[WIP][REFERENCE] Relationships know limitations / edge cases

[pxpm]

• BelongsToMany/MorphToMany with pivot fields

  • ⚠️ need manual code and an ajax field to don't allow the selection of the same entry as pivot relation - fixed by [Pivot Relations] Pivot Selector should not allow to re-select the same. #4064
  • don't allow re-order of items, we can
    • (A) unsync and sync again everytime the entry is updated, might mess with id column in pivot, and/or timestamps
    • (B) create a way of repeatable storing the order in a defined developer column

• HasOne / MorphOne

  • unable to add nested belongsTo subfields by foreign_id (they work as relationName though)
  • relations with pivot cannot be chainned (I have a PR to fix this, will submit after the "regular scenarios" are working)
  • cannot delete data from HasOne input (see [Bug] Unable to save empty input with relation HasOne #3944)

• HasMany / MorphMany

  • after GRR Step 5 - HasMany and MorphMany (Granular Relationships Refactor) #4016, when using the repeatable field for these relationships, the up/down arrows will not show (repeatable will have reorder => false on it); we should add a new attribute & functionality to the repeatable field: order_input (default null); when order_field is not null, we assume there's an input inside the group that stores the order, with that name; so we take that into account in the JS, by
    • respecting that order at pageload;
    • updating those hidden inputs when the arrows are pressed, with the new order;

[tabacitu]

In addition to the quirks above, we also have the following things to do after #4054 (for reference, we have a breakdown of all relationships and their interfaces here).

TODOs:

• MUST merge [4.2] Clean up relationship directory - move partials to inc subdirectory & rename relationship_select and repeatable_relation #4062
• MUST rename - related issue [Discussion] rename pivotFields and fields into subfields #4065
  • pivotFields to subfields inside repeatable_relation (should also support pivotFields and fields just in case that's what the dev gave, though); fixed in Rename fields to subfields inside repeatable and relationship field types #4078
  • pivot_selector to pivotSelect inside relationship;
  • fields to subfields inside repeatable (should also support fields if that's what the user gave, though); fixed in Rename fields to subfields inside repeatable and relationship field types #4078
• MUST create relationship.entry field - shows a repeatable with one item for HasOne and MorphOne relationships, so that the admin can remove that secondary entry entirely from the table; - PR Add relationship.entry subfield for single HasOne/MorphOne #4066
• COULD create relationship.multiselect field - for MorphTo and MorphedByMany relationships, allows the admin to select multiple IDs from multiple tables; too complicated to do in 4.2; see relationship.multiselect field - for MorphTo and MorphedByMany relationships community-forum#124
• COULD show the hasOneThrough, hasOneThrough, morphOneThrough and morphManyThrough relationships in a disabled select (instead of aborting); but it only makes sense inside the Edit Operation; see relationship field - show disabled inputs for hasOneThrough, hasOneThrough, morphOneThrough and morphManyThrough community-forum#123

As of this moment, I think we should only do the quirks and the MUSTs. The other stuff can wait until 4.2.x, they will be non-breaking changes. Instead of aborting in those cases, it'll show a field.

[tabacitu]

@pxpm head's up, I just finished the docs for relationship on 4.2 and I've decided we're going to use subfields (not fields, not pivotFields). From now on, we're going to use subfields for both relationship and repeatable (but the code should still work if you give fields or pivotFields, as aliases). I've written more about this here - Laravel-Backpack/docs#303 if you want. Feel free to argue with me if you think this is a bad direction.

[tabacitu]

Update - I'm done refactoring and merging things inside relationship. The only thing left in order to close this issue and consider relationship finished is... fix the edge cases at the top of the issue. All yours @pxpm ! Let's tackle them one by one 💪

[tabacitu]

Fixed in #4095