fix: avoid uncatchable rejection

src/data-fetching_new/defineColadaLoader.spec.ts

@@ -116,6 +116,29 @@ describe(
         app,
       }
     }
+
+    it.todo('avoids refetching fresh data when navigating', async () => {
+      const query = vi.fn().mockResolvedValue('data')
+      const useData = defineColadaLoader({
+        query,
+        key: (to) => [to.query.q as string],
+      })
+
+      const { router } = singleLoaderOneRoute(useData)
+
+      // same key
+      await router.push('/fetch?q=1&v=1')
+      expect(query).toHaveBeenCalledTimes(1)
+      await router.push('/fetch?q=1&v=2')
+      expect(query).toHaveBeenCalledTimes(1)
+
+      // different key
+      await router.push('/fetch?q=2&v=3')
+      expect(query).toHaveBeenCalledTimes(2)
+      // already fetched
+      await router.push('/fetch?q=1&v=4')
+      expect(query).toHaveBeenCalledTimes(2)
+    })
   },
   // fail faster on unresolved promises
   { timeout: 100 }

src/data-fetching_new/defineColadaLoader.ts

@@ -368,11 +368,17 @@ export function defineColadaLoader<Data, isLazy extends boolean>(
     } satisfies UseDataLoaderResult
 
     // load ensures there is a pending load
-    const promise = entry.pendingLoad!.then(() => {
-      // nested loaders might wait for all loaders to be ready before setting data
-      // so we need to return the staged value if it exists as it will be the latest one
-      return entry!.staged === STAGED_NO_VALUE ? ext!.data.value : entry!.staged
-    })
+    const promise = entry
+      .pendingLoad!.then(() => {
+        // nested loaders might wait for all loaders to be ready before setting data
+        // so we need to return the staged value if it exists as it will be the latest one
+        return entry!.staged === STAGED_NO_VALUE
+          ? ext!.data.value
+          : entry!.staged
+      })
+      // we only want the error if we are nesting the loader
+      // otherwise this will end up in "Unhandled promise rejection"
+      .catch((e) => (parentEntry ? Promise.reject(e) : null))
 
     return Object.assign(promise, useDataLoaderResult)
   }

src/data-fetching_new/defineLoader.ts

@@ -305,11 +305,15 @@ export function defineBasicLoader<Data, isLazy extends boolean>(
     } satisfies UseDataLoaderResult
 
     // load ensures there is a pending load
-    const promise = entry.pendingLoad!.then(() => {
-      // nested loaders might wait for all loaders to be ready before setting data
-      // so we need to return the staged value if it exists as it will be the latest one
-      return entry!.staged === STAGED_NO_VALUE ? data.value : entry!.staged
-    })
+    const promise = entry
+      .pendingLoad!.then(() => {
+        // nested loaders might wait for all loaders to be ready before setting data
+        // so we need to return the staged value if it exists as it will be the latest one
+        return entry!.staged === STAGED_NO_VALUE ? data.value : entry!.staged
+      })
+      // we only want the error if we are nesting the loader
+      // otherwise this will end up in "Unhandled promise rejection"
+      .catch((e) => (parentEntry ? Promise.reject(e) : null))
 
     return Object.assign(promise, useDataLoaderResult)
   }

tests/data-loaders/tester.ts

@@ -327,6 +327,29 @@ export function testDefineLoader<Context = void>(
         expect(data.value).toBe(undefined)
         expect(router.currentRoute.value.path).toBe('/fetch')
       })
+
+      it('propagates errors from nested loaders', async () => {
+        const l1 = mockedLoader({
+          key: 'nested',
+          commit,
+          lazy: false,
+        })
+        const { wrapper, app, router, useData } = singleLoaderOneRoute(
+          loaderFactory({
+            fn: async (to) => {
+              const data = await l1.loader()
+              return `${data},${to.query.p}`
+            },
+            key: 'root',
+          })
+        )
+
+        const p = router.push('/fetch?p=one')
+        await vi.runOnlyPendingTimersAsync()
+
+        l1.reject(new Error('nope'))
+        await expect(p).rejects.toThrow('nope')
+      })
     }
   )