From 2e9122ca8107cc9bb8405b511ca6ba384bd7b122 Mon Sep 17 00:00:00 2001
From: Andrew Kingston <aptkingston@ssl-mail.com>
Date: Wed, 10 Feb 2021 19:42:56 +0000
Subject: [PATCH] Fix reactive store derivation overriding actions

---
 .../client/src/components/Provider.svelte     | 12 ++-----
 packages/client/src/store/context.js          | 31 ++++++++++++-------
 2 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/packages/client/src/components/Provider.svelte b/packages/client/src/components/Provider.svelte
index 3c894f6723..6f56e62abe 100644
--- a/packages/client/src/components/Provider.svelte
+++ b/packages/client/src/components/Provider.svelte
@@ -11,17 +11,13 @@
   // Clone and create new data context for this component tree
   const context = getContext("context")
   const component = getContext("component")
-  const newContext = createContextStore()
+  const newContext = createContextStore(context)
   setContext("context", newContext)
 
-  let initiated = false
   $: providerKey = key || $component.id
 
   // Add data context
-  $: {
-    newContext.actions.provideData(providerKey, $context, data)
-    initiated = true
-  }
+  $: newContext.actions.provideData(providerKey, data)
 
   // Instance ID is unique to each instance of a provider
   let instanceId
@@ -56,6 +52,4 @@
   })
 </script>
 
-{#if initiated}
-  <slot />
-{/if}
+<slot />
diff --git a/packages/client/src/store/context.js b/packages/client/src/store/context.js
index 5725f94231..e9d307d4f3 100644
--- a/packages/client/src/store/context.js
+++ b/packages/client/src/store/context.js
@@ -1,20 +1,27 @@
-import { writable } from "svelte/store"
+import { writable, derived } from "svelte/store"
 
-export const createContextStore = () => {
-  const store = writable({})
+export const createContextStore = oldContext => {
+  const newContext = writable({})
+  const contexts = oldContext ? [oldContext, newContext] : [newContext]
+  const totalContext = derived(contexts, $contexts => {
+    return $contexts.reduce((total, context) => ({ ...total, ...context }), {})
+  })
 
   // Adds a data context layer to the tree
-  const provideData = (providerId, context, data) => {
-    let newData = { ...context }
-    if (providerId && data !== undefined) {
-      newData[providerId] = data
+  const provideData = (providerId, data) => {
+    if (!providerId || data === undefined) {
+      return
+    }
+    newContext.update(state => {
+      state[providerId] = data
 
       // Keep track of the closest component ID so we can later hydrate a "data" prop.
       // This is only required for legacy bindings that used "data" rather than a
       // component ID.
-      newData.closestComponentId = providerId
-    }
-    store.set(newData)
+      state.closestComponentId = providerId
+
+      return state
+    })
   }
 
   // Adds an action context layer to the tree
@@ -22,14 +29,14 @@ export const createContextStore = () => {
     if (!providerId || !actionType) {
       return
     }
-    store.update(state => {
+    newContext.update(state => {
       state[`${providerId}_${actionType}`] = callback
       return state
     })
   }
 
   return {
-    subscribe: store.subscribe,
+    subscribe: totalContext.subscribe,
     actions: { provideData, provideAction },
   }
 }