[.NET Generator] Auto-generate ClientSettings class and IConfiguration-enabled constructors

[Copilot]

Automatically generates IConfiguration-based client construction support for every generated client, enabling standard .NET configuration patterns (appsettings.json, environment variables) and dependency injection registration.

What's Generated

A. {Client}Settings class

• Extends ClientSettings (from System.ClientModel.Primitives)
• Properties for endpoint URI, non-auth required constructor parameters, and client options
• Implements BindCore(IConfigurationSection section) override
• Marked [Experimental("SCME0002")]

B. internal {Client}Options(IConfigurationSection section) constructor

• Calls base(section) for common property forwarding
• Sets Version to the latest version string before the guard (ensuring it's always initialized)
• Guards with if (section is null || !section.Exists()) { return; } before binding
• Binds non-version option properties from configuration
• Marked [Experimental("SCME0002")]

C. public {Client}({Client}Settings settings) constructor

• Delegates to the primary constructor via this(...) initializer
• Extracts endpoint, non-auth required parameters, and options from settings
• For API key auth: uses settings?.Credential?.Key != null ? new ApiKeyCredential(settings?.Credential?.Key) : null
• For OAuth2 auth: uses settings?.CredentialProvider as AuthenticationTokenProvider
• Marked [Experimental("SCME0002")]

Changes Made

• ClientSettingsProvider.cs — new TypeProvider generating {Client}Settings; collects OtherRequiredParams (non-auth, non-endpoint required constructor parameters) and generates properties and BindCore bindings for them
• ClientOptionsProvider.cs — adds IConfigurationSection constructor with version initialization before guard; adds default parameterless constructor when no API versions are present
• ClientProvider.cs — adds settings constructor; passes non-auth required parameters in correct order using ?? default for value types
• ScmOutputLibrary.cs — registers ClientSettingsProvider in the output
• Packages.Data.props / .csproj — adds explicit Microsoft.Extensions.Configuration.Abstractions (v10.0.2) dependency
• CSharpType.cs — removed FromExternalType; uses direct typeof(ClientSettings) with scoped #pragma warning disable SCME0002

Testing

• 1170 tests passing
• Generate.ps1 completes successfully; full solution builds with 0 errors
• New tests for ClientSettingsProvider, ClientOptionsProvider IConfiguration constructor, and ClientProvider settings constructor

Original prompt

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This section details on the original issue you should resolve

<issue_title>[.NET Generator] Auto-generate ClientSettings class and IConfiguration-enabled constructors for clients</issue_title>
<issue_description>## Overview

Parent issue: Azure/azure-sdk-for-net#55491

The .NET generator should automatically produce IConfiguration-based client construction support for every generated client. This enables developers to configure clients using standard .NET configuration patterns (appsettings.json, environment variables) and register them with dependency injection containers.

Two services have been manually implemented as reference:

• Azure.Data.AppConfiguration PR microsoft/typespec#56537
• Azure.Security.KeyVault.Secrets PR microsoft/typespec#56409

The generator should produce these automatically so every client gets configuration support without manual customization.

What the Generator Needs to Produce

Three artifacts per client:

A. {Client}Settings class

• Extends ClientSettings (from System.ClientModel.Primitives)
• Properties derived from the client's primary constructor parameters (excluding credential)
• Implements BindCore(IConfigurationSection section) override
• Marked [Experimental("SCME0002")]

B. internal {Client}Options(IConfigurationSection section) constructor

• Calls base(section) — the base options class handles common properties (see Forwarding Binding)
• Guards with if (section is null || !section.Exists()) { return; } before binding any properties
• Binds each option-specific property from the section
• Marked [Experimental("SCME0002")]

