Ignore write-only properties in schema-aware diffs

[Steve Lee (SteveL-MSFT)]

Properties used only as resource instructions may not be returned by a resource, which caused schema-aware comparisons to report false differences.

This change makes get_diff_with_schema() skip properties marked writeOnly: true in the resource schema. The Windows Firewall resource now marks unspecifiedRulesAction as write-only, and unit and resource tests cover differing, omitted, and explicitly non-write-only properties.

Fix #1668

[Copilot]

Pull request overview

This PR reduces false-positive schema-aware differences when resources intentionally do not return “instruction-only” properties by making get_diff_with_schema() ignore schema properties marked writeOnly: true. It also updates the Windows Firewall resource schema and tests to reflect that unspecifiedRulesAction is write-only and should not affect desired-state comparisons.

Changes:

• Update get_diff_with_schema() to skip properties whose JSON Schema sets writeOnly: true, and add unit tests for write-only behavior.
• Mark unspecifiedRulesAction as writeOnly in the Windows Firewall resource schema.
• Adjust Windows Firewall resource tests to assert non-default unspecifiedRulesAction values do not cause diffs.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
resources/windows_firewall/windows_firewall.dsc.resource.json	Marks unspecifiedRulesAction as writeOnly so it’s excluded from schema-aware diffing.
resources/windows_firewall/tests/windows_firewall_schema_default.tests.ps1	Updates resource tests to assert unspecifiedRulesAction does not affect inDesiredState/diff output.
lib/dsc-lib/src/dscresources/dscresource.rs	Implements write-only skipping in schema-aware diffs and adds unit tests for the behavior.

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[github-actions]

😁 Code Coverage Report

Changed Code Coverage

95% (90%+ coverage)

Metric	Value
Changed lines analyzed	73
Lines covered by tests	70
Coverage percentage	95%

🔵 Full Codebase Coverage

82% (good)

Metric	Value
Total executable lines	18820
Lines covered by tests	15500
Coverage percentage	82%

Changed code coverage measures only Rust lines added/modified in this PR.
Full codebase coverage measures all instrumented Rust lines across the project.