Add excel custom functions to an existing excel add-in - Javascript Api - excel

Question

I have an existing excel add-in with UI (using react) and I would like to add some custom functions to it. When I add the add-ins in separate both work fine but when I try to merge them the custom functions don't appear.
I assume that my issue is on the manifest but I'm not sure what is it: I added the custom functions extension point, added the custom functions bit to the resources Urls and ShortStrings and replaced the html source location of the cf to be the task pane html.
Here is my manifest:
<?xml version="1.0" encoding="UTF-8"?>
<OfficeApp
xmlns="http://schemas.microsoft.com/office/appforoffice/1.1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0"
xmlns:ov="http://schemas.microsoft.com/office/taskpaneappversionoverrides"
xsi:type="TaskPaneApp">
<!-- Begin Basic Settings: Add-in metadata, used for all versions of Office unless override provided. -->
<!-- IMPORTANT! Id must be unique for your add-in, if you reuse this manifest ensure that you change this id to a new GUID. -->
<Id>1d9453a6-d50b-4b54-9076-eb0f1d9409c0</Id>
<!--Version. Updates from the store only get triggered if there is a version change. -->
<Version>1.0.0.0</Version>
<ProviderName>[Provider name]</ProviderName>
<DefaultLocale>en-US</DefaultLocale>
<!-- The display name of your add-in. Used on the store and various places of the Office UI such as the add-ins dialog. -->
<DisplayName DefaultValue="Iplicit Excel Add-in" />
<Description DefaultValue="[Workbook Add-in description]"/>
<!-- Icon for your add-in. Used on installation screens and the add-ins dialog. -->
<IconUrl DefaultValue="https://localhost:3000/assets/icon-32.png" />
<HighResolutionIconUrl DefaultValue="https://localhost:3000/assets/hi-res-icon.png"/>
<!--If you plan to submit this add-in to the Office Store, uncomment the SupportUrl element below-->
<!--<SupportUrl DefaultValue="[Insert the URL of a page that provides support information for the app]">-->
<!-- Domains that will be allowed when navigating. For example, if you use ShowTaskpane and then have an href link, navigation will only be allowed if the domain is on this list. -->
<AppDomains>
<AppDomain>AppDomain1</AppDomain>
<AppDomain>AppDomain2</AppDomain>
<AppDomain>AppDomain3</AppDomain>
</AppDomains>
<!--End Basic Settings. -->
<!--Begin TaskPane Mode integration. This section is used if there are no VersionOverrides or if the Office client version does not support add-in commands. -->
<Hosts>
<Host Name="Workbook" />
</Hosts>
<DefaultSettings>
<SourceLocation DefaultValue="https://localhost:3000/index.html" />
</DefaultSettings>
<!-- End TaskPane Mode integration. -->
<Permissions>ReadWriteDocument</Permissions>
<!-- Begin Add-in Commands Mode integration. -->
<VersionOverrides xmlns="http://schemas.microsoft.com/office/taskpaneappversionoverrides" xsi:type="VersionOverridesV1_0">
<!-- The Hosts node is required. -->
<Hosts>
<!-- Each host can have a different set of commands. -->
<!-- Excel host is Workbook, Word host is Document, and PowerPoint host is Presentation. -->
<!-- Make sure the hosts you override match the hosts declared in the top section of the manifest. -->
<Host xsi:type="Workbook">
<!-- Form factor. Currently only DesktopFormFactor is supported. -->
<DesktopFormFactor>
<!--"This code enables a customizable message to be displayed when the add-in is loaded successfully upon individual install."-->
<GetStarted>
<!-- Title of the Getting Started callout. resid points to a ShortString resource -->
<Title resid="Contoso.GetStarted.Title"/>
<!-- Description of the Getting Started callout. resid points to a LongString resource -->
<Description resid="Contoso.GetStarted.Description"/>
<!-- Point to a url resource which details how the add-in should be used. -->
<LearnMoreUrl resid="Contoso.GetStarted.LearnMoreUrl"/>
</GetStarted>
<!-- Function file is a HTML page that includes the JavaScript where functions for ExecuteAction will be called.
Think of the FunctionFile as the code behind ExecuteFunction. -->
<FunctionFile resid="Contoso.DesktopFunctionFile.Url" />
<!-- PrimaryCommandSurface is the main Office Ribbon. -->
<ExtensionPoint xsi:type="PrimaryCommandSurface">
<!-- Use OfficeTab to extend an existing Tab. Use CustomTab to create a new tab. -->
<OfficeTab id="TabHome">
<!-- Ensure you provide a unique id for the group. Recommendation for any IDs is to namespace using your company name. -->
<Group id="Contoso.Group1">
<!-- Label for your group. resid must point to a ShortString resource. -->
<Label resid="Contoso.Group1Label" />
<!-- Icons. Required sizes 16,32,80, optional 20, 24, 40, 48, 64. Strongly recommended to provide all sizes for great UX. -->
<!-- Use PNG icons. All URLs on the resources section must use HTTPS. -->
<Icon>
<bt:Image size="16" resid="Contoso.tpicon_16x16" />
<bt:Image size="32" resid="Contoso.tpicon_32x32" />
<bt:Image size="80" resid="Contoso.tpicon_80x80" />
</Icon>
<!-- Control. It can be of type "Button" or "Menu". -->
<Control xsi:type="Button" id="Contoso.TaskpaneButton">
<Label resid="Contoso.TaskpaneButton.Label" />
<Supertip>
<!-- ToolTip title. resid must point to a ShortString resource. -->
<Title resid="Contoso.TaskpaneButton.Label" />
<!-- ToolTip description. resid must point to a LongString resource. -->
<Description resid="Contoso.TaskpaneButton.Tooltip" />
</Supertip>
<Icon>
<bt:Image size="16" resid="Contoso.tpicon_16x16" />
<bt:Image size="32" resid="Contoso.tpicon_32x32" />
<bt:Image size="80" resid="Contoso.tpicon_80x80" />
</Icon>
<!-- This is what happens when the command is triggered (E.g. click on the Ribbon). Supported actions are ExecuteFunction or ShowTaskpane. -->
<Action xsi:type="ShowTaskpane">
<TaskpaneId>ButtonId1</TaskpaneId>
<!-- Provide a url resource id for the location that will be displayed on the task pane. -->
<SourceLocation resid="Contoso.Taskpane.Url" />
</Action>
</Control>
</Group>
</OfficeTab>
</ExtensionPoint>
<ExtensionPoint xsi:type="CustomFunctions">
<Script>
<SourceLocation resid="JS-URL" />
</Script>
<Page>
<SourceLocation resid="Contoso.Taskpane.Url"/>
</Page>
<Metadata>
<SourceLocation resid="JSON-URL" />
</Metadata>
<Namespace resid="namespace" />
</ExtensionPoint>
</DesktopFormFactor>
</Host>
</Hosts>
<!-- You can use resources across hosts and form factors. -->
<Resources>
<bt:Images>
<bt:Image id="Contoso.tpicon_16x16" DefaultValue="https://localhost:3000/assets/icon-16.png" />
<bt:Image id="Contoso.tpicon_32x32" DefaultValue="https://localhost:3000/assets/icon-32.png" />
<bt:Image id="Contoso.tpicon_80x80" DefaultValue="https://localhost:3000/assets/icon-80.png" />
</bt:Images>
<bt:Urls>
<bt:Url id="Contoso.Taskpane.Url" DefaultValue="https://localhost:3000/index.html" />
<bt:Url id="Contoso.GetStarted.LearnMoreUrl" DefaultValue="https://go.microsoft.com/fwlink/?LinkId=276812" />
<bt:Url id="Contoso.DesktopFunctionFile.Url" DefaultValue="https://localhost:3000/function-file/function-file.html" />
<bt:Url id="JSON-URL" DefaultValue="http://localhost:3000/cf/customfunctions.json"/>
<bt:Url id="JS-URL" DefaultValue="http://localhost:3000/cf/customfunctions.js"/>
</bt:Urls>
<!-- ShortStrings max characters==125. -->
<bt:ShortStrings>
<bt:String id="Contoso.TaskpaneButton.Label" DefaultValue="Show Taskpane" />
<bt:String id="Contoso.Group1Label" DefaultValue="Commands Group" />
<bt:String id="Contoso.GetStarted.Title" DefaultValue="Get started with your sample add-in!" />
<bt:String id="namespace" DefaultValue="IPLICIT" />
</bt:ShortStrings>
<!-- LongStrings max characters==250. -->
<bt:LongStrings>
<bt:String id="Contoso.TaskpaneButton.Tooltip" DefaultValue="Click to Show a Taskpane" />
<bt:String id="Contoso.GetStarted.Description" DefaultValue="Your sample add-in loaded succesfully. Go to the HOME tab and click the 'Show Taskpane' button to get started." />
</bt:LongStrings>
</Resources>
</VersionOverrides>
<!-- End Add-in Commands Mode integration. -->
</OfficeApp>
And this is a snippet of the html page of the two add-ins:
https://i.stack.imgur.com/PZqcG.png