C. public {Client}({Client}Settings settings) constructor on the client

• Delegates to the client's primary constructor (the one with the body implementation) — e.g., (AuthenticationPolicy, Options) or (Uri, AuthenticationPolicy, Options) depending on the client
• Creates the authentication policy via AuthenticationPolicy.Create(settings) to pass to the primary constructor
• Extracts other properties from settings and maps them to the primary constructor parameters (e.g., settings?.Endpoint, settings?.Options)
• Not all clients have a URI parameter — the settings class properties mirror whatever the primary constructor requires
• Marked [Experimental("SCME0002")]

How to Determine Settings Properties

The generator should inspect the client's primary public constructor (the one with the body implementation) parameters:

• Endpoint/URI parameters (if present) → become Uri? properties on Settings (e.g., VaultUri, Endpoint)
• Options parameter → becomes {Client}Options? property on Settings
• Credential/AuthenticationPolicy parameter → handled by base ClientSettings.Credential / CredentialProvider, NOT duplicated
• Any other non-credential constructor parameters may become settings properties

How to Implement BindCore

`csharp
protected override void BindCore(IConfigurationSection section)
{
if (section is null || !section.Exists())
{
return;
}

// String → use 'is string' pattern match
if (section["Endpoint"] is string endpoint)
{
    Endpoint = new Uri(endpoint);
}

// Options → GetSection + Exists check + internal ctor
IConfigurationSection optionsSection = section.GetSection("Options");
if (optionsSection.Exists())
{
    Options = new {Client}Options(optionsSection);
}

}
`

Key rule: If a configuration segment doesn't exist, bail early — don't set the property. No validation in BindCore. Let the client constructor that receives the settings do all required parameter validation (e.g., Argument.AssertNotNull).

Type Binding Patterns

The generator should use these patterns to bind properties from IConfigurationSection:

Type	Pattern	Example
string	section[name] is string val	TenantId = val
bool	bool.TryParse(section[name], out bool val)	DisableChallengeResourceVerification = val
Uri	Uri.TryCreate(section[name], UriKind.Absolute, out Uri val)	RedirectUri = val
TimeSpan	TimeSpan.TryParse(section[name], out TimeSpan val)	NetworkTimeout = val
int	int.TryParse(section[name], out int val)	MaxRetries = val
string[] / List<string>	section.GetSection(name).GetChildren().Where(c => c.Value is not null).Select(c => c.Value!).ToList()	AdditionallyAllowedTenants
Complex object	section.GetSection(name) + .Exists() + new Type(section)	BrowserCustomization = new BrowserCustomizationOptions(browserSection)
Custom struct/enum (extensible)	new TypeName(section[name]) after null check	Audience = new AppConfigurationAudience(audience)

For a comprehensive example of bin...

• Fixes [.NET Generator] Auto-generate ClientSettings class and IConfiguration-enabled constructors for clients #9842

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[JoshLove-msft]

@copilot we just need to upgrade to the version of System.ClientModel that has ClientSettings.

[Copilot]

Done in 78afaca. System.ClientModel 1.9.0 (already the pinned version) does have ClientSettings in System.ClientModel.Primitives. Replaced the FromExternalType string-based workaround with typeof(ClientSettings) (with scoped #pragma warning disable SCME0002 since it's experimental) and typeof(IConfigurationSection). Also removed the FromExternalType method from CSharpType.cs since it's no longer needed.

[JoshLove-msft]

@copilot run Generate.ps1 and investigate any failures.

[Copilot]

@copilot run Generate.ps1 and investigate any failures.

Run complete in 04121e3. Generate.ps1 succeeded and the full solution builds with 0 errors. Fixed issues found:

• Missing default constructor in ClientOptionsProvider when no API versions (suppressed the auto-generated one)
• Invalid CredentialProvider as ApiKeyCredential cast (replaced with settings?.Credential?.Key != null ? new ApiKeyCredential(settings?.Credential?.Key) : null)
• Missing non-auth required parameters in settings constructor (e.g. ClientType client, string serviceDeploymentVersion) — ClientSettingsProvider now collects and exposes OtherRequiredParams, generating properties and correct constructor args for them