support egctl x translate -f - (#1065)

* support `egctl x translate -f -` Fixes: #1057 Signed-off-by: Arko Dasgupta <arko@tetrate.io> * lint Signed-off-by: Arko Dasgupta <arko@tetrate.io> --------- Signed-off-by: Arko Dasgupta <arko@tetrate.io>
envoyproxy · Feb 21, 2023 · b97859d · b97859d
1 parent 2c57f3d
commit b97859d
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diff --git a/docs/latest/user/egctl.md b/docs/latest/user/egctl.md
@@ -10,7 +10,7 @@ In the below example, we will translate the Kubernetes resources (including the
 resources.
 
 ```
-cat <<EOF >> gateway-api-config.yaml
+cat <<EOF | egctl x translate --from gateway-api --to xds -f -
 apiVersion: gateway.networking.k8s.io/v1beta1
 kind: GatewayClass
 metadata:
@@ -76,10 +76,10 @@ spec:
             type: PathPrefix
             value: /
 EOF
+
 ```
 
 ```
-egctl x translate --from gateway-api --to xds -f gateway-api-config.yaml
 
 xDS
 

diff --git a/internal/cmd/egctl/translate.go b/internal/cmd/egctl/translate.go
@@ -6,6 +6,7 @@
 package egctl
 
 import (
+	"bufio"
 	"fmt"
 	"io"
 	"os"
@@ -91,14 +92,44 @@ func getValidOutputTypesStr() string {
 	return fmt.Sprintf("Valid types are %v.", validOutputTypes())
 }
 
-func translate(w io.Writer, inFile, inType, outType string) error {
+func getInputBytes(inFile string) ([]byte, error) {
+
+	// Get input from stdin
+	if inFile == "-" {
+		scanner := bufio.NewScanner(os.Stdin)
+		var input string
+		for {
+			if !scanner.Scan() {
+				break
+			}
+			input += scanner.Text() + "\n"
+		}
+		return []byte(input), nil
+	}
+	// Get input from file
+	return os.ReadFile(inFile)
+}
+
+func validate(inFile, inType, outType string) error {
 	if !isValidInputType(inType) {
 		return fmt.Errorf("%s is not a valid input type. %s", inType, getValidInputTypesStr())
 	}
 	if !isValidOutputType(outType) {
 		return fmt.Errorf("%s is not a valid output type. %s", outType, getValidOutputTypesStr())
 	}
-	inBytes, err := os.ReadFile(inFile)
+	if inFile == "" {
+		return fmt.Errorf("--file must be specified")
+	}
+
+	return nil
+}
+
+func translate(w io.Writer, inFile, inType, outType string) error {
+	if err := validate(inFile, inType, outType); err != nil {
+		return err
+	}
+
+	inBytes, err := getInputBytes(inFile)
 	if err != nil {
 		return fmt.Errorf("unable to read input file: %w", err)
 	}