feat: Add default field in parameters.valueFrom

api/openapi-spec/swagger.json

@@ -10,6 +10,7 @@
   ],
   "swagger": "2.0",
   "info": {
+    "description": "Workflow Service API performs CRUD actions against application resources",
     "title": "Argo",
     "version": "latest"
   },
@@ -2722,6 +2723,10 @@
       "type": "object",
       "title": "ValueFrom describes a location in which to obtain the value to a parameter",
       "properties": {
+        "default": {
+          "type": "string",
+          "title": "Default specifies a value to be used if retrieving the value from the specified source fails"
+        },
         "jqFilter": {
           "type": "string",
           "title": "JQFilter expression against the resource object in resource templates"
@@ -5874,5 +5879,31 @@
       "description": "HTTP Basic authentication",
       "type": "basic"
     }
+  },
+  "x-stream-definitions": {
+    "io.argoproj.workflow.v1alpha1.LogEntry": {
+      "properties": {
+        "error": {
+          "$ref": "#/definitions/grpc.gateway.runtime.StreamError"
+        },
+        "result": {
+          "$ref": "#/definitions/io.argoproj.workflow.v1alpha1.LogEntry"
+        }
+      },
+      "title": "Stream result of io.argoproj.workflow.v1alpha1.LogEntry",
+      "type": "object"
+    },
+    "io.argoproj.workflow.v1alpha1.WorkflowWatchEvent": {
+      "properties": {
+        "error": {
+          "$ref": "#/definitions/grpc.gateway.runtime.StreamError"
+        },
+        "result": {
+          "$ref": "#/definitions/io.argoproj.workflow.v1alpha1.WorkflowWatchEvent"
+        }
+      },
+      "title": "Stream result of io.argoproj.workflow.v1alpha1.WorkflowWatchEvent",
+      "type": "object"
+    }
   }
 }

examples/output-parameter.yaml

@@ -37,6 +37,7 @@ spec:
       parameters:
       - name: hello-param
         valueFrom:
+          default: "Foobar"   # Default value to use if retrieving valueFrom fails. If not provided workflow will fail instead
           path: /tmp/hello_world.txt
 
   - name: print-message

pkg/apiclient/cronworkflow/cron-workflow.swagger.json

@@ -1552,6 +1552,10 @@
         "parameter": {
           "type": "string",
           "title": "Parameter reference to a step or dag task in which to retrieve an output parameter value from\n(e.g. '{{steps.mystep.outputs.myparam}}')"
+        },
+        "default": {
+          "type": "string",
+          "title": "Default specifies a value to be used if retrieving the value from the specified source fails"
         }
       },
       "title": "ValueFrom describes a location in which to obtain the value to a parameter"

pkg/apiclient/workflow/workflow.swagger.json

@@ -1929,6 +1929,10 @@
         "parameter": {
           "type": "string",
           "title": "Parameter reference to a step or dag task in which to retrieve an output parameter value from\n(e.g. '{{steps.mystep.outputs.myparam}}')"
+        },
+        "default": {
+          "type": "string",
+          "title": "Default specifies a value to be used if retrieving the value from the specified source fails"
         }
       },
       "title": "ValueFrom describes a location in which to obtain the value to a parameter"

pkg/apiclient/workflowarchive/workflow-archive.swagger.json

@@ -1360,6 +1360,10 @@
         "parameter": {
           "type": "string",
           "title": "Parameter reference to a step or dag task in which to retrieve an output parameter value from\n(e.g. '{{steps.mystep.outputs.myparam}}')"
+        },
+        "default": {
+          "type": "string",
+          "title": "Default specifies a value to be used if retrieving the value from the specified source fails"
         }
       },
       "title": "ValueFrom describes a location in which to obtain the value to a parameter"

pkg/apiclient/workflowtemplate/workflow-template.swagger.json

@@ -1420,6 +1420,10 @@
         "parameter": {
           "type": "string",
           "title": "Parameter reference to a step or dag task in which to retrieve an output parameter value from\n(e.g. '{{steps.mystep.outputs.myparam}}')"
+        },
+        "default": {
+          "type": "string",
+          "title": "Default specifies a value to be used if retrieving the value from the specified source fails"
         }
       },
       "title": "ValueFrom describes a location in which to obtain the value to a parameter"

pkg/apis/workflow/v1alpha1/workflow_types.go

@@ -620,6 +620,9 @@ type ValueFrom struct {
 	// Parameter reference to a step or dag task in which to retrieve an output parameter value from
 	// (e.g. '{{steps.mystep.outputs.myparam}}')
 	Parameter string `json:"parameter,omitempty" protobuf:"bytes,4,opt,name=parameter"`
+
+	// Default specifies a value to be used if retrieving the value from the specified source fails
+	Default string `json:"default,omitempty" protobuf:"bytes,5,opt,name=default"`
 }
 
 // Artifact indicates an artifact to place at a specified path

test/e2e/functional_test.go

@@ -342,6 +342,64 @@ func (s *FunctionalSuite) TestTerminateBehavior() {
 		})
 }
 
