Apply template updates: Polyfill, netstandard2.0, and net481 Windows test evidence

[Copilot]

Syncs with TemplateDotNetLibrary, adds netstandard2.0 as a library target, and uses net481 on Windows CI as direct runtime evidence for that target.

Description

Template alignment

• LangVersion: 12 → latest
• SonarAnalyzer.CSharp → 10.20.0.135146, Microsoft.NET.Test.Sdk → 18.3.0
• Added Polyfill 9.12.0 (PrivateAssets=All, PolyArgumentExceptions=true) to library
• Added InternalsVisibleTo for test project

netstandard2.0 support

• Added netstandard2.0 to library TargetFrameworks
• System.Text.Json 10.0.3 referenced unconditionally
• Microsoft.Bcl.HashCode 6.0.0 conditioned on netstandard2.0 for HashCode.Combine
• [GeneratedRegex] in SpdxHelpers.cs guarded behind #if NET7_0_OR_GREATER with a static readonly Regex fallback

Windows net481 test target

• Test project targets net481;net8.0;net9.0;net10.0 on Windows, net8.0;net9.0;net10.0 elsewhere
• net481 provides direct runtime evidence that the netstandard2.0 library surface works on .NET Framework

Polyfill + InternalsVisibleTo interaction

• Polyfill injects internal static partial class Polyfill into the library; InternalsVisibleTo exposes it to the test project without importing the namespace
• Adding Polyfill directly to the test project caused CS0121 (ambiguous extension methods)
• Fix: <Using Include="Polyfills" /> adds a global using — no duplicate package, .ReplaceLineEndings() resolves to the library's compiled copy on all targets including net481

Portable ArgumentException assertions

• ArgumentException.Message format differs by runtime: .NET Framework appends \r\nParameter name: x; modern .NET appends (Parameter 'x')
• Tests that asserted the full ex.Message string failed on net481
• Fix: Assert.StartsWith(expectedBaseMessage, ex.Message) + Assert.AreEqual("relationship", ex.ParamName)

Requirements

• REQ-PLAT-004 updated to use net481@ evidence

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code quality improvement

Pre-Submission Checklist

Build and Test

• Code builds successfully: dotnet build --configuration Release
• All unit tests pass: dotnet test --configuration Release
• Code produces zero warnings

Code Quality

• Code formatting is correct: dotnet format --verify-no-changes
• New code has appropriate XML documentation comments
• Static analyzer warnings have been addressed

Quality Checks

• Spell checker passes: cspell "**/*.{md,cs}"
• Markdown linter passes: markdownlint "**/*.md"
• YAML linter passes: yamllint .

Testing

• Added unit tests for new functionality
• Updated existing tests if behavior changed
• All tests follow the AAA (Arrange, Act, Assert) pattern
• Test coverage is maintained or improved

Documentation

• Updated README.md (if applicable)
• Added code examples for new features (if applicable)
• Updated requirements.yaml (if applicable)
• Updated XML documentation comments for changed APIs

Additional Notes

net481 tests run only on Windows CI agents; Linux agents target net8.0;net9.0;net10.0. REQ-PLAT-004 remains unmet in reqstream until a Windows CI run produces net481 results.

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[Malcolmnixon]

@copilot I'm being told it's better to add Microsoft.Bcl.HashCode for HashCode.Combine rather than writing a custom polyfill. Additionally the code-quality lint checks failed.

[Copilot]

@copilot I'm being told it's better to add Microsoft.Bcl.HashCode for HashCode.Combine rather than writing a custom polyfill. Additionally the code-quality lint checks failed.

Done in d4430a2 — removed the custom HashCodePolyfill.cs and added Microsoft.Bcl.HashCode 6.0.0 (conditioned on netstandard2.0). Also fixed the spell-check failures by removing netstandard from C# comments in SpdxHelpers.cs.

[Malcolmnixon]

@copilot The Windows build is complaining of:

Error: D:\a\SpdxModel\SpdxModel\test\DemaConsulting.SpdxModel.Tests\TestHelpers.cs(44,35): error CS1061: 'string' does not contain a definition for 'ReplaceLineEndings' and no accessible extension method 'ReplaceLineEndings' accepting a first argument of type 'string' could be found (are you missing a using directive or an assembly reference?) [D:\a\SpdxModel\SpdxModel\test\DemaConsulting.SpdxModel.Tests\DemaConsulting.SpdxModel.Tests.csproj::TargetFramework=net481]

However the PolyFill library looks like it does contain such a method - https://github.com/SimonCropp/Polyfill/blob/88aed47fd70637a830bed2f2747401d9e9a68786/src/Polyfill/Polyfill_String.cs#L167

What gives?

[Copilot]

@copilot The Windows build is complaining of:

Error: D:\a\SpdxModel\SpdxModel\test\DemaConsulting.SpdxModel.Tests\TestHelpers.cs(44,35): error CS1061: 'string' does not contain...

Adding Polyfill to the test project caused ambiguity errors because the library's InternalsVisibleTo("DemaConsulting.SpdxModel.Tests") makes its internal Polyfill extension methods visible to the test project — so they'd be duplicated. Fixed in b7119eb by guarding the call in TestHelpers.cs behind #if NET6_0_OR_GREATER, falling back to .Replace("\r\n", "\n").Replace("\r", "\n") on net481.

[Malcolmnixon]

@copilot The Windows build still failed:

  Failed SpdxRelationships_AddSingle_MissingRelatedElement [214 ms]
  Error Message:
   Assert.AreEqual failed. Expected string length 85 but was 88. 'expected' expression: '"Element SPDXRef-Package-Missing not found in SPDX document (Parameter 'relationship')"', 'actual' expression: 'ex.Message'.
Expected: "...d in SPDX document (Parameter 'rela..."
But was:  "...d in SPDX document␍␊Parameter name:..."

[Copilot]

@copilot The Windows build still failed:

  Failed SpdxRelationships_AddSingle_MissingRelatedElement [214 ms]

...

Fixed in 2e2bab3. The root cause is that ArgumentException.Message appends the parameter name in a framework-specific format — .NET Framework uses \r\nParameter name: relationship while modern .NET uses (Parameter 'relationship'). The assertions now use StartsWith to check just the base message and assert ex.ParamName == "relationship" separately, which works correctly on all targets.