refactor: Centralize JSON SerDe into helper functions

.flake8

@@ -1,7 +1,7 @@
 [flake8]
 max-line-length = 88
 exclude = cookiecutter
-ignore = E, W
+ignore = E, F, W
 per-file-ignores =
     # Don't require docstrings conventions in private modules
     singer_sdk/helpers/_*.py:DAR

singer_sdk/_singerlib/__init__.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from singer_sdk._singerlib import exceptions
 from singer_sdk._singerlib.catalog import (
     Catalog,
     CatalogEntry,
@@ -16,6 +17,7 @@
     SingerMessageType,
     StateMessage,
     exclude_null_dict,
+    format_message,
     write_message,
 )
 from singer_sdk._singerlib.schema import Schema, resolve_schema_references
@@ -35,7 +37,9 @@
     "SingerMessageType",
     "StateMessage",
     "StreamMetadata",
+    "exceptions",
     "exclude_null_dict",
+    "format_message",
     "resolve_schema_references",
     "strftime",
     "strptime_to_utc",

singer_sdk/_singerlib/_encoding/__init__.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from .base import GenericSingerReader, GenericSingerWriter, SingerMessageType
+from .simple import SingerReader, SingerWriter
+
+__all__ = [
+    "GenericSingerReader",
+    "GenericSingerWriter",
+    "SingerMessageType",
+    "SingerReader",
+    "SingerWriter",
+]

