gh-101144: Allow open and read_text encoding to be positional. (#101145)

The zipfile.Path open() and read_text() encoding parameter can be supplied as a positional argument without causing a TypeError again. 3.10.0b1 included a regression that made it keyword only.

Documentation update included as users writing code to be compatible with a wide range of versions will need to consider this for some time.

Lib/test/test_zipfile/test_path.py

@@ -1,11 +1,12 @@
 import io
-import zipfile
+import itertools
 import contextlib
 import pathlib
-import unittest
-import string
 import pickle
-import itertools
+import string
+from test.support.script_helper import assert_python_ok
+import unittest
+import zipfile
 
 from ._test_params import parameterize, Invoked
 from ._functools import compose
@@ -145,7 +146,69 @@ def test_open(self, alpharep):
         a, b, g = root.iterdir()
         with a.open(encoding="utf-8") as strm:
             data = strm.read()
-        assert data == "content of a"
+        self.assertEqual(data, "content of a")
+        with a.open('r', "utf-8") as strm:  # not a kw, no gh-101144 TypeError
+            data = strm.read()
+        self.assertEqual(data, "content of a")
+
+    def test_open_encoding_utf16(self):
+        in_memory_file = io.BytesIO()
+        zf = zipfile.ZipFile(in_memory_file, "w")
+        zf.writestr("path/16.txt", "This was utf-16".encode("utf-16"))
+        zf.filename = "test_open_utf16.zip"
+        root = zipfile.Path(zf)
+        (path,) = root.iterdir()
+        u16 = path.joinpath("16.txt")
+        with u16.open('r', "utf-16") as strm:
+            data = strm.read()
+        self.assertEqual(data, "This was utf-16")
+        with u16.open(encoding="utf-16") as strm:
+            data = strm.read()
+        self.assertEqual(data, "This was utf-16")
+
+    def test_open_encoding_errors(self):
+        in_memory_file = io.BytesIO()
+        zf = zipfile.ZipFile(in_memory_file, "w")
+        zf.writestr("path/bad-utf8.bin", b"invalid utf-8: \xff\xff.")
+        zf.filename = "test_read_text_encoding_errors.zip"
+        root = zipfile.Path(zf)
+        (path,) = root.iterdir()
+        u16 = path.joinpath("bad-utf8.bin")
+
+        # encoding= as a positional argument for gh-101144.
+        data = u16.read_text("utf-8", errors="ignore")
+        self.assertEqual(data, "invalid utf-8: .")
+        with u16.open("r", "utf-8", errors="surrogateescape") as f:
+            self.assertEqual(f.read(), "invalid utf-8: \udcff\udcff.")
+
+        # encoding= both positional and keyword is an error; gh-101144.
+        with self.assertRaisesRegex(TypeError, "encoding"):
+            data = u16.read_text("utf-8", encoding="utf-8")
+
+        # both keyword arguments work.
+        with u16.open("r", encoding="utf-8", errors="strict") as f:
+            # error during decoding with wrong codec.
+            with self.assertRaises(UnicodeDecodeError):
+                f.read()
+
+    def test_encoding_warnings(self):
+        """EncodingWarning must blame the read_text and open calls."""
+        code = '''\
+import io, zipfile
+with zipfile.ZipFile(io.BytesIO(), "w") as zf:
+    zf.filename = '<test_encoding_warnings in memory zip file>'
+    zf.writestr("path/file.txt", b"Spanish Inquisition")
+    root = zipfile.Path(zf)
+    (path,) = root.iterdir()
+    file_path = path.joinpath("file.txt")
+    unused = file_path.read_text()  # should warn
+    file_path.open("r").close()  # should warn
+'''
+        proc = assert_python_ok('-X', 'warn_default_encoding', '-c', code)
+        warnings = proc.err.splitlines()
+        self.assertEqual(len(warnings), 2, proc.err)
+        self.assertRegex(warnings[0], rb"^<string>:8: EncodingWarning:")
+        self.assertRegex(warnings[1], rb"^<string>:9: EncodingWarning:")
 
     def test_open_write(self):
         """
@@ -187,6 +250,7 @@ def test_read(self, alpharep):
         root = zipfile.Path(alpharep)
         a, b, g = root.iterdir()
         assert a.read_text(encoding="utf-8") == "content of a"
+        a.read_text("utf-8")  # No positional arg TypeError per gh-101144.
         assert a.read_bytes() == b"content of a"
 
     @pass_alpharep