builder: raising an error if environment is unintentionally set to "A…

…ZURESTACKCLOUD"

Users should instead use the separate "azurestack" provider which offers integration
with Azure Stack via the Azure Stack Profiles

azurerm/internal/clients/builder.go

@@ -3,6 +3,7 @@ package clients
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/hashicorp/go-azure-helpers/authentication"
 	"github.com/hashicorp/go-azure-helpers/sender"
@@ -21,7 +22,21 @@ type ClientBuilder struct {
 	Features                    features.UserFeatures
 }
 
+const azureStackEnvironmentError = `
+The AzureRM Provider supports the different Azure Public Clouds - including China, Germany,
+Public and US Government - however it does not support Azure Stack due to differences in
+API and feature availability.
+
+Terraform instead offers a separate "azurestack" provider which supports the functionality
+and API's available in Azure Stack via Azure Stack Profiles.
+`
+
 func Build(ctx context.Context, builder ClientBuilder) (*Client, error) {
+	// point folks towards the separate Azure Stack Provider when using Azure Stack
+	if strings.EqualFold(builder.AuthConfig.Environment, "AZURESTACKCLOUD") {
+		return nil, fmt.Errorf(azureStackEnvironmentError)
+	}
+
 	env, err := authentication.DetermineEnvironment(builder.AuthConfig.Environment)
 	if err != nil {
 		return nil, err