Implemented implicit parameter propagation.

Implemented implicit parameter propagation.

Tekton Pipelines resources are verbose mostly because of explicitly propagating Parameters. Implicit Parameters feature was added to reduce the verbosity. However, there are challenges caused by mutating specifications to support Implicit Parameters. This proposal builds on this prior work by propagating Parameters without mutating specifications to improve usability of Tekton Pipelines.

examples/propagating_params_implicit_parameters.yaml

@@ -0,0 +1,18 @@
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  generateName: pr-echo-
+spec:
+  params:
+    - name: HELLO
+      value: "Pipeline Hello World!"
+  pipelineSpec:
+    tasks:
+      - name: echo-hello
+        taskSpec:
+          steps:
+            - name: echo
+              image: ubuntu
+              script: |
+                #!/usr/bin/env bash
+                echo "$(params.HELLO)"

examples/propagating_params_with_scope_precedence.yaml

@@ -0,0 +1,21 @@
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  generateName: pr-echo-
+spec:
+  params:
+    - name: HELLO
+      value: "Pipeline Hello World!"
+  pipelineSpec:
+    tasks:
+      - name: echo-hello
+        params:
+          - name: HELLO
+            value: "Task Hello World!"
+        taskSpec:
+          steps:
+            - name: echo
+              image: ubuntu
+              script: |
+                #!/usr/bin/env bash
+                echo "$(params.HELLO)"

examples/propagating_params_with_scope_precedence_default_only.yaml

@@ -0,0 +1,21 @@
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  generateName: pr-echo-
+spec:
+  params:
+    - name: HELLO
+      value: "Pipeline Hello World!"
+  pipelineSpec:
+    tasks:
+      - name: echo-hello
+        taskSpec:
+          params:
+            - name: HELLO
+              default: "Default Hello World!"
+          steps:
+            - name: echo
+              image: ubuntu
+              script: |
+                #!/usr/bin/env bash
+                echo "$(params.HELLO)"

pkg/apis/pipeline/v1beta1/task_validation.go

@@ -361,7 +361,9 @@ func validateStepVariables(step Step, prefix string, vars sets.String) *apis.Fie
 	errs := validateTaskVariable(step.Name, prefix, vars).ViaField("name")
 	errs = errs.Also(validateTaskVariable(step.Image, prefix, vars).ViaField("image"))
 	errs = errs.Also(validateTaskVariable(step.WorkingDir, prefix, vars).ViaField("workingDir"))
-	errs = errs.Also(validateTaskVariable(step.Script, prefix, vars).ViaField("script"))
+	if prefix != "params" {
+		errs = errs.Also(validateTaskVariable(step.Script, prefix, vars).ViaField("script"))
+	}
 	for i, cmd := range step.Command {
 		errs = errs.Also(validateTaskVariable(cmd, prefix, vars).ViaFieldIndex("command", i))
 	}

pkg/reconciler/pipelinerun/resources/apply.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"github.com/tektoncd/pipeline/pkg/apis/run/v1alpha1"
+	"github.com/tektoncd/pipeline/pkg/reconciler/taskrun/resources"
 
 	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1beta1"
 	"github.com/tektoncd/pipeline/pkg/substitution"
@@ -158,6 +159,29 @@ func ApplyReplacements(p *v1beta1.PipelineSpec, replacements map[string]string,
 			c.Params = replaceParamValues(c.Params, replacements, arrayReplacements)
 		}
 		p.Tasks[i].WhenExpressions = p.Tasks[i].WhenExpressions.ReplaceWhenExpressionsVariables(replacements, arrayReplacements)
+		if p.Tasks[i].TaskSpec != nil {
+			patterns := []string{
+				"params.%s",
+				"params[%q]",
+				"params['%s']",
+			}
+			// check if there are task parameters defined that match the params at pipeline level
+			if len(p.Tasks[i].Params) > 0 {
+				for _, par := range p.Tasks[i].Params {
+					for _, pattern := range patterns {
+						checkName := fmt.Sprintf(pattern, par.Name)
+						// Scoping. Task Params will replace Pipeline Params
+						if _, ok := replacements[checkName]; ok {
+							replacements[checkName] = par.Value.StringVal
+						}
+						if _, ok := arrayReplacements[checkName]; ok {
+							arrayReplacements[checkName] = par.Value.ArrayVal
+						}
+					}
+				}
+			}
+			p.Tasks[i].TaskSpec.TaskSpec = *resources.ApplyReplacements(&p.Tasks[i].TaskSpec.TaskSpec, replacements, arrayReplacements)
+		}
 	}
 
 	for i := range p.Finally {

pkg/reconciler/taskrun/validate_resources.go

@@ -20,7 +20,6 @@ import (
 	"context"
 	"fmt"
 
-	"github.com/tektoncd/pipeline/pkg/apis/config"
 	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1beta1"
 	resourcev1alpha1 "github.com/tektoncd/pipeline/pkg/apis/resource/v1alpha1"
 	"github.com/tektoncd/pipeline/pkg/list"
@@ -93,17 +92,6 @@ func validateParams(ctx context.Context, paramSpecs []v1beta1.ParamSpec, params
 	if len(missingParamsNoDefaults) > 0 {
 		return fmt.Errorf("missing values for these params which have no default values: %s", missingParamsNoDefaults)
 	}
-	// If alpha features are enabled, disable checking for extra params.
-	// Extra params are needed to support
-	// https://github.com/tektoncd/community/blob/main/teps/0023-implicit-mapping.md
-	// So that parent params can be passed down to subresources (even if they
-	// are not explicitly used).
-	if config.FromContextOrDefaults(ctx).FeatureFlags.EnableAPIFields != "alpha" {
-		extraParams := list.DiffLeft(providedParams, neededParams)
-		if len(extraParams) != 0 {
-			return fmt.Errorf("didn't need these params but they were provided anyway: %s", extraParams)
-		}
-	}
 
 	// Now that we have checked against missing/extra params, make sure each param's actual type matches
 	// the user-specified type.