improve error handling in pkg cat command to include package context

Signed-off-by: Aravindhan Ayyanathan <aravindhan.a@est.tech>

Author: aravindtga

thirdparty/cmdconfig/commands/cmdcat/cmdcat.go

@@ -14,7 +14,6 @@ import (
 
 	"github.com/kptdev/kpt/internal/docs/generated/pkgdocs"
 	kptfilev1 "github.com/kptdev/kpt/pkg/api/kptfile/v1"
-	"github.com/kptdev/kpt/pkg/printer"
 	"github.com/kptdev/kpt/thirdparty/cmdconfig/commands/runner"
 	"github.com/spf13/cobra"
 	"sigs.k8s.io/kustomize/kyaml/kio"
@@ -114,14 +113,13 @@ func (r *CatRunner) ExecuteCmd(w io.Writer, pkgPath string) error {
 	}.Execute()
 
 	if err != nil {
-		// Emit a contextual diagnostic on stderr so the user knows which
-		// package failed; the runner currently aborts on the first error.
-		fmt.Fprintf(printer.FromContextOrDie(r.Ctx).ErrStream(),
-			"kpt pkg cat: %s in package %q\n", err.Error(), pkgPath)
-		return err
+		// Wrap with package context so the user knows which package failed;
+		// the root command's error handler is responsible for printing.
+		return fmt.Errorf("kpt pkg cat: %q: %w", pkgPath, err)
 	}
-	fmt.Fprint(w, out.String())
-	if out.String() != "" {
+	outStr := out.String()
+	fmt.Fprint(w, outStr)
+	if outStr != "" {
 		fmt.Fprint(w, "---")
 	}
 	return nil

thirdparty/cmdconfig/commands/cmdcat/cmdcat_test.go

@@ -398,20 +398,25 @@ data:
 
 	_, err := runCat(t, d)
 	assert.Error(t, err)
+	// The returned error must carry the pkg-path context ("kpt pkg cat: "<pkg>":")
+	// as well as the underlying file that failed. The root cobra handler
+	// (main.handleErr) is responsible for printing; ExecuteCmd must not
+	// write to stderr itself, or the user would see the message twice.
+	assert.Contains(t, err.Error(), "kpt pkg cat:")
+	assert.Contains(t, err.Error(), d)
 	assert.Contains(t, err.Error(), "broken.yaml")
 
-	// Stderr must carry the contextual diagnostic. Inject a printer via
-	// context (mirroring how run.go wires the root cobra err stream) and
-	// assert on its err stream.
+	// Sanity-check that ExecuteCmd itself does not write to the printer's
+	// ErrStream — otherwise the root handler would duplicate the output.
 	var errBuf bytes.Buffer
 	ctx := printer.WithContext(context.Background(), printer.New(nil, &errBuf))
 	r := GetCatRunner(ctx, "")
 	r.Command.SetArgs([]string{d})
 	r.Command.SetOut(&bytes.Buffer{})
 	r.Command.SetErr(&bytes.Buffer{})
 	_ = r.Command.Execute()
-	assert.Contains(t, errBuf.String(), "kpt pkg cat:")
-	assert.Contains(t, errBuf.String(), "broken.yaml")
+	assert.Empty(t, errBuf.String(),
+		"ExecuteCmd must not print to ErrStream; the root handler prints the returned error")
 }
 
 // TestCmd_NonExistent verifies a clean error on a missing path.