Improve `initialState` definitions in store modules

Convert the `initialState` functions in store modules to `const` values
for modules where the state is static (ie. does not depend on
`settings`) and add better type documentation.

Most references to the state are not currently type-checked, but they
will be in future. In the interim this serves as useful documentation
for humans.

src/sidebar/store/modules/activity.js

@@ -6,10 +6,11 @@
 import { actionTypes } from '../util';
 import { createStoreModule } from '../create-store';
 
-function initialState() {
-  return {
+const initialState = {
   /**
    * Annotation `$tag`s that correspond to annotations with active API requests
+   *
+   * @type {string[]}
    */
   activeAnnotationSaveRequests: [],
   /**
@@ -27,10 +28,11 @@ function initialState() {
   /**
    * The number of total annotation results the service reported as
    * matching the most recent load/search request
+   *
+   * @type {number|null}
    */
   annotationResultCount: null,
-  };
-}
+};
 
 const reducers = {
   API_REQUEST_STARTED(state) {

src/sidebar/store/modules/annotations.js

@@ -89,21 +89,30 @@ function initializeAnnotation(annotation, tag) {
   });
 }
 
-function initialState() {
-  return {
-    /** @type {Annotation[]} */
+const initialState = {
+  /**
+   * Set of all currently loaded annotations.
+   *
+   * @type {Annotation[]}
+   */
   annotations: [],
-    // A set of annotations that are currently "focused" — e.g. hovered over in
-    // the UI
+  /**
+   * A set of annotations that are currently "focused" — e.g. hovered over in
+   * the UI.
+   *
+   * @type {Record<string, boolean>}
+   */
   focused: {},
-    // A map of annotations that should appear as "highlighted", e.g. the
-    // target of a single-annotation view
+  /**
+   * A map of annotations that should appear as "highlighted", e.g. the
+   * target of a single-annotation view
+   *
+   * @type {Record<string, boolean>}
+   */
   highlighted: {},
-    // The local tag to assign to the next annotation that is loaded into the
-    // app
+  /** The local tag to assign to the next annotation that is loaded into the app. */
   nextTag: 1,
-  };
-}
+};
 
 const reducers = {
   ADD_ANNOTATIONS: function (state, action) {

src/sidebar/store/modules/defaults.js

@@ -16,18 +16,10 @@ import { createStoreModule } from '../create-store';
  * `persistedDefaults` service.
  */
 
-function initialState() {
-  /**
-   * Note that the persisted presence of any of these defaults cannot be
-   * guaranteed, so consumers of said defaults should be prepared to handle
-   * missing (i.e. `null`) values. As `null` is a sentinal value indicating
-   * "not set/unavailable", a `null` value for a default is otherwise invalid.
-   */
-  return {
-    annotationPrivacy: null,
-    focusedGroup: null,
-  };
-}
+const initialState = {
+  annotationPrivacy: /** @type {'private'|'shared'|null} */ (null),
+  focusedGroup: /** @type {string|null} */ (null),
+};
 
 const reducers = {
   SET_DEFAULT: function (state, action) {

src/sidebar/store/modules/drafts.js

@@ -11,9 +11,8 @@ import { createStoreModule } from '../create-store';
  * existing annotations.
  */
 
-function initialState() {
-  return [];
-}
+/** @type {Draft[]} */
+const initialState = [];
 
 /**
  * Helper class to encapsulate the draft properties and a few simple methods.

src/sidebar/store/modules/frames.js

@@ -20,10 +20,8 @@ import { createStoreModule } from '../create-store';
  * @prop {string} uri - Current primary URI of the document being displayed
  */
 
-function initialState() {
-  // The list of frames connected to the sidebar app
-  return [];
-}
+/** @type {Frame[]} */
+const initialState = [];
 
 const reducers = {
   CONNECT_FRAME: function (state, action) {

src/sidebar/store/modules/groups.js

@@ -9,8 +9,7 @@ import session from './session';
  * @typedef {import('../../../types/api').Group} Group
  */
 
