fix(engine): honor CR 702.16n protection Aura exemption (Flickering Ward #6499)

PR_6499.md

@@ -0,0 +1,26 @@
+Closes #6499
+
+## Summary
+
+Discord report: **Flickering Ward** could not stay attached after choosing a color.
+
+Oracle: `Enchanted creature has protection from the chosen color. This effect doesn't remove this Aura.`
+
+Choosing white (the Aura's color) grants protection from white. Without the CR 702.16n rider, SBA CR 704.5m / CR 702.16c puts the Aura in the graveyard — which matches the report.
+
+## Root cause
+
+Coverage claimed the protection grant was supported, but the parser deliberately dropped `"This effect doesn't remove this Aura"` as inert prose so the keyword would parse. The exemption was never modeled, so runtime treated the grant like ordinary protection.
+
+## Changes
+
+- **`ProtectionDoesNotRemove`** on `StaticDefinition` — `Source` / `Auras` / `ControlledAttachmentsAlreadyAttached` (CR 702.16n / 702.16p class).
+- **Parser** — recover the rider onto the continuous static (`parse_protection_does_not_remove`); still strip it from the keyword leg so `Protection(ChosenColor)` parses cleanly. Source matches both `"this Aura"` and post-normalization `~`.
+- **Runtime** — `attachment_illegality` walks continuous protection grants and honors per-grant exemptions (other protection instances still apply).
+- **Tests** — parse Source exemption; choose white → Aura stays attached; printed protection without rider still blocks.
+
+## Test Plan
+
+- [ ] `cargo fmt --all -- --check`
+- [ ] `cargo test -p engine --lib -- protection_chosen_color_drops_trailing_this_aura`
+- [ ] `cargo test -p engine --test integration -- flickering_ward`

crates/engine/src/ai_support/mod.rs

@@ -4809,6 +4809,7 @@ mod tests {
                 source_controller: None,
                 source_object: None,
                 bypass_beneficiary: None,
+                protection_does_not_remove: None,
             };
             obj.static_definitions = vec![def].into();
         }
@@ -4931,6 +4932,7 @@ mod tests {
                 source_controller: None,
                 source_object: None,
                 bypass_beneficiary: None,
+                protection_does_not_remove: None,
             };
             obj.static_definitions = vec![def].into();
         }

crates/engine/src/game/casting_tests.rs

@@ -3467,6 +3467,7 @@ fn granted_freerunning_static_surfaces_freerunning_variant() {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         };
         obj.static_definitions = vec![def].into();
     }
@@ -11960,6 +11961,7 @@ fn x_cost_max_accounts_for_granted_affinity_exceeding_fixed_generic() {
                 source_controller: None,
                 source_object: None,
                 bypass_beneficiary: None,
+                protection_does_not_remove: None,
             }]
             .into();
         }
@@ -14737,6 +14739,7 @@ fn witherbloom_grants_affinity_to_instant_and_sorcery_spells() {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         };
         obj.static_definitions = vec![def].into();
     }
@@ -14854,6 +14857,7 @@ fn add_witherbloom_affinity_source(state: &mut GameState, player: PlayerId) -> O
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         }]
         .into();
     }

crates/engine/src/game/coverage.rs

@@ -12178,6 +12178,7 @@ mod tests {
                     source_controller: None,
                     source_object: None,
                     bypass_beneficiary: None,
+                    protection_does_not_remove: None,
                 }],
                 duration: Some(Duration::UntilEndOfTurn),
                 target: None,
@@ -12225,6 +12226,7 @@ mod tests {
                     source_controller: None,
                     source_object: None,
                     bypass_beneficiary: None,
+                    protection_does_not_remove: None,
                 }],
                 duration: Some(Duration::UntilEndOfTurn),
                 target: None,
@@ -13360,6 +13362,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         assert!(audit_card_lines(oracle, &face).is_empty());
@@ -13394,6 +13397,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         assert!(audit_card_lines(oracle, &face).is_empty());
@@ -13426,6 +13430,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         let findings = audit_card_lines(oracle, &face);
@@ -13576,6 +13581,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         assert!(
@@ -13608,6 +13614,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         assert!(
@@ -13650,6 +13657,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         let gaps = card_face_gaps(&face);
@@ -13683,6 +13691,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         let gaps = card_face_gaps(&face);
@@ -13718,6 +13727,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         let gaps = card_face_gaps(&face);
@@ -13759,6 +13769,7 @@ mod tests {
                 source_controller: None,
                 source_object: None,
                 bypass_beneficiary: None,
+                protection_does_not_remove: None,
             });
         }
 
@@ -13927,6 +13938,7 @@ mod tests {
             source_controller: None,
             source_object: None,
             bypass_beneficiary: None,
+            protection_does_not_remove: None,
         });
 
         assert!(

crates/engine/src/game/dungeon.rs

@@ -864,6 +864,7 @@ pub fn room_effects(
                         source_controller: None,
                         source_object: None,
                         bypass_beneficiary: None,
+                        protection_does_not_remove: None,
                     }],
                     triggers: Vec::new(),
                 },