String format validator (#775)

* String format validator
* Remove unused method from prior string validation

cel/decls.go

@@ -353,43 +353,3 @@ func ExprDeclToDeclaration(d *exprpb.Decl) (EnvOption, error) {
 		return nil, fmt.Errorf("unsupported decl: %v", d)
 	}
 }
-
-func typeValueToKind(tv ref.Type) (Kind, error) {
-	switch tv {
-	case types.BoolType:
-		return BoolKind, nil
-	case types.DoubleType:
-		return DoubleKind, nil
-	case types.IntType:
-		return IntKind, nil
-	case types.UintType:
-		return UintKind, nil
-	case types.ListType:
-		return ListKind, nil
-	case types.MapType:
-		return MapKind, nil
-	case types.StringType:
-		return StringKind, nil
-	case types.BytesType:
-		return BytesKind, nil
-	case types.DurationType:
-		return DurationKind, nil
-	case types.TimestampType:
-		return TimestampKind, nil
-	case types.NullType:
-		return NullTypeKind, nil
-	case types.TypeType:
-		return TypeKind, nil
-	default:
-		switch tv.TypeName() {
-		case "dyn":
-			return DynKind, nil
-		case "google.protobuf.Any":
-			return AnyKind, nil
-		case "optional":
-			return OpaqueKind, nil
-		default:
-			return 0, fmt.Errorf("no known conversion for type of %s", tv.TypeName())
-		}
-	}
-}

cel/options.go

@@ -447,6 +447,8 @@ const (
 	OptTrackCost EvalOption = 1 << iota
 
 	// OptCheckStringFormat enables compile-time checking of string.format calls for syntax/cardinality.
+	//
+	// Deprecated: use ext.ValidateFormatString() as this option is now a no-op.
 	OptCheckStringFormat EvalOption = 1 << iota
 )
 

cel/program.go

@@ -19,7 +19,7 @@ import (
 	"fmt"
 	"sync"
 
-	celast "github.com/google/cel-go/common/ast"
+	"github.com/google/cel-go/common/ast"
 	"github.com/google/cel-go/common/types"
 	"github.com/google/cel-go/common/types/ref"
 	"github.com/google/cel-go/interpreter"
@@ -148,7 +148,7 @@ func (p *prog) clone() *prog {
 // ProgramOption values.
 //
 // If the program cannot be configured the prog will be nil, with a non-nil error response.
-func newProgram(e *Env, ast *Ast, opts []ProgramOption) (Program, error) {
+func newProgram(e *Env, a *Ast, opts []ProgramOption) (Program, error) {
 	// Build the dispatcher, interpreter, and default program value.
 	disp := interpreter.NewDispatcher()
 
@@ -208,34 +208,6 @@ func newProgram(e *Env, ast *Ast, opts []ProgramOption) (Program, error) {
 	if len(p.regexOptimizations) > 0 {
 		decorators = append(decorators, interpreter.CompileRegexConstants(p.regexOptimizations...))
 	}
-	// Enable compile-time checking of syntax/cardinality for string.format calls.
-	if p.evalOpts&OptCheckStringFormat == OptCheckStringFormat {
-		var isValidType func(id int64, validTypes ...ref.Type) (bool, error)
-		if ast.IsChecked() {
-			isValidType = func(id int64, validTypes ...ref.Type) (bool, error) {
-				t := ast.typeMap[id]
-				if t.Kind() == DynKind {
-					return true, nil
-				}
-				for _, vt := range validTypes {
-					k, err := typeValueToKind(vt)
-					if err != nil {
-						return false, err
-					}
-					if t.Kind() == k {
-						return true, nil
-					}
-				}
-				return false, nil
-			}
-		} else {
-			// if the AST isn't type-checked, short-circuit validation
-			isValidType = func(id int64, validTypes ...ref.Type) (bool, error) {
-				return true, nil
-			}
-		}
-		decorators = append(decorators, interpreter.InterpolateFormattedString(isValidType))
-	}
 
 	// Enable exhaustive eval, state tracking and cost tracking last since they require a factory.
 	if p.evalOpts&(OptExhaustiveEval|OptTrackState|OptTrackCost) != 0 {
@@ -263,18 +235,18 @@ func newProgram(e *Env, ast *Ast, opts []ProgramOption) (Program, error) {
 				decs = append(decs, interpreter.Observe(observers...))
 			}
 
-			return p.clone().initInterpretable(ast, decs)
+			return p.clone().initInterpretable(a, decs)
 		}
 		return newProgGen(factory)
 	}
-	return p.initInterpretable(ast, decorators)
+	return p.initInterpretable(a, decorators)
 }
 
