Stash set_list not working as expected when used with playa, not outputting data

Question

I'm trying to extract from a list of products in the cart the (playa) related entries (i want the entry_id's), put them into stash and then i need to use those id's somewhere else to build a "related products" type thing. But as the products in the cart could have the same related entries, i need to make the list it spits out unique. Oh, and there are two playa fields i need to get data from that both have related products but from two different product channels!

So, first we have the setting of the data:

{!-- Get the current items in the basket --}
{exp:cartthrob:cart_items_info}
{!-- Check the products we're getting the info from are in the channel that actually has the related product fields --}
{if channel_id == 7}
    {!-- Channel entry loop to get the product data out from the id's the cart_items_info has given us --}
    {exp:channel:entries channel="events" entry_id="{entry_id}" dynamic="off"}
    {!-- First playa related products field--}
        {product_sub_product}
    {!-- Stash using unique name the list of entry_id's from playa --}
            {exp:stash:set_list name="sub_prods" parse_tags="yes"}
    {!-- Stash set name as item_id --}
                {stash:item_id}
                    {entry_id}
                {/stash:item_id}
            {/exp:stash:set_list}
        {/product_sub_product}
    {!-- Second playa related products field--}
    {product_related_races}
    {!-- Stash using unique name the list of entry_id's from playa --}
        {exp:stash:set_list name="rel_races" parse_tags="yes"}
    {!-- Stash set name as item_id --}
            {stash:item_id}
                {entry_id}
            {/stash:item_id}
        {/exp:stash:set_list}
    {/product_related_races}
{/exp:channel:entries}
{/if}
{/exp:cartthrob:cart_items_info}
{!-- End of current items in the basket --}

And then we have the getting of the data:

{!-- Get the data out from both sets --}
{exp:stash:get_list name="sub_prods" unique="yes"}
    prods - {item_id}<br />
{/exp:stash:get_list}

{exp:stash:get_list name="rel_races" unique="yes"}
    races - {item_id}<br />
{/exp:stash:get_list}

What's odd, is that i can see the data in the database so it is all working as expected. But stash get_list is not outputting the data.

Answer 1

Grab the related entry ids in one go like this:

{!-- Get the current items in the basket --}
{exp:cartthrob:cart_items_info}
{!-- Check the products we're getting the info from are in the channel that actually has the related product fields --}
{if channel_id == 7}
    {!-- Channel entry loop to get the product data out from the id's the cart_items_info has given us --}
    {exp:channel:entries channel="events" entry_id="{entry_id}" dynamic="off"}

        {!-- Capture a list of entry_ids from the various playa fields --}
        {exp:stash:set_list name="related_prods" parse_tags="yes"}

            {!-- First playa related products field--}
            {product_sub_product}
                {stash:item_id}{entry_id}{/stash:item_id}
                {stash:item_type}sub{/stash:item_type}
            {/product_sub_product}

            {!-- Second playa related products field--}
            {product_related_races}
                {stash:item_id}{entry_id}{/stash:item_id}
                {stash:item_type}related{/stash:item_type}   
            {/product_related_races}

        {/exp:stash:set_list}

    {/exp:channel:entries}
{/if}
{/exp:cartthrob:cart_items_info}
{!-- End of current items in the basket --}

Use like this to get only unique entries:

{exp:stash:get_list name="related_prods" unique="yes"}
    {item_id}<br />
{/exp:stash:get_list}

Or just the 'sub' type of entry ids:

{exp:stash:get_list name="related_prods" match="#^sub$#" against="item_type"}
    {item_id}<br />
{/exp:stash:get_list}