Snak hash should be stable and PHP independent

[JeroenDeDauw]

Right now the hash of snaks is created as follows:

    public function getHash() {
        return sha1( serialize( $this ) );
    }

This lacks the following desired properties:

• stability over multiple versions of the DataModel component (renaming of a private field will cause the serialization to change)
• constructibility of the hash by users that do not use PHP (or the DataModel component)

[JeroenDeDauw]

@thiemowmde this seems like something you'd have fun with? :)

[thiemowmde]

the values changed between DM 0.8.x and 1.x already

Hm, so what to do? In my opinion the best solution is to recreate the old 0.x hashes. Or is this really not necessary and we can just implement something completely new?

[JeroenDeDauw]

recreate the old 0.x hashes.

This is not possible without relying on the class name... That really is an incentive to change it.

Or is this really not necessary and we can just implement something completely new?

I'm not aware of any reasons why it would need to remain the same. I've been fetching entities from the Wikidata API using the new deserialization code and DataModel 1.0@dev, and did not see any issues there. Can you think of a reason?

[frimelle]

https://phabricator.wikimedia.org/T78303