-func (p *prog) initInterpretable(ast *Ast, decs []interpreter.InterpretableDecorator) (*prog, error) {
+func (p *prog) initInterpretable(a *Ast, decs []interpreter.InterpretableDecorator) (*prog, error) {
 	// Unchecked programs do not contain type and reference information and may be slower to execute.
-	if !ast.IsChecked() {
+	if !a.IsChecked() {
 		interpretable, err :=
-			p.interpreter.NewUncheckedInterpretable(ast.Expr(), decs...)
+			p.interpreter.NewUncheckedInterpretable(a.Expr(), decs...)
 		if err != nil {
 			return nil, err
 		}
@@ -283,12 +255,7 @@ func (p *prog) initInterpretable(ast *Ast, decs []interpreter.InterpretableDecor
 	}
 
 	// When the AST has been checked it contains metadata that can be used to speed up program execution.
-	checked := &celast.CheckedAST{
-		Expr:         ast.Expr(),
-		SourceInfo:   ast.SourceInfo(),
-		TypeMap:      ast.typeMap,
-		ReferenceMap: ast.refMap,
-	}
+	checked := astToCheckedAST(a)
 	interpretable, err := p.interpreter.NewInterpretable(checked, decs...)
 	if err != nil {
 		return nil, err
@@ -558,9 +525,16 @@ func (p *evalActivationPool) Put(value any) {
 	p.Pool.Put(a)
 }
 
-var (
-	emptyEvalState = interpreter.NewEvalState()
+func astToCheckedAST(a *Ast) *ast.CheckedAST {
+	return &ast.CheckedAST{
+		Expr:         a.Expr(),
+		SourceInfo:   a.SourceInfo(),
+		TypeMap:      a.typeMap,
+		ReferenceMap: a.refMap,
+	}
+}
 
+var (
 	// activationPool is an internally managed pool of Activation values that wrap map[string]any inputs
 	activationPool = newEvalActivationPool()
 

cel/validator.go

@@ -244,17 +244,6 @@ func (homogeneousAggregateLiteralValidator) Name() string {
 	return homogeneousValidatorName
 }
 
-// Configure implements the ASTValidatorConfigurer interface and currently sets the list of standard
-// and exempt functions from homogeneous aggregate literal checks.
-//
-// TODO: Move this call into the string.format() ASTValidator once ported.
-func (homogeneousAggregateLiteralValidator) Configure(c MutableValidatorConfig) error {
-	emptyList := []string{}
-	exemptFunctions := c.GetOrDefault(HomogeneousAggregateLiteralExemptFunctions, emptyList).([]string)
-	exemptFunctions = append(exemptFunctions, "format")
-	return c.Set(HomogeneousAggregateLiteralExemptFunctions, exemptFunctions)
-}
-
 // Validate validates that all lists and map literals have homogeneous types, i.e. don't contain dyn types.
 //
 // This validator makes an exception for list and map literals which occur at any level of nesting within

common/ast/BUILD.bazel

@@ -5,6 +5,7 @@ package(
         "//cel:__subpackages__",
         "//checker:__subpackages__",
         "//common:__subpackages__",
+        "//ext:__subpackages__",
         "//interpreter:__subpackages__",
     ],
     licenses = ["notice"],  # Apache 2.0

common/ast/expr.go

@@ -78,7 +78,7 @@ func KindMatcher(kind ExprKind) ExprMatcher {
 }
 
 // FunctionMatcher returns an ExprMatcher which will match NavigableExpr nodes of CallKind type whose
-// function name is equal to `funcName`.
+// function name is equal to `funcName` regardless of whether it is a member or a global function.
 func FunctionMatcher(funcName string) ExprMatcher {
 	return func(e NavigableExpr) bool {
 		if e.Kind() != CallKind {
@@ -217,6 +217,9 @@ type NavigableCallExpr interface {
 	// FunctionName returns the name of the function.
 	FunctionName() string
 
+	// IsMemberFunction returns whether the call has a non-nil target indicating it is a member function
+	IsMemberFunction() bool
+
 	// Target returns the target of the expression if one is present.
 	Target() NavigableExpr
 
@@ -444,6 +447,10 @@ func (call navigableCallImpl) FunctionName() string {
 	return call.ToExpr().GetCallExpr().GetFunction()
 }
 
+func (call navigableCallImpl) IsMemberFunction() bool {
+	return call.ToExpr().GetCallExpr().GetTarget() != nil
+}
+
 func (call navigableCallImpl) Target() NavigableExpr {
 	t := call.ToExpr().GetCallExpr().GetTarget()
 	if t != nil {

ext/BUILD.bazel

@@ -8,6 +8,7 @@ go_library(
     name = "go_default_library",
     srcs = [
         "encoders.go",
+        "formatting.go",
         "guards.go",
         "lists.go",
         "math.go",
@@ -21,6 +22,7 @@ go_library(
     deps = [
         "//cel:go_default_library",
         "//checker/decls:go_default_library",
+        "//common/ast:go_default_library",
         "//common/overloads:go_default_library",
         "//common/types:go_default_library",
         "//common/types/pb:go_default_library",