parser

package
v0.10.1 Latest Latest
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 Go to latest Published: Mar 10, 2022 License: Apache-2.0, BSD-3-Clause Imports: 13 Imported by: 41

Documentation

Overview

Package parser declares an expression parser with support for macro expansion.

Index

Constants

View Source 
const AccumulatorName = "__result__"

AccumulatorName is the traditional variable name assigned to the fold accumulator variable.

Variables

View Source 
var (
	// AllMacros includes the list of all spec-supported macros.
	AllMacros = []Macro{

		NewGlobalMacro(operators.Has, 1, makeHas),

		NewReceiverMacro(operators.All, 2, makeAll),

		NewReceiverMacro(operators.Exists, 2, makeExists),

		NewReceiverMacro(operators.ExistsOne, 2, makeExistsOne),

		NewReceiverMacro(operators.Map, 2, makeMap),

		NewReceiverMacro(operators.Map, 3, makeMap),

		NewReceiverMacro(operators.Filter, 2, makeFilter),
	}

	// NoMacros list.
	NoMacros = []Macro{}
)

Functions

func Parse deprecated 

func Parse(source common.Source) (*exprpb.ParsedExpr, *common.Errors)

Parse converts a source input a parsed expression. This function calls ParseWithMacros with AllMacros.

Deprecated: Use NewParser().Parse() instead.

func Unparse added in v0.3.0 

func Unparse(expr *exprpb.Expr, info *exprpb.SourceInfo) (string, error)

Unparse takes an input expression and source position information and generates a human-readable expression.

Note, unparsing an AST will often generate the same expression as was originally parsed, but some formatting may be lost in translation, notably:

- All quoted literals are doubled quoted. - Byte literals are represented as octal escapes (same as Google SQL). - Floating point values are converted to the small number of digits needed to represent the value. - Spacing around punctuation marks may be lost. - Parentheses will only be applied when they affect operator precedence.

Types

type ExprHelper 

type ExprHelper interface {
	// LiteralBool creates an Expr value for a bool literal.
	LiteralBool(value bool) *exprpb.Expr

	// LiteralBytes creates an Expr value for a byte literal.
	LiteralBytes(value []byte) *exprpb.Expr

	// LiteralDouble creates an Expr value for double literal.
	LiteralDouble(value float64) *exprpb.Expr

	// LiteralInt creates an Expr value for an int literal.
	LiteralInt(value int64) *exprpb.Expr

	// LiteralString creates am Expr value for a string literal.
	LiteralString(value string) *exprpb.Expr

	// LiteralUint creates an Expr value for a uint literal.
	LiteralUint(value uint64) *exprpb.Expr

	// NewList creates a CreateList instruction where the list is comprised of the optional set
	// of elements provided as arguments.
	NewList(elems ...*exprpb.Expr) *exprpb.Expr

	// NewMap creates a CreateStruct instruction for a map where the map is comprised of the
	// optional set of key, value entries.
	NewMap(entries ...*exprpb.Expr_CreateStruct_Entry) *exprpb.Expr

	// NewMapEntry creates a Map Entry for the key, value pair.
	NewMapEntry(key *exprpb.Expr, val *exprpb.Expr) *exprpb.Expr_CreateStruct_Entry

	// NewObject creates a CreateStruct instruction for an object with a given type name and
	// optional set of field initializers.
	NewObject(typeName string, fieldInits ...*exprpb.Expr_CreateStruct_Entry) *exprpb.Expr

	// NewObjectFieldInit creates a new Object field initializer from the field name and value.
	NewObjectFieldInit(field string, init *exprpb.Expr) *exprpb.Expr_CreateStruct_Entry

	// Fold creates a fold comprehension instruction.
	//
	// - iterVar is the iteration variable name.
	// - iterRange represents the expression that resolves to a list or map where the elements or
	//   keys (respectively) will be iterated over.
	// - accuVar is the accumulation variable name, typically parser.AccumulatorName.
	// - accuInit is the initial expression whose value will be set for the accuVar prior to
	//   folding.
	// - condition is the expression to test to determine whether to continue folding.
	// - step is the expression to evaluation at the conclusion of a single fold iteration.
	// - result is the computation to evaluate at the conclusion of the fold.
	//
	// The accuVar should not shadow variable names that you would like to reference within the
	// environment in the step and condition expressions. Presently, the name __result__ is commonly
	// used by built-in macros but this may change in the future.
	Fold(iterVar string,
		iterRange *exprpb.Expr,
		accuVar string,
		accuInit *exprpb.Expr,
		condition *exprpb.Expr,
		step *exprpb.Expr,
		result *exprpb.Expr) *exprpb.Expr

	// Ident creates an identifier Expr value.
	Ident(name string) *exprpb.Expr

	// GlobalCall creates a function call Expr value for a global (free) function.
	GlobalCall(function string, args ...*exprpb.Expr) *exprpb.Expr

