From 92a305c08464e6cac813951bd0907af0fd265c60 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Fri, 7 Feb 2020 16:02:44 -0500
Subject: [PATCH 01/13] added some vscode stuff to gitignore

---
 .gitignore | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index d5df56f92..6fa243c24 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,10 +7,12 @@ build
 review/api/temp
 *.tsbuildinfo
 
-# jetbrains IDE stuff
+# jetbrains ide stuff
 *.iml
 .idea/
 
-# ms IDE stuff
+# ms ide stuff
+*.code-workspace
+.history
 .vscode
 

From 20fc19ddb3ecbb325bb5dda521bfbac85f272040 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sat, 8 Feb 2020 19:54:25 -0500
Subject: [PATCH 02/13] added iconRenderer field to command and menu item

---
 packages/commands/package.json   |  3 ++-
 packages/commands/src/index.ts   | 36 ++++++++++++++++++++++++++++++++
 packages/commands/tsconfig.json  |  3 +++
 packages/virtualdom/src/index.ts |  3 ++-
 packages/widgets/src/menu.ts     | 21 ++++++++++++++++++-
 5 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/packages/commands/package.json b/packages/commands/package.json
index cf89fb9d5..ac053a9b4 100644
--- a/packages/commands/package.json
+++ b/packages/commands/package.json
@@ -46,7 +46,8 @@
     "@lumino/disposable": "^1.3.4",
     "@lumino/domutils": "^1.1.7",
     "@lumino/keyboard": "^1.1.6",
-    "@lumino/signaling": "^1.3.4"
+    "@lumino/signaling": "^1.3.4",
+    "@lumino/virtualdom": "^1.5.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.6.0",
diff --git a/packages/commands/src/index.ts b/packages/commands/src/index.ts
index 02fcda5cf..8a8c2912f 100644
--- a/packages/commands/src/index.ts
+++ b/packages/commands/src/index.ts
@@ -31,6 +31,9 @@ import {
   ISignal, Signal
 } from '@lumino/signaling';
 
+import {
+  VirtualElement
+} from '@lumino/virtualdom';
 
 /**
  * An object which manages a collection of commands.
@@ -225,6 +228,21 @@ class CommandRegistry {
     return cmd ? cmd.iconLabel.call(undefined, args) : '';
   }
 
+  /**
+   * Get the icon renderer for a specific command.
+   *
+   * @param id - The id of the command of interest.
+   *
+   * @param args - The arguments for the command.
+   *
+   * @returns The icon renderer for the command, or undefined if
+   *   the command is not registered.
+   */
+  iconRenderer(id: string, args: ReadonlyPartialJSONObject = JSONExt.emptyObject): VirtualElement.IRenderer {
+    let cmd = this._commands[id];
+    return cmd ? cmd.iconRenderer.call(undefined, args) : undefined;
+  }
+
   /**
    * Get the short form caption for a specific command.
    *
@@ -681,6 +699,17 @@ namespace CommandRegistry {
      */
     iconLabel?: string | CommandFunc<string>;
 
+    /**
+     * The icon renderer for the command.
+     *
+     * #### Notes
+     * This can be an IRenderer object, or a function which returns the
+     * renderer based on the provided command arguments.
+     *
+     * The default value is undefined.
+     */
+    iconRenderer?: VirtualElement.IRenderer | CommandFunc<VirtualElement.IRenderer>;
+
     /**
      * The caption for the command.
      *
@@ -1167,6 +1196,7 @@ namespace Private {
     readonly mnemonic: CommandFunc<number>;
     readonly iconClass: CommandFunc<string>;
     readonly iconLabel: CommandFunc<string>;
+    readonly iconRenderer: CommandFunc<VirtualElement.IRenderer | undefined>;
     readonly caption: CommandFunc<string>;
     readonly usage: CommandFunc<string>;
     readonly className: CommandFunc<string>;
@@ -1187,6 +1217,7 @@ namespace Private {
       mnemonic: asFunc(options.mnemonic, negativeOneFunc),
       iconClass: asFunc(options.iconClass || options.icon, emptyStringFunc),
       iconLabel: asFunc(options.iconLabel, emptyStringFunc),
+      iconRenderer: asFunc(options.iconRenderer, undefinedFunc),
       caption: asFunc(options.caption, emptyStringFunc),
       usage: asFunc(options.usage, emptyStringFunc),
       className: asFunc(options.className, emptyStringFunc),
@@ -1325,6 +1356,11 @@ namespace Private {
    */
   const emptyDatasetFunc = () => ({});
 
+  /**
+   * A singleton undefined function
+   */
+  const undefinedFunc = () => undefined;
+
   /**
    * Cast a value or command func to a command func.
    */
diff --git a/packages/commands/tsconfig.json b/packages/commands/tsconfig.json
index 4720810f0..8ba3a68c0 100644
--- a/packages/commands/tsconfig.json
+++ b/packages/commands/tsconfig.json
@@ -40,6 +40,9 @@
     },
     {
       "path": "../signaling"
+    },
+    {
+      "path": "../virtualdom"
     }
   ]
 }
diff --git a/packages/virtualdom/src/index.ts b/packages/virtualdom/src/index.ts
index 087d15852..ecb76c9f2 100644
--- a/packages/virtualdom/src/index.ts
+++ b/packages/virtualdom/src/index.ts
@@ -801,7 +801,8 @@ namespace VirtualElement {
      *
      * For example, if render calls `ReactDOM.render(..., host)`, then
      * there has to also be a corresponding implementation of unrender that
-     * calls `ReactDOM.unmountComponentAtNode(host)`.
+     * calls `ReactDOM.unmountComponentAtNode(host)` in order to prevent
+     * a memory leak.
      *
      * @param host - the DOM element to be removed.
      */
diff --git a/packages/widgets/src/menu.ts b/packages/widgets/src/menu.ts
index 48bd97dbe..4ae9fc2c2 100644
--- a/packages/widgets/src/menu.ts
+++ b/packages/widgets/src/menu.ts
@@ -1053,6 +1053,11 @@ namespace Menu {
      */
     readonly iconLabel: string;
 
