Fix: struct.error when reading ReadStruct-based types #111

pure_protobuf/descriptors/record.py

@@ -56,7 +56,7 @@ class RecordDescriptor(Generic[RecordT]):
 
     This behaves differently from the [`write`][pure_protobuf.descriptors.record.RecordDescriptor.write],
     because it's only supposed to read a single record from the stream
-    (it may be, for example, just one item of a repeated field).
+    (it may be, for example, just one item of a packed repeated field).
     Also, it assumes that the tag has already been read by [`BaseMessage`][base-message].
     """
 

pure_protobuf/helpers/io.py

@@ -24,6 +24,6 @@ def read_checked(io: IO[bytes], count: int) -> bytes:
         EOFError: the stream has ended
     """
     buffer = io.read(count)
-    if len(buffer) != count:
-        raise EOFError(f"{count} bytes expected, {len(buffer)} read")
+    if len(buffer) < count:
+        raise EOFError(f"{count} bytes expected, but only {len(buffer)} read")
     return buffer

pure_protobuf/helpers/itertools.py

@@ -9,6 +9,8 @@
 
 
 class ReadCallback(ReprWithInner, Generic[P, R]):
+    """Convert a reader, which returns a singular scalar value, into an iterable reader."""
+
     __slots__ = ("inner",)
 
     # noinspection PyProtocol

pure_protobuf/interfaces/_repr.py

@@ -14,7 +14,7 @@ def __str__(self) -> str:
 
     def __repr__(self) -> str:
         try:
-            orig_class = self.__orig_class__  # type: ignore
+            orig_class = self.__orig_class__  # type: ignore[attr-defined]
         except AttributeError:
             args = ""
         else:
@@ -27,7 +27,7 @@ class ReprWithInner(Repr, Protocol):
 
     def __repr__(self) -> str:
         try:
-            orig_class = self.__orig_class__  # type: ignore
+            orig_class = self.__orig_class__  # type: ignore[attr-defined]
         except AttributeError:
             args = ""
         else:

pure_protobuf/io/struct_.py

@@ -1,6 +1,7 @@
 from struct import Struct
 from typing import IO, Generic, Iterator
 
+from pure_protobuf.helpers.io import read_checked
 from pure_protobuf.interfaces._repr import ReprWithInner
 from pure_protobuf.interfaces._vars import RecordT_co, RecordT_contra
 from pure_protobuf.interfaces.read import Read
@@ -18,7 +19,7 @@ def __init__(self, format_: str) -> None:  # noqa: D107
 
     def __call__(self, io: IO[bytes]) -> Iterator[RecordT_co]:
         inner = self.inner
-        yield from inner.unpack(io.read(inner.size))
+        yield from inner.unpack(read_checked(io, inner.size))
 
 
 class WriteStruct(Write[RecordT_contra], ReprWithInner, Generic[RecordT_contra]):

pure_protobuf/io/wrappers.py

@@ -52,7 +52,12 @@ def __call__(self, io: IO[bytes], actual_wire_type: WireType) -> Iterator[Record
 
 
 class ReadLengthDelimited(Read[RecordT], ReprWithInner):
-    """Wraps the inner reader on a length-delimited buffer."""
+    """
+    Make the inner reader length-delimited.
+
+    This reader wraps the inner reader so that it would first read a byte string,
+    and then call the inner reader on that byte string.
+    """
 
     __slots__ = ("inner",)
 

pyproject.toml

@@ -43,7 +43,7 @@ optional = true
 
 [tool.poetry.group.dev.dependencies]
 black = "^22.12.0"
-mypy = "^1.0.0"
+mypy = "^1.2.0"
 pydantic = "^1.10.4"
 pytest = "^7.2.0"
 pytest-benchmark = "^4.0.0"

tests/descriptors/test_record.py

@@ -33,9 +33,15 @@ def test_from_inner_hint_unsupported(inner_hint: Any) -> None:
         (1.0, b"\x00\x00\x80\x3F"),
     ],
 )
-def test_struct(value: float, encoded: bytes) -> None:
-    assert to_bytes(FLOAT_DESCRIPTOR.write, value) == encoded
-    assert next(FLOAT_DESCRIPTOR.read(BytesIO(encoded), WireType.I32)) == value
+class TestStruct:
+    def test_write(self, value: float, encoded: bytes) -> None:
+        assert to_bytes(FLOAT_DESCRIPTOR.write, value) == encoded
+
+    def test_read(self, value: float, encoded: bytes) -> None:
+        io = BytesIO(encoded)
+        assert next(FLOAT_DESCRIPTOR.read(io, WireType.I32)) == value
+        with raises(EOFError):
+            next(FLOAT_DESCRIPTOR.read(io, WireType.I32))
 
 
 # noinspection PyArgumentList