Add check before creating task

Tasks with when expressions using variables that evaluated to false were
mistakenly executed because it missed an additional check to validate
that the task should be skipped after variable replacement.

Fixes tektoncd#3188

(cherry picked from commit c12b843)

examples/v1beta1/pipelineruns/pipelinerun-with-when-expressions.yaml

@@ -66,6 +66,16 @@ spec:
           - name: echo
             image: ubuntu
             script: 'echo file exists'
+    - name: echo-file-missing
+      when:
+        - input: "$(tasks.check-file.results.exists)"
+          operator: in
+          values: ["missing"]
+      taskSpec:
+        steps:
+          - name: echo
+            image: ubuntu
+            script: 'echo file missing'
     - name: task-should-be-skipped
       when:
         - input: "$(params.path)"

pkg/reconciler/pipelinerun/pipelinerun.go

@@ -522,7 +522,7 @@ func (c *Reconciler) runNextSchedulableTask(ctx context.Context, pr *v1beta1.Pip
 	resources.ApplyTaskResults(nextRprts, resolvedResultRefs)
 
 	for _, rprt := range nextRprts {
-		if rprt == nil {
+		if rprt == nil || rprt.Skip(pipelineState, d) {
 			continue
 		}
 		if rprt.ResolvedConditionChecks == nil || rprt.ResolvedConditionChecks.IsSuccess() {

pkg/reconciler/pipelinerun/pipelinerun_test.go

@@ -2081,6 +2081,21 @@ func TestReconcileWithWhenExpressionsWithParameters(t *testing.T) {
 	if d := cmp.Diff(actualSkippedTasks, expectedSkippedTasks); d != "" {
 		t.Errorf("expected to find Skipped Tasks %v. Diff %s", expectedSkippedTasks, diff.PrintWantGot(d))
 	}
+
+	skippedTasks := []string{"hello-world-2"}
+	for _, skippedTask := range skippedTasks {
+		labelSelector := fmt.Sprintf("tekton.dev/pipelineTask=%s,tekton.dev/pipelineRun=test-pipeline-run-different-service-accs", skippedTask)
+		actualSkippedTask, err := clients.Pipeline.TektonV1beta1().TaskRuns("foo").List(metav1.ListOptions{
+			LabelSelector: labelSelector,
+			Limit:         1,
+		})
+		if err != nil {
+			t.Fatalf("Failure to list TaskRun's %s", err)
+		}
+		if len(actualSkippedTask.Items) != 0 {
+			t.Fatalf("Expected 0 TaskRuns got %d", len(actualSkippedTask.Items))
+		}
+	}
 }
 
 func TestReconcileWithWhenExpressionsWithTaskResults(t *testing.T) {
@@ -2189,6 +2204,21 @@ func TestReconcileWithWhenExpressionsWithTaskResults(t *testing.T) {
 	if d := cmp.Diff(actualSkippedTasks, expectedSkippedTasks); d != "" {
 		t.Errorf("expected to find Skipped Tasks %v. Diff %s", expectedSkippedTasks, diff.PrintWantGot(d))
 	}
+
+	skippedTasks := []string{"c-task", "d-task"}
+	for _, skippedTask := range skippedTasks {
+		labelSelector := fmt.Sprintf("tekton.dev/pipelineTask=%s,tekton.dev/pipelineRun=test-pipeline-run-different-service-accs", skippedTask)
+		actualSkippedTask, err := clients.Pipeline.TektonV1beta1().TaskRuns("foo").List(metav1.ListOptions{
+			LabelSelector: labelSelector,
+			Limit:         1,
+		})
+		if err != nil {
+			t.Fatalf("Failure to list TaskRun's %s", err)
+		}
+		if len(actualSkippedTask.Items) != 0 {
+			t.Fatalf("Expected 0 TaskRuns got %d", len(actualSkippedTask.Items))
+		}
+	}
 }
 
 // TestReconcileWithAffinityAssistantStatefulSet tests that given a pipelineRun with workspaces,