+    /**
+     * The icon renderer for the menu item.
+     */
+    readonly iconRenderer?: VirtualElement.IRenderer;
+
     /**
      * The display caption for the menu item.
      */
@@ -1167,7 +1172,8 @@ namespace Menu {
      */
     renderIcon(data: IRenderData): VirtualElement {
       let className = this.createIconClass(data);
-      return h.div({ className }, data.item.iconLabel);
+      // if iconRenderer is undefined, it will just be ignored
+      return h.div({ className }, data.item.iconRenderer!, data.item.iconLabel);
     }
 
     /**
@@ -1777,6 +1783,19 @@ namespace Private {
       return '';
     }
 
+    /**
+     * The icon renderer for the menu item.
+     */
+    get iconRenderer(): VirtualElement.IRenderer {
+      if (this.type === 'command') {
+        return this._commands.iconRenderer(this.command, this.args);
+      }
+      if (this.type === 'submenu' && this.submenu) {
+        return this.submenu.title.iconRenderer;
+      }
+      return undefined!;
+    }
+
     /**
      * The display caption for the menu item.
      */

From de6c3381a644368659b974755a4e42d15860e6e4 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 01:43:03 -0500
Subject: [PATCH 03/13] deprecated title.iconRenderer in favor of reclaimed
 title.icon

---
 packages/widgets/src/tabbar.ts |  9 +++-
 packages/widgets/src/title.ts  | 85 ++++++++++++++++++++++------------
 2 files changed, 64 insertions(+), 30 deletions(-)

diff --git a/packages/widgets/src/tabbar.ts b/packages/widgets/src/tabbar.ts
index 137b2bff2..66c693dbb 100644
--- a/packages/widgets/src/tabbar.ts
+++ b/packages/widgets/src/tabbar.ts
@@ -1360,7 +1360,14 @@ namespace TabBar {
       const { title } = data;
       let className = this.createIconClass(data);
 
-      return h.div({className}, title.iconRenderer, title.iconLabel);
+      /* <DEPRECATED> */
+      if (typeof title.icon === 'string') {
+        return h.div({className}, title.iconLabel);
+      }
+      /* </DEPRECATED> */
+
+      // if title.icon is undefined, it will be ignored
+      return h.div({className}, title.icon!, title.iconLabel);
     }
 
     /**
diff --git a/packages/widgets/src/title.ts b/packages/widgets/src/title.ts
index 151b1263c..0156b09c4 100644
--- a/packages/widgets/src/title.ts
+++ b/packages/widgets/src/title.ts
@@ -38,7 +38,7 @@ class Title<T> {
       this._mnemonic = options.mnemonic;
     }
     if (options.icon !== undefined) {
-      this._iconClass = options.icon;
+      this.icon = options.icon;
     }
     if (options.iconClass !== undefined) {
       this._iconClass = options.iconClass;
@@ -47,7 +47,7 @@ class Title<T> {
       this._iconLabel = options.iconLabel;
     }
     if (options.iconRenderer !== undefined) {
-      this._iconRenderer = options.iconRenderer;
+      this._icon = options.iconRenderer;
     }
     if (options.caption !== undefined) {
       this._caption = options.caption;
@@ -116,17 +116,52 @@ class Title<T> {
   }
 
   /**
-   * @deprecated Use `iconClass` instead.
+   * Get the icon renderer for the title.
+   *
+   * #### Notes
+   * The default value is undefined.
+   *
+   * DEPRECATED: if set to a string value, the .icon field will function as
+   * an alias for the .iconClass field, for backwards compatibility
    */
-  get icon(): string {
-    return this.iconClass;
+  get icon(): VirtualElement.IRenderer | string | undefined {
+    /* <DEPRECATED> */
+    if (this._icon === null) {
+      // only alias .iconClass if ._icon has been explicitly nulled
+      return this.iconClass
+    }
+    /* </DEPRECATED> */
+
+    return this._icon;
   }
 
   /**
-   * @deprecated Use `iconClass` instead.
+   * Set the icon renderer for the title.
+   *
+   * #### Notes
+   * A renderer is an object that supplies a render and unrender function.
+   *
+   * DEPRECATED: if set to a string value, the .icon field will function as
+   * an alias for the .iconClass field, for backwards compatibility
    */
-  set icon(value: string) {
-    this.iconClass = value;
+  set icon(value: VirtualElement.IRenderer | string | undefined ) {
+    /* <DEPRECATED> */
+    if (typeof value === "string") {
+      // when ._icon is null, the .icon getter will alias .iconClass
+      this._icon = null;
+      this.iconClass = value;
+    } else {
+    /* </DEPRECATED> */
+
+      if (this._icon === value) {
+        return;
+      }
+      this._icon = value;
+      this._changed.emit(undefined);
+
+    /* <DEPRECATED> */
+    }
+    /* </DEPRECATED> */
   }
 
   /**
@@ -178,27 +213,17 @@ class Title<T> {
   }
 
   /**
-   * Get the icon renderer for the title.
-   *
-   * #### Notes
-   * The default value is undefined.
+   * @deprecated Use `icon` instead.
    */
-  get iconRenderer(): VirtualElement.IRenderer {
-    return this._iconRenderer;
+  get iconRenderer(): VirtualElement.IRenderer | undefined {
+    return this._icon || undefined;
   }
 
   /**
-   * Set the icon renderer for the title.
-   *
-   * #### Notes
-   * A renderer is an object that supplies a render and unrender function.
+   * @deprecated Use `icon` instead.
    */
-  set iconRenderer(value: VirtualElement.IRenderer) {
-    if (this._iconRenderer === value) {
-      return;
-    }
-    this._iconRenderer = value;
-    this._changed.emit(undefined);
+  set iconRenderer(value: VirtualElement.IRenderer | undefined) {
+    this.icon = value;
   }
 
   /**
@@ -297,9 +322,9 @@ class Title<T> {
   private _label = '';
   private _caption = '';
   private _mnemonic = -1;
+  private _icon: VirtualElement.IRenderer | null | undefined;
   private _iconClass = '';
   private _iconLabel = '';
-  private _iconRenderer: VirtualElement.IRenderer;
   private _className = '';
   private _closable = false;
   private _dataset: Title.Dataset;
@@ -339,9 +364,12 @@ namespace Title {
     mnemonic?: number;
 
