datalog: dl-magic-query handles mixed EDB+IDB relations (225/225)

Bug: dl-magic-query was skipping EDB facts for relations that had
rules ("rule-headed"). When a single relation has both EDB facts
and rules deriving more (mixed EDB+IDB), the rewritten run would
miss the EDB portion entirely, producing too few or zero results.

Fix: copy ALL existing facts to the internal mdb regardless of
whether the relation has rules. EDB-only relations bring their
tuples; mixed relations bring both EDB and any pre-saturated IDB
(which the rewritten rules would re-derive anyway).

1 new test: link relation seeded with 3 EDB tuples plus a
recursive rule via via/2. dl-magic-query rooted at `a` returns
2 results (a→b direct, a→c via via(a,e), link(e,c)).

lib/datalog/magic.sx

@@ -397,15 +397,18 @@
                 (mdb (dl-make-db))
                 (rule-heads (dl-magic-rule-heads rules)))
           (do
-            ;; Copy EDB facts (relations not headed by any caller rule).
+            ;; Copy ALL existing facts. EDB-only relations bring their
+            ;; tuples; mixed EDB+IDB relations bring both their EDB
+            ;; portion and any pre-saturated IDB tuples (which the
+            ;; rewritten rules would re-derive anyway). Skipping facts
+            ;; for rule-headed relations would leave the magic run
+            ;; without the EDB portion of mixed relations.
             (for-each
               (fn
                 (rel)
-                (when
-                  (not (dl-member-string? rel rule-heads))
-                  (for-each
-                    (fn (t) (dl-add-fact! mdb t))
-                    (dl-rel-tuples db rel))))
+                (for-each
+                  (fn (t) (dl-add-fact! mdb t))
+                  (dl-rel-tuples db rel)))
               (keys (get db :facts)))
             ;; Seed + rewritten rules.
             (dl-add-fact! mdb (get rewritten :seed))

lib/datalog/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "datalog",
-  "total_passed": 224,
+  "total_passed": 225,
   "total_failed": 0,
-  "total": 224,
+  "total": 225,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
@@ -13,8 +13,8 @@
     {"name":"negation","passed":10,"failed":0,"total":10},
     {"name":"aggregates","passed":19,"failed":0,"total":19},
     {"name":"api","passed":20,"failed":0,"total":20},
-    {"name":"magic","passed":24,"failed":0,"total":24},
+    {"name":"magic","passed":25,"failed":0,"total":25},
     {"name":"demo","passed":21,"failed":0,"total":21}
   ],
-  "generated": "2026-05-08T10:36:02+00:00"
+  "generated": "2026-05-08T10:40:13+00:00"
 }

lib/datalog/scoreboard.md

@@ -1,6 +1,6 @@
 # datalog scoreboard
 
-**224 / 224 passing** (0 failure(s)).
+**225 / 225 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -13,5 +13,5 @@
 | negation | 10 | 10 | ok |
 | aggregates | 19 | 19 | ok |
 | api | 20 | 20 | ok |
-| magic | 24 | 24 | ok |
+| magic | 25 | 25 | ok |
 | demo | 21 | 21 | ok |

lib/datalog/tests/magic.sx

@@ -197,6 +197,19 @@
         6)
 
       ;; dl-magic-query: end-to-end driver, doesn't mutate caller's db.
+      ;; Mixed EDB + IDB: a relation can be both EDB-seeded and
+      ;; rule-derived. dl-magic-query must include the EDB portion
+      ;; even though the relation has rules.
+      (dl-mt-test! "magic mixed EDB+IDB"
+        (len
+          (dl-magic-query
+            (dl-program
+              "link(a, b). link(c, d). link(e, c).
+               via(a, e).
+               link(X, Y) :- via(X, M), link(M, Y).")
+            (list (quote link) (quote a) (quote X))))
+        2)
+
       ;; dl-magic-query falls back to dl-query for built-in,
       ;; aggregate, and negation goals (the magic seed would
       ;; otherwise be non-ground).