Switch human logging to stderr to enable pipeable validation output

action/pipeline/validate.go

@@ -112,10 +112,10 @@ func (c *Config) ValidateLocal(client compiler.Engine) error {
 		return err
 	}
 
-	// output the message in stdout format
+	// output the message in stderr format
 	//
-	// https://pkg.go.dev/github.com/go-vela/cli/internal/output?tab=doc#Stdout
-	err = output.Stdout(fmt.Sprintf("%s is valid", path))
+	// https://pkg.go.dev/github.com/go-vela/cli/internal/output?tab=doc#Stderr
+	err = output.Stderr(fmt.Sprintf("%s is valid", path))
 	if err != nil {
 		return err
 	}

internal/output/driver.go

@@ -10,6 +10,10 @@ const (
 	// when outputting in stdout format.
 	DriverStdout = "stdout"
 
+	// DriverStderr defines the driver type
+	// when outputting in stderr format.
+	DriverStderr = "stderr"
+
 	// DriverDump defines the driver type
 	// when outputting in dump format.
 	DriverDump = "dump"

internal/output/stderr.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2023 Target Brands, Inc. All rights reserved.
+//
+// Use of this source code is governed by the LICENSE file in this repository.
+
+package output
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Stderr outputs the provided input to stderr.
+func Stderr(_input interface{}) error {
+	logrus.Debugf("creating output with %s driver", DriverStderr)
+
+	// validate the input provided
+	err := validate(DriverStderr, _input)
+	if err != nil {
+		return err
+	}
+
+	logrus.Tracef("sending output to stderr with %s driver", DriverStderr)
+
+	// ensure we output to stderr
+	fmt.Fprintln(os.Stderr, _input)
+
+	return nil
+}

internal/output/stderr_test.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2023 Target Brands, Inc. All rights reserved.
+//
+// Use of this source code is governed by the LICENSE file in this repository.
+
+package output
+
+import (
+	"testing"
+)
+
+func TestErrout_Default(t *testing.T) {
+	// setup tests
+	tests := []struct {
+		failure bool
+		input   interface{}
+	}{
+		{
+			failure: false,
+			input:   "hello",
+		},
+		{ // map
+			failure: false,
+			input:   map[string]string{"hello": "world"},
+		},
+		{ // slice
+			failure: false,
+			input:   []interface{}{1, 2, 3},
+		},
+		{ // slice complex
+			failure: false,
+			input:   []interface{}{struct{ Foo string }{Foo: "bar"}},
+		},
+		{ // complex
+			failure: false,
+			input:   []struct{ Foo string }{{"bar"}, {"baz"}},
+		},
+		{
+			failure: true,
+			input:   nil,
+		},
+		{
+			failure: true,
+			input:   "",
+		},
+	}
+
+	// run tests
+	for _, test := range tests {
+		err := Stderr(test.input)
+
+		if test.failure {
+			if err == nil {
+				t.Errorf("Stderr should have returned err")
+			}
+
+			continue
+		}
+
+		if err != nil {
+			t.Errorf("Stderr returned err: %v", err)
+		}
+	}
+}