Prevent panic on null values when iterating over map elements

[LouisBrunner]

📚 Context

I was writing a small module to create organizations from a list:

module "orgs" {
  source                 = "./orgs"
  orgs = [
    {
      name    = "org1-id"
      display = "Org1 Name"
      logo    = "https://some-url.example"
    },
    {
      name    = "org2-id"
      display = "Org2 Name"
      logo    = "https://some-url.example"
      branding = {
        primary    = "#7da5de"
        background = "#000000"
      }
    },
  ]
}

then defined my module as such

variable "orgs" {
  type = list(object({
    name    = string,
    display = string,
    logo    = string,
    branding = optional(object({
      primary    = string,
      background = string,
    }))
  }))
}

resource "auth0_organization" "org" {
  for_each     = { for org in var.orgs : org.name => org }
  name         = each.key
  display_name = each.value.display

  branding {
    logo_url = each.value.logo
    colors = {
      primary         = try(each.value.branding.primary, null)
      page_background = try(each.value.branding.background, null)
    }
  }
}

However, when I tried to apply, I got the following crash from this provider:

Stack trace from the terraform-provider-auth0_v0.40.0 plugin:

panic: value is null

goroutine 113 [running]:
github.com/hashicorp/go-cty/cty.Value.AsString({{{0x10117e0e0?, 0x1400003a189?}}, {0x0?, 0x0?}})
	github.com/hashicorp/[email protected]/cty/value_ops.go:1176 +0x11c
github.com/auth0/terraform-provider-auth0/internal/value.MapOfStrings({{{0x10117e188?, 0x1400078c170?}}, {0x1010836e0?, 0x1400078e270?}})
	github.com/auth0/terraform-provider-auth0/internal/value/value.go:99 +0x108
github.com/auth0/terraform-provider-auth0/internal/provider.expandOrganizationBranding.func1({{{0x140002472f0?, 0x1400078c1b0?}}, {0x101034fc0?, 0x14000796018?}}, {{{0x10117e1c0?, 0x1400066a050?}}, {0x1010836e0?, 0x1400078e2a0?}})
	github.com/auth0/terraform-provider-auth0/internal/provider/resource_auth0_organization.go:158 +0x8c
github.com/hashicorp/go-cty/cty.Value.ForEachElement({{{0x10117e150?, 0x1400078c1b0?}}, {0x101034fc0?, 0x14000796018?}}, 0x14000708dc8)
	github.com/hashicorp/[email protected]/cty/value_ops.go:1066 +0x98
github.com/auth0/terraform-provider-auth0/internal/provider.expandOrganizationBranding({{{0x10117e150?, 0x1400078c1b0?}}, {0x101034fc0?, 0x14000796018?}})
	github.com/auth0/terraform-provider-auth0/internal/provider/resource_auth0_organization.go:155 +0x4c
github.com/auth0/terraform-provider-auth0/internal/provider.expandOrganization(0x0?)
	github.com/auth0/terraform-provider-auth0/internal/provider/resource_auth0_organization.go:142 +0x98
github.com/auth0/terraform-provider-auth0/internal/provider.updateOrganization({0x10117da88, 0x1400010c720}, 0x1400053d500, {0x1010b6980?, 0x140003aa9a0?})
	github.com/auth0/terraform-provider-auth0/internal/provider/resource_auth0_organization.go:113 +0x54
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*Resource).update(0x1400047c9a0, {0x10117dac0, 0x140002558f0}, 0xd?, {0x1010b6980, 0x140003aa9a0})
	github.com/hashicorp/terraform-plugin-sdk/[email protected]/helper/schema/resource.go:741 +0xe8
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*Resource).Apply(0x1400047c9a0, {0x10117dac0, 0x140002558f0}, 0x140001405b0, 0x1400053d100, {0x1010b6980, 0x140003aa9a0})
	github.com/hashicorp/terraform-plugin-sdk/[email protected]/helper/schema/resource.go:847 +0x67c
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*GRPCProviderServer).ApplyResourceChange(0x1400053a000, {0x10117dac0?, 0x140002557d0?}, 0x14000568f00)
	github.com/hashicorp/terraform-plugin-sdk/[email protected]/helper/schema/grpc_provider.go:1021 +0xb70
github.com/hashicorp/terraform-plugin-go/tfprotov5/tf5server.(*server).ApplyResourceChange(0x14000540000, {0x10117dac0?, 0x140002551a0?}, 0x140000ab960)
	github.com/hashicorp/[email protected]/tfprotov5/tf5server/server.go:818 +0x3b8
github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/tfplugin5._Provider_ApplyResourceChange_Handler({0x101140680?, 0x14000540000}, {0x10117dac0, 0x140002551a0}, 0x140000ab8f0, 0x0)
	github.com/hashicorp/[email protected]/tfprotov5/internal/tfplugin5/tfplugin5_grpc.pb.go:385 +0x170
google.golang.org/grpc.(*Server).processUnaryRPC(0x14000440000, {0x1011814e0, 0x14000103040}, 0x1400070c000, 0x14000514660, 0x1016712a0, 0x0)
	google.golang.org/[email protected]/server.go:1295 +0x9c4
google.golang.org/grpc.(*Server).handleStream(0x14000440000, {0x1011814e0, 0x14000103040}, 0x1400070c000, 0x0)
	google.golang.org/[email protected]/server.go:1636 +0x82c
google.golang.org/grpc.(*Server).serveStreams.func1.2()
	google.golang.org/[email protected]/server.go:932 +0x84
created by google.golang.org/grpc.(*Server).serveStreams.func1
	google.golang.org/[email protected]/server.go:930 +0x290

Error: The terraform-provider-auth0_v0.40.0 plugin crashed!

This is always indicative of a bug within the plugin. It would be immensely
helpful if you could report the crash with the plugin's maintainers so that it
can be fixed. The output above should help diagnose the issue.

🔧 Changes

This checks IsNull on cty.Value before calling AsString which ensures that the provider doesn't panic if a value is missing. The crash is then replaced by:

╷
│ Error: 400 Bad Request: Payload validation error: 'Missing required property: page_background' on property branding.colors (Color scheme used to customize the login pages). (also) Payload validation error: 'Missing required property: primary' on property branding.colors (Color scheme used to customize the login pages).
│
│   with auth0_organization.my_organization,
│   on main.tf line 20, in resource "auth0_organization" "my_organization":
│   20: resource "auth0_organization" "my_organization" {
│
╵

🔬 Testing

I expanded the unit tests to check the edge case. Also I used this minimal reproducible example to check (crash with v0.40):

resource "auth0_organization" "my_organization" {
  name         = "auth0-inc"
  display_name = "Auth0 Inc."

  branding {
    logo_url = "https://example.com/assets/icons/icon.png"
    colors = {
      primary         = null
      page_background = null
    }
  }
}

Note: you will only get the crash on apply, not during planning, so if there are no difference to apply, it will just exit normally. Change the display name and try to apply and the crash will happen.

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• [N/A] I have added documentation for all new/changed functionality (or N/A)

[sergiught]

Thanks a lot for the contribution @LouisBrunner! Good catch!