     /**
-     * @deprecated Use `iconClass` instead.
+     * The icon renderer for the title.
+     *
+     * DEPRECATED: if set to a string value, the .icon field will function as
+     * an alias for the .iconClass field, for backwards compatibility
      */
-    icon?: string;
+    icon?: VirtualElement.IRenderer | string;
 
     /**
      * The icon class name for the title.
@@ -354,8 +382,7 @@ namespace Title {
     iconLabel?: string;
 
     /**
-     * An object that supplies render and unrender functions used
-     * to create and cleanup the icon of the title.
+     * @deprecated Use `icon` instead.
      */
     iconRenderer?: VirtualElement.IRenderer;
 

From 16cfe95ea222d03cb109957065f9320b8037a765 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 02:56:10 -0500
Subject: [PATCH 04/13] switched .iconRenderer => .icon in commands and menu
 items

---
 packages/commands/src/index.ts | 95 +++++++++++++++++++++-------------
 packages/widgets/src/menu.ts   | 47 ++++++++---------
 packages/widgets/src/title.ts  | 18 ++++---
 3 files changed, 94 insertions(+), 66 deletions(-)

diff --git a/packages/commands/src/index.ts b/packages/commands/src/index.ts
index 8a8c2912f..a5f32aa35 100644
--- a/packages/commands/src/index.ts
+++ b/packages/commands/src/index.ts
@@ -192,10 +192,23 @@ class CommandRegistry {
   }
 
   /**
-   * @deprecated Use `iconClass()` instead.
+   * Get the icon renderer for a specific command.
+   *
+   * @param id - The id of the command of interest.
+   *
+   * @param args - The arguments for the command.
+   *
+   * @returns The icon renderer for the command, or undefined if
+   *   the command is not registered.
+   *   
+   *   DEPRECATED: if set to a string value, the .icon field will function as
+   *   an alias for the .iconClass field, for backwards compatibility
    */
-  icon(id: string, args: ReadonlyPartialJSONObject = JSONExt.emptyObject): string {
-    return this.iconClass(id, args);
+  icon(id: string, args: ReadonlyPartialJSONObject = JSONExt.emptyObject): VirtualElement.IRenderer | undefined
+  /* <DEPRECATED> */ | string /* </DEPRECATED> */
+  {
+    let cmd = this._commands[id];
+    return cmd ? cmd.icon.call(undefined, args) : undefined;
   }
 
   /**
@@ -228,21 +241,6 @@ class CommandRegistry {
     return cmd ? cmd.iconLabel.call(undefined, args) : '';
   }
 
-  /**
-   * Get the icon renderer for a specific command.
-   *
-   * @param id - The id of the command of interest.
-   *
-   * @param args - The arguments for the command.
-   *
-   * @returns The icon renderer for the command, or undefined if
-   *   the command is not registered.
-   */
-  iconRenderer(id: string, args: ReadonlyPartialJSONObject = JSONExt.emptyObject): VirtualElement.IRenderer {
-    let cmd = this._commands[id];
-    return cmd ? cmd.iconRenderer.call(undefined, args) : undefined;
-  }
-
   /**
    * Get the short form caption for a specific command.
    *
@@ -665,10 +663,24 @@ namespace CommandRegistry {
     mnemonic?: number | CommandFunc<number>;
 
     /**
-     * @deprecated Use `iconClass` instead.
+     * The icon renderer for the command.
+     *
+     * #### Notes
+     * This can be an IRenderer object, or a function which returns the
+     * renderer based on the provided command arguments.
+     *
+     * The default value is undefined.
+     * 
+     * DEPRECATED: if set to a string value, the .icon field will function as
+     * an alias for the .iconClass field, for backwards compatibility
      */
-    icon?: string | CommandFunc<string>;
-
+    icon?: VirtualElement.IRenderer
+    /* <DEPRECATED> */ | string /* </DEPRECATED> */
+    | CommandFunc<
+      VirtualElement.IRenderer
+      /* <DEPRECATED> */ | string /* </DEPRECATED> */
+    >;
+    
     /**
      * The icon class for the command.
      *
@@ -699,17 +711,6 @@ namespace CommandRegistry {
      */
     iconLabel?: string | CommandFunc<string>;
 
-    /**
-     * The icon renderer for the command.
-     *
-     * #### Notes
-     * This can be an IRenderer object, or a function which returns the
-     * renderer based on the provided command arguments.
-     *
-     * The default value is undefined.
-     */
-    iconRenderer?: VirtualElement.IRenderer | CommandFunc<VirtualElement.IRenderer>;
-
     /**
      * The caption for the command.
      *
@@ -1194,9 +1195,15 @@ namespace Private {
     readonly execute: CommandFunc<any>;
     readonly label: CommandFunc<string>;
     readonly mnemonic: CommandFunc<number>;
+    
+    readonly icon: CommandFunc<
+      VirtualElement.IRenderer
+      | undefined
+      /* <DEPRECATED> */ | string /* </DEPRECATED> */
+    >;
+    
     readonly iconClass: CommandFunc<string>;
     readonly iconLabel: CommandFunc<string>;
-    readonly iconRenderer: CommandFunc<VirtualElement.IRenderer | undefined>;
     readonly caption: CommandFunc<string>;
     readonly usage: CommandFunc<string>;
     readonly className: CommandFunc<string>;
@@ -1211,13 +1218,31 @@ namespace Private {
    */
   export
   function createCommand(options: CommandRegistry.ICommandOptions): ICommand {
+    let icon;
+    let iconClass;
+    
+    /* <DEPRECATED> */
+    if (typeof options.icon === 'string') {
+      // alias icon to iconClass
+      iconClass = asFunc(options.iconClass || options.icon, emptyStringFunc);
+      icon = iconClass;
+    } else {
+    /* /<DEPRECATED> */
+
+    iconClass = asFunc(options.iconClass, emptyStringFunc);
+    icon = asFunc(options.icon, undefinedFunc);
+
+    /* <DEPRECATED> */
+    }
+    /* </DEPRECATED> */
+    
     return {
       execute: options.execute,
       label: asFunc(options.label, emptyStringFunc),
       mnemonic: asFunc(options.mnemonic, negativeOneFunc),
-      iconClass: asFunc(options.iconClass || options.icon, emptyStringFunc),
+      icon,
+      iconClass,
       iconLabel: asFunc(options.iconLabel, emptyStringFunc),
-      iconRenderer: asFunc(options.iconRenderer, undefinedFunc),
       caption: asFunc(options.caption, emptyStringFunc),
       usage: asFunc(options.usage, emptyStringFunc),
       className: asFunc(options.className, emptyStringFunc),
diff --git a/packages/widgets/src/menu.ts b/packages/widgets/src/menu.ts
index 4ae9fc2c2..825f9c5c9 100644
--- a/packages/widgets/src/menu.ts
+++ b/packages/widgets/src/menu.ts
@@ -1039,9 +1039,10 @@ namespace Menu {
     readonly mnemonic: number;
 
