Ant Problem deploying field on custom metadata type

Question

I am trying to deploy a field on a custom metadata type using Ant.

Here's my package.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
    <types>
        <members>*</members>
        <name>CustomMetadata</name>
    </types>
    <version>43.0</version>
</Package>

Then inside a customMetadata folder I have a file called nameOfMtdType.NameOfField.md. That file's content looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<CustomMetadata xmlns="http://soap.sforce.com/2006/04/metadata"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

    <values>
        <fullName>Number_Of_Balls__c</fullName>
        <description>The maximum number of balls that are allowed.</description>
        <externalId>false</externalId>
        <fieldManageability>DeveloperControlled</fieldManageability>
        <inlineHelpText>The maximum number of balls that are allowed.</inlineHelpText>
        <label>Number Of Balls</label>
        <precision>4</precision>
        <required>false</required>
        <scale>0</scale>
        <type>Number</type>
        <unique>false</unique>
    </values>
</CustomMetadata>

I am getting this error: Error parsing file: Element {http://soap.sforce.com/2006/04/metadata}fullName invalid at this location in type CustomMetadataValue

What am I doing wrong? The content inside the <values></values> is what I pulled from my scratch org using sfdx.

Also, I was trying to follow the documentation from this link: https://developer.salesforce.com/docs/atlas.en-us.api_meta.meta/api_meta/meta_custommetadata.htm

Is there a better resource?

Answer 1

The Metadata API type CustomMetadata is for deploying records of Custom Metadata Types, not the schema of the type itself. That's why you're getting back that error - you supplied part of the type definition where Salesforce was looking for record data.

The Custom Metadata Type itself, along with its fields, is deployed as a CustomObject, where properties like fullName are expected. There's an example in that documentation of what it looks like to deploy a Custom Metadata Type field for a type called ReusablePicklistOption__mdt:

ReusablePicklistOption__mdt.object

<?xml version="1.0" encoding="UTF-8"?>
<CustomObject xmlns="http://soap.sforce.com/2006/04/metadata">
   <fields>
      <fullName>AlphaSort__c</fullName>
      <defaultValue>false</defaultValue>
      <externalId>false</externalId>
      <label>Sorted Alphabetically</label>
      <type>Checkbox</type>
   </fields>
   <label>Reusable Picklist</label>
   <pluralLabel>Reusable Picklist</pluralLabel>
   <visibility>Public</visibility>
</CustomObject>

The easiest way to handle this, though, is just to let Salesforce DX convert the source for you with the force:source:convert command. You can then trim the converted Metadata API source and package.xml down to deploy just the elements you're interested in, like this single field.