feat(linter): rules:needs: validation (GL044)

Add GL044 to validate jobs listed in rules:needs: overrides (GitLab CI
16.4+). rules:needs: lets a specific rule override the job's top-level
needs: list; any referenced job must exist in the pipeline. Unknown jobs
produce an error; optional: true entries produce a warning, matching the
GL027 behaviour for top-level needs:. Cross-pipeline needs and skipped
jobs (when a context is active) are excluded from checking.

Implementation:
- model.Rule gains a Needs []any field (yaml:"needs")
- checkRulesNeeds(p, skipped) added to needs.go; wired into Lint
- GL044 / RuleRulesNeedsUnknown added to rules.go and explain.go
- 6 unit tests + 2 testdata fixtures; task validate updated

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/linter/explain.go

@@ -816,4 +816,41 @@ my-job:
 my-job:
   script: echo hi`,
 	},
+
+	RuleRulesNeedsUnknown: {
+		Title:    "'rules:needs:' references unknown job",
+		Severity: Error,
+		Description: "A job listed in a rule's 'needs:' override does not exist in " +
+			"the pipeline. 'rules:needs:' (GitLab CI 16.4+) overrides the top-level " +
+			"'needs:' list when that specific rule matches. GitLab will refuse to " +
+			"create the pipeline if any referenced job is missing.",
+		Example: `stages: [build, test]
+
+build:
+  stage: build
+  script: make
+
+test:
+  stage: test
+  script: make test
+  rules:
+    - if: $CI_COMMIT_BRANCH == "main"
+      needs: [build, lint]   # lint does not exist`,
+		Fix: `stages: [build, test]
+
+lint:
+  stage: build
+  script: make lint
+
+build:
+  stage: build
+  script: make
+
+test:
+  stage: test
+  script: make test
+  rules:
+    - if: $CI_COMMIT_BRANCH == "main"
+      needs: [build, lint]`,
+	},
 }

internal/linter/linter.go

@@ -62,6 +62,7 @@ func Lint(p *model.Pipeline, skipped map[string]bool) []Finding {
 	findings = append(findings, checkWorkflow(p)...)
 	findings = append(findings, checkJobs(p)...)
 	findings = append(findings, checkNeeds(p, skipped)...)
+	findings = append(findings, checkRulesNeeds(p, skipped)...)
 	findings = append(findings, checkDependencies(p, skipped)...)
 	findings = append(findings, checkVariableRefs(p)...)
 	findings = append(findings, checkRulesIfReachability(p)...)

internal/linter/needs.go

@@ -85,6 +85,44 @@ func checkNeeds(p *model.Pipeline, skipped map[string]bool) []Finding {
 	return findings
 }
 
+// checkRulesNeeds validates rules:needs: entries across all jobs. Each entry
+// in a rule's needs: list must reference a job that exists in the pipeline.
+// Cross-pipeline needs (maps with a "pipeline" key) are ignored. Skipped jobs
+// are excluded from checking (same semantics as top-level needs: via GL027).
+func checkRulesNeeds(p *model.Pipeline, skipped map[string]bool) []Finding {
+	var findings []Finding
+	for name, job := range p.Jobs {
+		if skipped[name] {
+			continue
+		}
+		for i, rule := range job.Rules {
+			if len(rule.Needs) == 0 {
+				continue
+			}
+			for _, entry := range parseNeedEntries(rule.Needs) {
+				if _, exists := p.Jobs[entry.job]; !exists {
+					sev := Error
+					if entry.optional {
+						sev = Warning
+					}
+					findings = append(findings, Finding{
+						Severity: sev,
+						Rule:     RuleRulesNeedsUnknown,
+						Job:      name,
+						File:     job.File,
+						Line:     job.Line,
+						Message: fmt.Sprintf(
+							"rules[%d].needs: references unknown job %q",
+							i, entry.job,
+						),
+					})
+				}
+			}
+		}
+	}
+	return findings
+}
+
 // parseNeedEntries extracts needs entries from a needs: list, preserving the
 // optional flag. Each element is a plain string (job name) or a map with a
 // "job" key. Cross-pipeline needs (maps with a "pipeline" key) are skipped.

