不为Cloud标记中的键赋值

我有以下云形成模板来创建专有网络。VPC名称是根据创建模板的区域和环境生成的。VPC创建时没有任何问题,并且正在运行 aws cloud formation validate-template --template-url https://foo.template 不抱怨任何语法。

我希望VPC的名称为:

vpc-uw1-d-fs

取而代之的是专有网络留下了一个空名称,而名称标签有一个空值。我没有正确使用该功能吗?如果我移除 Fn::FindInMap 函数用法,我得到生成的名称-它只是缺少环境映射值。

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "VPC for a new environment to use.",
    "Parameters": {
        "EnvironmentName": {
            "Description": "Name of the environment that this VPC will be used for.",
            "Type": "String",
            "MinLength": "2",
            "MaxLength": "20",
            "AllowedPattern": "[a-zA-Z]*",
            "AllowedValues": [
                "Development",
                "QA",
                "Test",
                "Production"
            ]
        }
    },
    "Resources": {
        "VPC": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/16",
                "EnableDnsSupport": false,
                "EnableDnsHostnames": false,
                "InstanceTenancy": "default",
                "Tags": [ { 
                    "Key": "Name",
                    "Value": {
                        "Fn::Join": [
                            "-",
                            [
                                "vpc",
                                { "Ref": "AWS::Region" },
                                { "Fn::FindInMap": [
                                    "EnvironmentMap", { "Ref": "EnvironmentName" }, "AbbreviatedName"
                                ]},
                                "fs"
                            ]
                        ]
                    }
                }]
            }
        }
    },
    "Mappings": {
        "RegionMap": {
            "us-east-1": {
                "regionName": "ue1"
            },
            "us-west-1": {
                "regionName": "uw1"
            }
        },
        "EnvironmentMap": {
            "Development": { 
                "AbbreviatedName": "d"
            },
            "QA": { 
                "AbbreviatedName": "qa"
            },
            "Test": { 
                "AbbreviatedName": "t"
            },
            "Production": { 
                "AbbreviatedName": "p"
            }
        }
    },
    "Outputs": {

    }
}