Validate single binding pair in let-like conditional macros

src/sci/impl/namespaces.cljc

@@ -174,10 +174,17 @@
           g
           (last steps)))))
 
+(defn- assert-single-binding-vector [expr macro-name bindings]
+  (when-not (vector? bindings)
+    (utils/throw-error-with-location (str macro-name " requires a vector for its binding") expr))
+  (when-not (= 2 (count bindings))
+    (utils/throw-error-with-location (str macro-name " requires exactly 2 forms in binding vector") expr)))
+
 (defn if-let*
   ([&form &env bindings then]
    (if-let* &form &env bindings then nil))
   ([&form _&env bindings then else & _oldform]
+   (assert-single-binding-vector &form "if-let" bindings)
    (let [form (bindings 0) tst (bindings 1)
          tmp (gensym "temp")]
      `(let [~tmp ~tst]
@@ -191,6 +198,7 @@
   ([&form &env bindings then]
    (if-some* &form &env bindings then nil))
   ([&form _&env bindings then else & _oldform]
+   (assert-single-binding-vector &form "if-some" bindings)
    (let [form (bindings 0) tst (bindings 1)
          tmp (gensym "temp")]
      `(let [~tmp ~tst]
@@ -203,6 +211,7 @@
 
 (defn when-let*
   [&form _&env bindings & body]
+  (assert-single-binding-vector &form "when-let" bindings)
   (let [form (bindings 0) tst (bindings 1)
         tmp (gensym "temp")]
     `(let [~tmp ~tst]
@@ -219,6 +228,7 @@
          ~@body))))
 
 (defn when-some* [&form _ bindings & body]
+  (assert-single-binding-vector &form "when-some" bindings)
   (let [form (bindings 0) tst (bindings 1)
         tmp (gensym "temp")]
     `(let [~tmp ~tst]

test/sci/core_test.cljc

@@ -1318,13 +1318,29 @@
   (is (= 2 (eval* "(if-let [foo nil] 1 2)")))
   (is (= 2 (eval* "(if-let [foo false] 1 2)")))
   (is (= 2 (eval* "(if-some [foo nil] 1 2)")))
-  (is (= 1 (eval* "(if-some [foo false] 1 2)"))))
+  (is (= 1 (eval* "(if-some [foo false] 1 2)")))
+  (is (thrown-with-msg?
+       #?(:clj Exception :cljs js/Error)
+       #"if-let requires exactly 2 forms in binding vector"
+       (eval* "(if-let [x (range 5) y (range 5)] x :else)")))
+  (is (thrown-with-msg?
+       #?(:clj Exception :cljs js/Error)
+       #"if-some requires exactly 2 forms in binding vector"
+       (eval* "(if-some [x (range 5) y (range 5)] x :else)"))))
 
 (deftest whens-test
   (is (= nil (eval* "(when-let [foo nil] 1)")))
   (is (= nil (eval* "(when-let [foo false] 1)")))
   (is (= nil (eval* "(when-some [foo nil] 1)")))
-  (is (= 1 (eval* "(when-some [foo false] 1)"))))
+  (is (= 1 (eval* "(when-some [foo false] 1)")))
+  (is (thrown-with-msg?
+       #?(:clj Exception :cljs js/Error)
+       #"when-let requires exactly 2 forms in binding vector"
+       (eval* "(when-let [x (range 5) y (range 5)] x)")))
+  (is (thrown-with-msg?
+       #?(:clj Exception :cljs js/Error)
+       #"when-some requires exactly 2 forms in binding vector"
+       (eval* "(when-some [x (range 5) y (range 5)] x)"))))
 
 (deftest read-string-eval-test
   (is (= 3 (eval* "(load-string \"1 2 3\")")))

test/sci/error_test.cljc

@@ -200,6 +200,21 @@
       (catch Exception e
         (is (= [line col] ((juxt :line :column) (ex-data e))) snippet)))))
 
+(deftest let-like-binding-arity-test
+  (doseq [[snippet expected-message]
+          [["(str (if-let [x 0 y 1] x))"     "if-let requires exactly 2 forms in binding vector"]
+           ["(str (when-let [x 0 y 1] x))"   "when-let requires exactly 2 forms in binding vector"]
+           ["(str (if-some [x 0 y 1] x))"    "if-some requires exactly 2 forms in binding vector"]
+           ["(str (when-some [x 0 y 1] x))"  "when-some requires exactly 2 forms in binding vector"]]]
+    (try
+      (sci.core/eval-string snippet)
+      (is false snippet)
+      (catch Exception e
+        (is (= expected-message #?(:clj (.getMessage e)
+                                   :cljs (.-message e)))
+            snippet)
+        (is (= [1 6] ((juxt :line :column) (ex-data e))) snippet)))))
+
 #?(:cljs
    (deftest js-interop-test
      (is (str/includes?