Add Position.Col

Previously it wasn't easy for users to get the Column information; this
has to be calculated from the Start field, but this isn't convenient.

decode.go

@@ -540,12 +540,13 @@ func (md *MetaData) badtype(dst string, data any) error {
 
 func (md *MetaData) parseErr(err error) error {
  k := md.context.String()
+ d := string(md.data)
  return ParseError{
  LastKey: k,
- Position: md.keyInfo[k].pos,
+ Position: md.keyInfo[k].pos.withCol(d),
  Line: md.keyInfo[k].pos.Line,
  err: err,
- input: string(md.data),
+ input: d,
  }
 }
 

error.go

@@ -67,8 +67,28 @@ type ParseError struct {
 // Position of an error.
 type Position struct {
  Line int // Line number, starting at 1.
+ Col int // Error column, starting at 1.
  Start int // Start of error, as byte offset starting at 0.
- Len int // Lenght in bytes.
+ Len int // Lenght of the error in bytes.
+}
+
+func (p Position) withCol(tomlFile string) Position {
+ var (
+ pos int
+ lines = strings.Split(tomlFile, "\n")
+ )
+ for i := range lines {
+ ll := len(lines[i]) + 1 // +1 for the removed newline
+ if pos+ll >= p.Start {
+ p.Col = p.Start - pos + 1
+ if p.Col < 1 { // Should never happen, but just in case.
+ p.Col = 1
+ }
+ break
+ }
+ pos += ll
+ }
+ return p
 }
 
 func (pe ParseError) Error() string {
@@ -94,7 +114,6 @@ func (pe ParseError) ErrorWithPosition() string {
 
  var (
  lines = strings.Split(pe.input, "\n")
- col = pe.column(lines)
  b = new(strings.Builder)
  )
 
@@ -108,10 +127,10 @@ func (pe ParseError) ErrorWithPosition() string {
 
  if pe.Position.Len == 1 {
  fmt.Fprintf(b, "toml: error: %s\n\nAt line %d, column %d:\n\n",
- msg, pe.Position.Line, col+1)
+ msg, pe.Position.Line, pe.Position.Col)
  } else {
  fmt.Fprintf(b, "toml: error: %s\n\nAt line %d, column %d-%d:\n\n",
- msg, pe.Position.Line, col, col+pe.Position.Len)
+ msg, pe.Position.Line, pe.Position.Col, pe.Position.Col+pe.Position.Len-1)
  }
  if pe.Position.Line > 2 {
  fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line-2, expandTab(lines[pe.Position.Line-3]))
@@ -129,7 +148,7 @@ func (pe ParseError) ErrorWithPosition() string {
  diff := len(expanded) - len(lines[pe.Position.Line-1])
 
  fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line, expanded)
- fmt.Fprintf(b, "% 10s%s%s\n", "", strings.Repeat(" ", col+diff), strings.Repeat("^", pe.Position.Len))
+ fmt.Fprintf(b, "% 10s%s%s\n", "", strings.Repeat(" ", pe.Position.Col-1+diff), strings.Repeat("^", pe.Position.Len))
  return b.String()
 }
 
@@ -151,23 +170,6 @@ func (pe ParseError) ErrorWithUsage() string {
  return m
 }
 
-func (pe ParseError) column(lines []string) int {
- var pos, col int
- for i := range lines {
- ll := len(lines[i]) + 1 // +1 for the removed newline
- if pos+ll >= pe.Position.Start {
- col = pe.Position.Start - pos
- if col < 0 { // Should never happen, but just in case.
- col = 0
- }
- break
- }
- pos += ll
- }
-
- return col
-}
-
 func expandTab(s string) string {
  var (
  b strings.Builder

error_test.go

@@ -37,7 +37,7 @@ At line 1, column 23:
  {"array/tables-2.toml", `
 toml: error: Key 'fruit.variety' has already been defined.
 
-At line 9, column 3-8:
+At line 9, column 4-8:
 
  7 | 
  8 | # This table conflicts with the previous table
@@ -46,7 +46,7 @@ At line 9, column 3-8:
  {"local-date/trailing-t.toml", `
 toml: error: invalid datetime: "2006-01-30T"
 
-At line 2, column 4-15:
+At line 2, column 5-15:
 
  1 | # Date cannot end with trailing T
  2 | d = 2006-01-30T

parse.go

@@ -65,7 +65,7 @@ func parse(data string) (p *parser, err error) {
  if i := strings.IndexRune(data[:ex], 0); i > -1 {
  return nil, ParseError{
  Message: "files cannot contain NULL bytes; probably using UTF-16; TOML files must be UTF-8",
- Position: Position{Line: 1, Start: i, Len: 1},
+ Position: Position{Line: 1, Col: 1, Start: i, Len: 1},
  Line: 1,
  input: data,
  }
@@ -93,7 +93,7 @@ func parse(data string) (p *parser, err error) {
 func (p *parser) panicErr(it item, err error) {
  panic(ParseError{
  err: err,
- Position: it.pos,
+ Position: it.pos.withCol(p.lx.input),
  Line: it.pos.Len,
  LastKey: p.current(),
  })
@@ -102,7 +102,7 @@ func (p *parser) panicErr(it item, err error) {
 func (p *parser) panicItemf(it item, format string, v ...any) {
  panic(ParseError{
  Message: fmt.Sprintf(format, v...),
- Position: it.pos,
+ Position: it.pos.withCol(p.lx.input),
  Line: it.pos.Len,
  LastKey: p.current(),
  })
@@ -111,7 +111,7 @@ func (p *parser) panicItemf(it item, format string, v ...any) {
 func (p *parser) panicf(format string, v ...any) {
  panic(ParseError{
  Message: fmt.Sprintf(format, v...),
- Position: p.pos,
+ Position: p.pos.withCol(p.lx.input),
  Line: p.pos.Line,
  LastKey: p.current(),
  })
@@ -123,7 +123,7 @@ func (p *parser) next() item {
  if it.typ == itemError {
  if it.err != nil {
  panic(ParseError{
- Position: it.pos,
+ Position: it.pos.withCol(p.lx.input),
  Line: it.pos.Line,
  LastKey: p.current(),
  err: it.err,