cue/errors: add Wrap

introduces new internal wrapping error that allows
harmonizing wrapped errors.

Issue #52

Change-Id: I93844d4cc7592521b70b6402a9670a941c2f6dfc
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9447
Reviewed-by: Marcel van Lohuizen <[email protected]>

Author: mpvl

cmd/cue/cmd/testdata/script/cmd_err.txt

@@ -10,6 +10,7 @@ command.ref.task.display.filename: invalid string argument: non-concrete value s
     ./task_tool.cue:6:8
     ./task_tool.cue:7:9
     tool/file:15:3
+    tool/file:15:16
 -- task_tool.cue --
 package home
 

cmd/cue/cmd/testdata/script/cmd_errpos.txt

@@ -12,6 +12,7 @@ command.prompter.contents: invalid bytes argument: non-concrete value string:
 command.prompter.filename: invalid string argument: non-concrete value string:
     ./task_tool.cue:9:10
     tool/file:9:3
+    tool/file:9:16
 -- task_tool.cue --
 package foo
 

cmd/cue/cmd/testdata/script/export_err.txt

@@ -13,6 +13,7 @@ cmp stderr expect-stderr
 a.b.2.c: incomplete value int
 out: invalid interpolation: undefined field d:
     ./exporterr/export_err.cue:7:6
+    ./exporterr/export_err.cue:7:16
 -- expect-stdout --
 -- exporterr/export_err.cue --
 package exporterr

cmd/cue/cmd/testdata/script/vet_yaml.txt

@@ -4,6 +4,7 @@ cmp stderr expect-stderr
 -- expect-stderr --
 phrases: invalid value "phrases:\n  # A quote from Mark Twain.\n  quote1:\n    lang: en\n    attribution: Mark Twain\n\n  # A Norwegian proverb.\n  proverb:\n    lang: no\n    text: Stemmen som sier at du ikke klarer det, lyver." (does not satisfy encoding/yaml.Validate({phrases:{},#Phrase:{lang:=~"^[a-zA-Z0-9-_]{2,}$" | false,text:!=""},#LanguageTag:=~"^[a-zA-Z0-9-_]{2,}$" | false})): error in call to encoding/yaml.Validate: incomplete value !="":
     ./yaml.cue:19:10
+    ./yaml.cue:11:17
     ./yaml.cue:21:10
 -- yaml.cue --
 import "encoding/yaml"

cue/errors/errors.go

@@ -170,25 +170,77 @@ func Newf(p token.Pos, format string, args ...interface{}) Error {
 // Wrapf creates an Error with the associated position and message. The provided
 // error is added for inspection context.
 func Wrapf(err error, p token.Pos, format string, args ...interface{}) Error {
-	a, ok := err.(list)
+	pErr := &posError{
+		pos:     p,
+		Message: NewMessage(format, args),
+	}
+	return Wrap(pErr, err)
+}
+
+// Wrap creates a new error where child is a subordinate error of parent.
+// If child is list of Errors, the result will itself be a list of errors
+// where child is a subordinate error of each parent.
+func Wrap(parent Error, child error) Error {
+	if child == nil {
+		return parent
+	}
+	a, ok := child.(list)
 	if !ok {
-		return &posError{
-			pos:     p,
-			Message: NewMessage(format, args),
-			err:     err,
-		}
+		return &wrapped{parent, child}
 	}
-	b := make([]Error, len(a))
+	b := make(list, len(a))
 	for i, err := range a {
-		b[i] = &posError{
-			pos:     p,
-			Message: NewMessage(format, args),
-			err:     err,
-		}
+		b[i] = &wrapped{parent, err}
+	}
+	return b
+}
+
+type wrapped struct {
+	main Error
+	wrap error
+}
+
+// Error implements the error interface.
+func (e *wrapped) Error() string {
+	switch msg := e.main.Error(); {
+	case e.wrap == nil:
+		return msg
+	case msg == "":
+		return e.wrap.Error()
+	default:
+		return fmt.Sprintf("%s: %s", msg, e.wrap)
+	}
+}
+
+func (e *wrapped) Msg() (format string, args []interface{}) {
+	return e.main.Msg()
+}
+
+func (e *wrapped) Path() []string {
+	if p := Path(e.main); p != nil {
+		return p
+	}
+	return Path(e.wrap)
+}
+
+func (e *wrapped) InputPositions() []token.Pos {
+	return append(e.main.InputPositions(), Positions(e.wrap)...)
+}
+
+func (e *wrapped) Position() token.Pos {
+	if p := e.main.Position(); p != token.NoPos {
+		return p
+	}
+	if wrap, ok := e.wrap.(Error); ok {
+		return wrap.Position()
 	}
-	return list(b)
+	return token.NoPos
 }
 
