data, test: withResultOfAvailabilityCheck: index mode

3 files changed, 33 insertions, 6 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});
diff --git a/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js b/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js
index 4c4be04a..2bcabb4f 100644
--- a/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js
+++ b/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js
@@ -38,7 +38,7 @@ const quickThrows = (t, {from, mode}) =>
   t.throws(() => composite.expose.compute({from, mode}));
 
 t.test(`withResultOfAvailabilityCheck: mode = null`, t => {
-  t.plan(10);
+  t.plan(11);
 
   quickCompare(t, true,  {mode: 'null', from: 'truthy string'});
   quickCompare(t, true,  {mode: 'null', from: 123});
@@ -46,6 +46,7 @@ t.test(`withResultOfAvailabilityCheck: mode = null`, t => {
 
   quickCompare(t, true,  {mode: 'null', from: ''});
   quickCompare(t, true,  {mode: 'null', from: 0});
+  quickCompare(t, true,  {mode: 'null', from: -1});
   quickCompare(t, true,  {mode: 'null', from: false});
 
   quickCompare(t, true,  {mode: 'null', from: [1, 2, 3]});
@@ -56,7 +57,7 @@ t.test(`withResultOfAvailabilityCheck: mode = null`, t => {
 });
 
 t.test(`withResultOfAvailabilityCheck: mode = empty`, t => {
-  t.plan(10);
+  t.plan(11);
 
   quickThrows(t, {mode: 'empty', from: 'truthy string'});
   quickThrows(t, {mode: 'empty', from: 123});
@@ -64,6 +65,7 @@ t.test(`withResultOfAvailabilityCheck: mode = empty`, t => {
 
   quickThrows(t, {mode: 'empty', from: ''});
   quickThrows(t, {mode: 'empty', from: 0});
+  quickThrows(t, {mode: 'empty', from: -1});
   quickThrows(t, {mode: 'empty', from: false});
 
   quickCompare(t, true,  {mode: 'empty', from: [1, 2, 3]});
@@ -74,7 +76,7 @@ t.test(`withResultOfAvailabilityCheck: mode = empty`, t => {
 });
 
 t.test(`withResultOfAvailabilityCheck: mode = falsy`, t => {
-  t.plan(10);
+  t.plan(11);
 
   quickCompare(t, true,  {mode: 'falsy', from: 'truthy string'});
   quickCompare(t, true,  {mode: 'falsy', from: 123});
@@ -82,6 +84,7 @@ t.test(`withResultOfAvailabilityCheck: mode = falsy`, t => {
 
   quickCompare(t, false, {mode: 'falsy', from: ''});
   quickCompare(t, false, {mode: 'falsy', from: 0});
+  quickCompare(t, true,  {mode: 'falsy', from: -1});
   quickCompare(t, false, {mode: 'falsy', from: false});
 
   quickCompare(t, true,  {mode: 'falsy', from: [1, 2, 3]});
@@ -91,6 +94,25 @@ t.test(`withResultOfAvailabilityCheck: mode = falsy`, t => {
   quickCompare(t, false, {mode: 'falsy', from: undefined});
 });
 
+t.test(`withResultOfAvailabilityCheck: mode = index`, t => {
+  t.plan(11);
+
+  quickCompare(t, false, {mode: 'index', from: 'truthy string'});
+  quickCompare(t, true,  {mode: 'index', from: 123});
+  quickCompare(t, false, {mode: 'index', from: true});
+
+  quickCompare(t, false, {mode: 'index', from: ''});
+  quickCompare(t, true,  {mode: 'index', from: 0});
+  quickCompare(t, false, {mode: 'index', from: -1});
+  quickCompare(t, false, {mode: 'index', from: false});
+
+  quickCompare(t, false, {mode: 'index', from: [1, 2, 3]});
+  quickCompare(t, false, {mode: 'index', from: []});
+
+  quickCompare(t, false, {mode: 'index', from: null});
+  quickCompare(t, false, {mode: 'index', from: undefined});
+});
+
 t.test(`withResultOfAvailabilityCheck: default mode`, t => {
   t.plan(1);
 
@@ -133,7 +155,7 @@ t.test(`withResultOfAvailabilityCheck: validate static inputs`, t => {
       mode: input.value('invalid'),
     }),
     {message: `Errors in input options passed to withResultOfAvailabilityCheck`, errors: [
-      {message: `mode: Expected one of null empty falsy, got invalid`},
+      {message: `mode: Expected one of null empty falsy index, got invalid`},
     ]});
 
   t.throws(() =>
@@ -157,7 +179,7 @@ t.test(`withResultOfAvailabilityCheck: validate dynamic inputs`, t => {
     {message: `Error computing composition`, cause:
       {message: `Error computing composition withResultOfAvailabilityCheck`, cause:
         {message: `Errors in input values provided to withResultOfAvailabilityCheck`, errors: [
-          {message: `mode: Expected one of null empty falsy, got banana`},
+          {message: `mode: Expected one of null empty falsy index, got banana`},
         ]}}});
 
   t.throws(