feat(react): useFragment hook (BETA)

examples/with-defer-stream-directives/src/App.jsx

@@ -13,6 +13,7 @@ const cache = cacheExchange({
 });
 
 const client = new Client({
+  suspense: true,
   url: 'http://localhost:3004/graphql',
   exchanges: [cache, fetchExchange],
 });

examples/with-defer-stream-directives/src/Songs.jsx

@@ -1,5 +1,5 @@
-import React from 'react';
-import { gql, useQuery } from 'urql';
+import React, { Suspense } from 'react';
+import { gql, useQuery, useFragment } from 'urql';
 
 const SecondVerseFragment = gql`
   fragment secondVerseFields on Song {
@@ -13,9 +13,6 @@ const SONGS_QUERY = gql`
       firstVerse
       ...secondVerseFields @defer
     }
-    alphabet @stream(initialCount: 3) {
-      char
-    }
   }
 
   ${SecondVerseFragment}
@@ -25,11 +22,22 @@ const Song = React.memo(function Song({ song }) {
   return (
     <section>
       <p>{song.firstVerse}</p>
+      <Suspense fallback={'Loading song 2...'}>
+        <DeferredSong data={song} />
+      </Suspense>
       <p>{song.secondVerse}</p>
     </section>
   );
 });
 
+const DeferredSong = ({ data }) => {
+  const result = useFragment({
+    query: SecondVerseFragment,
+    data,
+  });
+  return <p>{result.secondVerse}</p>;
+};
+
 const LocationsList = () => {
   const [result] = useQuery({
     query: SONGS_QUERY,
@@ -42,9 +50,6 @@ const LocationsList = () => {
       {data && (
         <>
           <Song song={data.song} />
-          {data.alphabet.map(i => (
-            <div key={i.char}>{i.char}</div>
-          ))}
         </>
       )}
     </div>

packages/react-urql/src/hooks/index.ts

@@ -1,3 +1,4 @@
 export * from './useMutation';
 export * from './useQuery';
+export * from './useFragment';
 export * from './useSubscription';