     /**
-     * @deprecated Use `iconClass` instead.
+     * The icon renderer for the menu item.
      */
-    readonly icon: string;
+    readonly icon: VirtualElement.IRenderer | undefined
+    /* <DEPRECATED> */ | string /* </DEPRECATED> */;
 
     /**
      * The icon class for the menu item.
@@ -1053,11 +1054,6 @@ namespace Menu {
      */
     readonly iconLabel: string;
 
-    /**
-     * The icon renderer for the menu item.
-     */
-    readonly iconRenderer?: VirtualElement.IRenderer;
-
     /**
      * The display caption for the menu item.
      */
@@ -1172,8 +1168,15 @@ namespace Menu {
      */
     renderIcon(data: IRenderData): VirtualElement {
       let className = this.createIconClass(data);
-      // if iconRenderer is undefined, it will just be ignored
-      return h.div({ className }, data.item.iconRenderer!, data.item.iconLabel);
+
+      /* <DEPRECATED> */
+      if (typeof data.item.icon === 'string') {
+        return h.div({className}, data.item.iconLabel);
+      }
+      /* </DEPRECATED> */
+
+      // if data.item.icon is undefined, it will be ignored
+      return h.div({className}, data.item.icon!, data.item.iconLabel);
     }
 
     /**
@@ -1751,10 +1754,18 @@ namespace Private {
     }
 
     /**
-     * @deprecated Use `iconClass` instead.
+     * The icon renderer for the menu item.
      */
-    get icon(): string {
-      return this.iconClass;
+    get icon(): VirtualElement.IRenderer | undefined 
+    /* <DEPRECATED> */ | string /* </DEPRECATED> */
+    {
+      if (this.type === 'command') {
+        return this._commands.icon(this.command, this.args);
+      }
+      if (this.type === 'submenu' && this.submenu) {
+        return this.submenu.title.icon;
+      }
+      return undefined!;
     }
 
     /**
@@ -1783,18 +1794,6 @@ namespace Private {
       return '';
     }
 
-    /**
-     * The icon renderer for the menu item.
-     */
-    get iconRenderer(): VirtualElement.IRenderer {
-      if (this.type === 'command') {
-        return this._commands.iconRenderer(this.command, this.args);
-      }
-      if (this.type === 'submenu' && this.submenu) {
-        return this.submenu.title.iconRenderer;
-      }
-      return undefined!;
-    }
 
     /**
      * The display caption for the menu item.
diff --git a/packages/widgets/src/title.ts b/packages/widgets/src/title.ts
index 0156b09c4..ea1640760 100644
--- a/packages/widgets/src/title.ts
+++ b/packages/widgets/src/title.ts
@@ -124,7 +124,9 @@ class Title<T> {
    * DEPRECATED: if set to a string value, the .icon field will function as
    * an alias for the .iconClass field, for backwards compatibility
    */
-  get icon(): VirtualElement.IRenderer | string | undefined {
+  get icon(): VirtualElement.IRenderer| undefined
+  /* <DEPRECATED> */ | string /* </DEPRECATED> */
+  {
     /* <DEPRECATED> */
     if (this._icon === null) {
       // only alias .iconClass if ._icon has been explicitly nulled
@@ -144,7 +146,9 @@ class Title<T> {
    * DEPRECATED: if set to a string value, the .icon field will function as
    * an alias for the .iconClass field, for backwards compatibility
    */
-  set icon(value: VirtualElement.IRenderer | string | undefined ) {
+  set icon(value: VirtualElement.IRenderer | undefined
+  /* <DEPRECATED> */ | string /* </DEPRECATED> */
+  ) {
     /* <DEPRECATED> */
     if (typeof value === "string") {
       // when ._icon is null, the .icon getter will alias .iconClass
@@ -153,11 +157,11 @@ class Title<T> {
     } else {
     /* </DEPRECATED> */
 
-      if (this._icon === value) {
-        return;
-      }
-      this._icon = value;
-      this._changed.emit(undefined);
+    if (this._icon === value) {
+      return;
+    }
+    this._icon = value;
+    this._changed.emit(undefined);
 
     /* <DEPRECATED> */
     }

From 410c3ddbd9172d13721c0dd2d8641bcb641d35a1 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 02:59:37 -0500
Subject: [PATCH 05/13] minor fix to title constructor

---
 packages/widgets/src/title.ts | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/packages/widgets/src/title.ts b/packages/widgets/src/title.ts
index ea1640760..de619e7c8 100644
--- a/packages/widgets/src/title.ts
+++ b/packages/widgets/src/title.ts
@@ -38,7 +38,19 @@ class Title<T> {
       this._mnemonic = options.mnemonic;
     }
     if (options.icon !== undefined) {
-      this.icon = options.icon;
+      /* <DEPRECATED> */
+      if (typeof options.icon === "string") {
+        // when ._icon is null, the .icon getter will alias .iconClass
+        this._icon = null;
+        this._iconClass = options.icon;
+      } else {
+      /* </DEPRECATED> */
+
+      this._icon = options.icon;
+
+      /* <DEPRECATED> */
+      }
+      /* </DEPRECATED> */
     }
     if (options.iconClass !== undefined) {
       this._iconClass = options.iconClass;

From 76f6766c498ab4d34b37b9fdcadef26c50ac2119 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 03:38:55 -0500
Subject: [PATCH 06/13] small type fix (added `| undefined`)

