[Fixes #70] Ignore missing columns in diff and past versions

lib/logidze/model.rb

@@ -132,7 +132,7 @@ def diff_from(ts = nil, version: nil, time: nil)
       time = parse_time(time) if time
       changes = log_data.diff_from(time: time, version: version).tap do |v|
         deserialize_changes!(v)
-      end
+      end.delete_if { |k, _v| deleted_column?(k) }
 
       { "id" => id, "changes" => changes }
     end
@@ -203,6 +203,7 @@ def apply_diff(version, diff)
     end
 
     def apply_column_diff(column, value)
+      return if deleted_column?(column)
       write_attribute column, deserialize_value(column, value)
     end
 
@@ -225,6 +226,10 @@ def deserialize_value(column, value)
       end
     end
 
+    def deleted_column?(column)
+      !@attributes.key?(column)
+    end
+
     def deserialize_changes!(diff)
       diff.each do |k, v|
         v["old"] = deserialize_value(k, v["old"])

spec/logidze/model_spec.rb

@@ -286,7 +286,7 @@
     end
   end
 
-  describe "Versioned associations" do
+  context "Versioned associations" do
     before(:all) { Logidze.associations_versioning = true }
 
     let(:user) do
@@ -447,7 +447,7 @@
     end
   end
 
-  describe "Serialized types" do
+  context "Serialized types" do
     let(:user) do
       User.create!(
         name: 'test',
@@ -495,4 +495,43 @@
       end
     end
   end
+
+  context "Schema changes" do
+    let(:user) do
+      User.create!(
+        name: 'test',
+        log_data: {
+          'v' => 3,
+          'h' =>
+            [
+              { 'v' => 1, 'ts' => time(100), 'c' => { 'age' => nil } },
+              { 'v' => 2, 'ts' => time(120), 'c' => { 'age' => 1, 'last_name' => 'Harry' } },
+              { 'v' => 3, 'ts' => time(200), 'c' => { 'name' => 'Harry', 'age' => 10 } }
+            ]
+        }
+      )
+    end
+
+    describe "#at" do
+      it "returns version at specified time", :aggregate_failures do
+        user_old = user.at(time: time(150))
+        expect(user_old.name).to eq 'test'
+        expect(user_old.age).to eq 1
+      end
+    end
+
+    describe "#diff_from" do
+      it "returns diff from specified time" do
+        expect(user.diff_from(version: 1))
+          .to eq(
+            "id" => user.id,
+            "changes" =>
+              {
+                "age" => { "old" => nil, "new" => 10 },
+                "name" => { "old" => nil, "new" => "Harry" }
+              }
+          )
+      end
+    end
+  end
 end