Add syntax for escaped field selectors.

cel/cel_test.go

@@ -2171,6 +2171,53 @@ func TestParserRecursionLimit(t *testing.T) {
 	}
 }
 
+func TestQuotedFields(t *testing.T) {
+	testCases := []struct {
+		expr        string
+		errorSubstr string
+		out         ref.Val
+	}{
+		{
+			expr: "{'key-1': 64}.`key-1`",
+			out:  types.Int(64),
+		},
+		{
+			expr:        "{'key-1': 64}.`key-2`",
+			errorSubstr: "no such key: key-2",
+		},
+		{
+			expr: "has({'key-1': 64}.`key-1`)",
+			out:  types.True,
+		},
+		{
+			expr: "has({'key-1': 64}.`key-2`)",
+			out:  types.False,
+		},
+	}
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.expr, func(t *testing.T) {
+			env := testEnv(t, ParserRecursionLimit(10),
+				EnableIdentifierEscapeSyntax())
+			out, err := interpret(t, env,
+				tc.expr, map[string]any{})
+
+			if tc.errorSubstr != "" {
+				if err == nil || !strings.Contains(err.Error(), tc.errorSubstr) {
+					t.Fatalf("prg.Eval() wanted error containing '%s' got %v", tc.errorSubstr, err)
+				}
+			}
+
+			if tc.out != nil {
+				if tc.out != out {
+					t.Errorf("prg.Eval() wanted %v got %v", tc.out, out)
+				}
+			}
+		})
+
+	}
+}
+
 func TestDynamicDispatch(t *testing.T) {
 	env := testEnv(t,
 		HomogeneousAggregateLiterals(),

cel/env.go

@@ -615,6 +615,9 @@ func (e *Env) configure(opts []EnvOption) (*Env, error) {
 	if e.HasFeature(featureVariadicLogicalASTs) {
 		prsrOpts = append(prsrOpts, parser.EnableVariadicOperatorASTs(true))
 	}
+	if e.HasFeature(featureIdentEscapeSyntax) {
+		prsrOpts = append(prsrOpts, parser.EnableIdentEscapeSyntax(true))
+	}
 	e.prsr, err = parser.NewParser(prsrOpts...)
 	if err != nil {
 		return nil, err

cel/options.go

@@ -65,6 +65,9 @@ const (
 	// Enable error generation when a presence test or optional field selection is
 	// performed on a primitive type.
 	featureEnableErrorOnBadPresenceTest
+
+	// Enable escape syntax for field identifiers (`).
+	featureIdentEscapeSyntax
 )
 
 // EnvOption is a functional interface for configuring the environment.
@@ -618,6 +621,12 @@ func EnableMacroCallTracking() EnvOption {
 	return features(featureEnableMacroCallTracking, true)
 }
 
+// EnableIdentifierEscapeSyntax enables identifier escaping (`) syntax for
+// fields.
+func EnableIdentifierEscapeSyntax() EnvOption {
+	return features(featureIdentEscapeSyntax, true)
+}
+
 // CrossTypeNumericComparisons makes it possible to compare across numeric types, e.g. double < int
 func CrossTypeNumericComparisons(enabled bool) EnvOption {
 	return features(featureCrossTypeNumericComparisons, enabled)

ext/protos_test.go

@@ -42,12 +42,21 @@ func TestProtos(t *testing.T) {
 		{expr: `proto.getExt(ExampleType{}, google.expr.proto2.test.nested_example) == ExampleType{}`},
 		{expr: `proto.getExt(ExampleType{}, google.expr.proto2.test.ExtendedExampleType.extended_examples) == []`},
 		{expr: `proto.getExt(ExampleType{}, google.expr.proto2.test.ExtendedExampleType.enum_ext) == GlobalEnum.GOO`},
+		{expr: "ExampleType{`in`: 64}.`in` == 64"},
+		// TODO(issue/1095): legal parse, but can't assign extension fields without updates to type checker and runtime
+		// ExampleType{`google.expr.proto2.test.int32_ext`: 42}.`google.expr.proto2.test.int32_ext` == 42
 		{expr: `proto.getExt(msg, google.expr.proto2.test.int32_ext) == 42`},
+		{expr: "msg.`google.expr.proto2.test.int32_ext` == 42"},
 		{expr: `proto.getExt(msg, google.expr.proto2.test.int32_wrapper_ext) == 21`},
+		{expr: "msg.`google.expr.proto2.test.int32_wrapper_ext` == 21"},
 		{expr: `proto.hasExt(msg, google.expr.proto2.test.nested_example)`},
+		{expr: "has(msg.`google.expr.proto2.test.nested_example`)"},
 		{expr: `proto.getExt(msg, google.expr.proto2.test.nested_example) == ExampleType{name: 'nested'}`},
+		{expr: "msg.`google.expr.proto2.test.nested_example` == ExampleType{name: 'nested'}"},
 		{expr: `proto.getExt(msg, google.expr.proto2.test.ExtendedExampleType.extended_examples) == ['example1', 'example2']`},
+		{expr: "msg.`google.expr.proto2.test.ExtendedExampleType.extended_examples` == ['example1', 'example2']"},
 		{expr: `proto.getExt(msg, google.expr.proto2.test.ExtendedExampleType.enum_ext) == GlobalEnum.GAZ`},
+		{expr: "msg.`google.expr.proto2.test.ExtendedExampleType.enum_ext` == GlobalEnum.GAZ"},
 	}
 
