Core: Add global args feature

app/vue/src/client/preview/index.ts

@@ -69,6 +69,7 @@ const defaultContext: StoryContext = {
   kind: 'unspecified',
   parameters: {},
   args: {},
+  globalArgs: {},
 };
 
 function decorateStory(

examples/dev-kits/manager.js

@@ -1,8 +1,8 @@
-import React from 'react';
+import React, { useState } from 'react';
 import { PropTypes } from 'prop-types';
 import { Button } from '@storybook/react/demo';
 import { addons } from '@storybook/addons';
-import { useAddonState, useStoryState } from '@storybook/api';
+import { useAddonState, useStoryState, useGlobalArgs } from '@storybook/api';
 import { themes } from '@storybook/theming';
 import { AddonPanel } from '@storybook/components';
 
@@ -59,3 +59,37 @@ addons.addPanel('useAddonState', {
   title: 'useAddonState',
   render: StatePanel,
 });
+
+const GlobalArgsPanel = ({ active, key }) => {
+  const [globalArgs, updateGlobalArgs] = useGlobalArgs();
+  const [globalArgsInput, updateGlobalArgsInput] = useState(JSON.stringify(globalArgs));
+  return (
+    <AddonPanel key={key} active={active}>
+      <div>
+        <h2>Global Args</h2>
+
+        <form
+          onSubmit={e => {
+            e.preventDefault();
+            updateGlobalArgs(JSON.parse(globalArgsInput));
+          }}
+        >
+          <textarea value={globalArgsInput} onChange={e => updateGlobalArgsInput(e.target.value)} />
+          <br />
+          <button type="submit">Change</button>
+        </form>
+      </div>
+    </AddonPanel>
+  );
+};
+
+GlobalArgsPanel.propTypes = {
+  active: PropTypes.bool.isRequired,
+  key: PropTypes.string.isRequired,
+};
+
+addons.addPanel('useGlobalArgs', {
+  id: 'useGlobalArgs',
+  title: 'useGlobalArgs',
+  render: GlobalArgsPanel,
+});

examples/dev-kits/stories/addon-useglobalargs.js

@@ -0,0 +1,32 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+export default {
+  title: 'addons/useGlobalArgs',
+};
+
+export const PassedToStory = ({ globalArgs }) => {
+  return (
+    <div>
+      <h3>Global args:</h3>
+      <pre>{JSON.stringify(globalArgs)}</pre>
+    </div>
+  );
+};
+
+PassedToStory.propTypes = {
+  globalArgs: PropTypes.shape({}).isRequired,
+};
+
+export const SecondStory = ({ globalArgs }) => {
+  return (
+    <div>
+      <h3>Global args (2):</h3>
+      <pre>{JSON.stringify(globalArgs)}</pre>
+    </div>
+  );
+};
+
+SecondStory.propTypes = {
+  globalArgs: PropTypes.shape({}).isRequired,
+};

examples/official-storybook/stories/core/globalArgs.stories.js

@@ -0,0 +1,68 @@
+import React, { useState } from 'react';
+import PropTypes from 'prop-types';
+
+import { useGlobalArgs } from '@storybook/client-api';
+
+// eslint-disable-next-line react/prop-types
+const ArgUpdater = ({ args, updateArgs }) => {
+  const [argsInput, updateArgsInput] = useState(JSON.stringify(args));
+
+  return (
+    <div>
+      <h3>Hooks args:</h3>
+      <pre>{JSON.stringify(args)}</pre>
+      <form
+        onSubmit={e => {
+          e.preventDefault();
+          updateArgs(JSON.parse(argsInput));
+        }}
+      >
+        <textarea value={argsInput} onChange={e => updateArgsInput(e.target.value)} />
+        <br />
+        <button type="submit">Change</button>
+      </form>
+    </div>
+  );
+};
+
+export default {
+  title: 'Core/Global Args',
+  decorators: [
+    story => {
+      const [globalArgs, updateGlobalArgs] = useGlobalArgs();
+
+      return (
+        <>
+          {story()}
+          <ArgUpdater args={globalArgs} updateArgs={updateGlobalArgs} />
+        </>
+      );
+    },
+  ],
+};
+
+export const PassedToStory = ({ globalArgs }) => {
+  return (
+    <div>
+      <h3>Global args:</h3>
+      <pre>{JSON.stringify(globalArgs)}</pre>
+    </div>
+  );
+};
+
+PassedToStory.propTypes = {
+  globalArgs: PropTypes.shape({}).isRequired,
+};
+
+export const SecondStory = ({ globalArgs }) => {
+  return (
+    <div>
+      <h3>Global args (2):</h3>
+      <pre>{JSON.stringify(globalArgs)}</pre>
+    </div>
+  );
+};
+
+SecondStory.propTypes = {
+  globalArgs: PropTypes.shape({}).isRequired,
+};