Answer 1

In your manifest file, you need to separate the custom function portion out of the DesktopFormFactor section into its own AllFormFactors section. So it should look like
...
<DesktopFormFactor>
<ExtensionPoint xsi:type="PrimaryCommandSurface">
...
</ExtensionPoint>
</DesktopFormFactor>
<AllFormFactors>
<ExtensionPoint xsi:type="CustomFunctions">
...
</ExtensionPoint>
</AllFormFactors>
...
I recently uploaded a sample that has custom functions and a task pane here if this helps for reference.

Answer 2

My response is too complicated for a comment, so I'll use an "answer" and later revise it or delete it as needed.
First a small terminology point: If you have one manifest, then you have one add-in. Your references to "two add-ins" is confusing the situation. Both a task pane and a set of custom functions can be deployed in the same add-in.
As I understand it, you have been able to successfully deploy custom functions in an add-in that does not include a task pane. To merge this into your task pane add-in, the html and JavaScript files that you used for the custom functions should be distinct files from the HTML and JavaScript files in your task pane add-in project. You should not try to have the same HTML file serve both as a page in the task pane and as the loader for the custom functions JavaScript.
I think what you need to do is essentially this: copy the html, javascript, and json files from the custom functions add-in to the exact same folder location in the task pane add-in project. Then copy the Extension point part of the manifest of the custom function add-in, and the resids that it declares, into the appropriate locations in the manifest for the task pane add-in.