wave.Wave_read loses frame position when underlying reads split frames

[augusto-rehfeldt]

Bug report

Bug description:

Documented behaviour: The module's reading API documentation states: "tell() -- return the current position" and "The position returned by tell() and the position given to setpos() are compatible and have nothing to do with the actual position in the file."

Expected: After returning both bytes of the single audio frame, tell() returns 1.

Actual: Two readframes(1) calls return one byte each; tell() remains 0 even after EOF.

import io
import struct
import wave

payload = b"\x00\x01"
case = dict(channels=1, sample_width=2, frames=1,
            short_read_limit=1, audio_payload=payload)
wav = (b"RIFF" + struct.pack("<I", 36 + len(payload)) + b"WAVEfmt " +
       struct.pack("<IHHIIHH", 16, 1, 1, 8000, 16000, 2, 16) +
       b"data" + struct.pack("<I", len(payload)) + payload)

class Fragmented(io.BytesIO):
    def read(self, size=-1):
        if self.tell() >= 44 and size > 0:
            size = min(size, case["short_read_limit"])
        return super().read(size)

try:
    with wave.open(io.BytesIO(wav), "rb") as reference:
        valid = (reference.getparams() == (1, 2, 8000, 1, "NONE", "not compressed")
                 and reference.readframes(2) == payload
                 and len(payload) % 2 == 0)
    if not valid:
        print("REFUTATION REJECTED:", "input is not the reported complete PCM WAVE")
    else:
        expected = (payload, len(payload) // (case["channels"] * case["sample_width"]))
        with wave.open(Fragmented(wav), "rb") as reader:
            chunks = []
            while True:
                chunk = reader.readframes(1)
                if not chunk:
                    break
                chunks.append(chunk)
            actual = (b"".join(chunks), reader.tell())
        if actual[0] == payload and actual != expected:
            print("REFUTATION CONFIRMED:", case, "actual:", actual, "expected:", expected)
        else:
            print("REFUTATION REJECTED:", "all-byte position mismatch not reproduced",
                  "actual:", actual, "expected:", expected)
except Exception as exc:
    print("REFUTATION REJECTED:", type(exc).__name__, str(exc))

Output on Python 3.14.6 (Windows-11-10.0.26220-SP0), standard library wave:

REFUTATION CONFIRMED: {'channels': 1, 'sample_width': 2, 'frames': 1, 'short_read_limit': 1, 'audio_payload': b'\x00\x01'} actual: (b'\x00\x01', 0) expected: (b'\x00\x01', 1)

This report was found and written by an automated property-testing tool I run (bugforge). The reproducer above was executed and its output is pasted unedited; no person reviewed the report before it was filed. The search script is in https://github.com/augusto-rehfeldt/bugforge-results/tree/main/wave-20261003-151720-c3

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[ZeroIntensity]

See #158748 (comment).