[TEP-0048] Add support for default results

docs/pipeline-api.md

@@ -1669,7 +1669,7 @@ Used to distinguish between a single string and an array of strings.</p>
 <h3 id="tekton.dev/v1.ParamValue">ParamValue
 </h3>
 <p>
-(<em>Appears on:</em><a href="#tekton.dev/v1.Param">Param</a>, <a href="#tekton.dev/v1.ParamSpec">ParamSpec</a>, <a href="#tekton.dev/v1.PipelineResult">PipelineResult</a>, <a href="#tekton.dev/v1.PipelineRunResult">PipelineRunResult</a>, <a href="#tekton.dev/v1.TaskRunResult">TaskRunResult</a>)
+(<em>Appears on:</em><a href="#tekton.dev/v1.Param">Param</a>, <a href="#tekton.dev/v1.ParamSpec">ParamSpec</a>, <a href="#tekton.dev/v1.PipelineResult">PipelineResult</a>, <a href="#tekton.dev/v1.PipelineRunResult">PipelineRunResult</a>, <a href="#tekton.dev/v1.TaskResult">TaskResult</a>, <a href="#tekton.dev/v1.TaskRunResult">TaskRunResult</a>)
 </p>
 <div>
 <p>ResultValue is a type alias of ParamValue</p>
@@ -4476,6 +4476,22 @@ string
 <p>Description is a human-readable description of the result</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>default</code><br/>
+<em>
+<a href="#tekton.dev/v1.ParamValue">
+ParamValue
+</a>
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>This is an alpha field. You must set the &ldquo;enable-api-fields&rdquo; feature flag to &ldquo;alpha&rdquo;
+for this field to be supported.</p>
+<p>Default is the value a result produces if no result is produced by Task</p>
+</td>
+</tr>
 </tbody>
 </table>
 <h3 id="tekton.dev/v1.TaskRunDebug">TaskRunDebug
@@ -8761,7 +8777,7 @@ Used to distinguish between a single string and an array of strings.</p>
 <h3 id="tekton.dev/v1beta1.ParamValue">ParamValue
 </h3>
 <p>
-(<em>Appears on:</em><a href="#tekton.dev/v1beta1.Param">Param</a>, <a href="#tekton.dev/v1beta1.ParamSpec">ParamSpec</a>, <a href="#tekton.dev/v1beta1.PipelineResult">PipelineResult</a>, <a href="#tekton.dev/v1beta1.PipelineRunResult">PipelineRunResult</a>, <a href="#tekton.dev/v1beta1.TaskRunResult">TaskRunResult</a>)
+(<em>Appears on:</em><a href="#tekton.dev/v1beta1.Param">Param</a>, <a href="#tekton.dev/v1beta1.ParamSpec">ParamSpec</a>, <a href="#tekton.dev/v1beta1.PipelineResult">PipelineResult</a>, <a href="#tekton.dev/v1beta1.PipelineRunResult">PipelineRunResult</a>, <a href="#tekton.dev/v1beta1.TaskResult">TaskResult</a>, <a href="#tekton.dev/v1beta1.TaskRunResult">TaskRunResult</a>)
 </p>
 <div>
 <p>ResultValue is a type alias of ParamValue</p>
@@ -12417,8 +12433,30 @@ string
 <p>Description is a human-readable description of the result</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>default</code><br/>
+<em>
+<a href="#tekton.dev/v1beta1.ParamValue">
+ParamValue
+</a>
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>This is an alpha field. You must set the &ldquo;enable-api-fields&rdquo; feature flag to &ldquo;alpha&rdquo;
+for this field to be supported.</p>
+<p>Default is the value a result produces if no result is produced by Task</p>
+</td>
+</tr>
 </tbody>
 </table>
+<h3 id="tekton.dev/v1beta1.TaskRunConditionType">TaskRunConditionType
+(<code>string</code> alias)</h3>
+<div>
+<p>TaskRunConditionType is an enum used to store TaskRun custom conditions
+conditions such as one used in spire results verification</p>
+</div>
 <h3 id="tekton.dev/v1beta1.TaskRunDebug">TaskRunDebug
 </h3>
 <p>

docs/tasks.md

@@ -847,6 +847,48 @@ available size will less than 4096 bytes.
 As a general rule-of-thumb, if a result needs to be larger than a kilobyte, you should likely use a
 [`Workspace`](#specifying-workspaces) to store and pass it between `Tasks` within a `Pipeline`.
 
