fix: generate parameterized accessor for subclients with subclient-specific parameters

[Copilot]

When a subclient (initialized by parent, or individually+parent) has parameters absent from the parent, the parent was generating a non-functional caching field and an accessor with no parameters — making it impossible to pass the subclient-specific values.

Root cause

BuildFields() always added _clientCachingField for any parent-initialized subclient. BuildMethods() had the accessorMethodParams > 0 branch to generate parameterized accessors, but the spurious caching field remained.

Changes

• ClientProvider.HasAccessorOnlyParameters() — new method that detects non-endpoint, non-apiversion subclient parameters absent from the parent
• BuildFields() — skips the caching field when HasAccessorOnlyParameters() is true (different param values → different instances → caching is wrong)
• New unit tests — TestBuildMethods_ForParent_InitializedByParentOnly_WithSubClientParams_HasParameterizedAccessor and TestBuildFields_ForParent_InitializedByParentOnly_WithSubClientParams_NoCachingField

Generated output

Before (wrong — blobName unreachable, dead caching field):

private IndividuallyParentNestedWithQueryClient _cachedIndividuallyParentNestedWithQueryClient;

public virtual IndividuallyParentNestedWithQueryClient GetIndividuallyParentNestedWithQueryClient()
    => Volatile.Read(ref _cachedIndividuallyParentNestedWithQueryClient) ?? ...;

After (correct):

public virtual IndividuallyParentNestedWithQueryClient GetIndividuallyParentNestedWithQueryClient(string blobName)
    => new IndividuallyParentNestedWithQueryClient(Pipeline, _endpoint, blobName);

Test coverage

• Updated SampleService/main.tsp to give Metrics a metricsNamespace client parameter not on the parent; SampleTypeSpecClient.GetMetricsClient(string metricsNamespace) now demonstrates the fix end-to-end
• Unit tests cover both the IndividuallyParent and Parent-only subclient scenarios with accessor-only parameters

Original prompt

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This section details on the original issue you should resolve

<issue_title>Subclient parameters need to be included in accessors</issue_title>
<issue_description>For subclients that can be created individually or from the parent, the subclient parameters are not included in the subclient accessors currently. </issue_description>

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

• Fixes Subclient parameters need to be included in accessors #9775

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commit: d253394

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• aka.ms
  • Triggering command: /usr/bin/curl curl -L REDACTED -o /tmp/install-dotnet.sh act-api |accessor\|Accessor de/node/bin/bash (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[JoshLove-msft]

@copilot run prettier on the tsp file being changed