, 0x60, 0x7B, 0x7D)
+        if i not in (0x20, 0x22, 0x23, 0x3C, 0x3E) + (0x3F, 0x60, 0x7B, 0x7C, 0x7D)
     ]
 )
 

tests/models/test_url.py

@@ -140,6 +140,13 @@ def test_path_query_fragment(url, raw_path, path, query, fragment):
     assert url.fragment == fragment
 
 
+def test_url_pipe_encoding_in_path():
+    # The pipe character should be percent-encoded in paths per RFC 3986.
+    url = httpx.URL("https://example.com/path|segment")
+    assert url.raw_path == b"/path%7Csegment"
+    assert url.path == "/path|segment"
+
+
 def test_url_query_encoding():
     url = httpx.URL("https://www.example.com/?a=b c&d=e/f")
     assert url.raw_path == b"/?a=b%20c&d=e/f"

tests/models/test_whatwg.py

@@ -27,6 +27,12 @@ def test_urlparse(test_case):
         # Anyone know what's going on here?
         return
 
+    # We percent-encode "|" in paths (unlike WHATWG), to align with RFC 3986
+    # and Python's stdlib. The pipe character is not a valid pchar and some
+    # servers reject or redirect URLs containing an unencoded "|".
+    if "|" in test_case.get("pathname", ""):
+        return
+
     p = urlparse(test_case["href"])
 
     # Test cases include the protocol with the trailing ":"