mod: Ext 18 — ergonomic defrule / ruleset surface, 375/375

mod/defrule collects trailing conditions via &rest; mod/ruleset assembles rules.
No macro needed — conditions are plain data, fn supports &rest here. Produces
structurally identical rules to mk-rule (asserted) and works in the engine
unchanged. Closes the roadmap's original defrule surface. +11 tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/mod/conformance.conf

@@ -12,6 +12,7 @@ PRELOADS=(
   lib/prolog/compiler.sx
   lib/mod/schema.sx
   lib/mod/policy.sx
+  lib/mod/defrule.sx
   lib/mod/engine.sx
   lib/mod/explain.sx
   lib/mod/severity.sx
@@ -53,4 +54,5 @@ SUITES=(
   "disjunction:lib/mod/tests/disjunction.sx:(mod-disjunction-tests-run!)"
   "activity:lib/mod/tests/activity.sx:(mod-activity-tests-run!)"
   "policies:lib/mod/tests/policies.sx:(mod-policies-tests-run!)"
+  "defrule:lib/mod/tests/defrule.sx:(mod-defrule-tests-run!)"
 )

lib/mod/defrule.sx

@@ -0,0 +1,16 @@
+;; lib/mod/defrule.sx — ergonomic rule / ruleset construction.
+;;
+;; The roadmap sketched a (defrule action :when conditions) surface. Conditions
+;; already evaluate to plain data, so this needs no macro — variadic functions
+;; suffice: mod/defrule collects its trailing condition forms via &rest (dropping
+;; the explicit outer (list ...)), and mod/ruleset assembles rules the same way.
+;;
+;;   (mod/ruleset
+;;     (mod/defrule "spam-hide" :hide (list :classification "spam"))
+;;     (mod/defrule "default-keep" :keep))
+
+(define
+  mod/defrule
+  (fn (name action &rest conds) (mod/mk-rule name action conds)))
+
+(define mod/ruleset (fn (&rest rules) rules))

lib/mod/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "mod",
-  "total_passed": 364,
+  "total_passed": 375,
   "total_failed": 0,
-  "total": 364,
+  "total": 375,
   "suites": [
     {"name":"decide","passed":31,"failed":0,"total":31},
     {"name":"audit","passed":29,"failed":0,"total":29},
@@ -22,7 +22,8 @@
     {"name":"wire","passed":16,"failed":0,"total":16},
     {"name":"disjunction","passed":10,"failed":0,"total":10},
     {"name":"activity","passed":17,"failed":0,"total":17},
-    {"name":"policies","passed":14,"failed":0,"total":14}
+    {"name":"policies","passed":14,"failed":0,"total":14},
+    {"name":"defrule","passed":11,"failed":0,"total":11}
   ],
-  "generated": "2026-06-06T19:32:52+00:00"
+  "generated": "2026-06-06T19:36:45+00:00"
 }

lib/mod/scoreboard.md

@@ -1,6 +1,6 @@
 # mod scoreboard
 
-**364 / 364 passing** (0 failure(s)).
+**375 / 375 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -23,3 +23,4 @@
 | disjunction | 10 | 10 | ok |
 | activity | 17 | 17 | ok |
 | policies | 14 | 14 | ok |
+| defrule | 11 | 11 | ok |

lib/mod/tests/defrule.sx

@@ -0,0 +1,95 @@
+;; lib/mod/tests/defrule.sx — Ext 18: ergonomic defrule / ruleset.
+
+(define mod-dr-count 0)
+(define mod-dr-pass 0)
+(define mod-dr-fail 0)
+(define mod-dr-failures (list))
+
+(define
+  mod-dr-test!
+  (fn
+    (name got expected)
+    (begin
+      (set! mod-dr-count (+ mod-dr-count 1))
+      (if
+        (= got expected)
+        (set! mod-dr-pass (+ mod-dr-pass 1))
+        (begin
+          (set! mod-dr-fail (+ mod-dr-fail 1))
+          (append!
+            mod-dr-failures
+            (str name "\n    expected: " expected "\n    got:      " got)))))))
+
+;; ── defrule produces the same structure as mk-rule ──
+
+(define
+  mod-dr-r
+  (mod/defrule "spam-hide" :hide (list :classification "spam")))
+(mod-dr-test! "defrule name" (mod/rule-name mod-dr-r) "spam-hide")
+(mod-dr-test! "defrule action" (mod/rule-action mod-dr-r) "hide")
+(mod-dr-test!
+  "defrule when wraps the conditions"
+  (mod/rule-when mod-dr-r)
+  (list (list :classification "spam")))
+(mod-dr-test!
+  "defrule equals mk-rule equivalent"
+  (mod/rule-when mod-dr-r)
+  (mod/rule-when
+    (mod/mk-rule "spam-hide" :hide (list (list :classification "spam")))))
+
+;; ── multi-condition + no-condition ──
+
+(define
+  mod-dr-multi
+  (mod/defrule
+    "strict"
+    :hide (list :classification "spam")
+    (list :not (list :attr "verified"))))
+(mod-dr-test!
+  "defrule collects multiple conditions"
+  (len (mod/rule-when mod-dr-multi))
+  2)
+
+(define mod-dr-catch (mod/defrule "default-keep" :keep))
+(mod-dr-test!
+  "defrule with no conditions is unconditional"
+  (mod/rule-when mod-dr-catch)
+  (list))
+
+;; ── ruleset assembles a list ──
+
+(define
+  mod-dr-rules
+  (mod/ruleset
+    (mod/defrule "spam-hide" :hide (list :classification "spam"))
+    (mod/defrule "default-keep" :keep)))
+
+(mod-dr-test! "ruleset length" (len mod-dr-rules) 2)
+(mod-dr-test!
+  "ruleset first rule name"
+  (mod/rule-name (first mod-dr-rules))
+  "spam-hide")
+
+;; ── engine works with defrule/ruleset-built policy ──
+
+(define mod-dr-spam (mod/mk-report "r1" "a" "b" "this is spam"))
+(define mod-dr-clean (mod/mk-report "r2" "a" "b" "a fine post"))
+
+(mod-dr-test!
+  "defrule policy: spam → hide"
+  (get
+    (mod/decide-report mod-dr-spam (list mod-dr-spam) mod-dr-rules)
+    :action)
+  "hide")
+(mod-dr-test!
+  "defrule policy: clean → keep"
+  (get
+    (mod/decide-report mod-dr-clean (list mod-dr-clean) mod-dr-rules)
+    :action)
+  "keep")
+(mod-dr-test!
+  "defrule policy: spam names the rule"
+  (get (mod/decide-report mod-dr-spam (list mod-dr-spam) mod-dr-rules) :rule)
+  "spam-hide")
+
+(define mod-defrule-tests-run! (fn () {:failures mod-dr-failures :total mod-dr-count :passed mod-dr-pass :failed mod-dr-fail}))