Python DSC Adapter and Test Resource implementation

[shammu1]

PR Summary

The Python adapter (Microsoft.DSC.Adapters/Python) enables DSC v3 to dynamically execute Python resource classes. It acts as a bridge between the DSC framework and Python-based resource implementations, handling all DSC operations (get, set, test, export, list, validate).

Key Features
Dynamic Resource Discovery: Reads resource mappings from pyproject.toml under [tool.dsc.resources]
Operation Routing: Routes DSC operations to appropriate Python resource class methods
Structured Logging: Full trace/debug/info/error logging with optional profiling capabilities
State Management: Handles JSON serialization and properly emits state + diffs per DSC specification
Error Handling: Graceful error handling with proper exit codes and stderr logging

Core Components
adapter.py: Main ResourceAdapter class managing operation routing, class loading, and resource discovery
discovery.py: Parses pyproject.toml and dynamically imports resource classes
cli.py: Command-line interface handling arguments and stdin input
dsc_logging.py: Environment variable-based logging configuration

Test Coverage
Three comprehensive test layers:

Unit Tests (Python/unittest) — Tests adapter internals: initialization, manifest discovery, class resolution, operation routing
Component Tests (Pester) — Validates adapter subprocess behavior directly: output shapes, exit codes, error handling
Integration Tests (Pester) — End-to-end DSC CLI integration testing through the full DSC framework

PR Context

DSC already supports adapters for non-native resource ecosystems, and this PR adds a Python adapter so Python-based resources can participate in the same DSC execution model as built-in and PowerShell resources.

This adapter is needed to:

1. Enable first-class Python resource support in DSC with the same get, set, test, export, list, and validate flow.
2. Improve extensibility of DSC by allowing teams with existing Python tooling and expertise to author/manage resources without switching implementation languages.

[shammu1]

@microsoft-github-policy-service agree company="Microsoft"

[shammu1]

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Pull request overview

Adds a new Python DSC adapter implementation with test fixtures and Pester/Python tests, intended to let DSC invoke Python resource classes through adapted resource manifests.

Changes:

• Adds Python adapter manifest and pyDscAdapter CLI/runtime modules.
• Adds Python test resources, manifests, pyproject mapping, and unit/component/integration tests.
• Updates ignore rules and one PowerShell adapter test stderr redirection.

Reviewed changes

Copilot reviewed 21 out of 27 changed files in this pull request and generated 46 comments.

Show a summary per file

File	Description
.gitignore	Adds Visual Studio and Python cache ignores.
adapters/__init__.py	Adds package marker.
adapters/powershell/Tests/powershellgroup.resource.tests.ps1	Redirects stderr for one adapted-resource test.
adapters/python/.project.data.json	Defines Python adapter build project metadata.
adapters/python/__init__.py	Adds package marker.
adapters/python/pythonadapter.dsc.resource.json	Adds DSC adapter manifest for Python operations.
adapters/python/pyDscAdapter/__init__.py	Adds adapter package marker.
adapters/python/pyDscAdapter/__main__.py	Adds Python adapter entry point.
adapters/python/pyDscAdapter/adapter.py	Implements operation routing, class loading, logging, and profiling.
adapters/python/pyDscAdapter/cli.py	Adds command-line parser and stdin/input handling.
adapters/python/pyDscAdapter/discovery.py	Adds pyproject class-map parsing and dynamic file import.
adapters/python/pyDscAdapter/dsc_logging.py	Adds structured DSC-style logging.
adapters/python/pyDscAdapter/utils.py	Adds JSON parsing helper.
adapters/python/tests/.project.data.json	Defines test project copy metadata.
adapters/python/tests/TEST_LAYERS.md	Documents unit/component/integration test layers.
adapters/python/tests/__init__.py	Adds test package marker.
adapters/python/tests/pythoncomponent.tests.ps1	Adds adapter subprocess component tests.
adapters/python/tests/pythonintegration.tests.ps1	Adds DSC CLI integration tests.
adapters/python/tests/pythonunit.tests.py	Adds Python unittest coverage for adapter internals.
adapters/python/tests/pyproject.toml	Maps PythonTest resource types to fixture classes.
adapters/python/tests/pythontest.dsc.manifests.json	Adds adapted resource manifests for Python test resources.
adapters/python/tests/src/.project.data.json	Defines fixture resource copy metadata.
adapters/python/tests/src/__init__.py	Adds fixture package marker.
adapters/python/tests/src/export.py	Adds export-only fixture resource.
adapters/python/tests/src/get.py	Adds get-only fixture resource.
adapters/python/tests/src/set.py	Adds set fixture resource.
adapters/python/tests/src/test.py	Adds test-only fixture resource.

[Copilot]

Pull request overview

Copilot reviewed 21 out of 27 changed files in this pull request and generated 12 comments.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 28 changed files in this pull request and generated 8 comments.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 28 changed files in this pull request and generated 8 comments.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 28 changed files in this pull request and generated 7 comments.

Comments suppressed due to low confidence (1)

adapters/python/tests/pythonintegration.tests.ps1:25

• This comment claims the Python adapter manifest has a condition on python3 availability, but the manifest added in this PR does not include a condition field. This is misleading for future maintainers and for interpreting failure expectations in this helper.

                # Python adapter manifest now has a condition on python3 availability.
                # If unavailable, resource discovery should fail cleanly rather than execution failing.

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Pull request overview

Copilot reviewed 22 out of 28 changed files in this pull request and generated no new comments.

Suppressed comments (4)

adapters/python/pyDscAdapter/adapter.py:164

• _instantiate_resource checks only for attribute existence with hasattr(cls, "from_json"), but doesn’t ensure it’s callable. If a resource defines a non-callable from_json attribute (e.g., a class variable/property), this will raise a TypeError and fail the operation unexpectedly. Prefer a callable() check on getattr().

        if hasattr(cls, "from_json"): 
            return cls.from_json(json_input, operation=operation)
        # Fallback: direct init from dict if needed
        data = json.loads(json_input or "{}")
        return cls(**data)

adapters/python/pyDscAdapter/adapter.py:197

• When resource introspection fails in _build_list_entry, capabilities is forced to ["get","set","test"]. This can advertise operations the resource does not implement, causing DSC to attempt unsupported operations later. It’s safer to return an empty capabilities list (or only those confirmed) when introspection fails.

        if not capabilities:
            capabilities = ["get", "set", "test"]  # remove this

adapters/python/pyDscAdapter/adapter.py:243

• _discover_python_resources appends list entries even when it can’t find a corresponding .py file for a discovered resource type. This can produce list results with non-existent paths and causes avoidable import/introspection failures. Skip the resource when no file can be resolved.

                resource_file = pyproject_path.parent / (discovered_type.split("/")[-1].lower() + ".py")
                if not resource_file.exists():
                    resource_file = pyproject_path.parent / (class_name.lower() + ".py")

adapters/python/pyDscAdapter/discovery.py:152

• The non-tomllib fallback parser in get_class_map_from_pyproject only supports a flat [tool.dsc.resources] key/value form, but this repo’s pyproject.toml uses per-resource tables like [tool.dsc.resources."PythonTest/Get"]. On Python < 3.11 (no tomllib), discovery will return an empty class map and the adapter won’t resolve any resources.

    class_map = {}
    in_section = False
    
    for line in content.splitlines():
        stripped = line.strip()
        if stripped == "[tool.dsc.resources]":