expression

Documentation

Index

• func Eval[T any](ctx context.Context, eng Engine, exp string, vars map[string]interface{}) (retval T, reterr error)
• func EvalAny(ctx context.Context, eng Engine, exp string, vars map[string]interface{}) (retval interface{}, reterr error)
• type Engine
• type ExprEngine
  • func (e *ExprEngine) Eval(ctx context.Context, exp string, vars map[string]interface{}) (interface{}, error)
  • func (e *ExprEngine) GetVariables(ctx context.Context, exp string) ([]Variable, error)
• type Variable
  • func GetVariables(ctx context.Context, eng Engine, exp string) ([]Variable, error)

Functions

func Eval

func Eval[T any](ctx context.Context, eng Engine, exp string, vars map[string]interface{}) (retval T, reterr error)

Eval evaluates an expression given a set of variables and returns a generic type.

func EvalAny

func EvalAny(ctx context.Context, eng Engine, exp string, vars map[string]interface{}) (retval interface{}, reterr error)

EvalAny evaluates an expression given a set of variables and returns a 'boxed' interface type.

Types

type Engine

type Engine interface {
	// Eval evaluates an expression given a set of variables and returns a generic type.
	Eval(ctx context.Context, expr string, vars map[string]interface{}) (interface{}, error)
	// GetVariables returns a list of variables mentioned in an expression
	GetVariables(ctx context.Context, expr string) ([]Variable, error)
}

Engine represents an expression engine implementation.

type ExprEngine

type ExprEngine struct {
}

ExprEngine is an implementation of the expr-lang an expression engine.

func (*ExprEngine) Eval

func (e *ExprEngine) Eval(ctx context.Context, exp string, vars map[string]interface{}) (interface{}, error)

Eval takes a context, an expression string, and a map of variables. It returns the result of the expression evaluation as an interface{} and any error encountered during the evaluation process. If the expression string is empty, it returns nil, nil. If the expression string starts with "=", the "=" character is removed from the expression. It then compiles the expression using expr.Compile() and returns any compilation error wrapped with an ErrWorkflowFatal error. It runs the compiled expression using expr.Run(), passing in the variables map, and returns the result and any evaluation error. If there is an evaluation error, it returns the error wrapped with an additional message. If the evaluation is successful, it returns the result and nil as the error.

func (*ExprEngine) GetVariables

func (e *ExprEngine) GetVariables(ctx context.Context, exp string) ([]Variable, error)

GetVariables takes a context and an expression string. It trims any leading and trailing white spaces from the expression string. If the expression string is empty, it returns nil, nil. If the expression string starts with "=", the "=" character is removed from the expression. It then parses the expression using parser.Parse() and returns any parse error. It walks through the AST of the parsed expression and collects all IdentifierNode types into a slice of Variable structs. Finally, it returns the collected variables and nil as the error.

type Variable

type Variable struct {
	Name string
}

Variable contains metadata about a variable.

func GetVariables

func GetVariables(ctx context.Context, eng Engine, exp string) ([]Variable, error)

GetVariables returns a list of variables mentioned in an expression