+func (s *FunctionalSuite) TestDefaultParameterOutputs() {
+	s.Given().
+		Workflow(`
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  name: default-params
+  labels:
+    argo-e2e: true
+spec:
+  entrypoint: start
+  templates:
+  - name: start
+    steps:
+      - - name: generate-1
+          template: generate
+      - - name: generate-2
+          when: "True == False"
+          template: generate
+    outputs:
+      parameters:
+        - name: nested-out-parameter
+          valueFrom:
+            default: "Default value"
+            parameter: "{{steps.generate-2.outputs.parameters.out-parameter}}"
+
+  - name: generate
+    container:
+      image: docker/whalesay:latest
+      command: [sh, -c]
+      args: ["
+        echo 'my-output-parameter' > /tmp/my-output-parameter.txt
+      "]
+    outputs:
+      parameters:
+      - name: out-parameter
+        valueFrom:
+          path: /tmp/my-output-parameter.txt
+`).
+		When().
+		SubmitWorkflow().
+		WaitForWorkflow(30 * time.Second).
+		Then().
+		ExpectWorkflow(func(t *testing.T, _ *metav1.ObjectMeta, status *wfv1.WorkflowStatus) {
+			assert.Equal(t, wfv1.NodeSucceeded, status.Phase)
+			assert.True(t, status.Nodes.Any(func(node wfv1.NodeStatus) bool {
+				if node.Outputs != nil {
+					for _, param := range node.Outputs.Parameters {
+						if param.Value != nil && *param.Value == "Default value" {
+							return true
+						}
+					}
+				}
+				return false
+			}))
+		})
+}
+
 func TestFunctionalSuite(t *testing.T) {
 	suite.Run(t, new(FunctionalSuite))
 }

workflow/controller/operator.go

@@ -1801,7 +1801,12 @@ func getTemplateOutputsFromScope(tmpl *wfv1.Template, scope *wfScope) (*wfv1.Out
 			}
 			val, err := scope.resolveParameter(param.ValueFrom.Parameter)
 			if err != nil {
-				return nil, err
+				// We have a default value to use instead of returning an error
+				if param.ValueFrom.Default != "" {
+					val = param.ValueFrom.Default
+				} else {
+					return nil, err
+				}
 			}
 			param.Value = &val
 			param.ValueFrom = nil

workflow/executor/executor.go

@@ -425,14 +425,24 @@ func (we *WorkflowExecutor) SaveParameters() error {
 			log.Infof("Copying %s from base image layer", param.ValueFrom.Path)
 			output, err = we.RuntimeExecutor.GetFileContents(mainCtrID, param.ValueFrom.Path)
 			if err != nil {
-				return err
+				// We have a default value to use instead of returning an error
+				if param.ValueFrom.Default != "" {
+					output = param.ValueFrom.Default
+				} else {
+					return err
+				}
 			}
 		} else {
 			log.Infof("Copying %s from from volume mount", param.ValueFrom.Path)
 			mountedPath := filepath.Join(common.ExecutorMainFilesystemDir, param.ValueFrom.Path)
 			out, err := ioutil.ReadFile(mountedPath)
 			if err != nil {
-				return err
+				// We have a default value to use instead of returning an error
+				if param.ValueFrom.Default != "" {
+					output = param.ValueFrom.Default
+				} else {
+					return err
+				}
 			}
 			output = string(out)
 		}

workflow/executor/executor_test.go

@@ -1,6 +1,7 @@
 package executor
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -104,3 +105,35 @@ func TestIsBaseImagePath(t *testing.T) {
 	assert.False(t, we.isBaseImagePath("/user-mount/some-path/foo"))
 	assert.True(t, we.isBaseImagePath("/user-mount-coincidence"))
 }
+
+func TestDefaultParameters(t *testing.T) {
+	fakeClientset := fake.NewSimpleClientset()
+	mockRuntimeExecutor := mocks.ContainerRuntimeExecutor{}
+	templateWithOutParam := wfv1.Template{
+		Outputs: wfv1.Outputs{
+			Parameters: []wfv1.Parameter{
+				{
+					Name: "my-out",
+					ValueFrom: &wfv1.ValueFrom{
+						Default: "Default Value",
+						Path:    "/path",
+					},
+				},
+			},
+		},
+	}
+	we := WorkflowExecutor{
+		PodName:            fakePodName,
+		Template:           templateWithOutParam,
+		ClientSet:          fakeClientset,
+		Namespace:          fakeNamespace,
+		PodAnnotationsPath: fakeAnnotations,
+		ExecutionControl:   nil,
+		RuntimeExecutor:    &mockRuntimeExecutor,
+		mainContainerID:    fakeContainerID,
+	}
+	mockRuntimeExecutor.On("GetFileContents", fakeContainerID, "/path").Return("", fmt.Errorf("file not found"))
+	err := we.SaveParameters()
+	assert.NoError(t, err)
+	assert.Equal(t, "Default Value", *we.Template.Outputs.Parameters[0].Value)
+}

workflow/executor/resource.go

@@ -308,10 +308,15 @@ func (we *WorkflowExecutor) SaveResourceParameters(resourceNamespace string, res
 		log.Info(cmd.Args)
 		out, err := cmd.Output()
 		if err != nil {
-			if exErr, ok := err.(*exec.ExitError); ok {
-				log.Errorf("`%s` stderr:\n%s", cmd.Args, string(exErr.Stderr))
+			// We have a default value to use instead of returning an error
+			if param.ValueFrom.Default != "" {
+				out = []byte(param.ValueFrom.Default)
+			} else {
+				if exErr, ok := err.(*exec.ExitError); ok {
+					log.Errorf("`%s` stderr:\n%s", cmd.Args, string(exErr.Stderr))
+				}
+				return errors.InternalWrapError(err)
 			}
-			return errors.InternalWrapError(err)
 		}
 		output := string(out)
 		we.Template.Outputs.Parameters[i].Value = &output