+func (e *wrapped) Unwrap() error { return e.wrap }
+
+func (e *wrapped) Cause() error { return e.wrap }
+
 // Promote converts a regular Go error to an Error if it isn't already one.
 func Promote(err error, msg string) Error {
 	switch x := err.(type) {
@@ -209,27 +261,11 @@ type posError struct {
 	pos    token.Pos
 	inputs []token.Pos
 	Message
-
-	// The underlying error that triggered this one, if any.
-	err error
 }
 
-func (e *posError) Path() []string              { return Path(e.err) }
+func (e *posError) Path() []string              { return nil }
 func (e *posError) InputPositions() []token.Pos { return e.inputs }
 func (e *posError) Position() token.Pos         { return e.pos }
-func (e *posError) Unwrap() error               { return e.err }
-func (e *posError) Cause() error                { return e.err }
-
-// Error implements the error interface.
-func (e *posError) Error() string {
-	if e.err == nil {
-		return e.Message.Error()
-	}
-	if e.Message.format == "" {
-		return e.err.Error()
-	}
-	return fmt.Sprintf("%s: %s", e.Message.Error(), e.err)
-}
 
 // Append combines two errors, flattening Lists as necessary.
 func Append(a, b Error) Error {

cue/testdata/eval/dynamic_field.txtar

@@ -25,6 +25,8 @@ parenExprRefEqual: {
 Errors:
 invalid interpolation: conflicting values 2 and 1:
     ./in.cue:12:31
+    ./in.cue:12:34
+    ./in.cue:12:36
 
 Result:
 (_|_){
@@ -40,6 +42,8 @@ Result:
     issue799: (_|_){
       // [eval] invalid interpolation: conflicting values 2 and 1:
       //     ./in.cue:12:31
+      //     ./in.cue:12:34
+      //     ./in.cue:12:36
       key: (int){ &(>=-2147483648, <=2147483647, int) }
     }
   }

cue/testdata/fulleval/055_issue318.txtar

@@ -45,8 +45,10 @@
 Errors:
 #T.out1: invalid interpolation: undefined field y:
     ./in.cue:3:8
+    ./in.cue:3:24
 #T.out2: invalid interpolation: undefined field y:
     ./in.cue:4:8
+    ./in.cue:4:15
 #T.vy: undefined field y:
     ./in.cue:6:12
 
@@ -61,10 +63,12 @@ Result:
     out1: (_|_){
       // [eval] #T.out1: invalid interpolation: undefined field y:
       //     ./in.cue:3:8
+      //     ./in.cue:3:24
     }
     out2: (_|_){
       // [eval] #T.out2: invalid interpolation: undefined field y:
       //     ./in.cue:4:8
+      //     ./in.cue:4:15
     }
     vx: (string){ string }
     vy: (_|_){

cue/testdata/interpolation/041_interpolation.txtar

@@ -35,6 +35,7 @@ e: _|_ // expression in interpolation must evaluate to a number kind or string (
 Errors:
 e: invalid interpolation: cannot use [] (type list) as type (bool|string|bytes|number):
     ./in.cue:7:4
+    ./in.cue:7:7
 
 Result:
 (_|_){
@@ -49,10 +50,12 @@ Result:
   u: (_|_){
     // [incomplete] u: invalid interpolation: non-concrete value _ (type _):
     //     ./in.cue:5:4
+    //     ./in.cue:5:7
   }
   r: (_){ _ }
   e: (_|_){
     // [eval] e: invalid interpolation: cannot use [] (type list) as type (bool|string|bytes|number):
     //     ./in.cue:7:4
+    //     ./in.cue:7:7
   }
 }

cue/testdata/interpolation/incomplete.txtar

@@ -27,6 +27,7 @@ out: """
   out: (_|_){
     // [incomplete] out: invalid interpolation: undefined field #d:
     //     ./in.cue:8:6
+    //     ./in.cue:13:21
   }
 }
 -- out/compile --

cue/testdata/references/errors.txtar

@@ -80,10 +80,12 @@ Result:
     r1: (_|_){
       // [incomplete] missingFieldNestedInInterpolation.r1: invalid interpolation: undefined field b:
       //     ./references.cue:27:9
+      //     ./references.cue:27:14
     }
     r2: (_|_){
       // [incomplete] missingFieldNestedInInterpolation.r2: invalid interpolation: undefined field d:
       //     ./references.cue:30:9
+      //     ./references.cue:30:14
     }
   }
 }