Add deprecation warning to where_object_changes

See discussion at https://github.com/airblade/paper_trail/issues/803

CHANGELOG.md

@@ -11,6 +11,8 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Added
 
+- [#803](https://github.com/airblade/paper_trail/issues/803)
+  Deprecate `where_object_changes` when reading json from a text column
 - [#976](https://github.com/airblade/paper_trail/pull/976)
   `PaperTrail.whodunnit` accepts a `Proc`
 

lib/paper_trail/serializers/json.rb

@@ -4,6 +4,13 @@ module PaperTrail
   module Serializers
     # An alternate serializer for, e.g. `versions.object`.
     module JSON
+      E_WHERE_OBJ_CHANGES = <<-STR.squish.freeze
+        where_object_changes has a known issue. When reading json from a text
+        column, it may return more records than expected. Instead of a warning,
+        this method may raise an error in the future. Please join the discussion
+        at https://github.com/airblade/paper_trail/issues/803
+      STR
+
       extend self # makes all instance methods become module methods as well
 
       def load(string)
@@ -35,6 +42,8 @@ module PaperTrail
       # Returns a SQL LIKE condition to be used to match the given field and
       # value in the serialized `object_changes`.
       def where_object_changes_condition(arel_field, field, value)
+        ::ActiveSupport::Deprecation.warn(E_WHERE_OBJ_CHANGES)
+
         # Convert to JSON to handle strings and nulls correctly.
         json_value = value.to_json
 

spec/models/version_spec.rb

@@ -225,8 +225,6 @@ module PaperTrail
             end
 
             context "YAML serializer" do
-              specify { expect(PaperTrail.serializer).to be PaperTrail::Serializers::YAML }
-
               it "locates versions according to their `object_changes` contents" do
                 expect(
                   widget.versions.where_object_changes(name: name)
@@ -248,7 +246,13 @@ module PaperTrail
 
             context "JSON serializer" do
               before(:all) { PaperTrail.serializer = PaperTrail::Serializers::JSON }
-              specify { expect(PaperTrail.serializer).to be PaperTrail::Serializers::JSON }
+              before do
+                unless override
+                  expect(::ActiveSupport::Deprecation).to(
+                    receive(:warn).at_least(:once).with(/^where_object_changes/)
+                  )
+                end
+              end
 
               it "locates versions according to their `object_changes` contents" do
                 expect(