---
 packages/commands/src/index.ts | 7 +++----
 packages/widgets/src/title.ts  | 5 ++++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/packages/commands/src/index.ts b/packages/commands/src/index.ts
index a5f32aa35..0863697d3 100644
--- a/packages/commands/src/index.ts
+++ b/packages/commands/src/index.ts
@@ -674,10 +674,10 @@ namespace CommandRegistry {
      * DEPRECATED: if set to a string value, the .icon field will function as
      * an alias for the .iconClass field, for backwards compatibility
      */
-    icon?: VirtualElement.IRenderer
+    icon?: VirtualElement.IRenderer | undefined
     /* <DEPRECATED> */ | string /* </DEPRECATED> */
     | CommandFunc<
-      VirtualElement.IRenderer
+      VirtualElement.IRenderer | undefined
       /* <DEPRECATED> */ | string /* </DEPRECATED> */
     >;
     
@@ -1197,8 +1197,7 @@ namespace Private {
     readonly mnemonic: CommandFunc<number>;
     
     readonly icon: CommandFunc<
-      VirtualElement.IRenderer
-      | undefined
+      VirtualElement.IRenderer | undefined
       /* <DEPRECATED> */ | string /* </DEPRECATED> */
     >;
     
diff --git a/packages/widgets/src/title.ts b/packages/widgets/src/title.ts
index de619e7c8..68397b560 100644
--- a/packages/widgets/src/title.ts
+++ b/packages/widgets/src/title.ts
@@ -338,7 +338,10 @@ class Title<T> {
   private _label = '';
   private _caption = '';
   private _mnemonic = -1;
-  private _icon: VirtualElement.IRenderer | null | undefined;
+
+  private _icon: VirtualElement.IRenderer | undefined
+  /* <DEPRECATED> */ | null /* </DEPRECATED> */;
+
   private _iconClass = '';
   private _iconLabel = '';
   private _className = '';

From 4b64274f2f962cad6abf03f3bcaa7fa9e202188a Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 20:02:16 -0500
Subject: [PATCH 07/13] fixed tests for tabbar and title

---
 packages/widgets/package.json             |  2 +-
 packages/widgets/src/title.ts             |  8 +++++++
 packages/widgets/tests/src/tabbar.spec.ts | 27 +++++++++++++++++++----
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/packages/widgets/package.json b/packages/widgets/package.json
index 4f0753b66..0d01c49bb 100644
--- a/packages/widgets/package.json
+++ b/packages/widgets/package.json
@@ -41,7 +41,7 @@
     "test:chrome-headless": "cd tests && karma start --browsers=ChromeHeadless",
     "test:debug": "npm run test:debug:firefox",
     "test:debug:chrome": "cd tests && karma start --browsers=Chrome --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
-    "test:debug:chrome-headless": "cd tests && karma start  --browsers=ChromeHeadless --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
+    "test:debug:chrome-headless": "cd tests && karma start --browsers=ChromeHeadless --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
     "test:debug:firefox": "cd tests && karma start --browsers=Firefox --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
     "test:firefox": "cd tests && karma start --browsers=Firefox",
     "test:ie": "cd tests && karma start --browsers=IE",
diff --git a/packages/widgets/src/title.ts b/packages/widgets/src/title.ts
index 68397b560..556587867 100644
--- a/packages/widgets/src/title.ts
+++ b/packages/widgets/src/title.ts
@@ -52,6 +52,14 @@ class Title<T> {
       }
       /* </DEPRECATED> */
     }
+
+    /* <DEPRECATED> */
+    else {
+      // if unset, default to aliasing .iconClass
+      this._icon = null;
+    }
+    /* </DEPRECATED> */
+
     if (options.iconClass !== undefined) {
       this._iconClass = options.iconClass;
     }
diff --git a/packages/widgets/tests/src/tabbar.spec.ts b/packages/widgets/tests/src/tabbar.spec.ts
index 32334842e..573c193aa 100644
--- a/packages/widgets/tests/src/tabbar.spec.ts
+++ b/packages/widgets/tests/src/tabbar.spec.ts
@@ -1297,10 +1297,17 @@ describe('@lumino/widgets', () => {
           expect(node.classList.contains('lm-mod-closable')).to.equal(true);
           expect(node.title).to.equal(title.caption);
 
-          let icon = node.getElementsByClassName('lm-TabBar-tabIcon')[0] as HTMLElement;
           let label = node.getElementsByClassName('lm-TabBar-tabLabel')[0] as HTMLElement;
-          expect(icon.classList.contains(title.icon)).to.equal(true);
           expect(label.textContent).to.equal(title.label);
+
+          let icon = node.getElementsByClassName('lm-TabBar-tabIcon')[0] as HTMLElement;
+          expect(icon.classList.contains(title.iconClass)).to.equal(true);
+
+          /* <DEPRECATED> */
+          // since a string was assigned to .icon, it should alias .iconClass
+          expect(icon.classList.contains(title.icon as string)).to.equal(true);
+          expect(title.icon).to.equal(title.iconClass);
+          /* </DEPRECATED> */
         });
 
       });
@@ -1312,7 +1319,13 @@ describe('@lumino/widgets', () => {
           let vNode = renderer.renderIcon({ title, current: true, zIndex: 1 });
           let node = VirtualDOM.realize(vNode as VirtualElement);
           expect(node.className).to.contain('lm-TabBar-tabIcon');
-          expect(node.classList.contains(title.icon)).to.equal(true);
+          expect(node.classList.contains(title.iconClass)).to.equal(true);
+
+          /* <DEPRECATED> */
+          // make sure that icon and iconClass match
+          expect(node.classList.contains(title.icon as string)).to.equal(true);
+          expect(title.icon).to.equal(title.iconClass);
+          /* </DEPRECATED> */
         });
 
       });
@@ -1383,7 +1396,13 @@ describe('@lumino/widgets', () => {
             title, current: true, zIndex: 1
           });
           expect(className).to.contain('lm-TabBar-tabIcon');
-          expect(className).to.contain(title.icon);
+          expect(className).to.contain(title.iconClass);
+
+          /* <DEPRECATED> */
+          // make sure that icon and iconClass match
+          expect(className).to.contain(title.icon as string);
+          expect(title.icon).to.equal(title.iconClass);
+          /* </DEPRECATED> */
         });
 
       });

From e6acd5ce21cecd41cccc509ce201e49459ca5ee0 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 23:23:28 -0500
Subject: [PATCH 08/13] fixed tests for menu

