what does a claims path pointer error actually mean

As per @marcoscaceres comment in #743_

On the first two of those four outcomes, there may be a question upstream of the guidance: what a claims path pointer error actually means. This was raised in #491 with a proposed one sentence resolution, and I could not find that sentence or an equivalent in the current editor's draft.

From #491:

Section 7 defines how the claims path pointer is used to select claims. It also provides processing rules with errors or selected elements, but we are missing the explicit link between the these sections and how the processing rules apply.

and, in the same comment:

I think it's sufficient to say that a request for a claim by a verifier is met if the corresponding processing rules for the path return an element (and not an error).

Without that link, the everyday case is undetermined. Where a Credential does not contain a requested claim, both profiles reach an error: the mdoc rules directly,

Select the data element referenced by the second component. If the data element does not exist in the Credential then abort processing and return an error.

and the JSON rules by removing the element and then

If the set of elements currently selected is empty, abort processing and return an error.

Section 6.4.1, Selecting Claims, converts one cause into a non-match, a value mismatch, where the claim "should be treated the same as if it did not exist in the Credential", but I could not find an equivalent for a processing error. So a Wallet reading the error as the claim not being delivered drops that Credential and, where the Credential Set is not required, returns a VP Token with the others: partial results, your second outcome. A Wallet reading it as a request error returns invalid_request and no token: your third.

PR #745 needs this answered too, since it adds "The Wallet MUST return a VP Token only if it contains a set of Presentations that satisfy the requirements of the DCQL query according to (#dcql_query_lang_processing_rules)", and whether an error means those requirements are unsatisfied is the undetermined point.

Does #491's proposed resolution still stand? If so, stating it would settle when to send which of the four.

Read the discussion in issues #491, #743, and #745, then compare Section 7 with Section 6.4.1 and the mdoc and JSON processing rules quoted here. Determine whether #491's proposed sentence resolves how a claims path pointer error affects claim satisfaction and the four wallet outcomes. Done means the specification states this link unambiguously.