data, test: withResultOfAvailabilityCheck: index mode

2 files changed, 6 insertions, 1 deletions

diff --git a/src/data/composite/control-flow/inputAvailabilityCheckMode.js b/src/data/composite/control-flow/inputAvailabilityCheckMode.js
index d74a1149..8008fdeb 100644
--- a/src/data/composite/control-flow/inputAvailabilityCheckMode.js
+++ b/src/data/composite/control-flow/inputAvailabilityCheckMode.js
@@ -3,7 +3,7 @@ import {is} from '#validators';
 
 export default function inputAvailabilityCheckMode() {
   return input({
-    validate: is('null', 'empty', 'falsy'),
+    validate: is('null', 'empty', 'falsy', 'index'),
     defaultValue: 'null',
   });
 }
diff --git a/src/data/composite/control-flow/withResultOfAvailabilityCheck.js b/src/data/composite/control-flow/withResultOfAvailabilityCheck.js
index bcbd0b37..a6942014 100644
--- a/src/data/composite/control-flow/withResultOfAvailabilityCheck.js
+++ b/src/data/composite/control-flow/withResultOfAvailabilityCheck.js
@@ -10,6 +10,7 @@
 // * 'falsy': Check that the value isn't false when treated as a boolean
 //            (nor an empty array). Keep in mind this will also be false
 //            for values like zero and the empty string!
+// * 'index': Check that the value is a number, and is at least zero.
 //
 // See also:
 //  - exitWithoutDependency
@@ -57,6 +58,10 @@ export default templateCompositeFrom({
           case 'falsy':
             availability = !!value && (!Array.isArray(value) || !empty(value));
             break;
+
+          case 'index':
+            availability = typeof value === 'number' && value >= 0;
+            break;
         }
 
         return continuation({'#availability': availability});