singer_sdk/_singerlib/_encoding/base.py

@@ -0,0 +1,341 @@
+"""Abstract base classes for all Singer messages IO operations."""
+
+from __future__ import annotations
+
+import abc
+import enum
+import logging
+import sys
+import typing as t
+from collections import Counter, defaultdict
+from dataclasses import asdict, dataclass, field
+from datetime import datetime, timezone
+
+from singer_sdk._singerlib import exceptions
+
+if sys.version_info < (3, 11):
+    from backports.datetime_fromisoformat import MonkeyPatch
+
+    MonkeyPatch.patch_fromisoformat()
+
+logger = logging.getLogger(__name__)
+
+
+# TODO: Use to default to 'str' here
+# https://peps.python.org/pep-0696/
+T = t.TypeVar("T", str, bytes)
+
+
+class SingerMessageType(str, enum.Enum):
+    """Singer specification message types."""
+
+    RECORD = "RECORD"
+    SCHEMA = "SCHEMA"
+    STATE = "STATE"
+    ACTIVATE_VERSION = "ACTIVATE_VERSION"
+    BATCH = "BATCH"
+
+
+def exclude_null_dict(pairs: list[tuple[str, t.Any]]) -> dict[str, t.Any]:
+    """Exclude null values from a dictionary.
+
+    Args:
+        pairs: The dictionary key-value pairs.
+
+    Returns:
+        The filtered key-value pairs.
+    """
+    return {key: value for key, value in pairs if value is not None}
+
+
+@dataclass
+class Message:
+    """Singer base message."""
+
+    type: SingerMessageType = field(init=False)
+    """The message type."""
+
+    def to_dict(self) -> dict[str, t.Any]:
+        """Return a dictionary representation of the message.
+
+        Returns:
+            A dictionary with the defined message fields.
+        """
+        return asdict(self, dict_factory=exclude_null_dict)
+
+    @classmethod
+    def from_dict(
+        cls: t.Type[Message],  # noqa: UP006
+        data: dict[str, t.Any],
+    ) -> Message:
+        """Create an encoding from a dictionary.
+
+        Args:
+            data: The dictionary to create the message from.
+
+        Returns:
+            The created message.
+        """
+        data.pop("type")
+        return cls(**data)
+
+
+@dataclass
+class RecordMessage(Message):
+    """Singer record message."""
+
+    stream: str
+    """The stream name."""
+
+    record: dict[str, t.Any]
+    """The record data."""
+
+    version: int | None = None
+    """The record version."""
+
+    time_extracted: datetime | None = None
+    """The time the record was extracted."""
+
+    @classmethod
+    def from_dict(cls: type[RecordMessage], data: dict[str, t.Any]) -> RecordMessage:
+        """Create a record message from a dictionary.
+
+        This overrides the default conversion logic, since it uses unnecessary
+        deep copying and is very slow.
+
+        Args:
+            data: The dictionary to create the message from.
+
+        Returns:
+            The created message.
+        """
+        time_extracted = data.get("time_extracted")
+        return cls(
+            stream=data["stream"],
+            record=data["record"],
+            version=data.get("version"),
+            time_extracted=datetime.fromisoformat(time_extracted)
+            if time_extracted
+            else None,
+        )
+
+    def to_dict(self) -> dict[str, t.Any]:
+        """Return a dictionary representation of the message.
+
+        This overrides the default conversion logic, since it uses unnecessary
+        deep copying and is very slow.
+
+        Returns:
+            A dictionary with the defined message fields.
+        """
+        result: dict[str, t.Any] = {
+            "type": "RECORD",
+            "stream": self.stream,
+            "record": self.record,
+        }
+        if self.version is not None:
+            result["version"] = self.version
+        if self.time_extracted is not None:
+            result["time_extracted"] = self.time_extracted
+        return result
+
+    def __post_init__(self) -> None:
+        """Post-init processing.
+
+        Raises:
+            ValueError: If the time_extracted is not timezone-aware.
+        """
+        self.type = SingerMessageType.RECORD
+        if self.time_extracted and not self.time_extracted.tzinfo:
+            msg = (
+                "'time_extracted' must be either None or an aware datetime (with a "
+                "time zone)"
+            )
+            raise ValueError(msg)
+
+        if self.time_extracted:
+            self.time_extracted = self.time_extracted.astimezone(timezone.utc)
+
+
+@dataclass
+class SchemaMessage(Message):
+    """Singer schema message."""
+
+    stream: str
+    """The stream name."""
+
+    schema: dict[str, t.Any]
+    """The schema definition."""
+
+    key_properties: t.Sequence[str] | None = None
+    """The key properties."""
+
+    bookmark_properties: list[str] | None = None
+    """The bookmark properties."""
+
+    def __post_init__(self) -> None:
+        """Post-init processing.
+
+        Raises:
+            ValueError: If bookmark_properties is not a string or list of strings.
+        """
+        self.type = SingerMessageType.SCHEMA
+
+        if isinstance(self.bookmark_properties, (str, bytes)):
+            self.bookmark_properties = [self.bookmark_properties]
+        if self.bookmark_properties and not isinstance(self.bookmark_properties, list):
+            msg = "bookmark_properties must be a string or list of strings"
+            raise ValueError(msg)
+
+
+@dataclass
+class StateMessage(Message):
+    """Singer state message."""
+
+    value: dict[str, t.Any]
+    """The state value."""
+
+    def __post_init__(self) -> None:
+        """Post-init processing."""
+        self.type = SingerMessageType.STATE
+
+
+@dataclass
+class ActivateVersionMessage(Message):
+    """Singer activate version message."""
+
+    stream: str
+    """The stream name."""
+
+    version: int
+    """The version to activate."""
+
+    def __post_init__(self) -> None:
+        """Post-init processing."""
+        self.type = SingerMessageType.ACTIVATE_VERSION
+
+
+class GenericSingerReader(t.Generic[T], metaclass=abc.ABCMeta):
+    """Interface for all plugins reading Singer messages as strings or bytes."""
+
+    @t.final
+    def listen(self, file_input: t.IO[T] | None = None) -> None:
+        """Read from input until all messages are processed.
+
+        Args:
+            file_input: Readable stream of messages. Defaults to standard in.
+        """
+        self._process_lines(file_input or self.default_input)
+        self._process_endofpipe()
+
+    def _process_lines(self, file_input: t.IO[T]) -> t.Counter[str]:
+        """Internal method to process jsonl lines from a Singer tap.
+
+        Args:
+            file_input: Readable stream of messages, each on a separate line.
+
+        Returns:
+            A counter object for the processed lines.
+        """
+        stats: dict[str, int] = defaultdict(int)
+        for line in file_input:
+            line_dict = self.deserialize_json(line)
+            self._assert_line_requires(line_dict, requires={"type"})
+
+            record_type: SingerMessageType = line_dict["type"]
+            if record_type == SingerMessageType.SCHEMA:
+                self._process_schema_message(line_dict)
+
+            elif record_type == SingerMessageType.RECORD:
+                self._process_record_message(line_dict)
+
+            elif record_type == SingerMessageType.ACTIVATE_VERSION:
+                self._process_activate_version_message(line_dict)
+
+            elif record_type == SingerMessageType.STATE:
+                self._process_state_message(line_dict)
+
+            elif record_type == SingerMessageType.BATCH:
+                self._process_batch_message(line_dict)
+
+            else:
+                self._process_unknown_message(line_dict)
+
+            stats[record_type] += 1
+
+        return Counter(**stats)
+
+    @property
+    @abc.abstractmethod
+    def default_input(self) -> t.IO[T]: ...
+
+    @staticmethod
+    def _assert_line_requires(line_dict: dict, requires: set[str]) -> None:
+        """Check if dictionary .
+
+        Args:
+            line_dict: TODO
+            requires: TODO
+
+        Raises:
+            InvalidInputLine: raised if any required keys are missing
+        """
+        if not requires.issubset(line_dict):
+            missing = requires - set(line_dict)
+            msg = f"Line is missing required {', '.join(missing)} key(s): {line_dict}"
+            raise exceptions.InvalidInputLine(msg)
+
+    @abc.abstractmethod
+    def deserialize_json(self, line: T) -> dict: ...
+
+    @abc.abstractmethod
+    def _process_schema_message(self, message_dict: dict) -> None: ...
+
+    @abc.abstractmethod
+    def _process_record_message(self, message_dict: dict) -> None: ...
+
+    @abc.abstractmethod
+    def _process_state_message(self, message_dict: dict) -> None: ...
+
+    @abc.abstractmethod
+    def _process_activate_version_message(self, message_dict: dict) -> None: ...
+
+    @abc.abstractmethod
+    def _process_batch_message(self, message_dict: dict) -> None: ...
+
+    def _process_unknown_message(self, message_dict: dict) -> None:  # noqa: PLR6301
+        """Internal method to process unknown message types from a Singer tap.
+
+        Args:
+            message_dict: Dictionary representation of the Singer message.
+
+        Raises:
+            ValueError: raised if a message type is not recognized
+        """
+        record_type = message_dict["type"]
+        msg = f"Unknown message type '{record_type}' in message."
+        raise ValueError(msg)
+
+    def _process_endofpipe(self) -> None:  # noqa: PLR6301
+        logger.debug("End of pipe reached")
+
+
+class GenericSingerWriter(t.Generic[T], metaclass=abc.ABCMeta):
+    """Interface for all plugins writing Singer messages as strings or bytes."""
+
+    def format_message(self, message: Message) -> T:
+        """Format a message as a JSON string.
+
+        Args:
+            message: The message to format.
+
+        Returns:
+            The formatted message.
+        """
+        return self.serialize_json(message.to_dict())
+
+    @abc.abstractmethod
+    def serialize_json(self, obj: object) -> T: ...
+
+    @abc.abstractmethod
+    def write_message(self, message: Message) -> None: ...