	// ReceiverCall creates a function call Expr value for a receiver-style function.
	ReceiverCall(function string, target *exprpb.Expr, args ...*exprpb.Expr) *exprpb.Expr

	// PresenceTest creates a Select TestOnly Expr value for modelling has() semantics.
	PresenceTest(operand *exprpb.Expr, field string) *exprpb.Expr

	// Select create a field traversal Expr value.
	Select(operand *exprpb.Expr, field string) *exprpb.Expr

	// OffsetLocation returns the Location of the expression identifier.
	OffsetLocation(exprID int64) common.Location
}

ExprHelper assists with the manipulation of proto-based Expr values in a manner which is consistent with the source position and expression id generation code leveraged by both the parser and type-checker.

type Macro 

type Macro interface {
	// Function name to match.
	Function() string

	// ArgCount for the function call.
	//
	// When the macro is a var-arg style macro, the return value will be zero, but the MacroKey
	// will contain a `*` where the arg count would have been.
	ArgCount() int

	// IsReceiverStyle returns true if the macro matches a receiver style call.
	IsReceiverStyle() bool

	// MacroKey returns the macro signatures accepted by this macro.
	//
	// Format: `<function>:<arg-count>:<is-receiver>`.
	//
	// When the macros is a var-arg style macro, the `arg-count` value is represented as a `*`.
	MacroKey() string

	// Expander returns the MacroExpander to apply when the macro key matches the parsed call
	// signature.
	Expander() MacroExpander
}

Macro interface for describing the function signature to match and the MacroExpander to apply.

Note: when a Macro should apply to multiple overloads (based on arg count) of a given function, a Macro should be created per arg-count.

func NewGlobalMacro 

func NewGlobalMacro(function string, argCount int, expander MacroExpander) Macro

NewGlobalMacro creates a Macro for a global function with the specified arg count.

func NewGlobalVarArgMacro 

func NewGlobalVarArgMacro(function string, expander MacroExpander) Macro

NewGlobalVarArgMacro creates a Macro for a global function with a variable arg count.

func NewReceiverMacro 

func NewReceiverMacro(function string, argCount int, expander MacroExpander) Macro

NewReceiverMacro creates a Macro for a receiver function matching the specified arg count.

func NewReceiverVarArgMacro 

func NewReceiverVarArgMacro(function string, expander MacroExpander) Macro

NewReceiverVarArgMacro creates a Macro for a receiver function matching a variable arg count.

type MacroExpander 

type MacroExpander func(eh ExprHelper,
	target *exprpb.Expr,
	args []*exprpb.Expr) (*exprpb.Expr, *common.Error)

MacroExpander converts the target and args of a function call that matches a Macro.

Note: when the Macros.IsReceiverStyle() is true, the target argument will be nil.

type Option added in v0.8.0 

type Option func(*options) error

Option configures the behavior of the parser.

func ErrorRecoveryLimit added in v0.8.0 

func ErrorRecoveryLimit(limit int) Option

ErrorRecoveryLimit limits the number of attempts the parser will perform to recover from an error.

func ErrorRecoveryLookaheadTokenLimit added in v0.8.0 

func ErrorRecoveryLookaheadTokenLimit(limit int) Option

ErrorRecoveryLookaheadTokenLimit limits the number of lexer tokens that may be considered during error recovery.

Error recovery often involves looking ahead in the input to determine if there's a point at which parsing may successfully resume. In some pathological cases, the parser can look through quite a large set of input which in turn generates a lot of back-tracking and performance degredation.

The limit must be > 1, and is recommended to be less than the default of 256.

func ExpressionSizeCodePointLimit added in v0.8.0 

func ExpressionSizeCodePointLimit(expressionSizeCodePointLimit int) Option

ExpressionSizeCodePointLimit is an option which limits the maximum code point count of an expression.

func Macros added in v0.8.0 

func Macros(macros ...Macro) Option

Macros adds the given macros to the parser.

func MaxRecursionDepth added in v0.8.0 

func MaxRecursionDepth(limit int) Option

MaxRecursionDepth limits the maximum depth the parser will attempt to parse the expression before giving up.

func PopulateMacroCalls added in v0.9.0 

func PopulateMacroCalls(populateMacroCalls bool) Option

PopulateMacroCalls ensures that the original call signatures replaced by expanded macros are preserved in the `SourceInfo` of parse result.

type Parser added in v0.8.0 

type Parser struct {
	// contains filtered or unexported fields
}

Parser encapsulates the context necessary to perform parsing for different expressions.

func NewParser added in v0.8.0 

func NewParser(opts ...Option) (*Parser, error)

NewParser builds and returns a new Parser using the provided options.

func (*Parser) Parse added in v0.8.0 

func (p *Parser) Parse(source common.Source) (*exprpb.ParsedExpr, *common.Errors)

Parse parses the expression represented by source and returns the result.

Source Files

View all Source files

Directories

Path Synopsis
Package gen contains all of the ANTLR-generated sources used by the cel-go parser.
 Package gen contains all of the ANTLR-generated sources used by the cel-go parser.

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