[Copilot]

The UseDisabledWhen() extension silently fails when called before ConfigureFunctionsWebApplication() because the Functions worker resolves the last registered IFunctionMetadataProvider, finding none if mis-ordered.

Changes

• Validation at registration-time: Check that an underlying IFunctionMetadataProvider exists in the service collection before registering DisabledWhenMetadataProvider
• Clear error message: Throw InvalidOperationException specifying that UseDisabledWhen() must be called after ConfigureFunctionsWebApplication() or ConfigureFunctionsWorkerDefaults()

Example

// ❌ This now throws immediately with clear error:
var builder = new HostBuilder();
builder.UseDisabledWhen();  // InvalidOperationException

// ✅ Correct ordering still works:
var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .UseDisabledWhen()  // Validation passes
    .Build();

This ensures fail-fast behavior at startup instead of runtime failures when the host attempts to resolve metadata providers.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Anders-Toegersen]

fixed in main