packages/react-urql/src/hooks/useFragment.ts

@@ -0,0 +1,262 @@
+/* eslint-disable react-hooks/exhaustive-deps */
+
+import * as React from 'react';
+import type {
+  FragmentDefinitionNode,
+  SelectionSetNode,
+} from '@0no-co/graphql.web';
+import { Kind } from '@0no-co/graphql.web';
+
+import type {
+  GraphQLRequestParams,
+  AnyVariables,
+  Client,
+  OperationContext,
+  OperationResult,
+  GraphQLRequest,
+} from '@urql/core';
+
+import { useClient } from '../context';
+import { useRequest } from './useRequest';
+import { getCacheForClient } from './cache';
+
+import { initialState, computeNextState, hasDepsChanged } from './state';
+
+/** Input arguments for the {@link useFragment} hook. */
+export type UseFragmentArgs<Data = any> = {
+  /** Updates the {@link OperationContext} for the executed GraphQL query operation.
+   *
+   * @remarks
+   * `context` may be passed to {@link useFragment}, to update the {@link OperationContext}
+   * of a query operation. This may be used to update the `context` that exchanges
+   * will receive for a single hook.
+   *
+   * Hint: This should be wrapped in a `useMemo` hook, to make sure that your
+   * component doesn’t infinitely update.
+   *
+   * @example
+   * ```ts
+   * const result = useFragment({
+   *   query,
+   *   data,
+   *   context: useMemo(() => ({
+   *     suspense: true,
+   *   }), [])
+   * });
+   * ```
+   */
+  context: Partial<OperationContext>;
+  /** A GraphQL document to mask this fragment against.
+   *
+   * @remarks
+   * This Document should contain atleast one FragmentDefinitionNode or
+   * a FragmentDefinitionNode with the same name as the `name` property.
+   */
+  query: GraphQLRequestParams<Data, AnyVariables>['query'];
+  /** A JSON object which we will extract properties from to get to the
+   * masked fragment.
+   */
+  data: Data;
+  /** An optional name of the fragment to use. */
+  name?: string;
+};
+
+/** State of the current query, your {@link useFragment} hook is executing.
+ *
+ * @remarks
+ * `UseFragmentState` is returned by {@link useFragment} and
+ * gives you the masked data for the fragment.
+ */
+export interface UseFragmentState<Data = any> {
+  /** Indicates whether `useFragment` is waiting for a new result.
+   *
+   * @remarks
+   * When `useFragment` is passed a new query and/or variables, it will
+   * start executing the new query operation and `fetching` is set to
+   * `true` until a result arrives.
+   */
+  fetching: boolean;
+  /** The {@link OperationResult.data} for the masked fragment. */
+  data?: Data;
+}
+
+const isSuspense = (client: Client, context?: Partial<OperationContext>) =>
+  context && context.suspense !== undefined
+    ? !!context.suspense
+    : client.suspense;
+
+/** Hook to mask a GraphQL Fragment given its data. (BETA)
+ *
+ * @param args - a {@link UseFragmentArgs} object, to pass a `fragment` and `data`.
+ * @returns a {@link UseFragmentState} result.
+ *
+ * @remarks
+ * `useFragments` allows GraphQL fragments to mask their data.
+ * Given {@link UseFragmentArgs.query} and {@link UseFragmentArgs.data}, it will
+ * return the masked data for the fragment contained in query.
+ *
+ * Additionally, if the `suspense` option is enabled on the `Client`,
+ * the `useFragment` hook will suspend instead of indicating that it’s
+ * waiting for a result via {@link UseFragmentState.fetching}.
+ *
+ * @example
+ * ```ts
+ * import { gql, useFragment } from 'urql';
+ *
+ * const TodoFields = gql`
+ *   fragment TodoFields on Todo { id name }
+ * `;
+ *
+ * const Todo = (props) => {
+ *   const result = useQuery({
+ *     data: props.todo,
+ *     query: TodoFields,
+ *     variables: {},
+ *   });
+ *   // ...
+ * };
+ * ```
+ */
+export function useFragment<
+  Data extends Record<string, any> = Record<string, any>,
+>(args: UseFragmentArgs<Data>): UseFragmentState<Data> {
+  const client = useClient();
+  const cache = getCacheForClient(client);
+  const suspense = isSuspense(client, args.context);
+  const request = useRequest(args.query, args.data);
+
+  const getSnapshot = React.useCallback(
+    (
+      request: GraphQLRequest<Data, AnyVariables>,
+      data: Data,
+      suspense: boolean
+    ): Partial<UseFragmentState<Data>> => {
+      const cached = cache.get(request.key);
+      if (!cached) {
+        const fragment = request.query.definitions.find(
+          x =>
+            x.kind === Kind.FRAGMENT_DEFINITION &&
+            ((args.name && x.name.value === args.name) || !args.name)
+        ) as FragmentDefinitionNode | undefined;
+
+        if (!fragment) {
+          throw new Error(
+            'Passed document did not contain a fragment definition' + args.name
+              ? ` for ${args.name}`
+              : ''
+          );
+        }
+
+        const newResult = maskFragment<Data>(data, fragment.selectionSet);
+        if (newResult.fulfilled) {
+          cache.set(request.key, newResult.data as any);
+          return { data: newResult.data as any, fetching: false };
+        } else if (suspense) {
+          const promise = new Promise(() => {});
+          cache.set(request.key, promise);
+          throw promise;
+        } else {
+          return { fetching: true, data: newResult.data };
+        }
+      } else if (suspense && cached != null && 'then' in cached) {
+        throw cached;
+      }
+
+      return { fetching: false, data: (cached as OperationResult).data };
+    },
+    [cache, request]
+  );
+
+  const deps = [client, request, args.context, args.data] as const;
+
+  const [state, setState] = React.useState(
+    () =>
+      [
+        computeNextState(
+          initialState,
+          getSnapshot(request, args.data, suspense)
+        ),
+        deps,
+      ] as const
+  );
+
+  let currentResult = state[0];
+  if (hasDepsChanged(state[1], deps)) {
+    setState([
+      (currentResult = computeNextState(
+        state[0],
+        getSnapshot(request, args.data, suspense)
+      )),
+      deps,
+    ]);
+  }
+
+  return currentResult;
+}
+
+const maskFragment = <Data extends Record<string, any>>(
+  data: Data,
+  selectionSet: SelectionSetNode
+): { data: Data; fulfilled: boolean } => {
+  const maskedData = {};
+  let isDataComplete = true;
+  selectionSet.selections.forEach(selection => {
+    if (selection.kind === Kind.FIELD) {
+      const fieldAlias = selection.alias
+        ? selection.alias.value
+        : selection.name.value;
+      if (selection.selectionSet) {
+        if (data[fieldAlias] === undefined) {
+          isDataComplete = false;
+        } else if (data[fieldAlias] === null) {
+          maskedData[fieldAlias] = null;
+        } else if (Array.isArray(data[fieldAlias])) {
+          maskedData[fieldAlias] = data[fieldAlias].map(item => {
+            const result = maskFragment(
+              item,
+              selection.selectionSet as SelectionSetNode
+            );
+            if (!result.fulfilled) {
+              isDataComplete = false;
+            }
+            return result.data;
+          });
+        } else {
+          const result = maskFragment(data[fieldAlias], selection.selectionSet);
+          if (!result.fulfilled) {
+            isDataComplete = false;
+          }
+          maskedData[fieldAlias] = result.data;
+        }
+      } else {
+        if (data[fieldAlias] === undefined) {
+          isDataComplete = false;
+        } else if (data[fieldAlias] === null) {
+          maskedData[fieldAlias] = null;
+        } else if (Array.isArray(data[fieldAlias])) {
+          maskedData[fieldAlias] = data[fieldAlias].map(item => item);
+        } else {
+          maskedData[fieldAlias] = data[fieldAlias];
+        }
+      }
+      maskedData[selection.name.value] = data[selection.name.value];
+    } else if (selection.kind === Kind.INLINE_FRAGMENT) {
+      if (
+        selection.typeCondition &&
+        selection.typeCondition.name.value !== data.__typename
+      ) {
+        return;
+      }
+
+      const result = maskFragment(data, selection.selectionSet);
+      if (!result.fulfilled) {
+        isDataComplete = false;
+      }
+      Object.assign(maskedData, result.data);
+    } else if (selection.kind === Kind.FRAGMENT_SPREAD) {
+      // TODO: do we want to support this?
+    }
+  });
+
+  return { data: maskedData as Data, fulfilled: isDataComplete };
+};