fix(PageConnection): fallback to 0, not -1 on empty pages

[Hanskrogh]

This pull request makes a minor change to the default value for the TotalCount property in the PageConnection class. The default value is now 0 instead of -1 when the total count is not available.

[Copilot]

Pull request overview

This PR changes the default TotalCount value exposed by PageConnection<TNode> when the underlying GreenDonut.Data.Page<TNode>.TotalCount is not available, switching the fallback from -1 to 0.

Changes:

• Update PageConnection<TNode>.TotalCount to return 0 when _page.TotalCount is null (previously -1).

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[Copilot]

This changes the sentinel value for "total count not available" from -1 to 0 for PageConnection, but other paging implementations in this repo still use -1 when the total count is unknown (e.g. CursorPagingHandler and OffsetPaginationAlgorithm). Consider aligning the behavior across paging result types or documenting the differing semantics to avoid surprising API consumers.

[Hanskrogh]

@michaelstaib Is this a valid argument? should I change it, so only Page.Empty adds a 0 count?

    /// <summary>
    /// An empty page.
    /// </summary>
    public static new ValueCursorPage<T> Empty { get; } = new([], false, false, _ => string.Empty, 0);

[michaelstaib]

This is wrong. I thought we had this fallback in a different location.

TotalCount should not be displayed if, like not be in the typesystem if the page does not provide it. If you have this it seems there is something misconfigured.

Actually, what we should do here is throw a GraphQLException that no count is available.

[Hanskrogh]

@michaelstaib
Added Graphql Exception and setting Page.TotalCount Explicitly to 0 on Page.Empty

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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[Copilot]

This implementation no longer “falls back to 0” when the total count is unavailable; it now throws a GraphQLException when _page.TotalCount is null. That’s a behavior change vs both the PR description/title and existing Page->Connection conversion which uses page.TotalCount ?? 0 (e.g. HotChocolatePaginationResultExtensions.CreateConnection: page.TotalCount ?? 0). Consider returning 0 (or keeping the existing sentinel) instead of throwing, or make the GraphQL field nullable if “not available” must be represented explicitly.

[Copilot]

Setting ValueCursorPage<T>.Empty to have totalCount = 0 changes the public behavior of Page<T>.Empty.TotalCount from null (unknown) to a concrete value (known 0). Since Page<T>.Empty is returned in paging code paths when no items are fetched (e.g. PagingQueryableExtensions.ToPageAsync returns Page<T>.Empty when builder.Count == 0, even when the underlying dataset might not be empty), this can cause TotalCount to be reported as 0 when it’s actually unknown/non-zero. Consider keeping TotalCount as null on Empty and handling any GraphQL-facing fallback (0 vs -1) at the connection layer instead.

Suggested change

	public static new ValueCursorPage<T> Empty { get; } = new([], false, false, _ => string.Empty, 0);
	public static new ValueCursorPage<T> Empty { get; } = new([], false, false, _ => string.Empty);