---
 packages/commands/src/index.ts | 16 +++++++++-------
 packages/widgets/src/menu.ts   | 10 +++++++++-
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/packages/commands/src/index.ts b/packages/commands/src/index.ts
index 0863697d3..b1261dc7b 100644
--- a/packages/commands/src/index.ts
+++ b/packages/commands/src/index.ts
@@ -194,21 +194,23 @@ class CommandRegistry {
   /**
    * Get the icon renderer for a specific command.
    *
+   * DEPRECATED: if set to a string value, the .icon field will
+   * function as an alias for the .iconClass field, for backwards
+   * compatibility. In the future when this is removed, the default
+   * return type will become undefined.
+   *
    * @param id - The id of the command of interest.
    *
    * @param args - The arguments for the command.
    *
-   * @returns The icon renderer for the command, or undefined if
-   *   the command is not registered.
-   *   
-   *   DEPRECATED: if set to a string value, the .icon field will function as
-   *   an alias for the .iconClass field, for backwards compatibility
+   * @returns The icon renderer for the command, or
+   *   an empty string if the command is not registered.
    */
   icon(id: string, args: ReadonlyPartialJSONObject = JSONExt.emptyObject): VirtualElement.IRenderer | undefined
   /* <DEPRECATED> */ | string /* </DEPRECATED> */
   {
     let cmd = this._commands[id];
-    return cmd ? cmd.icon.call(undefined, args) : undefined;
+    return cmd ? cmd.icon.call(undefined, args) : /* <DEPRECATED> */ '' /* </DEPRECATED> */ /* <FUTURE> undefined </FUTURE> */;
   }
 
   /**
@@ -1221,7 +1223,7 @@ namespace Private {
     let iconClass;
     
     /* <DEPRECATED> */
-    if (typeof options.icon === 'string') {
+    if (!(options.icon) || typeof options.icon === 'string') {
       // alias icon to iconClass
       iconClass = asFunc(options.iconClass || options.icon, emptyStringFunc);
       icon = iconClass;
diff --git a/packages/widgets/src/menu.ts b/packages/widgets/src/menu.ts
index 825f9c5c9..6113c7756 100644
--- a/packages/widgets/src/menu.ts
+++ b/packages/widgets/src/menu.ts
@@ -1765,7 +1765,15 @@ namespace Private {
       if (this.type === 'submenu' && this.submenu) {
         return this.submenu.title.icon;
       }
-      return undefined!;
+
+      /* <DEPRECATED> */
+      // alias to icon class if not otherwise defined
+      return this.iconClass;
+      /* </DEPRECATED> */
+
+      /* <FUTURE>
+      return undefined;
+      </FUTURE> */
     }
 
     /**

From b068940c4ab45a379da051351675346b23c4e44f Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 23:35:36 -0500
Subject: [PATCH 09/13] updated renderIcon for menubar to use title.icon

---
 packages/widgets/src/menubar.ts | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/packages/widgets/src/menubar.ts b/packages/widgets/src/menubar.ts
index 71fdaef81..88a8cffc2 100644
--- a/packages/widgets/src/menubar.ts
+++ b/packages/widgets/src/menubar.ts
@@ -787,7 +787,15 @@ namespace MenuBar {
      */
     renderIcon(data: IRenderData): VirtualElement {
       let className = this.createIconClass(data);
-      return h.div({ className }, data.title.iconLabel);
+
+      /* <DEPRECATED> */
+      if (typeof data.title.icon === 'string') {
+        return h.div({className}, data.title.iconLabel);
+      }
+      /* </DEPRECATED> */
+
+      // if data.title.icon is undefined, it will be ignored
+      return h.div({className}, data.title.icon!, data.title.iconLabel);
     }
 
     /**

From dfa9a7249366c27e192fadf6bf0a3a5b6841834c Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Sun, 9 Feb 2020 23:58:56 -0500
Subject: [PATCH 10/13] updated renderItemIcon for commandpalette to use
 command.icon

---
 packages/widgets/src/commandpalette.ts | 25 ++++++++++++++++++++++++-
 packages/widgets/src/menu.ts           |  2 +-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/packages/widgets/src/commandpalette.ts b/packages/widgets/src/commandpalette.ts
index d11053720..079f839b2 100644
--- a/packages/widgets/src/commandpalette.ts
+++ b/packages/widgets/src/commandpalette.ts
@@ -587,6 +587,12 @@ namespace CommandPalette {
      */
     readonly caption: string;
 
+    /**
+     * The icon renderer for the command item.
+     */
+    readonly icon: VirtualElement.IRenderer | undefined
+    /* <DEPRECATED> */ | string /* </DEPRECATED> */;
+
     /**
      * The icon class for the command item.
      */
@@ -779,7 +785,15 @@ namespace CommandPalette {
      */
     renderItemIcon(data: IItemRenderData): VirtualElement {
       let className = this.createIconClass(data);
-      return h.div({ className }, data.item.iconLabel);
+
+      /* <DEPRECATED> */
+      if (typeof data.item.icon === 'string') {
+        return h.div({className}, data.item.iconLabel);
+      }
+      /* </DEPRECATED> */
+
+      // if data.item.icon is undefined, it will be ignored
+      return h.div({className}, data.item.icon!, data.item.iconLabel);
     }
 
     /**
@@ -1446,6 +1460,15 @@ namespace Private {
       return this._commands.label(this.command, this.args);
     }
 
+    /**
+     * The icon renderer for the command item.
+     */
+    get icon(): VirtualElement.IRenderer | undefined
+    /* <DEPRECATED> */ | string /* </DEPRECATED> */
+    {
+      return this._commands.icon(this.command, this.args);
+    }
+
     /**
      * The icon class for the command item.
      */
diff --git a/packages/widgets/src/menu.ts b/packages/widgets/src/menu.ts
index 6113c7756..49c3d19d1 100644
--- a/packages/widgets/src/menu.ts
+++ b/packages/widgets/src/menu.ts
@@ -1756,7 +1756,7 @@ namespace Private {
     /**
      * The icon renderer for the menu item.
      */
-    get icon(): VirtualElement.IRenderer | undefined 
+    get icon(): VirtualElement.IRenderer | undefined
     /* <DEPRECATED> */ | string /* </DEPRECATED> */
     {
       if (this.type === 'command') {