 	env := testProtosEnv(t)
@@ -174,6 +183,15 @@ func TestProtosParseErrors(t *testing.T) {
 		| proto.getExt(ExtendedExampleType{}, has(google.expr.proto2.test.int32_ext))
 		| .......................................^`,
 		},
+		{
+			expr: `ExampleType{}.in`,
+			err: `ERROR: <input>:1:15: Syntax error: no viable alternative at input '.in'
+			| ExampleType{}.in
+			| ..............^
+		   ERROR: <input>:1:17: Syntax error: mismatched input '<EOF>' expecting {'[', '{', '(', '.', '-', '!', 'true', 'false', 'null', NUM_FLOAT, NUM_INT, NUM_UINT, STRING, BYTES, IDENTIFIER}
+			| ExampleType{}.in
+			| ................^`,
+		},
 	}
 	env := testProtosEnv(t)
 	for i, tst := range protosTests {
@@ -198,6 +216,7 @@ func testProtosEnv(t *testing.T, opts ...cel.EnvOption) *cel.Env {
 		cel.Container("google.expr.proto2.test"),
 		cel.Types(&proto2pb.ExampleType{}, &proto2pb.ExternalMessageType{}),
 		cel.Variable("msg", cel.ObjectType("google.expr.proto2.test.ExampleType")),
+		cel.EnableIdentifierEscapeSyntax(),
 		Protos(),
 	}
 	env, err := cel.NewEnv(append(baseOpts, opts...)...)

parser/gen/CEL.g4

@@ -52,13 +52,14 @@ unary
 
 member
     : primary                                                       # PrimaryExpr
-    | member op='.' (opt='?')? id=IDENTIFIER                        # Select
+    | member op='.' (opt='?')? id=escapeIdent                       # Select
     | member op='.' id=IDENTIFIER open='(' args=exprList? ')'       # MemberCall
     | member op='[' (opt='?')? index=expr ']'                       # Index
     ;
 
 primary
-    : leadingDot='.'? id=IDENTIFIER (op='(' args=exprList? ')')?    # IdentOrGlobalCall
+    : leadingDot='.'? id=IDENTIFIER                                # Ident
+    | leadingDot='.'? id=IDENTIFIER (op='(' args=exprList? ')')     # GlobalCall
     | '(' e=expr ')'                                                # Nested
     | op='[' elems=listInit? ','? ']'                               # CreateList
     | op='{' entries=mapInitializerList? ','? '}'                   # CreateStruct
@@ -80,13 +81,18 @@ fieldInitializerList
     ;
 
 optField
-    : (opt='?')? IDENTIFIER
+    : (opt='?')? escapeIdent
     ;
 
 mapInitializerList
     : keys+=optExpr cols+=':' values+=expr (',' keys+=optExpr cols+=':' values+=expr)*
     ;
 
+escapeIdent
+    : id=IDENTIFIER      # SimpleIdentifier
+    | id=ESC_IDENTIFIER  # EscapedIdentifier
+;
+
 optExpr
     : (opt='?')? e=expr
     ;
@@ -198,3 +204,4 @@ STRING
 BYTES : ('b' | 'B') STRING;
 
 IDENTIFIER : (LETTER | '_') ( LETTER | DIGIT | '_')*;
+ESC_IDENTIFIER : '`' (LETTER | DIGIT | '_' | '.' | '-' | '/' | ' ')+ '`';

parser/gen/CEL.tokens

@@ -34,6 +34,7 @@ NUM_UINT=33
 STRING=34
 BYTES=35
 IDENTIFIER=36
+ESC_IDENTIFIER=37
 '=='=1
 '!='=2
 'in'=3