Fix MSTGQLStore.subscribe() when a DocumentNode is passed as query

src/MSTGQLStore.ts

@@ -15,6 +15,7 @@ import { deflateHelper } from "./deflateHelper"
 import { mergeHelper } from "./mergeHelper"
 import { Query, QueryHttpClientOptions, QueryOptions } from "./Query"
 import { getFirstValue } from "./utils"
+import { print } from "graphql/language/printer"
 
 type RequestOptions = {
   document: string
@@ -154,7 +155,11 @@ export const MSTGQLStore = types
       if (self.graphqlWsClient) {
         cleanup = self.graphqlWsClient.subscribe(
           {
-            query: query ? query.toString() : "",
+            query: query
+              ? typeof query === "string"
+                ? query
+                : print(query)
+              : "",
             variables: variables
           },
           {
@@ -181,7 +186,11 @@ export const MSTGQLStore = types
         if (!self.gqlWsClient) throw new Error("No WS client available")
         const sub = self.gqlWsClient
           .request({
-            query: query ? query.toString() : "",
+            query: query
+              ? typeof query === "string"
+                ? query
+                : print(query) // Here we could actually pass query as is, gqlWsClient can work with DocumentNode
+              : "",
             variables
           })
           .subscribe({

tests/cra-test/.yarnrc.yml

@@ -0,0 +1 @@
+nodeLinker: node-modules

tests/cra-test/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "cra-test",
+  "packageManager": "yarn@3.2.1",
+  "private": true,
+  "workspaces": [
+    "cra-tmp/cra-app"
+  ],
+  "dependencies": {
+    "graphql": "16.5.0",
+    "graphql-request": "4.3.0",
+    "graphql-tag": "2.12.6",
+    "mobx": "6.6.1",
+    "mobx-react": "7.5.2",
+    "mobx-state-tree": "5.1.5"
+  }
+}