Moved GraphQL-related data into a mixin

The same GraphQL props/data/query will be used for the Edit
application as well

Default schema for snippet

app/assets/javascripts/snippets/components/show.vue

 <script>
-import GetSnippetQuery from '../queries/snippet.query.graphql';
 import SnippetHeader from './snippet_header.vue';
 import SnippetTitle from './snippet_title.vue';
 import SnippetBlob from './snippet_blob_view.vue';
 import { GlLoadingIcon } from '@gitlab/ui';
 
+import { getSnippetMixin } from '../mixins/snippets';
+
 export default {
   components: {
     SnippetHeader,
@@ -12,33 +13,7 @@ export default {
     GlLoadingIcon,
     SnippetBlob,
   },
-  apollo: {
-    snippet: {
-      query: GetSnippetQuery,
-      variables() {
-        return {
-          ids: this.snippetGid,
-        };
-      },
-      update: data => data.snippets.edges[0].node,
-    },
-  },
-  props: {
-    snippetGid: {
-      type: String,
-      required: true,
-    },
-  },
-  data() {
-    return {
-      snippet: {},
-    };
-  },
-  computed: {
-    isLoading() {
-      return this.$apollo.queries.snippet.loading;
-    },
-  },
+  mixins: [getSnippetMixin],
 };
 </script>
 <template>

app/assets/javascripts/snippets/mixins/snippets.js

+import GetSnippetQuery from '../queries/snippet.query.graphql';
+
+export const getSnippetMixin = {
+  apollo: {
+    snippet: {
+      query: GetSnippetQuery,
+      variables() {
+        return {
+          ids: this.snippetGid,
+        };
+      },
+      update: data => data.snippets.edges[0]?.node,
+      result(res) {
+        if (this.onSnippetFetch) {
+          this.onSnippetFetch(res);
+        }
+      },
+    },
+  },
+  props: {
+    snippetGid: {
+      type: String,
+      required: true,
+    },
+  },
+  data() {
+    return {
+      snippet: {},
+      newSnippet: false,
+    };
+  },
+  computed: {
+    isLoading() {
+      return this.$apollo.queries.snippet.loading;
+    },
+  },
+};
+
+export default () => {};