Enable custom columns printing in kubectl

pkg/kubectl/custom_column_printer.go

@@ -17,6 +17,8 @@ limitations under the License.
 package kubectl
 
 import (
+	"bufio"
+	"bytes"
 	"fmt"
 	"io"
 	"reflect"
@@ -35,6 +37,95 @@ const (
 	flags             = 0
 )
 
+// MassageJSONPath attempts to be flexible with JSONPath expressions, it accepts:
+//   * metadata.name (no leading '.' or curly brances '{...}'
+//   * {metadata.name} (no leading '.')
+//   * .metadata.name (no curly braces '{...}')
+//   * {.metadata.name} (complete expression)
+// And transforms them all into a valid jsonpat expression:
+//   {.metadata.name}
+func massageJSONPath(pathExpression string) string {
+	if len(pathExpression) == 0 {
+		return pathExpression
+	}
+	if pathExpression[0] != '{' {
+		if pathExpression[0] == '.' {
+			return fmt.Sprintf("{%s}", pathExpression)
+		} else {
+			return fmt.Sprintf("{.%s}", pathExpression)
+		}
+	} else {
+		if pathExpression[1] == '.' {
+			return pathExpression
+		} else {
+			return fmt.Sprintf("{.%s}", pathExpression[1:len(pathExpression)-1])
+		}
+	}
+}
+
+// NewCustomColumnsPrinterFromSpec creates a custom columns printer from a comma separated list of <header>:<jsonpath-field-spec> pairs.
+// e.g. NAME:metadata.name,API_VERSION:apiVersion creates a printer that prints:
+//
+//      NAME               API_VERSION
+//      foo                bar
+func NewCustomColumnsPrinterFromSpec(spec string) (*CustomColumnsPrinter, error) {
+	parts := strings.Split(spec, ",")
+	if len(parts) == 0 {
+		return nil, fmt.Errorf("custom-columns format specified but no custom columns given")
+	}
+	columns := make([]Column, len(parts))
+	for ix := range parts {
+		colSpec := strings.Split(parts[ix], ":")
+		if len(colSpec) != 2 {
+			return nil, fmt.Errorf("unexpected custom-columns spec: %s, expected <header>:<json-path-expr>", parts[ix])
+		}
+		columns[ix] = Column{Header: colSpec[0], FieldSpec: massageJSONPath(colSpec[1])}
+	}
+	return &CustomColumnsPrinter{Columns: columns}, nil
+}
+
+func splitOnWhitespace(line string) []string {
+	lineScanner := bufio.NewScanner(bytes.NewBufferString(line))
+	lineScanner.Split(bufio.ScanWords)
+	result := []string{}
+	for lineScanner.Scan() {
+		result = append(result, lineScanner.Text())
+	}
+	return result
+}
+
+// NewCustomColumnsPrinterFromTemplate creates a custom columns printer from a template stream.  The template is expected
+// to consist of two lines, whitespace separated.  The first line is the header line, the second line is the jsonpath field spec
+// For example the template below:
+// NAME               API_VERSION
+// {metadata.name}    {apiVersion}
+func NewCustomColumnsPrinterFromTemplate(templateReader io.Reader) (*CustomColumnsPrinter, error) {
+	scanner := bufio.NewScanner(templateReader)
+	if !scanner.Scan() {
+		return nil, fmt.Errorf("invalid template, missing header line")
+	}
+	headers := splitOnWhitespace(scanner.Text())
+
+	if !scanner.Scan() {
+		return nil, fmt.Errorf("invalid template, missing spec line")
+	}
+	specs := splitOnWhitespace(scanner.Text())
+	fmt.Printf("SPECS: %v", specs)
+
+	if len(headers) != len(specs) {
+		return nil, fmt.Errorf("number of headers (%d) and field specifications (%d) don't match", len(headers), len(specs))
+	}
+
+	columns := make([]Column, len(headers))
+	for ix := range headers {
+		columns[ix] = Column{
+			Header:    headers[ix],
+			FieldSpec: massageJSONPath(specs[ix]),
+		}
+	}
+	return &CustomColumnsPrinter{Columns: columns}, nil
+}
+
 // Column represents a user specified column
 type Column struct {
 	// The header to print above the column, general style is ALL_CAPS
@@ -105,3 +196,7 @@ func (s *CustomColumnsPrinter) printOneObject(obj runtime.Object, parsers []*jso
 	fmt.Fprintln(out, strings.Join(columns, "\t"))
 	return nil
 }
+
+func (s *CustomColumnsPrinter) HandledResources() []string {
+	return []string{}
+}

pkg/kubectl/custom_column_printer_test.go

@@ -18,12 +18,177 @@ package kubectl
 
 import (
 	"bytes"
+	"reflect"
 	"testing"
 
 	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/runtime"
 )
 