+#### Default value
+
+> **Note**: This is an alpha gated feature.
+
+Results declarations (within Tasks and Pipelines) can include default values which will be used if the Result is
+not produced, for example to specify defaults for both string params and array params
+([full example](../examples/v1beta1/taskruns/alpha/default-result.yaml)) :
+
+```yaml
+apiVersion: tekton.dev/v1beta1
+kind: Task
+metadata:
+  name: task-with-default-result
+spec:
+  results:
+  - name: branch
+    default: main
+```
+
+**Note**: If a Task doesn't specify any default value for a particular `Result`
+and also fails to emit that `Result`, in that case, the following `Task` is going
+to be marked as `Failed` as specified in [TEP-0048](https://github.com/tektoncd/community/blob/main/teps/0048-task-results-without-results.md). Below is the example in which the TaskRun
+is going to fail as one of the Result wasn't produced.
+
+```yaml
+apiVersion: tekton.dev/v1beta1
+kind: TaskRun
+metadata:
+  generateName: test-tr-
+spec:
+  taskSpec:
+    results:
+      - name: result1
+        description: will be produced
+      - name: result2
+        description: will not be produced
+    steps:
+      - name: failing-step
+        image: busybox
+        script: "echo -n 123 | tee $(results.result1.path)"
+```
+
 ### Specifying `Volumes`
 
 Specifies one or more [`Volumes`](https://kubernetes.io/docs/concepts/storage/volumes/) that the `Steps` in your

examples/v1beta1/pipelineruns/alpha/pipeline-emitting-default-results.yaml

@@ -0,0 +1,72 @@
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  name: pipelinerun-emit-default-results
+spec:
+  pipelineSpec:
+    tasks:
+      - name: task1
+        taskSpec:
+          results:
+            - name: array-results
+              type: array
+              description: The array results
+              default:
+              - "1"
+              - "2"
+              - "3"
+          steps:
+            - name: write-array
+              image: bash:latest
+              script: |
+                #!/usr/bin/env bash
+                echo -n "this script won't emit array result"
+      - name: task2
+        taskSpec:
+          results:
+            - name: object-results
+              type: object
+              description: The object results
+              properties:
+                foo: {type: string}
+                hello: {type: string}
+              default:
+                foo: bar
+                hello: world
+          steps:
+            - name: write-array
+              image: bash:latest
+              script: |
+                #!/usr/bin/env bash
+                echo -n "this script won't emit object result"
+    results:
+      - name: array-results
+        type: array
+        description: whole array
+        value: $(tasks.task1.results.array-results[*])
+      - name: array-results-from-array-indexing-and-object-elements
+        type: array
+        description: whole array
+        value:
+          [
+            "$(tasks.task1.results.array-results[0])",
+            "$(tasks.task2.results.object-results.foo)",
+          ]
+      - name: array-indexing-results
+        type: string
+        description: array element
+        value: $(tasks.task1.results.array-results[1])
+      - name: object-results
+        type: object
+        description: whole object
+        value: $(tasks.task2.results.object-results[*])
+      - name: object-results-from-array-indexing-and-object-elements
+        type: object
+        description: whole object
+        value:
+          key1: $(tasks.task1.results.array-results[1])
+          key2: $(tasks.task2.results.object-results.hello)
+      - name: object-element
+        type: string
+        description: object element
+        value: $(tasks.task2.results.object-results.foo)

examples/v1beta1/taskruns/alpha/default-result.yaml

@@ -0,0 +1,33 @@
+apiVersion: tekton.dev/v1beta1
+kind: TaskRun
+metadata:
+  generateName: default-result-run-
+spec:
+  taskSpec:
+    results:
+      - name: result1
+        description: will be produced
+      - name: string-result
+        description: will not be produced by step but has default value
+        default: "string value"
+      - name: array-result
+        description: default array result will be produced
+        default:
+          - "foo"
+          - "bar"
+      - name: eight-results
+        type: object
+        properties:
+          IMAGE_URL: {type: string}
+          IMAGE_DIGEST: {type: string}
+        default:
+          IMAGE_URL: "default.com"
+          IMAGE_DIGEST: "defaultsha"
+    steps:
+      - name: failing-step
+        onError: continue
+        image: busybox
+        script: |
+          echo -n 123 | tee $(results.result1.path)
+          exit 1
+          echo -n 456 | tee $(results.string-result.path)

pkg/apis/pipeline/v1/result_types.go

@@ -32,6 +32,13 @@ type TaskResult struct {
 	// Description is a human-readable description of the result
 	// +optional
 	Description string `json:"description,omitempty"`
+
+	// This is an alpha field. You must set the "enable-api-fields" feature flag to "alpha"
+	// for this field to be supported.
+	//
+	// Default is the value a result produces if no result is produced by Task
+	// +optional
+	Default *ResultValue `json:"default,omitempty"`
 }
 
