Set :validate of any primitive: completion + list values in error

src/babashka/cli.cljc

@@ -479,7 +479,10 @@
              (when-not (if (set? f) (contains? f v) (f v))
                (let [ex-msg-fn (or (:ex-msg vf)
                                    (fn [{:keys [flag value]}]
-                                     (str "Invalid value for option " flag ": " value)))
+                                     (str "Invalid value for option " flag ": " value
+                                          (when (set? f)
+                                            (str ". Expected one of: "
+                                                 (str/join ", " (sort (map #(if (keyword? %) (kw->str %) (str %)) f))))))))
                      flag (get opt->flag k)]
                  (error-fn (cond-> {:cause :validate
                                     :msg (ex-msg-fn {:option k :value v :flag (flag-for k)})

test/babashka/cli/completion_test.cljc

@@ -223,6 +223,14 @@
     (is (= #{"a" "b"}
            (set (complete-options {:spec {:mode {:coerce :keyword :validate #{:a :b}}}}
                                   ["--mode" ""])))))
+  (testing "set-valued :validate auto-completes strings"
+    (is (= #{"production" "staging"}
+           (set (complete-options {:spec {:env {:validate #{"production" "staging"}}}}
+                                  ["--env" ""])))))
+  (testing "set-valued :validate auto-completes numbers"
+    (is (= #{"1" "2" "3"}
+           (set (complete-options {:spec {:n {:coerce :long :validate #{1 2 3}}}}
+                                  ["--n" ""])))))
   (testing ":complete-fn receives :to-complete and parsed :opts (dependent completion)"
     (let [spec {:from {:coerce :string :complete ["x" "y"]}
                 :to {:coerce :string

test/babashka/cli_test.cljc

@@ -671,6 +671,26 @@
       (is (str/includes? help "Custom"))
       (is (not (str/includes? help "Does a thing")))))))
 
+(deftest set-validate-test
+  (testing "a set :validate of strings validates, and lists the values on error"
+    (is (submap? {:env "staging"}
+                 (cli/parse-opts ["--env" "staging"]
+                                 {:spec {:env {:validate #{"production" "staging"}}}})))
+    (is (thrown-with-msg?
+         #?(:cljd Object :default Exception)
+         #"Invalid value for option --env: foo\. Expected one of: production, staging"
+         (cli/parse-opts ["--env" "foo"]
+                         {:spec {:env {:validate #{"production" "staging"}}}}))))
+  (testing "a set :validate of numbers (coerced) validates, and lists the values on error"
+    (is (submap? {:n 2}
+                 (cli/parse-opts ["--n" "2"]
+                                 {:spec {:n {:coerce :long :validate #{1 2 3}}}})))
+    (is (thrown-with-msg?
+         #?(:cljd Object :default Exception)
+         #"Invalid value for option --n: 5\. Expected one of: 1, 2, 3"
+         (cli/parse-opts ["--n" "5"]
+                         {:spec {:n {:coerce :long :validate #{1 2 3}}}})))))
+
 (defn- listed-command-names
   "Command names from the `Commands:` section of help/error output, in order."
   [s]