feat: Support patternProperties in JSON schema helpers

.pre-commit-config.yaml

@@ -20,7 +20,13 @@ repos:
             cookiecutter/.*/meltano.yml
         )$
   - id: end-of-file-fixer
-    exclude: (cookiecutter/.*|docs/.*|samples/.*\.json)
+    exclude: |
+      (?x)^(
+        cookiecutter/.*|
+        docs/.*|
+        samples/.*\.json|
+        tests/snapshots/.*/.*\.json
+      )$
   - id: trailing-whitespace
     exclude: |
         (?x)^(

docs/CONTRIBUTING.md

@@ -111,6 +111,18 @@ def test_windows_only():
 
 Supported platform markers are `windows`, `darwin`, and `linux`.
 
+### Snapshot Testing
+
+We use [pytest-snapshot](https://pypi.org/project/pytest-snapshot/) for snapshot testing.
+To update snapshots, run:
+
+```bash
+nox -rs update_snapshots
+```
+
+This will run all tests with the `snapshot` marker and update any snapshots that have changed.
+Commit the updated snapshots to your branch if they are expected to change.
+
 ## Testing Updates to Docs
 
 Documentation runs on Sphinx, using ReadtheDocs style template, and hosting from

noxfile.py

@@ -28,6 +28,23 @@
     "tests",
     "doctest",
 )
+test_dependencies = [
+    "coverage[toml]",
+    "pytest",
+    "pytest-snapshot",
+    "freezegun",
+    "pandas",
+    "requests-mock",
+    # Cookiecutter tests
+    "black",
+    "cookiecutter",
+    "PyYAML",
+    "darglint",
+    "flake8",
+    "flake8-annotations",
+    "flake8-docstrings",
+    "mypy",
+]
 
 
 @session(python=python_versions)
@@ -53,22 +70,8 @@ def mypy(session: Session) -> None:
 def tests(session: Session) -> None:
     """Execute pytest tests and compute coverage."""
     session.install(".")
-    session.install(
-        "coverage[toml]",
-        "pytest",
-        "freezegun",
-        "pandas",
-        "requests-mock",
-        # Cookiecutter tests
-        "black",
-        "cookiecutter",
-        "PyYAML",
-        "darglint",
-        "flake8",
-        "flake8-annotations",
-        "flake8-docstrings",
-        "mypy",
-    )
+    session.install(*test_dependencies)
+
     # temp fix until pyarrow is supported on python 3.11
     if session.python != "3.11":
         session.install(
@@ -91,6 +94,16 @@ def tests(session: Session) -> None:
             session.notify("coverage", posargs=[])
 
 
+@session(python=main_python_version)
+def update_snapshots(session: Session) -> None:
+    """Update pytest snapshots."""
+    args = session.posargs or ["-m", "snapshot"]
+
+    session.install(".")
+    session.install(*test_dependencies)
+    session.run("pytest", "--snapshot-update", *args)
+
+
 @session(python=python_versions)
 def doctest(session: Session) -> None:
     """Run examples with xdoctest."""

pyproject.toml

@@ -111,6 +111,9 @@ flake8 = "^3.9.0"
 flake8-annotations = "^2.9.1"
 flake8-docstrings = "^1.6.0"
 
+[tool.poetry.group.dev.dependencies]
+pytest-snapshot = "^0.9.0"
+
 [tool.black]
 exclude = ".*simpleeval.*"
 
@@ -125,6 +128,7 @@ addopts = '-vvv --ignore=singer_sdk/helpers/_simpleeval.py -m "not external"'
 markers = [
     "external: Tests relying on external resources",
     "windows: Tests that only run on Windows",
+    "snapshot: Tests that use pytest-snapshot",
 ]
 
 [tool.commitizen]

singer_sdk/_singerlib/__init__.py

@@ -17,3 +17,22 @@
     write_message,
 )
 from singer_sdk._singerlib.schema import Schema, resolve_schema_references
+
+__all__ = [
+    "Catalog",
+    "CatalogEntry",
+    "Metadata",
+    "MetadataMapping",
+    "SelectionMask",
+    "StreamMetadata",
+    "ActivateVersionMessage",
+    "Message",
+    "RecordMessage",
+    "SchemaMessage",
+    "SingerMessageType",
+    "StateMessage",
+    "exclude_null_dict",
+    "write_message",
+    "Schema",
+    "resolve_schema_references",
+]

singer_sdk/typing.py

@@ -45,6 +45,7 @@
 
 from __future__ import annotations
 
+import json
 import sys
 from typing import Any, Generic, Mapping, TypeVar, Union, cast
 
@@ -449,16 +450,20 @@ def __init__(
         self,
         *properties: Property,
         additional_properties: W | type[W] | None = None,
+        pattern_properties: Mapping[str, W | type[W]] | None = None,
     ) -> None:
         """Initialize ObjectType from its list of properties.
 
         Args:
             properties: Zero or more attributes for this JSON object.
             additional_properties: A schema to match against unnamed properties in
                 this object.
+            pattern_properties: A dictionary of regex patterns to match against
+                property names, and the schema to match against the values.
         """
         self.wrapped: list[Property] = list(properties)
         self.additional_properties = additional_properties
+        self.pattern_properties = pattern_properties
 
     @property
     def type_dict(self) -> dict:  # type: ignore  # OK: @classproperty vs @property
@@ -481,8 +486,24 @@ def type_dict(self) -> dict:  # type: ignore  # OK: @classproperty vs @property
         if self.additional_properties:
             result["additionalProperties"] = self.additional_properties.type_dict
 
+        if self.pattern_properties:
+            result["patternProperties"] = {
+                k: v.type_dict for k, v in self.pattern_properties.items()
+            }
+
         return result
 
+    def to_json(self, **kwargs: Any) -> str:
+        """Return a JSON string representation of the object.
+
+        Args:
+            **kwargs: Additional keyword arguments to pass to `json.dumps`.
+
+        Returns:
+            A JSON string.
+        """
+        return json.dumps(self.type_dict, **kwargs)
+
 
 class CustomType(JSONTypeHelper):
     """Accepts an arbitrary JSON Schema dictionary."""

tests/conftest.py

@@ -44,3 +44,9 @@ def outdir() -> str:
 
     yield name
     shutil.rmtree(name)
+
+
+@pytest.fixture(scope="session")
+def snapshot_dir() -> pathlib.Path:
+    """Return the path to the snapshot directory."""
+    return pathlib.Path("tests/snapshots/")