Refuse Fbe.delete_one when several facts share the id

lib/fbe/delete_one.rb

@@ -18,6 +18,7 @@
 # @param [Factbase] fb The factbase to use (defaults to Fbe.fb)
 # @param [String] id The property name used as unique identifier (defaults to '_id')
 # @return [nil] Nothing
+# @raise [Fbe::Error] If fact is nil, has no ID, or shares its ID with another fact
 def Fbe.delete_one(fact, prop, value, fb: Fbe.fb, id: '_id')
   raise(Fbe::Error, 'The fact is nil') if fact.nil?
   prop = prop.to_s
@@ -28,15 +29,15 @@ def Fbe.delete_one(fact, prop, value, fb: Fbe.fb, id: '_id')
   fact.all_properties.each do |k|
     before[k] = fact[k]
   end
-  return unless before[prop]
-  nv = before[prop].dup
-  at = nv.index(value)
+  at = before.fetch(prop, []).index(value)
   return if at.nil?
+  nv = before[prop].dup
   nv.delete_at(at)
   before[prop] = nv
   before.delete(prop) if nv.empty?
   fb.txn do |fbt|
-    fbt.query("(eq #{id} #{i})").delete!
+    deleted = fbt.query("(eq #{id} #{i})").delete!
+    raise(Fbe::Error, "#{deleted} facts share #{id} = #{i}, cannot delete one of them") if deleted > 1
     c = fbt.insert
     f = c
     while f.instance_variable_defined?(:@fact) || f.instance_variable_defined?(:@origin)

test/fbe/test_delete_one.rb

@@ -105,4 +105,39 @@ def test_preserves_system_props_on_decorated_fb
     assert_equal(snapshot[:job], after._job)
     assert_equal([22], after['bar'])
   end
+
+  def test_rejects_facts_sharing_the_id
+    seed = Random.new_seed
+    rnd = Random.new(seed)
+    fb = Factbase.new
+    id = rnd.rand(1..1000)
+    tags = Array.new(2) { |i| "t\u00e4g-#{i}-#{rnd.rand(1000)}" }
+    facts =
+      tags.map do |t|
+        f = fb.insert
+        f._id = id
+        f.tag = t
+        f
+      end
+    assert_raises(Fbe::Error, "delete_one destroyed every fact with _id #{id}, seed #{seed}") do
+      Fbe.delete_one(facts.first, 'tag', tags.first, fb:)
+    end
+  end
+
+  def test_rejects_facts_sharing_a_custom_id
+    seed = Random.new_seed
+    rnd = Random.new(seed)
+    fb = Factbase.new
+    key = rnd.rand(1..1000)
+    facts =
+      Array.new(rnd.rand(2..5)) do |i|
+        f = fb.insert
+        f.key = key
+        f.k = i
+        f
+      end
+    assert_raises(Fbe::Error, "delete_one destroyed #{facts.size} facts with key #{key}, seed #{seed}") do
+      Fbe.delete_one(facts.last, 'k', facts.size - 1, fb:, id: 'key')
+    end
+  end
 end