 // TaskRunResult used to describe the results of a task

pkg/apis/pipeline/v1/swagger.json

@@ -1615,6 +1615,10 @@
         "name"
       ],
       "properties": {
+        "default": {
+          "description": "This is an alpha field. You must set the \"enable-api-fields\" feature flag to \"alpha\" for this field to be supported.\n\nDefault is the value a result produces if no result is produced by Task",
+          "$ref": "#/definitions/v1.ParamValue"
+        },
         "description": {
           "description": "Description is a human-readable description of the result",
           "type": "string"

pkg/apis/pipeline/v1beta1/result_conversion.go

@@ -15,6 +15,23 @@ func (r TaskResult) convertTo(ctx context.Context, sink *v1.TaskResult) {
 		properties[k] = v1.PropertySpec{Type: v1.ParamType(v.Type)}
 	}
 	sink.Properties = properties
+	if r.Default != nil {
+		sink.Default = &v1.ParamValue{
+			Type: v1.ParamType(r.Default.Type),
+		}
+		switch r.Default.Type {
+		case ParamTypeString:
+			sink.Default.StringVal = r.Default.StringVal
+		case ParamTypeArray:
+			sink.Default.ArrayVal = r.Default.ArrayVal
+		default: // In case of ParamTypeObject
+			defaults := make(map[string]string)
+			for k, v := range r.Default.ObjectVal {
+				defaults[k] = v
+			}
+			sink.Default.ObjectVal = defaults
+		}
+	}
 }
 
 func (r *TaskResult) convertFrom(ctx context.Context, source v1.TaskResult) {
@@ -26,4 +43,21 @@ func (r *TaskResult) convertFrom(ctx context.Context, source v1.TaskResult) {
 		properties[k] = PropertySpec{Type: ParamType(v.Type)}
 	}
 	r.Properties = properties
+	if source.Default != nil {
+		r.Default = &ParamValue{
+			Type: ParamType(source.Default.Type),
+		}
+		switch source.Default.Type {
+		case v1.ParamTypeString:
+			r.Default.StringVal = source.Default.StringVal
+		case v1.ParamTypeArray:
+			r.Default.ArrayVal = source.Default.ArrayVal
+		default:
+			defaults := make(map[string]string)
+			for k, v := range source.Default.ObjectVal {
+				defaults[k] = v
+			}
+			r.Default.ObjectVal = defaults
+		}
+	}
 }

pkg/apis/pipeline/v1beta1/result_types.go

@@ -32,6 +32,13 @@ type TaskResult struct {
 	// Description is a human-readable description of the result
 	// +optional
 	Description string `json:"description,omitempty"`
+
+	// This is an alpha field. You must set the "enable-api-fields" feature flag to "alpha"
+	// for this field to be supported.
+	//
+	// Default is the value a result produces if no result is produced by Task
+	// +optional
+	Default *ResultValue `json:"default,omitempty"`
 }
 
 // TaskRunResult used to describe the results of a task

pkg/apis/pipeline/v1beta1/result_validation.go

@@ -27,6 +27,11 @@ func (tr TaskResult) Validate(ctx context.Context) (errs *apis.FieldError) {
 	if !resultNameFormatRegex.MatchString(tr.Name) {
 		return apis.ErrInvalidKeyName(tr.Name, "name", fmt.Sprintf("Name must consist of alphanumeric characters, '-', '_', and must start and end with an alphanumeric character (e.g. 'MyName',  or 'my-name',  or 'my_name', regex used for validation is '%s')", ResultNameFormat))
 	}
+	// Default results in alpha feature
+	if tr.Default != nil {
+		errs = errs.Also(version.ValidateEnabledAPIFields(ctx, "default results", config.AlphaAPIFields))
+		return errs
+	}
 	// Array and Object is alpha feature
 	if tr.Type == ResultsTypeArray || tr.Type == ResultsTypeObject {
 		errs := validateObjectResult(tr)