kolam: Support field alias.

* kolam/graphql.scm (tree->root+alias+args+children): New function.
(eval-graphql): Call tree->root+alias+args+children and use the
returned alias in the response.

1 files changed, 13 insertions, 6 deletions

diff --git a/kolam/graphql.scm b/kolam/graphql.scm
index 676caa4..c8cc706 100644
--- a/kolam/graphql.scm
+++ b/kolam/graphql.scm
@@ -139,12 +139,19 @@
      (eval-graphql tree (schema-query schema)))
     (operation (error "Invalid GraphQL operation:" operation))))
 
+(define (tree->root+alias+args+children tree)
+  (let ((root children (match tree
+                         ((root children ...) (values root children))
+                         (leaf (values leaf #f)))))
+    (match root
+      (#((? symbol? root) (? symbol? alias) args ...)
+       (values root alias args children))
+      (#((? symbol? root) args ...)
+       (values root #f args children))
+      (root (values root #f '() children)))))
+
 (define* (eval-graphql tree parent-type #:optional parent)
-  (let* ((root args children (match tree
-                               ((#(root args ...) children ...) (values root args children))
-                               ((root children ...) (values root '() children))
-                               (#(leaf args ...) (values leaf args #f))
-                               (leaf (values leaf '() #f))))
+  (let* ((root alias args children (tree->root+alias+args+children tree))
          ;; TODO: Check if required args are present.
          (root-field (or (find-field parent-type root)
                          (error "Unknown field:" root)))
@@ -161,7 +168,7 @@
                (not (or (scalar-type? underlying-type)
                         (enum-type? underlying-type))))
       (error "Leaf node must be scalar or enum type:" root-field underlying-type))
-    (cons root
+    (cons (or alias root)
           (cond
            ((eq? next-parent 'null) 'null)
            ;; List of non-object types