mod: Ext 5 — policy rule-set lint (unreachable/catch-all/dups), 190/190

Static analysis of a policy without running the engine: mod/unreachable-rules
flags rules after an unconditional rule (dead under first-match precedence),
mod/has-catchall? checks total coverage, mod/duplicate-rule-names + mod/rules-ok?
give a well-formedness verdict policy authors can assert. Own suite. +14 tests.

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

lib/mod/tests/lint.sx

@@ -0,0 +1,122 @@
+;; lib/mod/tests/lint.sx — Ext 5: policy rule-set static analysis.
+
+(define mod-lint-count 0)
+(define mod-lint-pass 0)
+(define mod-lint-fail 0)
+(define mod-lint-failures (list))
+
+(define
+  mod-lint-test!
+  (fn
+    (name got expected)
+    (begin
+      (set! mod-lint-count (+ mod-lint-count 1))
+      (if
+        (= got expected)
+        (set! mod-lint-pass (+ mod-lint-pass 1))
+        (begin
+          (set! mod-lint-fail (+ mod-lint-fail 1))
+          (append!
+            mod-lint-failures
+            (str name "\n    expected: " expected "\n    got:      " got)))))))
+
+;; ── the default rule set is well-formed ──
+
+(mod-lint-test!
+  "default rules: no unreachable"
+  (mod/unreachable-rules mod/default-rules)
+  (list))
+(mod-lint-test!
+  "default rules: has catch-all"
+  (mod/has-catchall? mod/default-rules)
+  true)
+(mod-lint-test!
+  "default rules: no duplicate names"
+  (mod/duplicate-rule-names mod/default-rules)
+  (list))
+(mod-lint-test!
+  "default rules: well-formed"
+  (mod/rules-ok? mod/default-rules)
+  true)
+
+;; ── unreachable detection ──
+
+(define
+  mod-lint-shadowed
+  (list
+    (mod/mk-rule "spam-hide" :hide (list (list :classification "spam")))
+    (mod/mk-rule "catch-all" :keep (list))
+    (mod/mk-rule
+      "abuse-remove"
+      :remove (list (list :classification "abuse")))
+    (mod/mk-rule
+      "repeated"
+      :escalate (list (list :count-at-least 3)))))
+
+(mod-lint-test!
+  "rules after catch-all are unreachable"
+  (mod/unreachable-rules mod-lint-shadowed)
+  (list "abuse-remove" "repeated"))
+(mod-lint-test!
+  "shadowed rule set is not ok"
+  (mod/rules-ok? mod-lint-shadowed)
+  false)
+
+;; ── missing catch-all ──
+
+(define
+  mod-lint-nocatch
+  (list
+    (mod/mk-rule "spam-hide" :hide (list (list :classification "spam")))
+    (mod/mk-rule
+      "abuse-remove"
+      :remove (list (list :classification "abuse")))))
+
+(mod-lint-test!
+  "no catch-all detected"
+  (mod/has-catchall? mod-lint-nocatch)
+  false)
+(mod-lint-test!
+  "no unreachable when no catch-all"
+  (mod/unreachable-rules mod-lint-nocatch)
+  (list))
+(mod-lint-test!
+  "no-catch-all rule set is not ok"
+  (mod/rules-ok? mod-lint-nocatch)
+  false)
+
+;; ── duplicate names ──
+
+(define
+  mod-lint-dups
+  (list
+    (mod/mk-rule "x" :hide (list (list :classification "spam")))
+    (mod/mk-rule "x" :remove (list (list :classification "abuse")))
+    (mod/mk-rule "default" :keep (list))))
+
+(mod-lint-test!
+  "duplicate names detected"
+  (mod/duplicate-rule-names mod-lint-dups)
+  (list "x"))
+(mod-lint-test!
+  "duplicate-name rule set is not ok"
+  (mod/rules-ok? mod-lint-dups)
+  false)
+
+;; ── helpers ──
+
+(mod-lint-test!
+  "rule-unconditional? true for empty when"
+  (mod/rule-unconditional? (mod/mk-rule "d" :keep (list)))
+  true)
+(mod-lint-test!
+  "rule-unconditional? false with conditions"
+  (mod/rule-unconditional?
+    (mod/mk-rule "s" :hide (list (list :classification "spam"))))
+  false)
+(mod-lint-test!
+  "count-eq counts occurrences"
+  (mod/count-eq "a" (list "a" "b" "a"))
+  2)
+
+(define mod-lint-tests-run! (fn () {:failures mod-lint-failures :total mod-lint-count :passed mod-lint-pass :failed mod-lint-fail}))