Validation for Task Result expressions in Pipeline Results

Prior to this commit, the validation for static strings for Task
Result expressions in Pipeline Results was not extensive.

This commit adds the case where a pipeline would be invalid if
there is no expression following the valid form
`$(tasks.<task-name>.results.<result-name>)`.

Please reference this [doc](https://github.com/tektoncd/pipeline/blob/main/docs/pipelines.md#emitting-results-from-a-pipeline) for more
information.

Fixes bug [#4922](#4922)

pkg/apis/pipeline/v1beta1/pipeline_validation.go

@@ -252,16 +252,20 @@ func filter(arr []string, cond func(string) bool) []string {
 func validatePipelineResults(results []PipelineResult) (errs *apis.FieldError) {
 	for idx, result := range results {
 		expressions, ok := GetVarSubstitutionExpressionsForPipelineResult(result)
-		if ok {
-			if LooksLikeContainsResultRefs(expressions) {
-				expressions = filter(expressions, looksLikeResultRef)
-				resultRefs := NewResultRefs(expressions)
-				if len(expressions) != len(resultRefs) {
-					errs = errs.Also(apis.ErrInvalidValue(fmt.Sprintf("expected all of the expressions %v to be result expressions but only %v were", expressions, resultRefs),
-						"value").ViaFieldIndex("results", idx))
-				}
+		if !ok {
+			errs = errs.Also(apis.ErrInvalidValue(("expected pipeline results to be task result expressions but no expressions were found"),
+				"value").ViaFieldIndex("results", idx))
+		}
+
+		if LooksLikeContainsResultRefs(expressions) {
+			expressions = filter(expressions, looksLikeResultRef)
+			resultRefs := NewResultRefs(expressions)
+			if len(expressions) != len(resultRefs) {
+				errs = errs.Also(apis.ErrInvalidValue(fmt.Sprintf("expected all of the expressions %v to be result expressions but only %v were", expressions, resultRefs),
+					"value").ViaFieldIndex("results", idx))
 			}
 		}
+
 	}
 
 	return errs

pkg/apis/pipeline/v1beta1/pipeline_validation_test.go

@@ -129,7 +129,7 @@ func TestPipeline_Validate_Success(t *testing.T) {
 				Results: []PipelineResult{{
 					Name:        "pipeline-result",
 					Description: "this is my pipeline result",
-					Value:       "pipeline-result-default",
+					Value:       "$(tasks.my-task.results.my-result)",
 				}},
 			},
 		},
@@ -1204,22 +1204,41 @@ func TestValidatePipelineResults_Success(t *testing.T) {
 }
 
 func TestValidatePipelineResults_Failure(t *testing.T) {
-	desc := "invalid pipeline result reference"
-	results := []PipelineResult{{
-		Name:        "my-pipeline-result",
-		Description: "this is my pipeline result",
-		Value:       "$(tasks.a-task.results.output.output)",
+	tests := []struct {
+		desc          string
+		results       []PipelineResult
+		expectedError apis.FieldError
+	}{{
+		desc: "invalid pipeline result reference",
+		results: []PipelineResult{{
+			Name:        "my-pipeline-result",
+			Description: "this is my pipeline result",
+			Value:       "$(tasks.a-task.results.output.output)",
+		}},
+		expectedError: apis.FieldError{
+			Message: `invalid value: expected all of the expressions [tasks.a-task.results.output.output] to be result expressions but only [] were`,
+			Paths:   []string{"results[0].value"},
+		},
+	}, {
+		desc: "invalid pipeline result value with static string",
+		results: []PipelineResult{{
+			Name:        "my-pipeline-result",
+			Description: "this is my pipeline result",
+			Value:       "foo.bar",
+		}},
+		expectedError: apis.FieldError{
+			Message: `invalid value: expected pipeline results to be task result expressions but no expressions were found`,
+			Paths:   []string{"results[0].value"},
+		},
 	}}
-	expectedError := apis.FieldError{
-		Message: `invalid value: expected all of the expressions [tasks.a-task.results.output.output] to be result expressions but only [] were`,
-		Paths:   []string{"results[0].value"},
-	}
-	err := validatePipelineResults(results)
-	if err == nil {
-		t.Errorf("Pipeline.validatePipelineResults() did not return for invalid pipeline: %s", desc)
-	}
-	if d := cmp.Diff(expectedError.Error(), err.Error(), cmpopts.IgnoreUnexported(apis.FieldError{})); d != "" {
-		t.Errorf("Pipeline.validateParamResults() errors diff %s", diff.PrintWantGot(d))
+	for _, tt := range tests {
+		err := validatePipelineResults(tt.results)
+		if err == nil {
+			t.Errorf("Pipeline.validatePipelineResults() did not return for invalid pipeline: %s", tt.desc)
+		}
+		if d := cmp.Diff(tt.expectedError.Error(), err.Error(), cmpopts.IgnoreUnexported(apis.FieldError{})); d != "" {
+			t.Errorf("Pipeline.validateParamResults() errors diff %s", diff.PrintWantGot(d))
+		}
 	}
 }