-function initialState() {
-  return {
+const initialState = {
   /**
    * List of groups.
    * @type {Group[]}
@@ -22,8 +21,7 @@ function initialState() {
    * @type {string|null}
    */
   focusedGroupId: null,
-  };
-}
+};
 
 const reducers = {
   FOCUS_GROUP(state, action) {

src/sidebar/store/modules/links.js

@@ -2,9 +2,7 @@ import { actionTypes } from '../util';
 import { replaceURLParams } from '../../util/url';
 import { createStoreModule } from '../create-store';
 
-function initialState() {
-  return null;
-}
+const initialState = /** @type {Record<string, string>|null} */ (null);
 
 const reducers = {
   UPDATE_LINKS(state, action) {

src/sidebar/store/modules/real-time-updates.js

@@ -16,17 +16,23 @@ import annotations from './annotations';
 import groups from './groups';
 import route from './route';
 
-function initialState() {
-  return {
-    // Map of ID -> updated annotation for updates that have been received over
-    // the WebSocket but not yet applied
+const initialState = {
+  /**
+   * Map of ID -> updated annotation for updates that have been received over
+   * the WebSocket but not yet applied
+   *
+   * @type {Record<string, Annotation>}
+   */
   pendingUpdates: {},
 
-    // Set of IDs of annotations which have been deleted but for which the
-    // deletion has not yet been applied
+  /**
+   * Set of IDs of annotations which have been deleted but for which the
+   * deletion has not yet been applied
+   *
+   * @type {Record<string, boolean>}
+   */
   pendingDeletions: {},
-  };
-}
+};
 
 const reducers = {
   RECEIVE_REAL_TIME_UPDATES(state, action) {

src/sidebar/store/modules/route.js

@@ -2,11 +2,15 @@ import { actionTypes } from '../util';
 
 import { createStoreModule } from '../create-store';
 
-function initialState() {
-  return {
+/**
+ * @typedef {'annotation'|'notebook'|'sidebar'|'stream'} RouteName
+ */
+
+const initialState = {
   /**
    * The current route.
-     * One of null (if no route active yet), "sidebar", "annotation" or "stream".
+   *
+   * @type {RouteName|null}
    */
   name: null,
 
@@ -16,10 +20,11 @@ function initialState() {
    * - The "annotation" route has an "id" (annotation ID) parameter.
    * - The "stream" route has a "q" (query) parameter.
    * - The "sidebar" route has no parameters.
+   *
+   * @type {Record<string, string>}
    */
   params: {},
-  };
-}
+};
 
 const reducers = {
   CHANGE_ROUTE(state, { name, params }) {

src/sidebar/store/modules/sidebar-panels.js

@@ -16,8 +16,7 @@ import * as util from '../util';
 
 import { createStoreModule } from '../create-store';
 
-function initialState() {
-  return {
+const initialState = {
   /*
    * The `panelName` of the currently-active sidebar panel.
    * Only one `panelName` may be active at a time, but it is valid (though not
@@ -27,10 +26,10 @@ function initialState() {
    * e.g. If `activePanelName` were `foobar`, all `SidebarPanel` components
    * with `panelName` of `foobar` would be active, and thus visible.
    *
+   * @type {PanelName|null}
    */
   activePanelName: null,
-  };
-}
+};
 
 const reducers = {
   OPEN_SIDEBAR_PANEL: function (state, action) {

src/sidebar/store/modules/toast-messages.js

@@ -16,11 +16,11 @@ import * as util from '../util';
  * maintains state only; it's up to other layers to handle the management
  * and interactions with these messages.
  */
-function initialState() {
-  return {
+
+const initialState = {
+  /** @type {ToastMessage[]} */
   messages: [],
-  };
-}
+};
 
 const reducers = {
   ADD_MESSAGE: function (state, action) {

src/sidebar/store/modules/viewer.js

@@ -7,14 +7,14 @@ import { createStoreModule } from '../create-store';
  * sidebar.
  */
 
-function initialState() {
-  return {
-    // Has the sidebar ever been opened? NB: This is not necessarily the
-    // current state of the sidebar, but tracks whether it has ever been open
+const initialState = {
+  /**
+   * Has the sidebar ever been opened? NB: This is not necessarily the
+   * current state of the sidebar, but tracks whether it has ever been open
+   */
   sidebarHasOpened: false,
   visibleHighlights: false,
-  };
-}
+};
 
 const reducers = {
   SET_HIGHLIGHTS_VISIBLE: function (state, action) {