Omit requireOneSlicingArgument if not set in listSize directive

[glen-84]

Summary of the changes (Less than 80 chars)

• Omitted requireOneSlicingArgument if not set in listSize directive.

Closes #7398

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• @michaelstaib to add another test.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.13%. Comparing base (e3c132c) to head (94a3c41).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7418   +/-   ##
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  Coverage   74.13%   74.13%           
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  Files        2674     2674           
  Lines      140657   140661    +4     
  Branches    16358    16358           
=======================================
+ Hits       104282   104286    +4     
- Misses      30780    30783    +3     
+ Partials     5595     5592    -3     

Flag	Coverage Δ
unittests	74.13% <ø> (+<0.01%)	⬆️

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[Copilot]

Pull request overview

Adjusts how @listSize is represented so that requireOneSlicingArgument is not emitted into SDL unless it was explicitly set, addressing #7398.

Changes:

• Track whether RequireOneSlicingArgument was explicitly set on ListSizeAttribute and forward a nullable value into the directive.
• Simplify ListSizeDirective to store RequireOneSlicingArgument as provided (nullable) so formatting can omit it.
• Add a snapshot-based test verifying SDL output for omitted/explicit requireOneSlicingArgument.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/HotChocolate/CostAnalysis/test/CostAnalysis.Tests/AttributeTests.cs	Adds coverage asserting SDL printing behavior for @listSize with and without requireOneSlicingArgument.
src/HotChocolate/CostAnalysis/src/CostAnalysis/Types/ListSizeDirective.cs	Changes directive construction to preserve “unset” (null) for RequireOneSlicingArgument.
src/HotChocolate/CostAnalysis/src/CostAnalysis/Types/ListSizeAttribute.cs	Adds nullable backing field so the attribute can distinguish “unset” vs explicit values and omit the SDL argument accordingly.

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[Copilot]

Changing ListSizeDirective to assign RequireOneSlicingArgument = requireOneSlicingArgument removes the previous defaulting behavior (enabled by default when SlicingArguments are provided). Since ValidateRequireOneSlicingArgument treats null as false, fields that specify slicingArguments but omit requireOneSlicingArgument will no longer enforce the directive type’s default (DefaultValue(true)), changing runtime cost-analysis semantics. Consider restoring the effective default (e.g., treat null as true when slicing arguments are present) while still omitting the argument from SDL when it wasn’t explicitly set.

[Copilot]

ListSizeAttribute.OnConfigure now forwards _requireOneSlicingArgument (nullable) instead of the RequireOneSlicingArgument property (defaulting to true). This means leaving the attribute property unset will produce a directive value of null even when SlicingArguments are provided, which (given current validation logic) effectively disables requireOneSlicingArgument by default. If the intended default remains true (as indicated by ListSizeDirectiveType), consider applying that default during analysis/validation when the backing field is null.

Suggested change

	_requireOneSlicingArgument));
	RequireOneSlicingArgument));

[Copilot]

The new snapshot test covers SDL omission when only AssumedSize is set, but it doesn’t cover the case where SlicingArguments are set and RequireOneSlicingArgument is left unset. Adding an assertion for that combination would help ensure the SDL omission change doesn’t unintentionally change the effective default behavior during cost analysis (per the directive argument default).

Suggested change

	listSizeDirective3Sdl.MatchInlineSnapshot("@listSize(requireOneSlicingArgument: false)");
	listSizeDirective3Sdl.MatchInlineSnapshot("@listSize(requireOneSlicingArgument: false)");
	// and the omitted argument still respects the directive default at runtime
	var listSizeDirective1 = query.Fields["examplesAssumedSizeOnly"]
	.Directives
	.Single(d => d.Type.Name == "listSize")
	.ToValue<ListSizeDirective>();
	Assert.True(listSizeDirective1.RequireOneSlicingArgument);