Partial Tag Helper 'for' attribute not forwarding model to controller correctly

[Whathecode]

While updating to .NET Core 2.1, I replaced my @Html.Partial loads to the new partial tag helper as recommended by the compiler warnings.

In two cases, I could rely on the for syntax, rather than using the model attribute:

The for attribute assigns a ModelExpression to be evaluated against the current model. A ModelExpression infers the @Model. syntax. For example, for="Product" can be used instead of for="@Model.Product".

At first, I had the impression this worked as my partials showed up correctly. However, I just found out my partial reloads stopped working due the the model not being transferred to my controllers correctly; something which worked just fine before.

I use the following javascript to intercept a form submission and send/handle a post request:

$(addForm).on("submit", function (e) {
    e.preventDefault();

    // Do not submit if form is invalid.
    if (!$(this).valid()) {
        return false;
    }

    $.ajax({
        url: $(this).attr("action"),
        type: "POST",
        data: $(this).serialize(),
        complete: function () {
            ...
        }
    }).done(function (result) {
        partialView.html(result);
        ...
    });
});

When I change my partials to use the model attribute instead, things work fine again: <partial name="Details/_CommentsPartial" model="@Model.Comments" />.

This seems like a bug to me? Possibly relevant, this is a nested partial (partial in partial).

[pranavkm]

Moved to aspnet/Mvc#8037