Support not-present relationships

src/components/documents/DocumentView.tsx

@@ -30,6 +30,9 @@ export function DocumentView({
     if (v.type === "ready") {
       return v.value.secondary.length.toString();
     }
+    if (v.type === "empty") {
+      return "0";
+    }
     return "...";
   });
 

src/context/document/reducer.ts

@@ -1,14 +1,15 @@
-import _ from "lodash";
+import { relationshipsForDocument } from "@/lib/relationships";
 import type { AnyDocument, DocumentId, Relationship } from "@/lib/types";
+import _ from "lodash";
 import type { DocumentAction } from "./actions";
 import {
-  ready,
+  empty,
   loading,
+  mapResult,
+  ready,
   unloaded,
   type DocumentState,
-  mapResult,
 } from "./state";
-import { relationshipsForDocument } from "@/lib/relationships";
 
 function setLoadingDocument(
   docId: DocumentId,
@@ -47,6 +48,36 @@ function setDocument(state: DocumentState, doc: AnyDocument): DocumentState {
   };
 }
 
+function setAllRelationshipsEmpty(
+  docId: DocumentId,
+  state: DocumentState,
+): DocumentState {
+  const prevDocResult = state.documents[docId];
+  if (prevDocResult?.type !== "ready") {
+    return state;
+  }
+
+  const prevDoc = prevDocResult.value.doc;
+  const relationships = prevDocResult.value.relationships;
+
+  return {
+    ...state,
+    documents: {
+      ...state.documents,
+      [docId]: ready({
+        ...prevDocResult.value,
+        relationships: Object.fromEntries(
+          relationshipsForDocument(prevDoc).map((relType) =>
+            relationships[relType]?.type === "ready"
+              ? [relType, relationships[relType]]
+              : [relType, empty()],
+          ),
+        ),
+      }),
+    },
+  };
+}
+
 function setRelationship(
   docId: DocumentId,
   state: DocumentState,
@@ -118,8 +149,11 @@ export function reducer(
         setDocument,
         action.relationships.reduce(
           setRelationship.bind(null, action.doc.id),
+          setAllRelationshipsEmpty(
+            action.doc.id,
             setDocument(state, action.doc),
           ),
+        ),
       );
     case "removeDocument":
       return removeDocument(action.docId, state);

src/context/document/state.ts

@@ -10,11 +10,13 @@ export type Result<V> =
   | { type: "unloaded" }
   | { type: "error"; err: unknown }
   | { type: "loading" }
+  | { type: "empty" }
   | { type: "ready"; value: V };
 
 export const unloaded = (): Result<any> => ({ type: "unloaded" });
 export const error = (err: unknown): Result<any> => ({ type: "error", err });
 export const loading = (): Result<any> => ({ type: "loading" });
+export const empty = (): Result<any> => ({ type: "empty" });
 export const ready = <V>(value: V): Result<V> => ({ type: "ready", value });
 
 export const mapResult = <A, B>(