Detect changed Check constraint expressions in migrations

crates/oxyde-migrate/src/diff.rs

@@ -316,6 +316,31 @@ pub fn compute_diff(old: &Snapshot, new: &Snapshot) -> Result<Vec<MigrationOp>>
                 }
             }
 
+            // Find dropped and changed check constraints
+            for old_check in &old_table.checks {
+                match new_table.checks.iter().find(|c| c.name == old_check.name) {
+                    Some(new_check) if new_check.expression != old_check.expression => {
+                        ops.push(MigrationOp::DropCheck {
+                            table: name.clone(),
+                            name: old_check.name.clone(),
+                            check_def: Some(old_check.clone()),
+                        });
+                        ops.push(MigrationOp::AddCheck {
+                            table: name.clone(),
+                            check: new_check.clone(),
+                        });
+                    }
+                    None => {
+                        ops.push(MigrationOp::DropCheck {
+                            table: name.clone(),
+                            name: old_check.name.clone(),
+                            check_def: Some(old_check.clone()),
+                        });
+                    }
+                    _ => {}
+                }
+            }
+
             // Find added check constraints
             for new_check in &new_table.checks {
                 if !old_table.checks.iter().any(|c| c.name == new_check.name) {
@@ -325,17 +350,6 @@ pub fn compute_diff(old: &Snapshot, new: &Snapshot) -> Result<Vec<MigrationOp>>
                     });
                 }
             }
-
-            // Find dropped check constraints
-            for old_check in &old_table.checks {
-                if !new_table.checks.iter().any(|c| c.name == old_check.name) {
-                    ops.push(MigrationOp::DropCheck {
-                        table: name.clone(),
-                        name: old_check.name.clone(),
-                        check_def: Some(old_check.clone()),
-                    });
-                }
-            }
         }
     }
 

crates/oxyde-migrate/tests/migration_tests.rs

@@ -65,6 +65,50 @@ fn test_snapshot_serialization_roundtrip() {
     assert_eq!(snapshot, deserialized);
 }
 
+#[test]
+fn test_check_constraint_expression_change_generates_drop_and_add() {
+    let mut old = Snapshot::new();
+    let mut old_table = sample_table();
+    old_table.checks.push(CheckDef {
+        name: "age_positive".into(),
+        expression: "age >= 0".into(),
+    });
+    old.add_table(old_table);
+
+    let mut new = Snapshot::new();
+    let mut new_table = sample_table();
+    new_table.checks.push(CheckDef {
+        name: "age_positive".into(),
+        expression: "age > 0".into(),
+    });
+    new.add_table(new_table);
+
+    let ops = compute_diff(&old, &new).unwrap();
+    assert_eq!(ops.len(), 2);
+
+    match &ops[0] {
+        MigrationOp::DropCheck {
+            table,
+            name,
+            check_def,
+        } => {
+            assert_eq!(table, "users");
+            assert_eq!(name, "age_positive");
+            assert_eq!(check_def.as_ref().unwrap().expression, "age >= 0");
+        }
+        op => panic!("expected DropCheck, got {:?}", op),
+    }
+
+    match &ops[1] {
+        MigrationOp::AddCheck { table, check } => {
+            assert_eq!(table, "users");
+            assert_eq!(check.name, "age_positive");
+            assert_eq!(check.expression, "age > 0");
+        }
+        op => panic!("expected AddCheck, got {:?}", op),
+    }
+}
+
 #[test]
 fn test_migration_create_table_generates_sql() {
     let sql = MigrationOp::CreateTable {

python/oxyde/tests/unit/test_migrations_execution.py

@@ -909,6 +909,27 @@ def test_roundtrip_add_check(self, dialect):
         assert any(op["type"] == "add_check" for op in json.loads(ops_json))
         migration_to_sql(ops_json, dialect)
 
+    @pytest.mark.parametrize("dialect", NON_SQLITE)
+    def test_roundtrip_change_check_expression(self, dialect):
+        old = _base_snapshot()
+        old["tables"]["users"]["checks"].append(
+            {"name": "chk_users_age", "expression": "age >= 0"}
+        )
+        new = _base_snapshot()
+        new["tables"]["users"]["checks"].append(
+            {"name": "chk_users_age", "expression": "age > 0"}
+        )
+
+        ops_json = migration_compute_diff(json.dumps(old), json.dumps(new))
+        ops = json.loads(ops_json)
+
+        assert [op["type"] for op in ops] == ["drop_check", "add_check"]
+        assert ops[0]["name"] == "chk_users_age"
+        assert ops[0]["check_def"]["expression"] == "age >= 0"
+        assert ops[1]["check"]["name"] == "chk_users_age"
+        assert ops[1]["check"]["expression"] == "age > 0"
+        migration_to_sql(ops_json, dialect)
+
     @pytest.mark.parametrize("dialect", NON_SQLITE)
     def test_roundtrip_drop_check(self, dialect):
         old = _base_snapshot()