data: withReverse{Reference,Contribution}List: better exiting

An existing test for withAlbum (which is semi-newly based on
withUniqueReferencingThing, and thus withReverseReferenceList)
indicates that if we just can't *find* the album in a provided
data array, that's not an exit condition. This commit adapts
withReverseReferencingList to respect that when the data list
is empty.

(Treating an empty array as the same thing as an array that
 isn't provided at all - the existing behavior - is really just
 a bug!)

1 files changed, 9 insertions, 1 deletions

diff --git a/src/data/composite/wiki-data/withReverseReferenceList.js b/src/data/composite/wiki-data/withReverseReferenceList.js
index 2d7a421..8cd540a 100644
--- a/src/data/composite/wiki-data/withReverseReferenceList.js
+++ b/src/data/composite/wiki-data/withReverseReferenceList.js
@@ -13,7 +13,8 @@
 
 import {input, templateCompositeFrom} from '#composite';
 
-import {exitWithoutDependency} from '#composite/control-flow';
+import {exitWithoutDependency, raiseOutputWithoutDependency}
+  from '#composite/control-flow';
 
 import inputWikiData from './inputWikiData.js';
 
@@ -34,10 +35,17 @@ export default templateCompositeFrom({
   outputs: ['#reverseReferenceList'],
 
   steps: () => [
+    // Early exit with an empty array if the data list isn't available.
     exitWithoutDependency({
       dependency: input('data'),
       value: input.value([]),
+    }),
+
+    // Raise an empty array (don't early exit) if the data list is empty.
+    raiseOutputWithoutDependency({
+      dependency: input('data'),
       mode: input.value('empty'),
+      output: input.value({'#reverseReferenceList': []}),
     }),
 
     {