mod: Ext 1 — negation-as-failure conditions (:not / :attr), 146/146

Report attributes (:attrs) project to attr(Id, name) facts; policy gains (:attr x)
and (:not <cond>) conditions. The Prolog substrate exposes negation as a functor
not(Goal) (the prefix \+ operator doesn't parse here). Closed-world example:
hide spam unless author verified. Default policy untouched — feature proven via
custom rule sets, so all 132 base tests stay green. +14 extension tests.

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

lib/mod/tests/extensions.sx

@@ -0,0 +1,153 @@
+;; lib/mod/tests/extensions.sx — beyond-roadmap extensions.
+;;
+;; Ext 1: negation-as-failure conditions (:not / :attr) + report attributes.
+;; These exercise closed-world reasoning: "hide spam UNLESS the author is
+;; verified". Demonstrated with custom rule sets so the default policy (and its
+;; 132 conformance tests) stays untouched.
+
+(define mod-ext-count 0)
+(define mod-ext-pass 0)
+(define mod-ext-fail 0)
+(define mod-ext-failures (list))
+
+(define
+  mod-ext-test!
+  (fn
+    (name got expected)
+    (begin
+      (set! mod-ext-count (+ mod-ext-count 1))
+      (if
+        (= got expected)
+        (set! mod-ext-pass (+ mod-ext-pass 1))
+        (begin
+          (set! mod-ext-fail (+ mod-ext-fail 1))
+          (append!
+            mod-ext-failures
+            (str name "\n    expected: " expected "\n    got:      " got)))))))
+
+;; ── report attributes ──
+
+(define mod-ext-r0 (mod/mk-report "r1" "a" "b" "this is spam"))
+(mod-ext-test!
+  "fresh report has no attrs"
+  (len (mod/report-attrs mod-ext-r0))
+  0)
+(define mod-ext-rv (mod/attach-attr mod-ext-r0 "verified"))
+(mod-ext-test!
+  "attach-attr adds one attr"
+  (len (mod/report-attrs mod-ext-rv))
+  1)
+(mod-ext-test!
+  "attach-attr preserves evidence field"
+  (len
+    (mod/report-evidence
+      (mod/attach-evidence mod-ext-rv (mod/mk-evidence "x" "y"))))
+  1)
+(mod-ext-test!
+  "attach-evidence preserves attrs"
+  (len
+    (mod/report-attrs
+      (mod/attach-evidence mod-ext-rv (mod/mk-evidence "x" "y"))))
+  1)
+
+;; ── negation-as-failure: spam hidden unless author verified ──
+
+(define
+  mod-ext-rules
+  (list
+    (mod/mk-rule
+      "spam-unverified-hide"
+      :hide (list
+        (list :classification "spam")
+        (list :not (list :attr "verified"))))
+    (mod/mk-rule "default-keep" :keep (list))))
+
+(define mod-ext-spam-plain (mod/mk-report "p1" "a" "b" "this is spam"))
+(define
+  mod-ext-spam-verified
+  (mod/attach-attr (mod/mk-report "p2" "a" "b" "this is spam") "verified"))
+(define mod-ext-clean (mod/mk-report "p3" "a" "b" "a fine post"))
+
+(mod-ext-test!
+  "unverified spam → hide"
+  (get
+    (mod/decide-report
+      mod-ext-spam-plain
+      (list mod-ext-spam-plain)
+      mod-ext-rules)
+    :action)
+  "hide")
+(mod-ext-test!
+  "verified author spam → keep (negation blocks)"
+  (get
+    (mod/decide-report
+      mod-ext-spam-verified
+      (list mod-ext-spam-verified)
+      mod-ext-rules)
+    :action)
+  "keep")
+(mod-ext-test!
+  "clean post → keep"
+  (get
+    (mod/decide-report mod-ext-clean (list mod-ext-clean) mod-ext-rules)
+    :action)
+  "keep")
+
+;; ── negation appears in the goal text + proof ──
+
+(define
+  mod-ext-dec
+  (mod/decide-report
+    mod-ext-spam-plain
+    (list mod-ext-spam-plain)
+    mod-ext-rules))
+(define mod-ext-goals (get (get mod-ext-dec :proof) :goals))
+
+(mod-ext-test!
+  "rule that matched is spam-unverified-hide"
+  (get mod-ext-dec :rule)
+  "spam-unverified-hide")
+(mod-ext-test! "proof has two goals" (len mod-ext-goals) 2)
+(mod-ext-test!
+  "negation goal text"
+  (get (nth mod-ext-goals 1) :goal)
+  "not(attr(p1, verified))")
+(mod-ext-test!
+  "negation goal solved for unverified"
+  (get (nth mod-ext-goals 1) :solved)
+  true)
+
+;; ── cond->goal compiles :attr and :not directly ──
+
+(mod-ext-test!
+  "cond->goal :attr"
+  (mod/cond->goal (list :attr "verified") "Id")
+  "attr(Id, verified)")
+(mod-ext-test!
+  "cond->goal :not wraps inner"
+  (mod/cond->goal (list :not (list :classification "spam")) "Id")
+  "not(classification(Id, spam))")
+
+;; ── positive :attr condition (allowlist-style) ──
+
+(define
+  mod-ext-allow-rules
+  (list
+    (mod/mk-rule "trusted-keep" :keep (list (list :attr "trusted")))
+    (mod/mk-rule "spam-hide" :hide (list (list :classification "spam")))
+    (mod/mk-rule "default-keep" :keep (list))))
+
+(define
+  mod-ext-trusted-spam
+  (mod/attach-attr (mod/mk-report "t1" "a" "b" "this is spam") "trusted"))
+(mod-ext-test!
+  "trusted attr exempts spam → keep"
+  (get
+    (mod/decide-report
+      mod-ext-trusted-spam
+      (list mod-ext-trusted-spam)
+      mod-ext-allow-rules)
+    :action)
+  "keep")
+
+(define mod-extensions-tests-run! (fn () {:failures mod-ext-failures :total mod-ext-count :passed mod-ext-pass :failed mod-ext-fail}))