Introduce Value in TaskResults

This PR introduces the field `Value` in `TaskResults`.
This field is necessary to capture the results produced by `StepActions`
if the Task needs to resolve name conflicts.

This is part of issue #7259.
Following this PR, we will add support for extracting StepAction results
via termination message and sidecar logs.

docs/pipeline-api.md

@@ -1741,7 +1741,7 @@ 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>
@@ -4931,6 +4931,20 @@ string
 <p>Description is a human-readable description of the result</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>value</code><br/>
+<em>
+<a href="#tekton.dev/v1.ParamValue">
+ParamValue
+</a>
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>Value the expression used to retrieve the value of the result from an underlying Step.</p>
+</td>
+</tr>
 </tbody>
 </table>
 <h3 id="tekton.dev/v1.TaskRunDebug">TaskRunDebug
@@ -10232,7 +10246,7 @@ 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>
@@ -14135,6 +14149,20 @@ string
 <p>Description is a human-readable description of the result</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>value</code><br/>
+<em>
+<a href="#tekton.dev/v1beta1.ParamValue">
+ParamValue
+</a>
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>Value the expression used to retrieve the value of the result from an underlying Step.</p>
+</td>
+</tr>
 </tbody>
 </table>
 <h3 id="tekton.dev/v1beta1.TaskRunConditionType">TaskRunConditionType

pkg/apis/pipeline/v1/result_types.go

@@ -32,6 +32,10 @@ type TaskResult struct {
 	// Description is a human-readable description of the result
 	// +optional
 	Description string `json:"description,omitempty"`
+
+	// Value the expression used to retrieve the value of the result from an underlying Step.
+	// +optional
+	Value *ResultValue `json:"value,omitempty"`
 }
 
 // TaskRunResult used to describe the results of a task

pkg/apis/pipeline/v1/result_validation.go

@@ -16,7 +16,10 @@ package v1
 import (
 	"context"
 	"fmt"
+	"regexp"
 
+	"github.com/tektoncd/pipeline/pkg/apis/config"
+	"k8s.io/apimachinery/pkg/util/validation"
 	"knative.dev/pkg/apis"
 )
 
@@ -28,20 +31,16 @@ func (tr TaskResult) Validate(ctx context.Context) (errs *apis.FieldError) {
 
 	switch {
 	case tr.Type == ResultsTypeObject:
-		errs := validateObjectResult(tr)
-		return errs
+		errs = errs.Also(validateObjectResult(tr))
 	case tr.Type == ResultsTypeArray:
-		return nil
 	// Resources created before the result. Type was introduced may not have Type set
 	// and should be considered valid
 	case tr.Type == "":
-		return nil
 	// By default, the result type is string
 	case tr.Type != ResultsTypeString:
-		return apis.ErrInvalidValue(tr.Type, "type", "type must be string")
+		errs = errs.Also(apis.ErrInvalidValue(tr.Type, "type", "type must be string"))
 	}
-
-	return nil
+	return errs.Also(tr.validateValue(ctx))
 }
 
 // validateObjectResult validates the object result and check if the Properties is missing
@@ -66,3 +65,60 @@ func validateObjectResult(tr TaskResult) (errs *apis.FieldError) {
 	}
 	return nil
 }
+
+// validateValue validates the value of the TaskResult.
+// It requires that enable-step-actions is true, the value is of type string
+// and format $(steps.<stepName>.results.<resultName>)
+func (tr TaskResult) validateValue(ctx context.Context) (errs *apis.FieldError) {
+	if tr.Value == nil {
+		return nil
+	}
+	if !config.FromContextOrDefaults(ctx).FeatureFlags.EnableStepActions {
+		return apis.ErrGeneric("feature flag %s should be set to true to fetch Results from Steps using StepActions.", config.EnableStepActions)
+	}
+	if tr.Value.Type != ParamTypeString {
+		return &apis.FieldError{
+			Message: fmt.Sprintf(
+				"Invalid Type. Wanted string but got: \"%v\"", tr.Value.Type),
+			Paths: []string{
+				fmt.Sprintf("%s.type", tr.Name),
+			},
+		}
+	}
+	if tr.Value.StringVal != "" {
+		stepName, resultName, err := ExtractStepResultName(tr.Value.StringVal)
+		if err != nil {
+			return &apis.FieldError{
+				Message: fmt.Sprintf("%v", err),
+				Paths:   []string{fmt.Sprintf("%s.value", tr.Name)},
+			}
+		}
+		if e := validation.IsDNS1123Label(stepName); len(e) > 0 {
+			errs = errs.Also(&apis.FieldError{
+				Message: fmt.Sprintf("invalid extracted step name %q", stepName),
+				Paths:   []string{fmt.Sprintf("%s.value", tr.Name)},
+				Details: "stepName in $(steps.<stepName>.results.<resultName>) must be a valid DNS Label, For more info refer to https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names",
+			})
+		}
+		if !resultNameFormatRegex.MatchString(resultName) {
+			errs = errs.Also(&apis.FieldError{
+				Message: fmt.Sprintf("invalid extracted result name %q", resultName),
+				Paths:   []string{fmt.Sprintf("%s.value", tr.Name)},
+				Details: fmt.Sprintf("resultName in $(steps.<stepName>.results.<resultName>) 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),
+			})
+		}
+	}
+	return errs
+}
+
+// ExtractStepResultName extracts the step name and result name from a string matching
+// formtat $(steps.<stepName>.results.<resultName>).
+// If a match is not found, an error is retured.
+func ExtractStepResultName(value string) (string, string, error) {
+	re := regexp.MustCompile(`\$\(steps\.(.*?)\.results\.(.*?)\)`)
+	rs := re.FindStringSubmatch(value)
+	if len(rs) != 3 {
+		return "", "", fmt.Errorf("Could not extract step name and result name. Expected value to look like $(steps.<stepName>.results.<resultName>) but got \"%v\"", value)
+	}
+	return rs[1], rs[2], nil
+}