Add several values for the same property

[CharlesNepote]

Reported by Alizarine on Slack (2024-03-24).

Indeed, the example provides a simple use case: a product could have multiple producer_data_issue.

Option 1: do not change the API, manage it with the UI

With the UI it would be possible to enter a property several times.
In the database, the different values would be stored in a unique property/value, separated by a given sign (a ; for example).
The UI would have to manage the following cases:

• allowing to enter a property more than one time, and saving the value along with the existing values (it should not save a value if it is already existing)
• taking care of multiple values in the list of all the possible values for a given property: eg. https://world.openfoodfacts.org/property/producer_data_issue
• taking care of multiple values in the search as you type feature: when entering a value, the UI is listing all possible values depending on the property

Option 2: change the API, do not change the UI

There would be probably no change at all in the UI.

[alexgarel]

@cquest do you have an opinion on that (or can you share OSM experience on that ?)

[alexgarel]

On my side, I think option 1 is best for now.

Option 2 would:

• either require a huge rethinking of the code, the API and the database… so I don't see it as a good option.
• either require an upper layer of abstraction that encode the multiple value into one value, but would require you to reprovide all values, etc. which, I fear, would feel alien to current API.

For option 1, it should be well documented what the UI does. I think going for "," as a separator is better than ";" because it's more standard (for example it's permitted to represent parameters as list in OpenAPI).

Then you have either to deal with values containing "," or refuse them. If you deal with them, I strongly encourage using csv style (handling quote) as there are a lot of libs to deal with it and avoid silly bugs.

In my opinion, the UI should clearly handle lists (one input box per value) instead of trying to magically guess, which have the risk to lead to complicated cases (explicit is better than implicit).

Also don't try to handle more than lists, as dict, for example must be encoded in property name. (one could even argue that list could be encoded as my::value::1="value 1", my::value::2="value 2", etc., but it might be overcomplicated !)

We could even argue that list could be handled by property name: `

[alexgarel]

BTW, this also relates to #151