Modernize C# patterns and eliminate inconsistencies

[Copilot]

Codebase contained inconsistent patterns (old-style null checks, string concatenation, verbose initializations) deviating from modern C# conventions.

Changes

Null check pattern modernization

• Replaced == null/!= null with is null/is not null across 14 instances
• Updated: CommandLineOptionsParser.cs, LicenseValidator.cs, PackageInformationReader.cs, CachingDisposableSourceRepository.cs

Before:

if (licenseMapping == null) { ... }
if (metadata != null) { ... }

After:

if (licenseMapping is null) { ... }
if (metadata is not null) { ... }

String handling improvements

• Converted concatenation to interpolation in StringExtensions.cs, LicenseValidator.cs, LicenseValidationResult.cs

Before:

"^" + Regex.Escape(pattern).Replace(@"\*", ".*") + "$"
new Uri(licenseUrl.ToString() + "?raw=true")

After:

$"^{Regex.Escape(pattern).Replace(@"\*", ".*")}$"
new Uri($"{licenseUrl}?raw=true")

Field initialization modernization

• Updated verbose initializers to target-typed new() in 5 files

Before:

private readonly List<string[][]> _rows = new List<string[][]>();
private readonly SemaphoreSlim _limiter = new SemaphoreSlim(10, 10);

After:

private readonly List<string[][]> _rows = new();
private readonly SemaphoreSlim _limiter = new(10, 10);

Exclusions

SPDX code (Java port) deliberately untouched to maintain upstream alignment.

Impact

9 files modified, ~50 lines simplified. Zero functionality changes - all tests pass.

Original prompt

Investigate inconsistencies in the code and also shortcomings (where suboptimal patterns are followed) and fix those. Be sure to not alter any functionality.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud