Fix validation for empty check runs

Fixes bug introduced by #31 that did not allow no/op In configuration
Validates check config before running execute

internal/dtr/check.go

@@ -21,6 +21,7 @@
 package dtr
 
 import (
+	"fmt"
 	"io"
 )
 
@@ -30,6 +31,11 @@ func Check(in io.Reader) (CheckResult, error) {
 		return nil, err
 	}
 
+	err = validateCheckConfig(config.Source.Check)
+	if err != nil {
+		return nil, err
+	}
+
 	output, err := execute(config.Source.Check)
 	if err != nil {
 		return nil, err
@@ -52,3 +58,10 @@ func Check(in io.Reader) (CheckResult, error) {
 
 	return result, nil
 }
+
+func validateCheckConfig(c Custom) error {
+	if c.Run == "" {
+		return fmt.Errorf("run command not specified. Bailing out")
+	}
+	return nil
+}

internal/dtr/common.go

@@ -104,10 +104,6 @@ func execute(entry Custom) ([]string, error) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	if entry.Run == "" {
-		return nil, fmt.Errorf("run command not specified. Bailing out")
-	}
-
 	if entry.Before != "" {
 		before := command(ctx, entry.Env, entry.Before, os.Stderr)
 		if err := before.Run(); err != nil {
@@ -116,9 +112,16 @@ func execute(entry Custom) ([]string, error) {
 	}
 
 	var outStream bytes.Buffer
-	run := command(ctx, entry.Env, entry.Run, &outStream)
-	if err := run.Run(); err != nil {
-		return nil, fmt.Errorf("failure while running run command: %w", err)
+	// User does not always need to define Run
+	// e.g. user just implements Check but not In to trigger jobs
+	// In this scenario a user would still use get on the resource. Then In would be executed.
+	// For this scenario we would still like to allow no-op In runs
+	// Therefore we can skip command execution if nothing is defined
+	if entry.Run != "" {
+		run := command(ctx, entry.Env, entry.Run, &outStream)
+		if err := run.Run(); err != nil {
+			return nil, fmt.Errorf("failure while running run command: %w", err)
+		}
 	}
 
 	var result []string

internal/dtr/in_test.go

@@ -59,4 +59,23 @@ var _ = Describe("In", func() {
 			}))
 		})
 	})
+
+	Context("empty/no-op configuration", func() {
+		It("should not fail", func() {
+			_, err := In(feed(Config{}))
+
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		It("should return given version", func() {
+			version := Version{"ref": "foobar"}
+			result, _ := In(feed(Config{
+				Version: version,
+			}))
+
+			Expect(result).To(Equal(InOutResult{
+				Version: version,
+			}))
+		})
+	})
 })