#620: raise Fbe::Error when a fact lacks the fid property in kill_if

lib/fbe/kill_if.rb

@@ -10,14 +10,18 @@
 #
 # @param [Array] facts List of facts to kill
 # @param [Factbase] fb The factbase to use (defaults to Fbe.fb)
+# @param [String] fid The name of the property that holds the ID (defaults to '_id')
+# @raise [Fbe::Error] If a fact does not have the +fid+ property
 def Fbe.kill_if(facts, fb: Fbe.fb, fid: '_id')
   ids = []
   facts.each do |f|
     if block_given?
       t = yield(f)
       next unless t
     end
-    ids << f[fid].first
+    id = f[fid]&.first
+    raise(Fbe::Error, "There is no #{fid} in the fact, cannot use Fbe.kill_if") if id.nil?
+    ids << id
   end
   return 0 if ids.empty?
   fb.query("(or #{ids.map { |id| "(eq #{fid} #{id})" }.join(' ')})").delete!

test/fbe/test_kill_if.rb

@@ -59,4 +59,13 @@ def test_returns_zero_when_block_rejects_all
     assert_equal(0, Fbe.kill_if(fb.query('(always)').each.to_a, fb:) { false })
     assert_equal(2, fb.size)
   end
+
+  def test_raises_when_fact_lacks_the_id_property
+    fb = Factbase.new
+    f = fb.insert
+    f.foo = 42
+    assert_raises(Fbe::Error) do
+      Fbe.kill_if([f], fb:)
+    end
+  end
 end