feat(drift): add devops-drift-set for state checks

devops-drift.el

@@ -294,4 +294,41 @@ the buffer."
       (tabulated-list-print))
     (pop-to-buffer buf)))
 
+;;; State checks
+
+(defun devops-drift--set-lines (value)
+  "Normalize VALUE to a list of trimmed, non-empty lines.
+VALUE is a string (split on newlines) or a possibly nested list, the
+two shapes org-babel passes for :var references to blocks and tables."
+  (cond
+   ((stringp value)
+    (seq-remove #'string-empty-p
+                (mapcar #'string-trim (split-string value "\n"))))
+   ((listp value) (mapcan #'devops-drift--set-lines value))
+   (t (list (string-trim (format "%s" value))))))
+
+;;;###autoload
+(defun devops-drift-set (actual expected)
+  "Compare ACTUAL and EXPECTED as unordered sets of lines.
+Each argument is a string or a list, as org-babel passes :var values;
+lines are trimmed and blanks dropped.  Return \"ok (N lines)\" when the
+sets match, otherwise a DRIFT report listing expected lines missing
+from ACTUAL and extra lines not in EXPECTED.  Meant for state-check
+blocks that compare live command output against a declared expectation:
+
+  #+begin_src elisp :var actual=live-cmd() expected=expected-block
+  (devops-drift-set actual expected)
+  #+end_src"
+  (let* ((actual (devops-drift--set-lines actual))
+         (expected (devops-drift--set-lines expected))
+         (missing (seq-difference expected actual))
+         (extra (seq-difference actual expected)))
+    (if (not (or missing extra))
+        (format "ok (%d lines)" (length expected))
+      (string-join
+       (cons "DRIFT"
+             (nconc (mapcar (lambda (l) (concat "missing: " l)) missing)
+                    (mapcar (lambda (l) (concat "extra: " l)) extra)))
+       "\n"))))
+
 (provide 'devops-drift)

devops-test.el

@@ -752,6 +752,40 @@ afterwards), in an org buffer visiting the formatted text."
         (kill-buffer report)
         (should-not (file-directory-p root))))))
 
+;;; State-check set comparison (devops-drift.el)
+
+(ert-deftest devops-drift-set-match-test ()
+  "Matching line sets report ok, ignoring order, blanks and whitespace."
+  (should (equal (devops-drift-set "b.service\na.service\n"
+                                   "  a.service  \n\nb.service")
+                 "ok (2 lines)")))
+
+(ert-deftest devops-drift-set-drift-test ()
+  "Missing and extra lines are each reported."
+  (should (equal (devops-drift-set "a.service\nc.service"
+                                   "a.service\nb.service")
+                 "DRIFT\nmissing: b.service\nextra: c.service")))
+
+(ert-deftest devops-drift-set-table-input-test ()
+  "Org table :var values (nested lists) normalize like strings."
+  (should (equal (devops-drift-set '(("a.service") ("b.service"))
+                                   "a.service\nb.service")
+                 "ok (2 lines)")))
+
+(ert-deftest devops-drift-set-org-block-test ()
+  "An elisp check block compares a named block against a named example."
+  (devops-test--with-org
+      (concat "#+name: actual\n"
+              "#+begin_src emacs-lisp\n\"a.service\\nb.service\\n\"\n#+end_src\n\n"
+              "#+name: expected\n"
+              "#+begin_example\na.service\nb.service\n#+end_example\n\n"
+              "#+begin_src emacs-lisp :var a=actual() e=expected\n"
+              "(devops-drift-set a e)\n#+end_src\n")
+    (goto-char (point-max))
+    (re-search-backward ":var a=actual")
+    (let ((org-confirm-babel-evaluate nil))
+      (should (equal (org-babel-execute-src-block) "ok (2 lines)")))))
+
 ;;; devops-lob (README: per-project tools.org)
 
 (defvar devops-test--tools-org