Expose basic cluster information to jsonnet

This change adds two new jsonnet native functions:

- `kubernetesVersion` returns (eg) `[1, 7]` for a K8s 1.7 server.
- `kubernetesGroupVersionSupported` returns a bool indicating whether
  a given GroupVersion is supported by the current server

Note the latter does not provide a way to iterate over all supported
GroupVersions, for privacy.

cmd/apply.go

@@ -100,7 +100,7 @@ var applyCmd = &cobra.Command{
 			return err
 		}
 
-		objs, err := expandEnvCmdObjs(cmd, args)
+		objs, err := expandEnvCmdObjs(cmd, args, c.Discovery)
 		if err != nil {
 			return err
 		}

cmd/delete.go

@@ -55,7 +55,7 @@ var deleteCmd = &cobra.Command{
 			return err
 		}
 
-		objs, err := expandEnvCmdObjs(cmd, args)
+		objs, err := expandEnvCmdObjs(cmd, args, c.Discovery)
 		if err != nil {
 			return err
 		}

cmd/diff.go

@@ -53,7 +53,7 @@ var diffCmd = &cobra.Command{
 			return err
 		}
 
-		objs, err := expandEnvCmdObjs(cmd, args)
+		objs, err := expandEnvCmdObjs(cmd, args, c.Discovery)
 		if err != nil {
 			return err
 		}

cmd/root.go

@@ -25,11 +25,10 @@ import (
 	"path/filepath"
 	"strings"
 
-	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
-
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"golang.org/x/crypto/ssh/terminal"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/tools/clientcmd"
@@ -170,7 +169,7 @@ func (f *logFormatter) Format(e *log.Entry) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-func newExpander(cmd *cobra.Command) (*template.Expander, error) {
+func newExpander(cmd *cobra.Command, disco discovery.DiscoveryInterface) (*template.Expander, error) {
 	flags := cmd.Flags()
 	spec := template.Expander{}
 	var err error
@@ -211,6 +210,8 @@ func newExpander(cmd *cobra.Command) (*template.Expander, error) {
 		return nil, err
 	}
 
+	spec.Discovery = disco
+
 	return &spec, nil
 }
 
@@ -273,7 +274,7 @@ func parseEnvCmd(cmd *cobra.Command, args []string) (*string, []string, error) {
 // the user passes a list of files, we will expand all templates in those files,
 // while if a user passes an environment name, we will expand all component
 // files using that environment.
-func expandEnvCmdObjs(cmd *cobra.Command, args []string) ([]*unstructured.Unstructured, error) {
+func expandEnvCmdObjs(cmd *cobra.Command, args []string, disco discovery.DiscoveryInterface) ([]*unstructured.Unstructured, error) {
 	env, fileNames, err := parseEnvCmd(cmd, args)
 	if err != nil {
 		return nil, err
@@ -284,7 +285,7 @@ func expandEnvCmdObjs(cmd *cobra.Command, args []string) ([]*unstructured.Unstru
 		return nil, err
 	}
 
-	expander, err := newExpander(cmd)
+	expander, err := newExpander(cmd, disco)
 	if err != nil {
 		return nil, err
 	}

cmd/show.go

@@ -45,7 +45,12 @@ var showCmd = &cobra.Command{
 			return err
 		}
 
-		objs, err := expandEnvCmdObjs(cmd, args)
+		_, disco, err := restClientPool(cmd)
+		if err != nil {
+			return err
+		}
+
+		objs, err := expandEnvCmdObjs(cmd, args, disco)
 		if err != nil {
 			return err
 		}

cmd/update.go

@@ -81,7 +81,7 @@ local configuration. Accepts JSON, YAML, or Jsonnet.`,
 			return err
 		}
 
-		objs, err := expandEnvCmdObjs(cmd, args)
+		objs, err := expandEnvCmdObjs(cmd, args, c.Discovery)
 		if err != nil {
 			return err
 		}

cmd/validate.go

@@ -39,7 +39,7 @@ var validateCmd = &cobra.Command{
 			return err
 		}
 
-		objs, err := expandEnvCmdObjs(cmd, args)
+		objs, err := expandEnvCmdObjs(cmd, args, c.Discovery)
 		if err != nil {
 			return err
 		}

lib/kubecfg.libsonnet

@@ -65,4 +65,14 @@
   // to refer to submatches.  Regex is as implemented in golang regexp
   // package (python-ish).
   regexSubst:: std.native("regexSubst"),
+
+  // kubernetesVersion(): Return [major, minor] representing the
+  // Kubernetes server version.
+  kubernetesVersion:: std.native("kubernetesVersion"),
+
+  // kubernetesGroupVersionSupported(gv): Return true iff the
+  // Kubernetes server advertises support for the specified API
+  // "group/version" (eg: "storage.k8s.io/v1beta1").  Legacy core is
+  // "v1" (and hopefully always supported).
+  kubernetesGroupVersionSupported:: std.native("kubernetesGroupVersionSupported"),
 }

lib/kubecfg_test.jsonnet

@@ -65,6 +65,9 @@ assert r == "f\\[o" : "got " + r;
 local r = kubecfg.regexSubst("e", "tree", "oll");
 assert r == "trolloll" : "got " + r;
 
+// NB: kubernetes* functions are tested via integration tests, since
+// they require access to a k8s server.
+
 // Kubecfg wants to see something that looks like a k8s object
 {
   apiVersion: "test",

template/expander.go

@@ -6,11 +6,12 @@ import (
 	"os"
 	"strings"
 
+	log "github.com/sirupsen/logrus"
+	jsonnet "github.com/strickyak/jsonnet_cgo"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/client-go/discovery"
 