lib/addons/src/hooks.ts

@@ -5,6 +5,7 @@ import {
   STORY_RENDERED,
   DOCS_RENDERED,
   UPDATE_STORY_ARGS,
+  UPDATE_GLOBAL_ARGS,
 } from '@storybook/core-events';
 import { addons } from './index';
 import { StoryGetter, StoryContext, Args } from './types';
@@ -427,3 +428,16 @@ export function useArgs(): [Args, (newArgs: Args) => void] {
 
   return [args, updateArgs];
 }
+
+/* Returns current value of global args */
+export function useGlobalArgs(): [Args, (newGlobalArgs: Args) => void] {
+  const channel = addons.getChannel();
+  const { globalArgs } = useStoryContext();
+
+  const updateGlobalArgs = useCallback(
+    (newGlobalArgs: Args) => channel.emit(UPDATE_GLOBAL_ARGS, newGlobalArgs),
+    [channel]
+  );
+
+  return [globalArgs, updateGlobalArgs];
+}

lib/addons/src/types.ts

@@ -39,12 +39,13 @@ export interface StoryIdentifier {
   name: StoryName;
 }
 
-export interface StoryContext extends StoryIdentifier {
+export type StoryContext = StoryIdentifier & {
   [key: string]: any;
   parameters: Parameters;
   args: Args;
+  globalArgs: Args;
   hooks?: HooksContext;
-}
+};
 
 export interface WrapperSettings {
   options: OptionsParameter;

lib/api/src/index.tsx

@@ -46,6 +46,10 @@ import initVersions, {
   SubState as VersionsSubState,
   SubAPI as VersionsAPI,
 } from './modules/versions';
+import initGlobalArgs, {
+  SubState as GlobalArgsSubState,
+  SubAPI as GlobalArgsAPI,
+} from './modules/globalArgs';
 
 export { Options as StoreOptions, Listener as ChannelListener };
 export { ActiveTabs };
@@ -66,7 +70,8 @@ export type State = Other &
   NotificationState &
   VersionsSubState &
   RouterData &
-  ShortcutsSubState;
+  ShortcutsSubState &
+  GlobalArgsSubState;
 
 export type API = AddonsAPI &
   ChannelAPI &
@@ -77,6 +82,7 @@ export type API = AddonsAPI &
   ShortcutsAPI &
   VersionsAPI &
   UrlAPI &
+  GlobalArgsAPI &
   OtherAPI;
 
 interface OtherAPI {
@@ -172,6 +178,7 @@ class ManagerProvider extends Component<ManagerProviderProps, State> {
       initStories,
       initURL,
       initVersions,
+      initGlobalArgs,
     ].map(initModule =>
       initModule({ ...routeData, ...apiData, state: this.state, fullAPI: this.api })
     );
@@ -405,3 +412,12 @@ export function useArgs(): [Args, (newArgs: Args) => void] {
 
   return [args, (newArgs: Args) => updateStoryArgs(id, newArgs)];
 }
+
+export function useGlobalArgs(): [Args, (newGlobalArgs: Args) => void] {
+  const {
+    state: { globalArgs },
+    api: { updateGlobalArgs },
+  } = useContext(ManagerContext);
+
+  return [globalArgs, updateGlobalArgs];
+}

lib/api/src/modules/globalArgs.ts

@@ -0,0 +1,41 @@
+import { UPDATE_GLOBAL_ARGS, GLOBAL_ARGS_UPDATED } from '@storybook/core-events';
+import { Args, Module, API } from '../index';
+
+export interface SubState {
+  globalArgs: Args;
+}
+
+export interface SubAPI {
+  updateGlobalArgs: (newGlobalArgs: Args) => void;
+}
+
+const initGlobalArgsApi = ({ store }: Module) => {
+  let fullApi: API;
+  const updateGlobalArgs = (newGlobalArgs: Args) => {
+    if (!fullApi) throw new Error('Cannot set global args until api has been initialized');
+
+    fullApi.emit(UPDATE_GLOBAL_ARGS, newGlobalArgs);
+  };
+
+  const api: SubAPI = {
+    updateGlobalArgs,
+  };
+
+  const state: SubState = {
+    // Currently global args always start empty. TODO -- should this be set on the channel at init time?
+    globalArgs: {},
+  };
+
+  const init = ({ api: inputApi }: { api: API }) => {
+    fullApi = inputApi;
+    fullApi.on(GLOBAL_ARGS_UPDATED, (globalArgs: Args) => store.setState({ globalArgs }));
+  };
+
+  return {
+    api,
+    state,
+    init,
+  };
+};
+
+export default initGlobalArgsApi;

