MAS-WP-0005-T09: generator destination transforms with round-trip refusal; example profiles

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 252470@bnt-lap001
Assistant-Session: ad628c8f-4be2-4979-94c9-76c7ed6f8241

tests/test_destination.py

@@ -0,0 +1,78 @@
+"""v0.2 destination transforms (spec v0.2 section 12.1)."""
+import pytest
+
+from mas_conformance import statute_document
+from mas_core.generator import DESTINATION_PROFILES, CannotExpress, for_destination
+from mas_core.statute import build_statute
+
+
+def statute(resource=True, interaction=True, id_case="insensitive", version="0.2"):
+    doc = statute_document("valid-great-service.json")
+    doc["mas_version"] = version
+    if version == "0.2":
+        doc["alternate_syntax"] = {"resource": resource, "interaction": interaction}
+        doc["equivalence"]["resource_id_case"] = id_case
+    return build_statute(doc, "great-service.example")
+
+
+V2 = statute()
+IONOS = DESTINATION_PROFILES["ionos-forward"]
+
+
+def test_canonical_when_nothing_is_needed():
+    r = for_destination("ticket=GS-1+comments", V2, ())
+    assert (r.local_part, r.applied) == ("ticket=GS-1+comments", ())
+
+
+def test_ionos_forward_profile():
+    # the MAS-WP-0003 case: IONOS refuses '=' and forces lower case
+    r = for_destination("ticket=GS-85QJ8WC09P+comments", V2, IONOS)
+    assert r.local_part == "ticket--gs-85qj8wc09p+comments"
+    assert r.applied == ("resource-alternate", "lowercase")
+
+
+def test_transforms_apply_only_where_they_change_something():
+    assert for_destination("support", V2, IONOS).applied == ()
+    assert for_destination("ticket=gs-1", V2, IONOS).applied == ("resource-alternate",)
+
+
+def test_interaction_alternate():
+    assert for_destination("ticket!callback", V2, ("interaction-alternate",)).local_part == "ticket---callback"
+
+
+@pytest.mark.parametrize("st, code", [
+    (statute(resource=False), "transform-not-permitted"),     # no '--' switch
+    (statute(version="0.1"), "transform-not-permitted"),      # v0.1 statute
+    (statute(id_case="exact"), "would-be-misread"),           # lower-casing changes the id
+])
+def test_refuses_what_the_namespace_would_misread(st, code):
+    with pytest.raises(CannotExpress) as e:
+        for_destination("ticket=GS-1", st, IONOS)
+    assert e.value.code == code
+
+
+def test_refuses_id_containing_equals():
+    with pytest.raises(CannotExpress) as e:
+        for_destination("ticket=RE=2026-4711", V2, ("resource-alternate",))
+    assert e.value.code == "cannot-express"
+
+
+def test_refuses_case_change_in_facet():
+    with pytest.raises(CannotExpress) as e:
+        for_destination("ticket=gs-1+Comments", V2, ("lowercase",))
+    assert e.value.code == "would-be-misread"
+
+
+def test_length_is_checked_after_transforms():
+    lp = "ticket=" + "a" * 57          # 64 octets canonical, 65 with '--'
+    assert len(lp) == 64
+    with pytest.raises(CannotExpress) as e:
+        for_destination(lp, V2, ("resource-alternate",))
+    assert e.value.code == "too-long"
+
+
+def test_lossy_transforms_need_explicit_permission():
+    with pytest.raises(CannotExpress):
+        for_destination("ticket=gs-1+comments", V2, ("drop-facet",))
+    r = for_destination("ticket!callback", V2, ("drop-interaction",), allow_lossy=True)
+    assert r.local_part == "ticket" and r.warnings