Implement options for enabling CEL extensions

repl/BUILD.bazel

@@ -56,6 +56,7 @@ go_test(
     embed = [":go_default_library"],
     deps = [
         "//cel:go_default_library",
+        "//test/proto2pb:go_default_library",
         "@org_golang_google_genproto//googleapis/api/expr/v1alpha1:go_default_library",
         "@org_golang_google_protobuf//proto:go_default_library",
     ],

repl/evaluator.go

@@ -431,12 +431,7 @@ type Evaluator struct {
 
 // NewEvaluator returns an inialized evaluator
 func NewEvaluator() (*Evaluator, error) {
-	env, err := cel.NewEnv(
-		ext.Strings(),
-		ext.Protos(),
-		ext.Math(),
-		ext.Encoders(),
-	)
+	env, err := cel.NewEnv()
 	if err != nil {
 		return nil, err
 	}
@@ -685,6 +680,39 @@ func (o *containerOption) Option() cel.EnvOption {
 	return cel.Container(o.container)
 }
 
+// extensionOption implements optional for loading a specific extension into the environment (String, Math, Proto, Encoder)
+type extensionOption struct {
+	extensionType string
+	option        cel.EnvOption
+}
+
+func (o *extensionOption) String() string {
+	return fmt.Sprintf("%%option --extension '%s'", o.extensionType)
+}
+
+func (o extensionOption) Option() cel.EnvOption {
+	return o.option
+}
+
+func newExtensionOption(extType string) (*extensionOption, error) {
+	var extOption cel.EnvOption
+	extType = strings.ToLower(extType)
+	switch op := extType; op {
+	case "strings":
+		extOption = ext.Strings()
+	case "protos":
+		extOption = ext.Protos()
+	case "math":
+		extOption = ext.Math()
+	case "encoders":
+		extOption = ext.Encoders()
+	default:
+		return nil, fmt.Errorf("Unknown option: %s. Available options are: ['strings', 'protos', 'math', 'encoders']", op)
+	}
+
+	return &extensionOption{extensionType: extType, option: extOption}, nil
+}
+
 // setOption sets a number of options on the environment. returns an error if
 // any of them fail.
 func (e *Evaluator) setOption(args []string) error {
@@ -702,6 +730,12 @@ func (e *Evaluator) setOption(args []string) error {
 			if err != nil {
 				issues = append(issues, fmt.Sprintf("container: %v", err))
 			}
+		} else if arg == "--extension" {
+			err := e.loadExtensionOption(idx, args)
+			idx++
+			if err != nil {
+				issues = append(issues, fmt.Sprintf("extension: %v", err))
+			}
 		} else {
 			issues = append(issues, fmt.Sprintf("unsupported option '%s'", arg))
 		}
@@ -712,6 +746,25 @@ func (e *Evaluator) setOption(args []string) error {
 	return nil
 }
 
+func (e *Evaluator) loadExtensionOption(idx int, args []string) error {
+	if idx >= len(args) {
+		return fmt.Errorf("not enough args for extension")
+	}
+
+	extType := args[idx]
+	extensionOption, err := newExtensionOption(extType)
+	if err != nil {
+		return err
+	}
+
+	err = e.AddOption(extensionOption)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func loadFileDescriptorSet(path string, textfmt bool) (*descpb.FileDescriptorSet, error) {
 	data, err := ioutil.ReadFile(path)
 	if err != nil {

repl/evaluator_test.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/google/cel-go/cel"
 
+	proto2pb "github.com/google/cel-go/test/proto2pb"
 	exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
 )
 
@@ -527,6 +528,78 @@ func TestProcess(t *testing.T) {
 			wantExit:  false,
 			wantError: false,
 		},
+		{
+			name: "OptionExtensionStrings",
+			commands: []Cmder{
+				&simpleCmd{
+					cmd: "option",
+					args: []string{
+						"--extension",
+						"strings",
+					},
+				},
+				&evalCmd{
+					expr: "'test'.substring(2)",
+				},
+			},
+			wantText:  "st : string",
+			wantExit:  false,
+			wantError: false,
+		},
+		{
+			name: "OptionExtensionProtos",
+			commands: []Cmder{
+				&simpleCmd{
+					cmd: "option",
+					args: []string{
+						"--extension",
+						"protos",
+					},
+				},
+				&evalCmd{
+					expr: "proto.getExt(google.expr.proto2.test.ExampleType{}, google.expr.proto2.test.int32_ext) == 0",
+				},
+			},
+			wantText:  "true : bool",
+			wantExit:  false,
+			wantError: false,
+		},
+		{
+			name: "OptionExtensionMath",
+			commands: []Cmder{
+				&simpleCmd{
+					cmd: "option",
+					args: []string{
+						"--extension",
+						"math",
+					},
+				},
+				&evalCmd{
+					expr: "math.greatest(1,2)",
+				},
+			},
+			wantText:  "2 : int",
+			wantExit:  false,
+			wantError: false,
+		},
+		{
+			name: "OptionExtensionEncoders",
+			commands: []Cmder{
+				&simpleCmd{
+					cmd: "option",
+					args: []string{
+						"--extension",
+						"encoders",
+					},
+				},
+				&evalCmd{
+					expr: "base64.encode(b'hello')",
+				},
+			},
+			wantText:  "aGVsbG8= : string",
+			wantExit:  false,
+			wantError: false,
+		},
 		{
 			name: "LoadDescriptorsError",
 			commands: []Cmder{
@@ -651,6 +724,7 @@ func TestProcess(t *testing.T) {
 			if err != nil {
 				t.Fatalf("NewEvaluator returned error: %v, wanted nil", err)
 			}
+			eval.env, _ = eval.env.Extend(cel.Types(&proto2pb.ExampleType{}, &proto2pb.ExternalMessageType{}))
 			n := len(tc.commands)
 			for _, cmd := range tc.commands[:n-1] {
 				// only need output of last command

repl/main/README.md

@@ -118,10 +118,14 @@ may take string arguments.
 
 `--container <string>` sets the expression container for name resolution.
 
+`--extension <extensionType>` enables CEL extensions. Valid options are: `strings`, `protos`, `math`, `encoders`.
+
 example:
 
 `%option --container 'google.protobuf'` 
 
+`%option --extension 'strings'`
+
 #### reset
 
 `%reset` drops all options and let expressions, returning the evaluator to a 

test/proto2pb/BUILD.bazel

@@ -9,6 +9,7 @@ package(
         "//ext:__subpackages__",
         "//interpreter:__subpackages__",
         "//parser:__subpackages__",
+        "//repl:__subpackages__",
         "//server:__subpackages__",
         "//test:__subpackages__",
     ],
@@ -24,13 +25,13 @@ go_library(
     importpath = "github.com/google/cel-go/test/proto2pb",
     deps = [
         "@org_golang_google_protobuf//proto:go_default_library",
+        "@org_golang_google_protobuf//reflect/protoreflect:go_default_library",
+        "@org_golang_google_protobuf//runtime/protoimpl:go_default_library",
         "@org_golang_google_protobuf//types/known/anypb:go_default_library",
         "@org_golang_google_protobuf//types/known/durationpb:go_default_library",
         "@org_golang_google_protobuf//types/known/structpb:go_default_library",
         "@org_golang_google_protobuf//types/known/timestamppb:go_default_library",
         "@org_golang_google_protobuf//types/known/wrapperspb:go_default_library",
-        "@org_golang_google_protobuf//reflect/protoreflect:go_default_library",
-        "@org_golang_google_protobuf//runtime/protoimpl:go_default_library",
     ],
 )