Example of an F# DSL designed for building ARM Templates

1. types.fsx

open ARM

let template =
    { Parameters = [
        "environment"
        "location"
        "pricingTier"
      ]
      Variables = [
          "environment", "[toLower(parameters('environment'))]"
          "prefix", "[concat('safe-', variables('environment'))]"
          "appServicePlan", "[concat(variables('prefix'), '-web-host')]"
          "web", "[concat(variables('prefix'), '-web')]"
          "storage", "[concat('safe', variables('environment'), 'storage')]"
          "insights", "[concat(variables('prefix'), '-insights')]"
      ]
      Outputs = [
          "webAppName", Variable "web"
          "webAppPassword", WebSite.PUBLISHING_PASSWORD (Variable "web")
      ]
      Resources = [
        let appInsights = { Name = Variable "insights"; LinkedWebsite = Variable "web"; Location = Variable "location" }
        let storage = { Name = Variable "storage"; Sku = Standard; Location = Variable "location" }
        let serverFarm =
            { Sku = Parameter "pricingTier"
              Name = Variable "appServicePlan"
              Location = Parameter "location"
              WebApps = [
                { Name = Variable "web"
                  AppSettings =
                    { Settings = [
                          "public_path", Literal "./public"
                          "APPINSIGHTS_INSTRUMENTATIONKEY", Literal appInsights.InstrumentationKey
                          "STORAGE_CONNECTIONSTRING", Literal storage.Key
                          AppSettings.RUN_FROM_PACKAGE
                          AppSettings.WEBSITE_NODE_DEFAULT_VERSION "8.1.4"
                      ]
                      Dependencies = [
                          StorageAccount storage
                          AppInsights appInsights
                      ]
                    }
                  AppInsights = Some (Variable "insights")
                  Dependencies = [
                      StorageAccount storage
                      AppInsights appInsights
                  ]
                }
              ]
            }
        yield AppInsights appInsights
        yield StorageAccount storage
        yield ServerFarm serverFarm
      ]
    }

2. computation.fsx

let template = arm {
    parameters [ "environment"; "location"; "pricingTier" ]

    variable "environment" (toLower (Parameter "environment"))
    variable "prefix" (concat [ Literal "safe-"; Variable "environment" ])
    variable "appServicePlan" (withPostfix "-web-host")
    variable "web" (withPostfix "-web")
    variable "storage" (concat [ Literal "safe"; Variable "environment"; Literal "storage" ])
    variable "insights" (withPostfix "-insights")

    location (Parameter "location")

    resource "storage" Standard
    resource "web"
        (webApp {
            service_plan_name (Variable "appServicePlan")
            sku (Parameter "pricingTier")

            use_app_insights (Variable "insights")
            run_from_package

            website_node_default_version "8.1.4"
            setting "public_path" "./public"
            setting "STORAGE_CONNECTIONSTRING" (Storage.accountKey (Variable "storage"))

            depends_on AStorageAccount (Variable "storage")
        })

    output "webAppName" (Variable "web")
    output "webAppPassword" (WebSite.PUBLISHING_PASSWORD (Variable "web"))
}

3. output.json

{
    "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "environment": {
            "type": "string"
        },
        "location": {
            "type": "string"
        },
        "pricingTier": {
            "type": "string"
        }
    },
    "variables": {
        "environment": "[toLower(parameters('environment'))]",
        "prefix": "[concat('safe-', variables('environment'))]",
        "appServicePlan": "[concat(variables('prefix'), '-web-host')]",
        "web": "[concat(variables('prefix'), '-web')]",
        "storage": "[concat('safe', variables('environment'), 'storage')]",
        "insights": "[concat(variables('prefix'), '-insights')]"
    },
    "resources": [
        {
            "type": "Microsoft.Insights/components",
            "kind": "web",
            "name": "[variables('insights')]",
            "location": "[parameters('location')]",
            "apiVersion": "2014-04-01",
            "scale": null,
            "tags": {
                "[concat('hidden-link:', resourceGroup().id, '/providers/Microsoft.Web/sites/', variables('web'))]": "Resource",
                "displayName": "AppInsightsComponent"
            },
            "properties": {
                "name": "[variables('insights')]"
            }
        },
        {
            "type": "Microsoft.Storage/storageAccounts",
            "sku": {
                "name": "Standard_LRS",
                "tier": "Standard"
            },
            "kind": "Storage",
            "name": "[variables('storage')]",
            "apiVersion": "2017-10-01",
            "location": "[parameters('location')]",
            "tags": {}
        },
        {
            "type": "Microsoft.Web/serverfarms",
            "sku": {
                "name": "[parameters('pricingTier')]"
            },
            "name": "[variables('appServicePlan')]",
            "apiVersion": "2016-09-01",
            "location": "[parameters('location')]",
            "properties": {
                "name": "[variables('appserviceplan')]",
                "perSiteScaling": false,
                "reserved": false
            }
        },
        {
            "type": "Microsoft.Web/sites",
            "name": "[variables('web')]",
            "apiVersion": "2016-08-01",
            "location": "[parameters('location')]",
            "properties": {
                "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', variables('appServicePlan'))]",
                "siteConfig": {
                    "appSettings": [
                        {
                            "name": "public_path",
                            "value": "./public"
                        },
                        {
                            "name": "APPINSIGHTS_INSTRUMENTATIONKEY",
                            "value": "[reference(concat('Microsoft.Insights/components/', variables('insights'))).InstrumentationKey]"
                        },
                        {
                            "name": "STORAGE_CONNECTIONSTRING",
                            "value": "[concat('DefaultEndpointsProtocol=https;AccountName=', variables('storage'), ';AccountKey=', listKeys(resourceId('Microsoft.Storage/storageAccounts/', variables('storage')), '2017-10-01').keys[0].value)]"
                        },
                        {
                            "name": "WEBSITE_RUN_FROM_PACKAGE",
                            "value": "1"
                        },
                        {
                            "name": "WEBSITE_NODE_DEFAULT_VERSION",
                            "value": "8.1.4"
                        }
                    ]
                }
            },
            "dependsOn": [
                "[resourceId('Microsoft.Web/serverfarms', variables('appServicePlan'))]",
                "[resourceId('Microsoft.Storage/storageAccounts/', variables('storage'))]",
                "[resourceId('Microsoft.Insights/components/', variables('insights'))]"
            ],
            "resources": [
                {
                    "apiVersion": "2016-08-01",
                    "name": "Microsoft.ApplicationInsights.AzureWebSites",
                    "type": "siteextensions",
                    "dependsOn": [
                        "[resourceId('Microsoft.Web/sites/', variables('web'))]"
                    ],
                    "properties": {}
                }
            ]
        }
    ],
    "outputs": {
        "webAppName": {
            "type": "string",
            "value": "[variables('web')]"
        },
        "webAppPassword": {
            "type": "string",
            "value": "[list(resourceId('Microsoft.Web/sites/config', variables('web'), 'publishingcredentials'), '2014-06-01').properties.publishingPassword]"
        }
    }
}