Prototype causal rewriting with a syntax DAG

test_syntax_dag.py

@@ -0,0 +1,54 @@
+import unittest
+from dataclasses import replace
+from graphlib import CycleError
+
+from syntax_dag import Decoder, Edge, Encoder, Proposal
+
+
+class SyntaxDAGTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.encoder = Encoder()
+        cls.decoder = Decoder()
+
+    def test_round_trip(self):
+        for text in ("", "  \t", "  It rained.\n\nThe road flooded.  "):
+            with self.subTest(text=text):
+                graph = self.encoder.encode(text)
+                self.assertEqual(self.decoder.decode(graph), text)
+                self.assertFalse(graph.proposals)
+
+    def test_causal_commit(self):
+        text = "The road flooded because it rained.  They waited."
+        graph = self.encoder.encode(text)
+        proposal, = graph.proposals
+        self.assertTrue(any(
+            len({edge.source for edge in graph.edges if edge.target == node}) > 1
+            for node in range(len(graph.tokens))
+        ))
+        committed = graph.commit(proposal)
+        self.assertEqual(self.decoder.decode(graph), text)
+        self.assertEqual(
+            self.decoder.decode(committed),
+            "Cause: it rained. Effect: The road flooded.  They waited.",
+        )
+        self.assertEqual(committed.history, (proposal,))
+        self.assertIs(committed.commit(proposal), committed)
+        self.assertNotIn(proposal.edge, graph.edges)
+
+    def test_cycle_rejects_entire_commit(self):
+        graph = self.encoder.encode("The road flooded because it rained.")
+        original, = graph.proposals
+        reverse = Proposal(Edge(original.edge.target, original.edge.source, "causes"),
+                           original.marker, "test")
+        committed = replace(graph.commit(original), proposals=(original, reverse))
+        with self.assertRaises(CycleError):
+            committed.commit(reverse)
+        self.assertEqual(committed.history, (original,))
+        self.assertNotIn(reverse.edge, committed.edges)
+
+    def test_negation_and_questions_are_left_alone(self):
+        for text in ("The road did not flood because it rained.",
+                     "Did the road flood because it rained?"):
+            with self.subTest(text=text):
+                self.assertFalse(self.encoder.encode(text).proposals)