lib/api/src/tests/globalArgs.test.ts

@@ -0,0 +1,59 @@
+import EventEmitter from 'event-emitter';
+import { UPDATE_GLOBAL_ARGS, GLOBAL_ARGS_UPDATED } from '@storybook/core-events';
+
+import { Module, API } from '../index';
+import initGlobalArgs from '../modules/globalArgs';
+
+function createMockStore() {
+  let state = {};
+  return {
+    getState: jest.fn().mockImplementation(() => state),
+    setState: jest.fn().mockImplementation(s => {
+      state = { ...state, ...s };
+    }),
+  };
+}
+
+function createMockModule() {
+  // This mock module doesn't have all the fields but we don't use them all in this sub-module
+  return ({ store: createMockStore() } as unknown) as Module;
+}
+
+describe('stories API', () => {
+  it('sets a sensible initialState', () => {
+    const { state } = initGlobalArgs(createMockModule());
+
+    expect(state).toEqual({
+      globalArgs: {},
+    });
+  });
+
+  it('updates the state when the preview emits GLOBAL_ARGS_UPDATED', () => {
+    const mod = createMockModule();
+    const { state, init } = initGlobalArgs(mod);
+    mod.store.setState(state);
+
+    const api = new EventEmitter() as API;
+    init({ api });
+
+    api.emit(GLOBAL_ARGS_UPDATED, { a: 'b' });
+    expect(mod.store.getState()).toEqual({ globalArgs: { a: 'b' } });
+
+    api.emit(GLOBAL_ARGS_UPDATED, { a: 'c' });
+    expect(mod.store.getState()).toEqual({ globalArgs: { a: 'c' } });
+
+    // SHOULD NOT merge global args
+    api.emit(GLOBAL_ARGS_UPDATED, { d: 'e' });
+    expect(mod.store.getState()).toEqual({ globalArgs: { d: 'e' } });
+  });
+
+  it('emits UPDATE_GLOBAL_ARGS when updateGlobalArgs is called', () => {
+    const { init, api } = initGlobalArgs({} as Module);
+
+    const fullApi = ({ emit: jest.fn(), on: jest.fn() } as unknown) as API;
+    init({ api: fullApi });
+
+    api.updateGlobalArgs({ a: 'b' });
+    expect(fullApi.emit).toHaveBeenCalledWith(UPDATE_GLOBAL_ARGS, { a: 'b' });
+  });
+});

lib/client-api/README.md

@@ -96,7 +96,27 @@ Note that arg values are passed directly to a story -- you should only store the
 Both `@storybook/client-api` (preview) and `@storybook/api` (manager) export a `useArgs()` hook that you can use to access args in decorators or addon panels. The API is as follows:
 
 ```js
+import { useArgs } from '@storybook/client-api'; // or '@storybook/api'
+
 // `args` is the args of the currently rendered story
 // `updateArgs` will update its args. You can pass a subset of the args; other args will not be changed.
 const [args, updateArgs] = useArgs();
 ```
+
+## Global Args
+
+Global args are args that are "global" across all stories. They are used for things like themes and internationalization (i18n) in stories, where you want Storybook to "remember" your setting as you browse between stories.
+
+### Initial values of global args
+
+To set initial values of global args, set the `parameters.globalArgs` parameters. Addons can use parameter enhancers (see above) to do this.
+
+### Using global args in an addon
+
+Similar to args, global args are syncronized to the manager and can be accessed via the `useGlobalArgs` hook.
+
+```js
+import { useGlobalArgs } from '@storybook/client-api'; // or '@storybook/api'
+
+const [globalArgs, updateGlobalArgs] = useGlobalArgs();
+```

lib/client-api/src/decorators.ts

@@ -11,6 +11,7 @@ const defaultContext: StoryContext = {
   kind: 'unspecified',
   parameters: {},
   args: {},
+  globalArgs: {},
 };
 
 export const defaultDecorateStory = (storyFn: StoryFn, decorators: DecoratorFunction[]) =>