Hide long and multiline strings when printing

Currently both long strings and multiline strings can potentially
"break" printing. I'm adding extra formatting to ensure we cut strings
either at newline or at 100 chars with information that more information
is available.

staging/src/k8s.io/cli-runtime/pkg/printers/tableprinter.go

@@ -32,6 +32,8 @@ import (
 	"k8s.io/apimachinery/pkg/watch"
 )
 
+const maxStringLength = 100
+
 var _ ResourcePrinter = &HumanReadablePrinter{}
 
 type printHandler struct {
@@ -208,7 +210,28 @@ func printTable(table *metav1.Table, output io.Writer, options PrintOptions) err
 				fmt.Fprint(output, "\t")
 			}
 			if cell != nil {
-				fmt.Fprint(output, cell)
+				switch val := cell.(type) {
+				case string:
+					print := val
+					more := 0
+					// cut to maxStringLength
+					if len(val) > maxStringLength {
+						more = len(print) - maxStringLength
+						print = print[:maxStringLength]
+					}
+					// and also check for newlines
+					newline := strings.Index(print, "\n")
+					if newline >= 0 {
+						more = more + len(print) - newline
+						print = print[:newline]
+					}
+					fmt.Fprint(output, print)
+					if more > 0 {
+						fmt.Fprintf(output, " + %d more...", more)
+					}
+				default:
+					fmt.Fprint(output, val)
+				}
 			}
 		}
 		fmt.Fprintln(output)

staging/src/k8s.io/cli-runtime/pkg/printers/tableprinter_test.go

@@ -722,3 +722,70 @@ func TestUnknownTypePrinting(t *testing.T) {
 		t.Errorf("An error was expected from printing unknown type")
 	}
 }
+
+func TestStringPrinting(t *testing.T) {
+	tests := []struct {
+		columns  []metav1.TableColumnDefinition
+		rows     []metav1.TableRow
+		expected string
+	}{
+		// multiline string
+		{
+			columns: []metav1.TableColumnDefinition{
+				{Name: "Name", Type: "string"},
+				{Name: "Age", Type: "string"},
+				{Name: "Description", Type: "string"},
+			},
+			rows: []metav1.TableRow{
+				{Cells: []interface{}{"test1", "20h", "This is first line\nThis is second line\nThis is third line\nand another one\n"}},
+			},
+			expected: `NAME    AGE   DESCRIPTION
+test1   20h   This is first line + 56 more...
+`,
+		},
+		// lengthy string
+		{
+			columns: []metav1.TableColumnDefinition{
+				{Name: "Name", Type: "string"},
+				{Name: "Age", Type: "string"},
+				{Name: "Description", Type: "string"},
+			},
+			rows: []metav1.TableRow{
+				{Cells: []interface{}{"test1", "20h", "This is first line which is long and goes for on and on and on an on and on and on and on and on and on and on and on and on and on and on"}},
+			},
+			expected: `NAME    AGE   DESCRIPTION
+test1   20h   This is first line which is long and goes for on and on and on an on and on and on and on and on and + 38 more...
+`,
+		},
+		// lengthy string + newline
+		{
+			columns: []metav1.TableColumnDefinition{
+				{Name: "Name", Type: "string"},
+				{Name: "Age", Type: "string"},
+				{Name: "Description", Type: "string"},
+			},
+			rows: []metav1.TableRow{
+				{Cells: []interface{}{"test1", "20h", "This is first\n line which is long and goes for on and on and on an on and on and on and on and on and on and on and on and on and on and on"}},
+			},
+			expected: `NAME    AGE   DESCRIPTION
+test1   20h   This is first + 126 more...
+`,
+		},
+	}
+
+	for _, test := range tests {
+		// Create the table from the columns and rows.
+		table := &metav1.Table{
+			ColumnDefinitions: test.columns,
+			Rows:              test.rows,
+		}
+		// Print the table
+		out := bytes.NewBuffer([]byte{})
+		printer := NewTablePrinter(PrintOptions{})
+		printer.PrintObj(table, out)
+
+		if test.expected != out.String() {
+			t.Errorf("Table printing error: expected \n(%s), got \n(%s)", test.expected, out.String())
+		}
+	}
+}