core: Error when 'then' 2nd form not 'else'

core/src/yamlscript/transformers.clj

@@ -54,11 +54,13 @@
      rhs (if (> (count (:pairs v1)) 2)
            (update-in rhs [:pairs 0] (fn [_] (Sym 'do)))
            (update-in rhs [:pairs 0] (fn [_] (Sym '=>))))]
-    (if (and (> (count pairs) 2) (= k2 (Sym 'else)))
-      (if (> (count (:pairs v2)) 2)
-        [lhs (update-in rhs [:pairs 2] (fn [_] (Sym 'do)))]
-        [lhs (update-in rhs [:pairs 2] (fn [_] (Sym '=>)))])
-      [lhs rhs])))
+    (if (> (count pairs) 2)
+      (if (= k2 (Sym 'else))
+        (if (> (count (:pairs v2)) 2)
+          [lhs (update-in rhs [:pairs 2] (fn [_] (Sym 'do)))]
+          [lhs (update-in rhs [:pairs 2] (fn [_] (Sym '=>)))])
+        (die "Form after 'then' must be 'else'"))
+        [lhs rhs])))
 
 ;;-----------------------------------------------------------------------------
 ;; require

core/test/transformer.yaml

@@ -135,3 +135,15 @@
         e: f
   clojure: |
     (if (= x 1) (a b) (do (c d) (e f)))
+
+
+- name: Error when using then and not else
+  yamlscript: |
+    !yamlscript/v0
+    if (x = 1):
+      then: a(b)
+      =>:
+        c: d
+        e: f
+  error: |
+    Form after 'then' must be 'else'

core/test/yamlscript/transformer_test.clj

@@ -29,3 +29,21 @@
            (-> test
              :transform
              edn/read-string))})
+
+(test/load-yaml-test-files
+  ["test/transformer.yaml"]
+  {:add-tests true
+   :pick #(test/has-keys? [:yamlscript :error] %1)
+   :test (fn [test]
+           (try
+             (-> test
+               :yamlscript
+               parser/parse
+               composer/compose
+               resolver/resolve
+               builder/build
+               transformer/transform)
+             ""
+             (catch Exception e
+               (:cause (Throwable->map e)))))
+   :want :error})