+func TestMassageJSONPath(t *testing.T) {
+	tests := []struct {
+		input          string
+		expectedOutput string
+	}{
+		{input: "foo.bar", expectedOutput: "{.foo.bar}"},
+		{input: "{foo.bar}", expectedOutput: "{.foo.bar}"},
+		{input: ".foo.bar", expectedOutput: "{.foo.bar}"},
+		{input: "{.foo.bar}", expectedOutput: "{.foo.bar}"},
+		{input: "", expectedOutput: ""},
+	}
+	for _, test := range tests {
+		output := massageJSONPath(test.input)
+		if output != test.expectedOutput {
+			t.Errorf("expected: %s, saw: %s", test.expectedOutput, output)
+		}
+	}
+}
+
+func TestNewColumnPrinterFromSpec(t *testing.T) {
+	tests := []struct {
+		spec            string
+		expectedColumns []Column
+		expectErr       bool
+		name            string
+	}{
+		{
+			spec:      "",
+			expectErr: true,
+			name:      "empty",
+		},
+		{
+			spec:      "invalid",
+			expectErr: true,
+			name:      "invalid1",
+		},
+		{
+			spec:      "invalid=foobar",
+			expectErr: true,
+			name:      "invalid2",
+		},
+		{
+			spec:      "invalid,foobar:blah",
+			expectErr: true,
+			name:      "invalid3",
+		},
+		{
+			spec: "NAME:metadata.name,API_VERSION:apiVersion",
+			name: "ok",
+			expectedColumns: []Column{
+				{
+					Header:    "NAME",
+					FieldSpec: "{.metadata.name}",
+				},
+				{
+					Header:    "API_VERSION",
+					FieldSpec: "{.apiVersion}",
+				},
+			},
+		},
+	}
+	for _, test := range tests {
+		printer, err := NewCustomColumnsPrinterFromSpec(test.spec)
+		if test.expectErr {
+			if err == nil {
+				t.Errorf("[%s] unexpected non-error", test.name)
+			}
+			continue
+		}
+		if !test.expectErr && err != nil {
+			t.Errorf("[%s] unexpected error: %v", test.name, err)
+			continue
+		}
+
+		if !reflect.DeepEqual(test.expectedColumns, printer.Columns) {
+			t.Errorf("[%s]\nexpected:\n%v\nsaw:\n%v\n", test.name, test.expectedColumns, printer.Columns)
+		}
+
+	}
+}
+
+const exampleTemplateOne = `NAME               API_VERSION
+{metadata.name}    {apiVersion}`
+
+const exampleTemplateTwo = `NAME               		API_VERSION
+							{metadata.name}    {apiVersion}`
+
+func TestNewColumnPrinterFromTemplate(t *testing.T) {
+	tests := []struct {
+		spec            string
+		expectedColumns []Column
+		expectErr       bool
+		name            string
+	}{
+		{
+			spec:      "",
+			expectErr: true,
+			name:      "empty",
+		},
+		{
+			spec:      "invalid",
+			expectErr: true,
+			name:      "invalid1",
+		},
+		{
+			spec:      "invalid=foobar",
+			expectErr: true,
+			name:      "invalid2",
+		},
+		{
+			spec:      "invalid,foobar:blah",
+			expectErr: true,
+			name:      "invalid3",
+		},
+		{
+			spec: exampleTemplateOne,
+			name: "ok",
+			expectedColumns: []Column{
+				{
+					Header:    "NAME",
+					FieldSpec: "{.metadata.name}",
+				},
+				{
+					Header:    "API_VERSION",
+					FieldSpec: "{.apiVersion}",
+				},
+			},
+		},
+		{
+			spec: exampleTemplateTwo,
+			name: "ok-2",
+			expectedColumns: []Column{
+				{
+					Header:    "NAME",
+					FieldSpec: "{.metadata.name}",
+				},
+				{
+					Header:    "API_VERSION",
+					FieldSpec: "{.apiVersion}",
+				},
+			},
+		},
+	}
+	for _, test := range tests {
+		reader := bytes.NewBufferString(test.spec)
+		printer, err := NewCustomColumnsPrinterFromTemplate(reader)
+		if test.expectErr {
+			if err == nil {
+				t.Errorf("[%s] unexpected non-error", test.name)
+			}
+			continue
+		}
+		if !test.expectErr && err != nil {
+			t.Errorf("[%s] unexpected error: %v", test.name, err)
+			continue
+		}
+
+		if !reflect.DeepEqual(test.expectedColumns, printer.Columns) {
+			t.Errorf("[%s]\nexpected:\n%v\nsaw:\n%v\n", test.name, test.expectedColumns, printer.Columns)
+		}
+
+	}
+}
+
 func TestColumnPrint(t *testing.T) {
 	tests := []struct {
 		columns        []Column

pkg/kubectl/resource_printer.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
 	"reflect"
 	"sort"
 	"strings"
@@ -99,6 +100,19 @@ func GetPrinter(format, formatArgument string) (ResourcePrinter, bool, error) {
 		if err != nil {
 			return nil, false, fmt.Errorf("error parsing template %s, %v\n", string(data), err)
                 }
+	case "custom-columns":
+		var err error
+		if printer, err = NewCustomColumnsPrinterFromSpec(formatArgument); err != nil {
+			return nil, false, err
+		}
+	case "custom-columns-file":
+		file, err := os.Open(formatArgument)
+		if err != nil {
+			return nil, false, fmt.Errorf("error reading template %s, %v\n", formatArgument, err)
+		}
+		if printer, err = NewCustomColumnsPrinterFromTemplate(file); err != nil {
+			return nil, false, err
+		}
 	case "wide":
 		fallthrough
 	case "":