internal/linter/needs_test.go

@@ -31,6 +31,129 @@ func TestCheckNeeds_SkippedJob(t *testing.T) {
 	}
 }
 
+// TestCheckRulesNeeds_UnknownJob verifies that an unknown job in rules:needs: produces GL044.
+func TestCheckRulesNeeds_UnknownJob(t *testing.T) {
+	p := &model.Pipeline{
+		Stages: []string{"build", "test"},
+		Jobs: map[string]model.Job{
+			"build-job": {
+				Name:   "build-job",
+				Stage:  "build",
+				Script: []any{"make"},
+			},
+			"test-job": {
+				Name:   "test-job",
+				Stage:  "test",
+				Script: []any{"make test"},
+				Rules: []model.Rule{
+					{
+						If:    `$CI_COMMIT_BRANCH == "main"`,
+						Needs: []any{"build-job", "nonexistent"},
+					},
+				},
+			},
+		},
+	}
+	findings := checkRulesNeeds(p, nil)
+	var got bool
+	for _, f := range findings {
+		if f.Rule == RuleRulesNeedsUnknown && f.Severity == Error {
+			got = true
+		}
+	}
+	if !got {
+		t.Errorf("expected GL044 error for unknown rules:needs: job; got %v", findings)
+	}
+}
+
+// TestCheckRulesNeeds_KnownJob verifies no finding when all rules:needs: jobs exist.
+func TestCheckRulesNeeds_KnownJob(t *testing.T) {
+	p := &model.Pipeline{
+		Stages: []string{"build", "test"},
+		Jobs: map[string]model.Job{
+			"build-job": {Name: "build-job", Stage: "build", Script: []any{"make"}},
+			"test-job": {
+				Name:   "test-job",
+				Stage:  "test",
+				Script: []any{"make test"},
+				Rules:  []model.Rule{{Needs: []any{"build-job"}}},
+			},
+		},
+	}
+	if findings := checkRulesNeeds(p, nil); len(findings) != 0 {
+		t.Errorf("expected no findings for valid rules:needs:; got %v", findings)
+	}
+}
+
+// TestCheckRulesNeeds_Optional verifies that optional: true downgrades to Warning.
+func TestCheckRulesNeeds_Optional(t *testing.T) {
+	p := &model.Pipeline{
+		Jobs: map[string]model.Job{
+			"test-job": {
+				Name:   "test-job",
+				Script: []any{"make test"},
+				Rules: []model.Rule{
+					{Needs: []any{map[string]any{"job": "ghost", "optional": true}}},
+				},
+			},
+		},
+	}
+	findings := checkRulesNeeds(p, nil)
+	if len(findings) != 1 || findings[0].Severity != Warning {
+		t.Errorf("optional unknown rules:needs: should produce Warning; got %v", findings)
+	}
+}
+
+// TestCheckRulesNeeds_CrossPipeline verifies that cross-pipeline needs are ignored.
+func TestCheckRulesNeeds_CrossPipeline(t *testing.T) {
+	p := &model.Pipeline{
+		Jobs: map[string]model.Job{
+			"test-job": {
+				Name:   "test-job",
+				Script: []any{"make test"},
+				Rules: []model.Rule{
+					{Needs: []any{map[string]any{"pipeline": "other", "job": "j"}}},
+				},
+			},
+		},
+	}
+	if findings := checkRulesNeeds(p, nil); len(findings) != 0 {
+		t.Errorf("cross-pipeline rules:needs: should be ignored; got %v", findings)
+	}
+}
+
+// TestCheckRulesNeeds_SkippedJob verifies that a skipped job's rules:needs: violations are suppressed.
+func TestCheckRulesNeeds_SkippedJob(t *testing.T) {
+	p := &model.Pipeline{
+		Jobs: map[string]model.Job{
+			"test-job": {
+				Name:   "test-job",
+				Script: []any{"make test"},
+				Rules:  []model.Rule{{Needs: []any{"nonexistent"}}},
+			},
+		},
+	}
+	if findings := checkRulesNeeds(p, map[string]bool{"test-job": true}); len(findings) != 0 {
+		t.Errorf("skipped job: expected no findings; got %v", findings)
+	}
+}
+
+// TestCheckRulesNeeds_NoNeeds verifies no findings when rules have no needs: override.
+func TestCheckRulesNeeds_NoNeeds(t *testing.T) {
+	p := &model.Pipeline{
+		Jobs: map[string]model.Job{
+			"test-job": {
+				Name:   "test-job",
+				Script: []any{"make test"},
+				Rules:  []model.Rule{{When: "on_success"}},
+			},
+		},
+	}
+	if findings := checkRulesNeeds(p, nil); len(findings) != 0 {
+		t.Errorf("rules without needs: should produce no findings; got %v", findings)
+	}
+}
+
 // TestCheckNeeds_StageOrder verifies that a job needing a job in a later stage
 // produces RuleNeedsStageOrder (line 64-76 in needs.go).
 func TestCheckNeeds_StageOrder(t *testing.T) {

internal/linter/rules.go

@@ -154,4 +154,8 @@ const (
 	// pipeline has no 'default:' block, making the declaration a no-op. Also fires
 	// when 'inherit: default: [list]' names fields not set in the default: block.
 	RuleInheritNoDefault = "GL043"
+
+	// GL044: a rules:needs: entry references a job that does not exist in the pipeline.
+	// rules:needs: overrides the top-level needs: when a specific rule matches (GitLab CI 16.4+).
+	RuleRulesNeedsUnknown = "GL044"
 )