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// Copyright 2020 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package adt
// This file contains error encodings.
//
//
// *Bottom:
// - an adt.Value
// - always belongs to a single vertex.
// - does NOT implement error
// - marks error code used for control flow
//
// errors.Error
// - CUE default error
// - implements error
// - tracks error locations
// - has error message details
// - supports multiple errors
//
import (
"cuelang.org/go/cue/ast"
"cuelang.org/go/cue/errors"
"cuelang.org/go/cue/token"
)
// ErrorCode indicates the type of error. The type of error may influence
// control flow. No other aspects of an error may influence control flow.
type ErrorCode int
const (
// An EvalError is a fatal evaluation error.
EvalError ErrorCode = iota
// A UserError is a fatal error originating from the user.
UserError
// NotExistError is used to indicate a value does not exist.
// Mostly used for legacy reasons.
NotExistError
// StructuralCycleError means a structural cycle was found. Structural
// cycles are permanent errors, but they are not passed up recursively,
// as a unification of a value with a structural cycle with one that
// doesn't may still give a useful result.
StructuralCycleError
// IncompleteError means an evaluation could not complete because of
// insufficient information that may still be added later.
IncompleteError
// A CycleError indicates a reference error. It is considered to be
// an incomplete error, as reference errors may be broken by providing
// a concrete value.
CycleError
)
func (c ErrorCode) String() string {
switch c {
case EvalError:
return "eval"
case UserError:
return "user"
case StructuralCycleError:
return "structural cycle"
case IncompleteError:
return "incomplete"
case CycleError:
return "cycle"
}
return "unknown"
}
// Bottom represents an error or bottom symbol.
//
// Although a Bottom node holds control data, it should not be created until the
// control information already resulted in an error.
type Bottom struct {
Src ast.Node
Err errors.Error
Code ErrorCode
HasRecursive bool
ChildError bool // Err is the error of the child
// Value holds the computed value so far in case
Value Value
}
func (x *Bottom) Source() ast.Node { return x.Src }
func (x *Bottom) Kind() Kind { return BottomKind }
func (x *Bottom) Specialize(k Kind) Value { return x } // XXX remove
func (b *Bottom) IsIncomplete() bool {
if b == nil {
return false
}
return b.Code == IncompleteError || b.Code == CycleError
}
// isLiteralBottom reports whether x is an error originating from a user.
func isLiteralBottom(x Expr) bool {
b, ok := x.(*Bottom)
return ok && b.Code == UserError
}
// isError reports whether v is an error or nil.
func isError(v Value) bool {
if v == nil {
return true
}
_, ok := v.(*Bottom)
return ok
}
// isIncomplete reports whether v is associated with an incomplete error.
func isIncomplete(v *Vertex) bool {
if v == nil {
return true
}
if b, ok := v.Value.(*Bottom); ok {
return b.IsIncomplete()
}
return false
}
// AddChildError updates x to record an error that occurred in one of
// its descendent arcs. The resulting error will record the worst error code of
// the current error or recursive error.
//
// If x is not already an error, the value is recorded in the error for
// reference.
//
func (v *Vertex) AddChildError(recursive *Bottom) {
v.ChildErrors = CombineErrors(nil, v.ChildErrors, recursive)
if recursive.IsIncomplete() {
return
}
x := v.Value
err, _ := x.(*Bottom)
if err == nil {
v.Value = &Bottom{
Code: recursive.Code,
Value: x,
HasRecursive: true,
ChildError: true,
Err: recursive.Err,
}
return
}
err.HasRecursive = true
if err.Code > recursive.Code {
err.Code = recursive.Code
}
v.Value = err
}
// CombineErrors combines two errors that originate at the same Vertex.
func CombineErrors(src ast.Node, x, y Value) *Bottom {
a, _ := Unwrap(x).(*Bottom)
b, _ := Unwrap(y).(*Bottom)
switch {
case a != nil && b != nil:
case a != nil:
return a
case b != nil:
return b
default:
return nil
}
if a.Code != b.Code {
if a.Code > b.Code {
a, b = b, a
}
if b.Code >= IncompleteError {
return a
}
}
return &Bottom{
Src: src,
Err: errors.Append(a.Err, b.Err),
Code: a.Code,
}
}
// A valueError is returned as a result of evaluating a value.
type valueError struct {
r Runtime
v *Vertex
pos token.Pos
auxpos []token.Pos
errors.Message
}
func (c *OpContext) errNode() *Vertex {
return c.vertex
}
// MarkPositions marks the current position stack.
func (c *OpContext) MarkPositions() int {
return len(c.positions)
}
// ReleasePositions sets the position state to one from a call to MarkPositions.
func (c *OpContext) ReleasePositions(p int) {
c.positions = c.positions[:p]
}
func (c *OpContext) AddPosition(n Node) {
c.positions = append(c.positions, n)
}
func (c *OpContext) Newf(format string, args ...interface{}) *valueError {
return c.NewPosf(c.pos(), format, args...)
}
func (c *OpContext) NewPosf(p token.Pos, format string, args ...interface{}) *valueError {
var a []token.Pos
if len(c.positions) > 0 {
a = make([]token.Pos, 0, len(c.positions))
for _, n := range c.positions {
if p := pos(n); p != token.NoPos {
a = append(a, p)
} else if v, ok := n.(*Vertex); ok {
for _, c := range v.Conjuncts {
if p := pos(c.x); p != token.NoPos {
a = append(a, p)
}
}
}
}
}
return &valueError{
r: c.Runtime,
v: c.errNode(),
pos: p,
auxpos: a,
Message: errors.NewMessage(format, args),
}
}
func (e *valueError) Error() string {
return errors.String(e)
}
func (e *valueError) Position() token.Pos {
return e.pos
}
func (e *valueError) InputPositions() (a []token.Pos) {
return e.auxpos
}
func (e *valueError) Path() (a []string) {
for _, f := range appendPath(nil, e.v) {
a = append(a, f.SelectorString(e.r))
}
return a
}