1 files changed, 94 insertions, 0 deletions
diff --git a/src/data/composite/data/withPropertyFromList.js b/src/data/composite/data/withPropertyFromList.js
new file mode 100644
index 00000000..760095c2
--- /dev/null
+++ b/src/data/composite/data/withPropertyFromList.js
@@ -0,0 +1,94 @@
+// Gets a property from each of a list of objects (in a dependency) and
+// provides the results.
+//
+// This doesn't alter any list indices, so positions which were null in the
+// original list are kept null here. Objects which don't have the specified
+// property are retained in-place as null.
+//
+// If the `internal` input is true, this reads the CacheableObject update value
+// of each object rather than its exposed value.
+//
+// See also:
+//  - withPropertiesFromList
+//  - withPropertyFromObject
+//
+
+import CacheableObject from '#cacheable-object';
+import {input, templateCompositeFrom} from '#composite';
+
+function getOutputName({list, property, prefix}) {
+  if (!property) return `#values`;
+  if (prefix) return `${prefix}.${property}`;
+  if (list) return `${list}.${property}`;
+  return `#list.${property}`;
+}
+
+export default templateCompositeFrom({
+  annotation: `withPropertyFromList`,
+
+  inputs: {
+    list: input({type: 'array'}),
+    property: input({type: 'string'}),
+    prefix: input.staticValue({type: 'string', defaultValue: null}),
+    internal: input({type: 'boolean', defaultValue: false}),
+  },
+
+  outputs: ({
+    [input.staticDependency('list')]: list,
+    [input.staticValue('property')]: property,
+    [input.staticValue('prefix')]: prefix,
+  }) =>
+    [getOutputName({list, property, prefix})],
+
+  steps: () => [
+    {
+      dependencies: [
+        input('list'),
+        input('property'),
+        input('internal'),
+      ],
+
+      compute: (continuation, {
+        [input('list')]: list,
+        [input('property')]: property,
+        [input('internal')]: internal,
+      }) => continuation({
+        ['#values']:
+          list.map(item =>
+            (item === null
+              ? null
+           : internal
+              ? CacheableObject.getUpdateValue(item, property)
+                  ?? null
+              : item[property]
+                  ?? null)),
+      }),
+    },
+
+    {
+      dependencies: [
+        input.staticDependency('list'),
+        input.staticValue('property'),
+        input.staticValue('prefix'),
+      ],
+
+      compute: (continuation, {
+        [input.staticDependency('list')]: list,
+        [input.staticValue('property')]: property,
+        [input.staticValue('prefix')]: prefix,
+      }) => continuation({
+        ['#outputName']:
+          getOutputName({list, property, prefix}),
+      }),
+    },
+
+    {
+      dependencies: ['#values', '#outputName'],
+      compute: (continuation, {
+        ['#values']: values,
+        ['#outputName']: outputName,
+      }) =>
+        continuation.raiseOutput({[outputName]: values}),
+    },
+  ],
+});