 	"github.com/ksonnet/kubecfg/utils"
-	log "github.com/sirupsen/logrus"
-	jsonnet "github.com/strickyak/jsonnet_cgo"
 )
 
 type Expander struct {
@@ -23,6 +24,8 @@ type Expander struct {
 
 	Resolver   string
 	FailAction string
+
+	Discovery discovery.DiscoveryInterface
 }
 
 func (spec *Expander) Expand(paths []string) ([]*unstructured.Unstructured, error) {
@@ -116,7 +119,7 @@ func (spec *Expander) jsonnetVM() (*jsonnet.VM, error) {
 	if err != nil {
 		return nil, err
 	}
-	utils.RegisterNativeFuncs(vm, resolver)
+	utils.RegisterNativeFuncs(vm, resolver, spec.Discovery)
 
 	return vm, nil
 }

utils/nativefuncs.go

@@ -20,12 +20,13 @@ import (
 	"encoding/json"
 	"io"
 	"regexp"
+	"strconv"
 	"strings"
 
 	goyaml "github.com/ghodss/yaml"
-
 	jsonnet "github.com/strickyak/jsonnet_cgo"
 	"k8s.io/apimachinery/pkg/util/yaml"
+	"k8s.io/client-go/discovery"
 )
 
 func resolveImage(resolver Resolver, image string) (string, error) {
@@ -42,7 +43,7 @@ func resolveImage(resolver Resolver, image string) (string, error) {
 }
 
 // RegisterNativeFuncs adds kubecfg's native jsonnet functions to provided VM
-func RegisterNativeFuncs(vm *jsonnet.VM, resolver Resolver) {
+func RegisterNativeFuncs(vm *jsonnet.VM, resolver Resolver, disco discovery.DiscoveryInterface) {
 	// NB: libjsonnet native functions can only pass primitive
 	// types, so some functions json-encode the arg.  These
 	// "*FromJson" functions will be replaced by regular native
@@ -105,4 +106,37 @@ func RegisterNativeFuncs(vm *jsonnet.VM, resolver Resolver) {
 		}
 		return r.ReplaceAllString(src, repl), nil
 	})
+
+	vm.NativeCallback("kubernetesVersion", []string{}, func() ([]interface{}, error) {
+		info, err := disco.ServerVersion()
+		if err != nil {
+			return nil, err
+		}
+
+		major, err := strconv.Atoi(info.Major)
+		if err != nil {
+			return nil, err
+		}
+		minor, err := strconv.Atoi(info.Minor)
+		if err != nil {
+			return nil, err
+		}
+		return []interface{}{major, minor}, nil
+	})
+
+	vm.NativeCallback("kubernetesGroupVersionSupported", []string{"gv"}, func(gv string) (bool, error) {
+		groups, err := disco.ServerGroups()
+		if err != nil {
+			return false, err
+		}
+
+		for _, g := range groups.Groups {
+			for _, v := range g.Versions {
+				if v.GroupVersion == gv {
+					return true, nil
+				}
+			}
+		}
+		return false, nil
+	})
 }

utils/nativefuncs_test.go

@@ -19,6 +19,9 @@ import (
 	"testing"
 
 	jsonnet "github.com/strickyak/jsonnet_cgo"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	fakedisco "k8s.io/client-go/discovery/fake"
+	ktesting "k8s.io/client-go/testing"
 )
 
 // check there is no err, and a == b.
@@ -30,10 +33,29 @@ func check(t *testing.T, err error, actual, expected string) {
 	}
 }
 
+func registerNativeFuncs(vm *jsonnet.VM) {
+	fake := &ktesting.Fake{
+		Resources: []*metav1.APIResourceList{
+			{
+				GroupVersion: "tests/v1alpha1",
+				APIResources: []metav1.APIResource{
+					{
+						Name: "tests",
+						Kind: "Test",
+					},
+				},
+			},
+		},
+	}
+	disco := &fakedisco.FakeDiscovery{Fake: fake}
+
+	RegisterNativeFuncs(vm, NewIdentityResolver(), disco)
+}
+
 func TestParseJson(t *testing.T) {
 	vm := jsonnet.Make()
 	defer vm.Destroy()
-	RegisterNativeFuncs(vm, NewIdentityResolver())
+	registerNativeFuncs(vm)
 
 	_, err := vm.EvaluateSnippet("failtest", `std.native("parseJson")("barf{")`)
 	if err == nil {
@@ -52,7 +74,7 @@ func TestParseJson(t *testing.T) {
 func TestParseYaml(t *testing.T) {
 	vm := jsonnet.Make()
 	defer vm.Destroy()
-	RegisterNativeFuncs(vm, NewIdentityResolver())
+	registerNativeFuncs(vm)
 
 	_, err := vm.EvaluateSnippet("failtest", `std.native("parseYaml")("[barf")`)
 	if err == nil {
@@ -76,7 +98,7 @@ func TestParseYaml(t *testing.T) {
 func TestRegexMatch(t *testing.T) {
 	vm := jsonnet.Make()
 	defer vm.Destroy()
-	RegisterNativeFuncs(vm, NewIdentityResolver())
+	registerNativeFuncs(vm)
 
 	_, err := vm.EvaluateSnippet("failtest", `std.native("regexMatch")("[f", "foo")`)
 	if err == nil {
@@ -93,7 +115,7 @@ func TestRegexMatch(t *testing.T) {
 func TestRegexSubst(t *testing.T) {
 	vm := jsonnet.Make()
 	defer vm.Destroy()
-	RegisterNativeFuncs(vm, NewIdentityResolver())
+	registerNativeFuncs(vm)
 
 	_, err := vm.EvaluateSnippet("failtest", `std.native("regexSubst")("[f",s "foo", "bar")`)
 	if err == nil {