From 02e0e19e927d87f45c86458995f6b14ce9280341 Mon Sep 17 00:00:00 2001
From: gemshrine <113778529+gemshrine@users.noreply.github.com>
Date: Sat, 3 Oct 2026 10:23:14 +0300
Subject: [PATCH] #977: Reject empty if_absent keys

---
 lib/fbe/if_absent.rb       |  4 +++-
 test/fbe/test_if_absent.rb | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/lib/fbe/if_absent.rb b/lib/fbe/if_absent.rb
index 0141b000..b60e84f4 100644
--- a/lib/fbe/if_absent.rb
+++ b/lib/fbe/if_absent.rb
@@ -65,7 +65,9 @@ def Fbe.if_absent(fb: Fbe.fb, always: false)
       end
     end
   yield(f)
-  q = attrs.except(:_id, :_time, :_version).map do |k, v|
+  matching = attrs.except(:_id, :_time, :_version)
+  raise(Fbe::Error, 'At least one non-system attribute is required by if_absent') if matching.empty?
+  q = matching.map do |k, v|
     raise(Fbe::Error, "Can't match #{k} by an array, only by one value") if v.is_a?(Array)
     vv = v.to_s
     if v.is_a?(String)
diff --git a/test/fbe/test_if_absent.rb b/test/fbe/test_if_absent.rb
index 08654c2a..916dafba 100644
--- a/test/fbe/test_if_absent.rb
+++ b/test/fbe/test_if_absent.rb
@@ -49,6 +49,25 @@ def test_ignores
     assert_nil(n)
   end
 
+  def test_raises_when_block_sets_no_attributes
+    fb = Factbase.new
+    fb.insert.foo = 'unrelated'
+    error = assert_raises(Fbe::Error) do
+      Fbe.if_absent(fb:) { |_fact| }
+    end
+    assert_equal('At least one non-system attribute is required by if_absent', error.message)
+    assert_equal(1, fb.size)
+  end
+
+  def test_raises_when_only_system_attributes_are_set
+    fb = Factbase.new
+    error = assert_raises(Fbe::Error) do
+      Fbe.if_absent(fb:) { |fact| fact._id = 42 }
+    end
+    assert_equal('At least one non-system attribute is required by if_absent', error.message)
+    assert_equal(0, fb.size)
+  end
+
   def test_raises_on_empty_value
     assert_raises(StandardError) do
       Fbe.if_absent(fb: Factbase.new) do |f|