Persistent diff when using gitlab_project_pull_mirror and gitlab_project resources together

Bug Report

When using the new resource gitlab_project_pull_mirror in conjunction with the gitlab_project resource, a persistent diff occurs for the gitlab_project.mirror and gitlab_project.import_url attributes.

The gitlab_project resource detects the changes made by the mirror resource and attempts to revert them (setting them to null), causing a diff on every plan.

Relevant Terraform Configuration

Example setup:

resource "gitlab_project" "this" {
  name         = "project-name"
  description  = "my description"
  namespace_id = 123

  default_branch = "main"
  
  ## Required workaround
  # lifecycle {
  #    ignore_changes = [mirror,import_url]
  # }
}

resource "gitlab_project_pull_mirror" "this" {
  project                             = gitlab_project.this.id
  url                                 = "https://github.com/example/repo.git"
  enabled                             = true
  auth_user                           = "user"
  auth_password                       = "pass"
  
  mirror_trigger_builds               = true
  only_mirror_protected_branches      = true
  mirror_overwrites_diverged_branches = true
}

The current workaround is to add lifecycle { ignore_changes = [mirror, import_url] } to the gitlab_project resource.

Relevant Log Output

Diff logs

00:10:32.070 STDOUT terraform:   # gitlab_project.this will be updated in-place
00:10:32.070 STDOUT terraform:   ~ resource "gitlab_project" "this" {
00:10:32.070 STDOUT terraform:         id                                               = "123"
00:10:32.070 STDOUT terraform:       - import_url                                       = "https://github.com/example/repo.git" -> null
00:10:32.070 STDOUT terraform:       - mirror                                           = true -> null
00:10:32.070 STDOUT terraform:         name                                             = "project-name"
00:10:32.070 STDOUT terraform:         tags                                             = []

Additional Details

• GitLab Terraform Provider Version: 18.8.0
• GitLab Instance Version: 17.11.7
• Terraform Version: 1.13.5
• License Tier: Premium