From 0af412019526f679f7e5d690c0598d24d714956c Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Sun, 2 Jan 2022 00:23:07 +0530
Subject: kolam: Allow null value for types.

* kolam/graphql.scm (correct-type?): Allow null values for all types
except non-nullable types.
---
 kolam/graphql.scm | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kolam/graphql.scm b/kolam/graphql.scm
index 59cc34f..0440f74 100644
--- a/kolam/graphql.scm
+++ b/kolam/graphql.scm
@@ -119,17 +119,19 @@
   "Return non-#f if VALUE is of GraphQL TYPE. Else, return #f."
   (cond
    ((scalar-type? type)
-    ((scalar-type-predicate type) value))
+    (or (eq? value 'null)
+        ((scalar-type-predicate type) value)))
    ((enum-type? type)
     (member value
-            (enum-type-enumerators type)))
+            (cons 'null (enum-type-enumerators type))))
    ((non-nullable-type? type)
     (and (not (eq? value 'null))
          (correct-type? value (non-nullable-type-subtype type))))
    ((list-type? type)
-    (and (list? value)
-         (every (cut correct-type? <> (list-type-subtype type))
-                value)))
+    (or (eq? value 'null)
+        (and (list? value)
+             (every (cut correct-type? <> (list-type-subtype type))
+                    value))))
    ((object-type? type) #t)
    (else (error "Unknown type:" type))))
 
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