Fix: `gitlab_project_hook` update fails when computed identity attributes are unknown in plan

Fix: gitlab_project_hook update fails when computed identity attributes are unknown in plan

Problem

When performing an in-place update of a gitlab_project_hook resource (e.g. toggling an event flag), Terraform would error with:

Error reading GitLab project hook: ... invalid id ""

This happened because the Update function read the resource ID from the plan rather than from state. The id attribute had no plan modifier, so it was unknown in the plan during an update cycle — data.ID.ValueString() therefore returned "", and the ID parse failed before any API call was made.

A secondary symptom was that the id attribute showed as (known after apply) in every update plan, producing noisy diffs even when nothing identity-related had changed.

Changes

internal/provider/resource_gitlab_project_hook.go

1. Add UseStateForUnknown() to id (bug fix)

Added stringplanmodifier.UseStateForUnknown() to the id schema attribute. This tells the framework to carry the known state value forward into the plan for update operations, so data.ID.ValueString() returns the correct value in Update and the ID parse succeeds.

2. Add RequiresReplace() to project

Added stringplanmodifier.RequiresReplace() to the project attribute so that changing the project a hook belongs to triggers a destroy+recreate, rather than an unsupported in-place move.

3. Remove RequiresReplace() from project_id

project_id is a read-only computed attribute — it cannot be set by the user and will never trigger a replace. The replace behaviour is now correctly expressed on the project attribute instead.

4. Add UseStateForUnknown() to token (bug fix)

Added stringplanmodifier.UseStateForUnknown() to the token schema attribute. This tells the framework to carry the known state value forward into the plan for update operations, so data.Token.ValueString() returns the correct value in Update.

5. Fix copy-paste error message in Update

// Before
resp.Diagnostics.AddError("Error creating GitLab project hook", err.Error())

// After
resp.Diagnostics.AddError("Error updating GitLab project hook", err.Error())

Testing

# Acceptance tests (requires GITLAB_TOKEN and GITLAB_BASE_URL)
make testacc RUN=TestAccGitlabProjectHook
TF_ACC=1 GITLAB_TOKEN=glpat-**** GITLAB_BASE_URL=http://127.0.0.1:8085/api/v4 GITLAB_EARLY_AUTH_CHECK=false go test --tags acceptance -v ./internal/provider/... -test.run TestAccGitlabProjectHook -timeout 120m
=== RUN   TestAccGitlabProjectHook_basic
=== PAUSE TestAccGitlabProjectHook_basic
=== RUN   TestAccGitlabProjectHook_customTemplate
=== PAUSE TestAccGitlabProjectHook_customTemplate
=== RUN   TestAccGitlabProjectHook_customHeaders
    resource_gitlab_project_hook_test.go:239: Test is skipped for CE (non-Enterprise) version of GitLab
--- SKIP: TestAccGitlabProjectHook_customHeaders (2.51s)
=== RUN   TestAccGitlabProjectHook_updateProject
=== PAUSE TestAccGitlabProjectHook_updateProject
=== RUN   TestAccGitlabProjectHook_importThenUpdate
=== PAUSE TestAccGitlabProjectHook_importThenUpdate
=== RUN   TestAccGitlabProjectHook_migrateFromSDKToFramework
=== PAUSE TestAccGitlabProjectHook_migrateFromSDKToFramework
=== RUN   TestAccGitlabProjectHook_validations
    resource_gitlab_project_hook_test.go:464: Test is skipped for CE (non-Enterprise) version of GitLab
--- SKIP: TestAccGitlabProjectHook_validations (0.00s)
=== CONT  TestAccGitlabProjectHook_basic
=== CONT  TestAccGitlabProjectHook_importThenUpdate
=== CONT  TestAccGitlabProjectHook_updateProject
=== CONT  TestAccGitlabProjectHook_migrateFromSDKToFramework
=== CONT  TestAccGitlabProjectHook_customTemplate
--- PASS: TestAccGitlabProjectHook_customTemplate (18.09s)
--- PASS: TestAccGitlabProjectHook_importThenUpdate (20.38s)
--- PASS: TestAccGitlabProjectHook_updateProject (29.38s)
--- PASS: TestAccGitlabProjectHook_migrateFromSDKToFramework (24.82s)
--- PASS: TestAccGitlabProjectHook_basic (36.68s)
PASS
ok  	gitlab.com/gitlab-org/terraform-provider-gitlab/internal/provider	54.803s
testing: warning: no tests to run
PASS
ok  	gitlab.com/gitlab-org/terraform-provider-gitlab/internal/provider/api	(cached) [no tests to run]
testing: warning: no tests to run
PASS
ok  	gitlab.com/gitlab-org/terraform-provider-gitlab/internal/provider/sdk	(cached) [no tests to run]
?   	gitlab.com/gitlab-org/terraform-provider-gitlab/internal/provider/testutil	[no test files]
?   	gitlab.com/gitlab-org/terraform-provider-gitlab/internal/provider/testutil/framework	[no test files]
testing: warning: no tests to run
PASS
ok  	gitlab.com/gitlab-org/terraform-provider-gitlab/internal/provider/utils	(cached) [no tests to run]

Fixes #6807 (closed)