Support RootNamespaceAttribute

[Copilot]

JsonStringLocalizerFactory was using assembly name to calculate resource paths, which fails when root namespace differs from assembly name (configured via <RootNamespace> in csproj).

Changes

• Added GetRootNamespace() method that checks for RootNamespaceAttribute on the assembly, falling back to assembly name
• Updated Create(Type resourceSource) to use root namespace instead of assembly name when computing type name
• Updated Create(string baseName, string location) to use root namespace when trimming the base name prefix
• Added comprehensive test infrastructure with two dedicated test class libraries:
  • ResourcesClassLibraryNoAttribute: Tests the fallback behavior when RootNamespaceAttribute is not present
  • ResourcesClassLibraryWithAttribute: Tests the attribute behavior with [assembly: RootNamespace("MyCustomNamespace")] where the assembly name differs from the root namespace
• Added unit tests to verify both scenarios with and without the attribute for both factory methods

This matches the behavior of Microsoft.Extensions.Localization.ResourceManagerStringLocalizerFactory.

Usage

// In assembly with [assembly: RootNamespace("MyCompany.MyProduct")]
// where assembly name is "MyCompany.MyProduct.Web"

// Before: looked for Resources/Web/Controllers/HomeController.json
// After:  looks for Resources/Controllers/HomeController.json
var localizer = factory.Create(typeof(HomeController));

Testing

• ✅ All 37 unit tests pass, including new tests for RootNamespaceAttribute support
• ✅ All 5 functional tests pass
• ✅ Tests verify behavior both with and without RootNamespaceAttribute

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Support RootNamespaceAttribute</issue_title>
<issue_description></issue_description>

<agent_instructions>Support Microsoft.Extensions.Localization.RootNamespaceAttribute</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Support RootNamespaceAttribute #51

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[hishamco]

@copilot add two class libraries in the test named ResourcesClassLibraryNoAttribute and ResourcesClassLibraryWithAttribute, then rewrite the unit tests to examine the RootNamespaceAttribute

[Copilot]

@copilot add two class libraries in the test named ResourcesClassLibraryNoAttribute and ResourcesClassLibraryWithAttribute, then rewrite the unit tests to examine the RootNamespaceAttribute

I've added the two test class libraries as requested:

1. ResourcesClassLibraryNoAttribute: Test library without RootNamespaceAttribute (assembly name equals root namespace)
2. ResourcesClassLibraryWithAttribute: Test library with [assembly: RootNamespace("MyCustomNamespace")] where the assembly name differs from the root namespace

Both libraries have:

• TestModel class with test resources
• ResourceLocationAttribute to separate resources into Resources/NoAttr and Resources/WithAttr subdirectories
• JSON resource files for en and fr-FR cultures

The unit tests have been rewritten to properly examine the RootNamespaceAttribute support with these scenarios:

• Without attribute: factory uses assembly name as root namespace
• With attribute: factory uses the specified root namespace instead of assembly name

All 37 unit tests pass. Commit: 222ee51

[hishamco]

@copilot fix the warnings