From d06928e0dc228e7d3b94649f284d73f29f5307d7 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Mon, 10 Feb 2020 05:36:10 -0500
Subject: [PATCH 11/13] attrs and children now passed consistently to custom
 vdom renderers

---
 packages/virtualdom/package.json | 19 +++++++++++++------
 packages/virtualdom/src/index.ts |  9 ++++++---
 packages/widgets/package.json    | 19 ++++++++++++-------
 3 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/packages/virtualdom/package.json b/packages/virtualdom/package.json
index b5fdd6650..2be8925c3 100644
--- a/packages/virtualdom/package.json
+++ b/packages/virtualdom/package.json
@@ -34,13 +34,20 @@
     "clean": "rimraf lib && rimraf *.tsbuildinfo",
     "clean:test": "rimraf tests/build",
     "docs": "typedoc --options tdoptions.json src",
+
     "test": "npm run test:firefox",
-    "test:chrome": "cd tests && karma start --browsers=Chrome",
-    "test:chrome-headless": "cd tests && karma start --browsers=ChromeHeadless",
-    "test:debug": "cd tests && karma start --browsers=Chrome --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
-    "test:debug:chrome-headless": "cd tests && karma start  --browsers=ChromeHeadless --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
-    "test:firefox": "cd tests && karma start --browsers=Firefox",
-    "test:ie": "cd tests && karma start --browsers=IE",
+    "test:chrome": "npm run test:nobrowser -- --browsers=Chrome",
+    "test:chrome-headless": "npm run test:nobrowser -- --browsers=ChromeHeadless",
+    "test:ie": "npm run test:nobrowser -- --browsers=IE",
+    "test:firefox": "npm run test:nobrowser -- --browsers=Firefox",
+    "test:nobrowser": "cd tests && karma start",
+
+    "test:debug": "npm run test:debug:firefox",
+    "test:debug:chrome-headless": "npm run test:debug:nobrowser -- --browsers=ChromeHeadless",
+    "test:debug:chrome": "npm run test:debug:nobrowser -- --browsers=Chrome",
+    "test:debug:firefox": "npm run test:debug:nobrowser -- --browsers=Firefox",
+    "test:debug:nobrowser": "cd tests && karma start --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
+
     "watch": "tsc --build --watch"
   },
   "dependencies": {
diff --git a/packages/virtualdom/src/index.ts b/packages/virtualdom/src/index.ts
index ecb76c9f2..c77dc09bc 100644
--- a/packages/virtualdom/src/index.ts
+++ b/packages/virtualdom/src/index.ts
@@ -805,8 +805,11 @@ namespace VirtualElement {
      * a memory leak.
      *
      * @param host - the DOM element to be removed.
+     *
+     * @param options - Will be populated with the .attrs and .children fields
+     * set on the VirtualElement being unrendered.
      */
-    unrender?: (host: HTMLElement) => void;
+    unrender?: (host: HTMLElement, options?: {attrs?: ElementAttrs, children?: ReadonlyArray<VirtualNode>}) => void;
   };
 }
 
@@ -1313,7 +1316,7 @@ namespace Private {
 
       // Update the element content.
       if (newVNode.renderer) {
-        newVNode.renderer.render(currElem as HTMLElement);
+        newVNode.renderer.render(currElem as HTMLElement, {attrs: newVNode.attrs, children: newVNode.children});
       } else {
         updateContent(currElem as HTMLElement, oldVNode.children, newVNode.children);
       }
@@ -1342,7 +1345,7 @@ namespace Private {
 
       // recursively clean up host children
       if (oldNode.type === 'text') {} else if (oldNode.renderer && oldNode.renderer.unrender) {
-        oldNode.renderer.unrender(child!);
+        oldNode.renderer.unrender(child!, {attrs: oldNode.attrs, children: oldNode.children});
       } else {
         removeContent(child!, oldNode.children, 0, false);
       }
diff --git a/packages/widgets/package.json b/packages/widgets/package.json
index 0d01c49bb..2db0fba68 100644
--- a/packages/widgets/package.json
+++ b/packages/widgets/package.json
@@ -36,15 +36,20 @@
     "clean": "rimraf lib && rimraf *.tsbuildinfo",
     "clean:test": "rimraf tests/build",
     "docs": "typedoc --options tdoptions.json src",
+
     "test": "npm run test:firefox",
-    "test:chrome": "cd tests && karma start --browsers=Chrome",
-    "test:chrome-headless": "cd tests && karma start --browsers=ChromeHeadless",
+    "test:chrome": "npm run test:nobrowser -- --browsers=Chrome",
+    "test:chrome-headless": "npm run test:nobrowser -- --browsers=ChromeHeadless",
+    "test:ie": "npm run test:nobrowser -- --browsers=IE",
+    "test:firefox": "npm run test:nobrowser -- --browsers=Firefox",
+    "test:nobrowser": "cd tests && karma start",
+
     "test:debug": "npm run test:debug:firefox",
-    "test:debug:chrome": "cd tests && karma start --browsers=Chrome --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
-    "test:debug:chrome-headless": "cd tests && karma start --browsers=ChromeHeadless --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
-    "test:debug:firefox": "cd tests && karma start --browsers=Firefox --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
-    "test:firefox": "cd tests && karma start --browsers=Firefox",
-    "test:ie": "cd tests && karma start --browsers=IE",
+    "test:debug:chrome-headless": "npm run test:debug:nobrowser -- --browsers=ChromeHeadless",
+    "test:debug:chrome": "npm run test:debug:nobrowser -- --browsers=Chrome",
+    "test:debug:firefox": "npm run test:debug:nobrowser -- --browsers=Firefox",
+    "test:debug:nobrowser": "cd tests && karma start --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
+
     "watch": "tsc --build --watch"
   },
   "dependencies": {

From fdcc50bf501ddcdff1e47d779b065e0770ef4bb7 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Mon, 10 Feb 2020 06:00:49 -0500
Subject: [PATCH 12/13] added test coverage for Title.icon backwards
 compatibility

