fix: Preserve tags on bulk edits (take 3) (#889)

* fix: handle tags separately from entryable_attributes in bulk updates

Tags use a join table (taggings) rather than a direct column, which means
empty tag_ids clears all tags rather than meaning "no change". This caused
bulk category-only edits to accidentally clear existing tags.

This fix:
- Removes tag_ids from entryable_attributes in Entry.bulk_update!
- Adds update_tags parameter to explicitly control tag updates
- Uses params.key?(:tag_ids) in controller to detect explicit tag changes
- Preserves existing tags when tag_ids is not provided in the request

This is a cleaner architectural solution compared to tracking "touched"
state in the frontend, as it properly acknowledges the semantic difference
between column attributes and join table associations.

https://claude.ai/code/session_014CsmTwjteP4qJs6YZqCKnY

* fix: handle tags separately in API transaction updates

Apply the same pattern to the API endpoint: tags are now handled
separately from entryable_attributes to distinguish between "not
provided" (preserve existing tags) and "explicitly set to empty"
(clear all tags).

This allows API consumers to:
- Update other fields without affecting tags (omit tag_ids)
- Clear all tags (send tag_ids: [])
- Set specific tags (send tag_ids: [id1, id2])

https://claude.ai/code/session_014CsmTwjteP4qJs6YZqCKnY

* Proposed fix

* fix: improve tag handling in bulk updates for transactions

* fix: allow bulk edit to clear/preserve tags by omitting hidden multi-select field

* PR comments

* Dumb copy/paste error

* Linter

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Juan José Mata <jjmata@jjmata.com>

app/controllers/api/v1/transactions_controller.rb

@@ -105,19 +105,29 @@ class Api::V1::TransactionsController < Api::V1::BaseController
 end
 
   def update
-    if @entry.update(entry_params_for_update)
-      @entry.sync_account_later
-      @entry.lock_saved_attributes!
-      @entry.transaction.lock_attr!(:tag_ids) if @entry.transaction.tags.any?
+    Entry.transaction do
+      if @entry.update(entry_params_for_update)
+        # Handle tags separately - only when explicitly provided in the request
+        # This allows clearing tags with tag_ids: [] while preserving tags when not specified
+        if tags_provided?
+          @entry.transaction.tag_ids = transaction_params[:tag_ids] || []
+          @entry.transaction.save!
+          @entry.transaction.lock_attr!(:tag_ids) if @entry.transaction.tags.any?
+        end
 
-      @transaction = @entry.transaction
-      render :show
-    else
-      render json: {
-        error: "validation_failed",
-        message: "Transaction could not be updated",
-        errors: @entry.errors.full_messages
-      }, status: :unprocessable_entity
+        @entry.sync_account_later
+        @entry.lock_saved_attributes!
+
+        @transaction = @entry.transaction
+        render :show
+      else
+        render json: {
+          error: "validation_failed",
+          message: "Transaction could not be updated",
+          errors: @entry.errors.full_messages
+        }, status: :unprocessable_entity
+        raise ActiveRecord::Rollback
+      end
     end
 
   rescue => e
@@ -283,8 +293,9 @@ end
         entryable_attributes: {
           id: @entry.entryable_id,
           category_id: transaction_params[:category_id],
-          merchant_id: transaction_params[:merchant_id],
-          tag_ids: transaction_params[:tag_ids]
+          merchant_id: transaction_params[:merchant_id]
+          # Note: tag_ids handled separately in update action to distinguish
+          # "not provided" from "explicitly set to empty"
         }.compact_blank
       }
 
@@ -296,6 +307,12 @@ end
       entry_params.compact
     end
 
+    # Check if tag_ids was explicitly provided in the request.
+    # This distinguishes between "user wants to update tags" vs "user didn't specify tags".
+    def tags_provided?
+      params[:transaction].key?(:tag_ids)
+    end
+
     def calculate_signed_amount
       amount = transaction_params[:amount].to_f
       nature = transaction_params[:nature]