convert source to a struct and fix minor issue displaying error

Author: diegommm

file/error.go

@@ -3,7 +3,6 @@ package file
 import (
 	"fmt"
 	"strings"
-	"unicode/utf8"
 )
 
 type Error struct {
@@ -19,43 +18,49 @@ func (e *Error) Error() string {
 	return e.format()
 }
 
+var tabReplacer = strings.NewReplacer("\t", " ")
+
 func (e *Error) Bind(source Source) *Error {
+	src := source.String()
+
 	e.Line = 1
-	for i, r := range source {
-		if i == e.From {
+	var runeCount, lineStart, lineOffset int
+	for i, r := range src {
+		if runeCount == e.From {
 			break
 		}
 		if r == '\n' {
+			lineStart = i
 			e.Line++
 			e.Column = 0
+			lineOffset = 0
 		} else {
 			e.Column++
 		}
+		runeCount++
+		lineOffset++
+	}
+
+	lineEnd := lineStart + strings.IndexByte(src[lineStart:], '\n')
+	if lineEnd < lineStart {
+		lineEnd = len(src)
+	}
+	if lineStart == lineEnd {
+		return e
 	}
-	if snippet, found := source.Snippet(e.Line); found {
-		snippet := strings.Replace(snippet, "\t", " ", -1)
-		srcLine := "\n | " + snippet
-		var bytes = []byte(snippet)
-		var indLine = "\n | "
-		for i := 0; i < e.Column && len(bytes) > 0; i++ {
-			_, sz := utf8.DecodeRune(bytes)
-			bytes = bytes[sz:]
-			if sz > 1 {
-				goto noind
-			} else {
-				indLine += "."
-			}
-		}
-		if _, sz := utf8.DecodeRune(bytes); sz > 1 {
-			goto noind
-		} else {
-			indLine += "^"
-		}
-		srcLine += indLine
 
-	noind:
-		e.Snippet = srcLine
+	const prefix = "\n | "
+	line := src[lineStart:lineEnd]
+	snippet := new(strings.Builder)
+	snippet.Grow(2*len(prefix) + len(line) + lineOffset + 1)
+	snippet.WriteString(prefix)
+	tabReplacer.WriteString(snippet, line)
+	snippet.WriteString(prefix)
+	for i := 0; i < lineOffset; i++ {
+		snippet.WriteByte('.')
 	}
+	snippet.WriteByte('^')
+	e.Snippet = snippet.String()
 	return e
 }
 

file/source.go

@@ -1,48 +1,36 @@
 package file
 
-import (
-	"strings"
-	"unicode/utf8"
-)
+import "strings"
 
-type Source []rune
+type Source struct {
+	raw string
+}
 
 func NewSource(contents string) Source {
-	return []rune(contents)
+	return Source{
+		raw: contents,
+	}
 }
 
 func (s Source) String() string {
-	return string(s)
+	return s.raw
 }
 
 func (s Source) Snippet(line int) (string, bool) {
-	if s == nil {
+	if s.raw == "" {
 		return "", false
 	}
-	lines := strings.Split(string(s), "\n")
-	lineOffsets := make([]int, len(lines))
-	var offset int
-	for i, line := range lines {
-		offset = offset + utf8.RuneCountInString(line) + 1
-		lineOffsets[i] = offset
-	}
-	charStart, found := getLineOffset(lineOffsets, line)
-	if !found || len(s) == 0 {
-		return "", false
+	var start int
+	for i := 1; i < line; i++ {
+		pos := strings.IndexByte(s.raw[start:], '\n')
+		if pos < 0 {
+			return "", false
+		}
+		start += pos + 1
 	}
-	charEnd, found := getLineOffset(lineOffsets, line+1)
-	if found {
-		return string(s[charStart : charEnd-1]), true
-	}
-	return string(s[charStart:]), true
-}
-
-func getLineOffset(lineOffsets []int, line int) (int, bool) {
-	if line == 1 {
-		return 0, true
-	} else if line > 1 && line <= len(lineOffsets) {
-		offset := lineOffsets[line-2]
-		return offset, true
+	end := start + strings.IndexByte(s.raw[start:], '\n')
+	if end < start {
+		end = len(s.raw)
 	}
-	return -1, false
+	return s.raw[start:end], true
 }

parser/lexer/lexer.go

@@ -9,7 +9,7 @@ import (
 
 func Lex(source file.Source) ([]Token, error) {
 	l := &lexer{
-		source: source,
+		source: []rune(source.String()),
 		tokens: make([]Token, 0),
 		start:  0,
 		end:    0,
@@ -28,7 +28,7 @@ func Lex(source file.Source) ([]Token, error) {
 }
 
 type lexer struct {
-	source     file.Source
+	source     []rune
 	tokens     []Token
 	start, end int
 	err        *file.Error

parser/lexer/lexer_test.go

@@ -335,6 +335,7 @@ literal not terminated (1:10)
 früh ♥︎
 unrecognized character: U+2665 '♥' (1:6)
  | früh ♥︎
+ | .....^
 `
 
 func TestLex_error(t *testing.T) {

vm/vm_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/expr-lang/expr/file"
 	"github.com/expr-lang/expr/internal/testify/require"
 
 	"github.com/expr-lang/expr"
@@ -609,10 +610,10 @@ func TestVM_DirectCallOpcodes(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			program := vm.NewProgram(
-				nil, // source
-				nil, // node
-				nil, // locations
-				0,   // variables
+				file.Source{}, // source
+				nil,           // node
+				nil,           // locations
+				0,             // variables
 				tt.consts,
 				tt.bytecode,
 				tt.args,
@@ -735,10 +736,10 @@ func TestVM_IndexAndCountOperations(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			program := vm.NewProgram(
-				nil, // source
-				nil, // node
-				nil, // locations
-				0,   // variables
+				file.Source{}, // source
+				nil,           // node
+				nil,           // locations
+				0,             // variables
 				tt.consts,
 				tt.bytecode,
 				tt.args,
@@ -1176,10 +1177,10 @@ func TestVM_DirectBasicOpcodes(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			program := vm.NewProgram(
-				nil, // source
-				nil, // node
-				nil, // locations
-				0,   // variables
+				file.Source{}, // source
+				nil,           // node
+				nil,           // locations
+				0,             // variables
 				tt.consts,
 				tt.bytecode,
 				tt.args,