Introduce ActiveStorage::Attached::{One,Many}#detach

activestorage/lib/active_storage/attached/many.rb

@@ -13,7 +13,6 @@ def attachments
     end
 
     # Associates one or several attachments with the current record, saving them to the database.
-    # Examples:
     #
     #   document.images.attach(params[:images]) # Array of ActionDispatch::Http::UploadedFile objects
     #   document.images.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
@@ -36,6 +35,11 @@ def attached?
       attachments.any?
     end
 
+    # Deletes associated attachments without purging them, leaving their respective blobs in place.
+    def detach
+      attachments.destroy_all if attached?
+    end
+
     # Directly purges each associated attachment (i.e. destroys the blobs and
     # attachments and deletes the files on the service).
     def purge

activestorage/lib/active_storage/attached/one.rb

@@ -14,7 +14,6 @@ def attachment
     end
 
     # Associates a given attachment with the current record, saving it to the database.
-    # Examples:
     #
     #   person.avatar.attach(params[:avatar]) # ActionDispatch::Http::UploadedFile object
     #   person.avatar.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
@@ -39,6 +38,14 @@ def attached?
       attachment.present?
     end
 
+    # Deletes the attachment without purging it, leaving its blob in place.
+    def detach
+      if attached?
+        attachment.destroy
+        write_attachment nil
+      end
+    end
+
     # Directly purges the attachment (i.e. destroys the blob and
     # attachment and deletes the file on the service).
     def purge
@@ -59,16 +66,12 @@ def purge_later
       def replace(attachable)
         blob.tap do
           transaction do
-            destroy_attachment
+            detach
             write_attachment create_attachment_from(attachable)
           end
         end.purge_later
       end
 
-      def destroy_attachment
-        attachment.destroy
-      end
-
       def create_attachment_from(attachable)
         ActiveStorage::Attachment.create!(record: record, name: name, blob: create_blob_from(attachable))
       end

activestorage/test/models/attachments_test.rb

@@ -98,6 +98,17 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "bar", blob.reload.metadata[:foo]
   end
 
+  test "detach blob" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+    avatar_blob_id = @user.avatar.blob.id
+    avatar_key = @user.avatar.key
+
+    @user.avatar.detach
+    assert_not @user.avatar.attached?
+    assert ActiveStorage::Blob.exists?(avatar_blob_id)
+    assert ActiveStorage::Blob.service.exist?(avatar_key)
+  end
+
   test "purge attached blob" do
     @user.avatar.attach create_blob(filename: "funky.jpg")
     avatar_key = @user.avatar.key
@@ -218,6 +229,21 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     end
   end
 
+  test "detach blobs" do
+    @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
+    highlight_blob_ids = @user.highlights.collect { |highlight| highlight.blob.id }
+    highlight_keys = @user.highlights.collect(&:key)
+
+    @user.highlights.detach
+    assert_not @user.highlights.attached?
+
+    assert ActiveStorage::Blob.exists?(highlight_blob_ids.first)
+    assert ActiveStorage::Blob.exists?(highlight_blob_ids.second)
+
+    assert ActiveStorage::Blob.service.exist?(highlight_keys.first)
+    assert ActiveStorage::Blob.service.exist?(highlight_keys.second)
+  end
+
   test "purge attached blobs" do
     @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
     highlight_keys = @user.highlights.collect(&:key)