azurerm_windows_web_app plugin crashes when app_settings is empty

[UntiIted]

Is there an existing issue for this?

• I have searched the existing issues

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Terraform Version

1.5.1

AzureRM Provider Version

3.64.0

Affected Resource(s)/Data Source(s)

azurerm_windows_web_app

Terraform Configuration Files

data "azurerm_container_registry" "this" {
  name                = "example"
  resource_group_name = "example"
}

data "azurerm_service_plan" "this" {
  name                = "example"
  resource_group_name = "example"
}

resource "azurerm_windows_web_app" "this" {
  name                = "example"
  resource_group_name = "example"
  location            = data.azurerm_service_plan.this.location
  service_plan_id     = data.azurerm_service_plan.this.id

  https_only              = true
  client_affinity_enabled = false

  site_config {
    always_on         = "true"
    ftps_state        = "Disabled"
    use_32_bit_worker = true

    application_stack {
      docker_image_name        = "hello-world:windows"
      docker_registry_url      = "https://${data.azurerm_container_registry.this.login_server}"
      docker_registry_username = data.azurerm_container_registry.this.admin_username
      docker_registry_password = data.azurerm_container_registry.this.admin_password
    }
  }
}

Debug Output/Panic Output

Stack trace from the terraform-provider-azurerm_v3.64.0_x5.exe plugin:

panic: assignment to entry in nil map

goroutine 104 [running]:
github.com/hashicorp/terraform-provider-azurerm/internal/services/appservice/helpers.(*SiteConfigWindows).ExpandForCreate(0xc001c56af0, 0x0)
        github.com/hashicorp/terraform-provider-azurerm/internal/services/appservice/helpers/windows_web_app_schema.go:525 +0xfe8
github.com/hashicorp/terraform-provider-azurerm/internal/services/appservice.WindowsWebAppResource.Create.func1({0x7f30cc8, 0xc001fb5050}, {0xc0008bc800, {0x7f31550, 0xc000529860}, 0xc001337580, 0x0, {0x7f32698, 0xc685730}})
        github.com/hashicorp/terraform-provider-azurerm/internal/services/appservice/windows_web_app_resource.go:329 +0xe10
github.com/hashicorp/terraform-provider-azurerm/internal/sdk.(*ResourceWrapper).Resource.func2({0x7f30cc8, 0xc001fb5050}, 0x7f30d00?, {0x6ae7e80?, 0xc0008bc800?})
        github.com/hashicorp/terraform-provider-azurerm/internal/sdk/wrapper_resource.go:55 +0x163
github.com/hashicorp/terraform-provider-azurerm/internal/sdk.diagnosticsWrapper.func1({0x7f30cc8, 0xc001fb5050}, 0x0?, {0x6ae7e80, 0xc0008bc800})
        github.com/hashicorp/terraform-provider-azurerm/internal/sdk/wrapper_resource.go:188 +0xb8
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*Resource).create(0xc0001f10a0, {0x7f30d00, 0xc001db4f00}, 0xd?, {0x6ae7e80, 0xc0008bc800})
        github.com/hashicorp/terraform-plugin-sdk/v2@v2.26.1/helper/schema/resource.go:707 +0x12e
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*Resource).Apply(0xc0001f10a0, {0x7f30d00, 0xc001db4f00}, 0xc0021a12b0, 0xc001337400, {0x6ae7e80, 0xc0008bc800})
        github.com/hashicorp/terraform-plugin-sdk/v2@v2.26.1/helper/schema/resource.go:837 +0xa85
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*GRPCProviderServer).ApplyResourceChange(0xc001327ed8, {0x7f30d00?, 0xc001db4de0?}, 0xc0001469b0)
        github.com/hashicorp/terraform-plugin-sdk/v2@v2.26.1/helper/schema/grpc_provider.go:1021 +0xe8d
github.com/hashicorp/terraform-plugin-go/tfprotov5/tf5server.(*server).ApplyResourceChange(0xc0007b5a40, {0x7f30d00?, 0xc001db43f0?}, 0xc000566fc0)
        github.com/hashicorp/terraform-plugin-go@v0.14.3/tfprotov5/tf5server/server.go:818 +0x574
github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/tfplugin5._Provider_ApplyResourceChange_Handler({0x72f42a0?, 0xc0007b5a40}, {0x7f30d00, 0xc001db43f0}, 0xc000566f50, 0x0)
        github.com/hashicorp/terraform-plugin-go@v0.14.3/tfprotov5/internal/tfplugin5/tfplugin5_grpc.pb.go:385 +0x170
google.golang.org/grpc.(*Server).processUnaryRPC(0xc0001d21e0, {0x7f41400, 0xc001a7a000}, 0xc002348d80, 0xc001985ef0, 0xc620840, 0x0)
        google.golang.org/grpc@v1.53.0/server.go:1336 +0xd33
google.golang.org/grpc.(*Server).handleStream(0xc0001d21e0, {0x7f41400, 0xc001a7a000}, 0xc002348d80, 0x0)
        google.golang.org/grpc@v1.53.0/server.go:1704 +0xa36
google.golang.org/grpc.(*Server).serveStreams.func1.2()
        google.golang.org/grpc@v1.53.0/server.go:965 +0x98
created by google.golang.org/grpc.(*Server).serveStreams.func1
        google.golang.org/grpc@v1.53.0/server.go:963 +0x28a

Error: The terraform-provider-azurerm_v3.64.0_x5.exe plugin crashed!

Expected Behaviour

Web app is created successfully.

Actual Behaviour

Web app fails to create with plugin crash.

Steps to Reproduce

1. Use terraform to create a web app with a docker image and don't specify app_settings
2. terraform init
3. terraform apply

Important Factoids

No response

References

No response

[xiaxyi]

Thanks @UntiIted for raising this issue, let me try reproducing it from my side and update once I have any progress.

[wuxu92]

@xiaxyi this should just the same scenario as #22347

[xiaxyi]

Thanks @wuxu92 for helping to resolve this bug. There is another issue that need to be fixed based on your pr and I will handle it. :)

[UntiIted]

If this is the same issue as linux web apps, then slot resources for windows and linux should also be tested

[github-actions]

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