chore: re-enable nilnil lint for models/actions/task.go (#12768)

I added sentinel error values for jobs not being found and no jobs being updated by the `CreateTaskForRunner` function. This avoids the nilnil antipattern and allows the nilnil lint to be enabled for the `models/actions/task.go` file again.

The handling of these new errors was added to the `PickTask` function in `services/actions/task.go`.

Related issue: https://codeberg.org/forgejo/forgejo/issues/11261

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12768
Reviewed-by: limiting-factor <limiting-factor@noreply.codeberg.org>
Reviewed-by: elle <0xllx0@noreply.codeberg.org>

tests/integration/actions_create_task_for_runner_test.go

@@ -0,0 +1,78 @@
+// Copyright 2026 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package integration
+
+import (
+	"errors"
+	"sync"
+	"testing"
+	"time"
+
+	actions_model "forgejo.org/models/actions"
+	"forgejo.org/models/unittest"
+	"forgejo.org/modules/setting"
+	"forgejo.org/tests"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCreateTaskForRunnerNoMatchingJobFound(t *testing.T) {
+	defer unittest.OverrideFixtures("tests/integration/fixtures/TestCreateTaskForRunner")()
+	defer tests.PrepareTestEnv(t)()
+
+	runner := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionRunner{ID: 1004})
+
+	_, err := actions_model.CreateTaskForRunner(t.Context(), runner, nil, nil)
+	require.ErrorIs(t, err, actions_model.ErrNoMatchingJobFound)
+}
+
+// We need to concurrently choose the same job with two requests to CreateTaskForRunner.  The second
+// request that tries to update the job in the database (that was already updated by the first
+// request) then chokes and returns the error ErrNoJobUpdated.
+func TestCreateTaskForRunnerNoJobUpdated(t *testing.T) {
+	if setting.Database.Type.IsSQLite3() {
+		// SQLite locks on the transaction and the desired race condition can't be achieved
+		t.Skip()
+	}
+
+	defer unittest.OverrideFixtures("tests/integration/fixtures/TestCreateTaskForRunner")()
+	defer tests.PrepareTestEnv(t)()
+
+	assert.Eventually(
+		t,
+		func() bool {
+			unittest.LoadFixtures()
+
+			runner := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionRunner{ID: 1005})
+
+			var w sync.WaitGroup
+			errs := make(chan error, 2)
+			for range 2 {
+				w.Go(func() {
+					_, err := actions_model.CreateTaskForRunner(t.Context(), runner, nil, nil)
+					errs <- err
+				})
+			}
+			w.Wait()
+			close(errs)
+
+			gotNoJobUpdated := false
+			succeded := false
+			for err := range errs {
+				if errors.Is(err, actions_model.ErrNoJobUpdated) {
+					gotNoJobUpdated = true
+				}
+				if err == nil {
+					succeded = true
+				}
+			}
+
+			return succeded && gotNoJobUpdated
+		},
+		30*time.Second,
+		500*time.Microsecond,
+		"one call to CreateTaskForRunner should succeed and the other one should return the error ErrNoJobUpdated",
+	)
+}

tests/integration/fixtures/TestCreateTaskForRunner/action_run.yml

@@ -0,0 +1,6 @@
+-
+  id: 900
+  index: 1
+  status: 5 # StatusWaiting
+  repo_id: 4
+  owner_id: 1

tests/integration/fixtures/TestCreateTaskForRunner/action_run_job.yml

@@ -0,0 +1,18 @@
+-
+  id: 1000
+  run_id: 900
+  repo_id: 4
+  owner_id: 1
+  name: "crate task - no job updated test job"
+  job_id: create_task_no_job_updated
+  task_id: 0
+  status: 5 # StatusWaiting
+  runs_on: '["ubuntu"]'
+  workflow_payload: |
+    name: test
+    on: push
+    jobs:
+      concurrent_test_job:
+        runs-on: ubuntu-latest
+        steps:
+          - run: echo hello

tests/integration/fixtures/TestCreateTaskForRunner/action_runner.yml

@@ -0,0 +1,13 @@
+-
+  id: 1004
+  name: "create task - no matching job found test runner"
+  owner_id: 0
+  repo_id: 0
+  agent_labels: '["fedora"]'
+
+-
+  id: 1005
+  name: "create task - no job updated test runner"
+  owner_id: 0
+  repo_id: 0
+  agent_labels: '["ubuntu"]'