---
 packages/widgets/tests/src/title.spec.ts | 31 ++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/packages/widgets/tests/src/title.spec.ts b/packages/widgets/tests/src/title.spec.ts
index d38f6f738..f781299b0 100644
--- a/packages/widgets/tests/src/title.spec.ts
+++ b/packages/widgets/tests/src/title.spec.ts
@@ -143,6 +143,14 @@ describe('@lumino/widgets', () => {
 
     describe('#icon', () => {
 
+      const iconRenderer = {
+        render: (host: HTMLElement, options?: any) => {
+          const renderNode = document.createElement('div');
+          renderNode.className = 'p-render';
+          host.appendChild(renderNode);
+        }
+      };
+
       it('should default to an empty string', () => {
         let title = new Title({ owner });
         expect(title.icon).to.equal('');
@@ -181,6 +189,29 @@ describe('@lumino/widgets', () => {
         expect(called).to.equal(false);
       });
 
+      /* <DEPRECATED> */
+      it('should be able to switch string => renderer', () => {
+        let title = new Title({ owner, icon: 'foo' });
+        expect(title.icon).to.equal('foo');
+
+        // when initialized with string, should alias .iconClass
+        expect(title.icon).to.equal(title.iconClass);
+
+        title.icon = iconRenderer;
+        expect(title.icon).to.equal(iconRenderer);
+      });
+
+      it('should be able to switch renderer => string', () => {
+        let title = new Title({ owner, icon: iconRenderer });
+        expect(title.icon).to.equal(iconRenderer);
+        title.icon = 'foo';
+        expect(title.icon).to.equal('foo');
+
+        // when switched to string, should alias .iconClass
+        expect(title.icon).to.equal(title.iconClass);
+      });
+      /* </DEPRECATED> */
+
     });
 
     describe('#caption', () => {

From c8284dfb2142a589cf33d79f67d26da21e52d4c1 Mon Sep 17 00:00:00 2001
From: telamonian <mklein@jhu.edu>
Date: Mon, 10 Feb 2020 06:14:54 -0500
Subject: [PATCH 13/13] added test coverage for CommandRegistry.icon backwards
 compatibility

---
 packages/commands/package.json            | 16 +++++++++---
 packages/commands/tests/src/index.spec.ts | 31 +++++++++++++++++++++--
 packages/widgets/tests/src/title.spec.ts  |  5 ++++
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/packages/commands/package.json b/packages/commands/package.json
index ac053a9b4..3729e6558 100644
--- a/packages/commands/package.json
+++ b/packages/commands/package.json
@@ -34,10 +34,20 @@
     "clean": "rimraf lib && rimraf *.tsbuildinfo",
     "clean:test": "rimraf tests/build",
     "docs": "typedoc --options tdoptions.json src",
+
     "test": "npm run test:firefox",
-    "test:chrome": "cd tests && karma start --browsers=Chrome",
-    "test:firefox": "cd tests && karma start --browsers=Firefox",
-    "test:ie": "cd tests && karma start --browsers=IE",
+    "test:chrome": "npm run test:nobrowser -- --browsers=Chrome",
+    "test:chrome-headless": "npm run test:nobrowser -- --browsers=ChromeHeadless",
+    "test:ie": "npm run test:nobrowser -- --browsers=IE",
+    "test:firefox": "npm run test:nobrowser -- --browsers=Firefox",
+    "test:nobrowser": "cd tests && karma start",
+
+    "test:debug": "npm run test:debug:firefox",
+    "test:debug:chrome-headless": "npm run test:debug:nobrowser -- --browsers=ChromeHeadless",
+    "test:debug:chrome": "npm run test:debug:nobrowser -- --browsers=Chrome",
+    "test:debug:firefox": "npm run test:debug:nobrowser -- --browsers=Firefox",
+    "test:debug:nobrowser": "cd tests && karma start --singleRun=false --debug=true --browserNoActivityTimeout=10000000 --browserDisconnectTimeout=10000000",
+
     "watch": "tsc --build --watch"
   },
   "dependencies": {
diff --git a/packages/commands/tests/src/index.spec.ts b/packages/commands/tests/src/index.spec.ts
index 4f7b43f49..822877e5e 100644
--- a/packages/commands/tests/src/index.spec.ts
+++ b/packages/commands/tests/src/index.spec.ts
@@ -275,13 +275,21 @@ describe('@lumino/commands', () => {
 
     describe('#icon()', () => {
 
+      const iconRenderer = {
+        render: (host: HTMLElement, options?: any) => {
+          const renderNode = document.createElement('div');
+          renderNode.className = 'p-render';
+          host.appendChild(renderNode);
+        }
+      };
+
       it('should get the icon for a specific command', () => {
         let cmd = {
           execute: (args: JSONObject) => { return args; },
-          icon: 'foo'
+          icon: iconRenderer
         };
         registry.addCommand('test', cmd);
-        expect(registry.icon('test')).to.equal('foo');
+        expect(registry.icon('test')).to.equal(iconRenderer);
       });
 
       it('should give the appropriate icon given arguments', () => {
@@ -302,6 +310,25 @@ describe('@lumino/commands', () => {
         expect(registry.icon('test')).to.equal('');
       });
 
+      /* <DEPRECATED> */
+      it('should be able to return a string value', () => {
+        let cmd = {
+          execute: (args: JSONObject) => { return args; },
+          icon: 'foo'
+        };
+        registry.addCommand('test', cmd);
+        expect(registry.icon('test')).to.equal('foo');
+      });
+
+      it('should alias .iconClass() if cmd.icon is unset', () => {
+        let cmd = {
+          execute: (args: JSONObject) => { return args; },
+          iconClass: 'foo'
+        };
+        registry.addCommand('test', cmd);
+        expect(registry.icon('test')).to.equal('foo');
+      });
+      /* </DEPRECATED> */
     });
 
     describe('#caption()', () => {
diff --git a/packages/widgets/tests/src/title.spec.ts b/packages/widgets/tests/src/title.spec.ts
index f781299b0..18e924e33 100644
--- a/packages/widgets/tests/src/title.spec.ts
+++ b/packages/widgets/tests/src/title.spec.ts
@@ -210,6 +210,11 @@ describe('@lumino/widgets', () => {
         // when switched to string, should alias .iconClass
         expect(title.icon).to.equal(title.iconClass);
       });
+
+      it('should alias .iconClass if unset', () => {
+        let title = new Title({ owner, iconClass: 'foo' });
+        expect(title.icon).to.equal('foo');
+      });
       /* </DEPRECATED> */
 
     });