1 files changed, 56 insertions, 0 deletions
diff --git a/src/data/composite/data/withPropertyFromList.js b/src/data/composite/data/withPropertyFromList.js
new file mode 100644
index 0000000..3ce05fd
--- /dev/null
+++ b/src/data/composite/data/withPropertyFromList.js
@@ -0,0 +1,56 @@
+// 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.
+//
+// See also:
+//  - withPropertiesFromList
+//  - withPropertyFromObject
+//
+// More list utilities:
+//  - excludeFromList
+//  - fillMissingListItems
+//  - withFlattenedList
+//  - withUnflattenedList
+//
+
+import {empty} from '#sugar';
+
+// todo: OUHHH THIS ONE'S NOT UPDATED YET LOL
+export default function({
+  list,
+  property,
+  into = null,
+}) {
+  into ??=
+    (list.startsWith('#')
+      ? `${list}.${property}`
+      : `#${list}.${property}`);
+
+  return {
+    annotation: `withPropertyFromList`,
+    flags: {expose: true, compose: true},
+
+    expose: {
+      mapDependencies: {list},
+      mapContinuation: {into},
+      options: {property},
+
+      compute(continuation, {list, '#options': {property}}) {
+        if (list === undefined || empty(list)) {
+          return continuation({into: []});
+        }
+
+        return continuation({
+          into:
+            list.map(item =>
+              (item === null || item === undefined
+                ? null
+                : item[property] ?? null)),
+        });
+      },
+    },
+  };
+}