test

lib/fbe/overwrite.rb

@@ -42,7 +42,7 @@ def Fbe.overwrite(fact, property, value, fb: Fbe.fb)
   fact.all_properties.each do |prop|
     before[prop.to_s] = fact[prop]
   end
-  id = fact['_id'].first
+  id = fact['_id']&.first
   raise 'There is no _id in the fact, cannot use Fbe.overwrite' if id.nil?
   raise "No facts by _id = #{id}" if fb.query("(eq _id #{id})").delete!.zero?
   n = fb.insert

test/fbe/test_overwrite.rb

@@ -54,6 +54,14 @@ def test_simple_insert
     assert_equal(42, fb.query('(always)').each.to_a.first['foo'].first)
   end
 
+  def test_without_id
+    fb = Factbase.new
+    f = fb.insert
+    assert_raises do
+      Fbe.overwrite(f, :foo, 42, fb:)
+    end
+  end
+
   def test_safe_insert
     fb = Factbase.new
     f1 = fb.insert