Runtime error trace format (#111)

* Runtime error format

* Parser and Compiler error formats updated

cmd/tengo/main.go

@@ -201,27 +201,23 @@ func runREPL(in io.Reader, out io.Writer) {
 		srcFile := fileSet.AddFile("repl", -1, len(line))
 		file, err := parser.ParseFile(srcFile, []byte(line), nil)
 		if err != nil {
-			_, _ = fmt.Fprintf(out, "error: %s\n", err.Error())
+			_, _ = fmt.Fprintln(out, err.Error())
 			continue
 		}
 
 		file = addPrints(file)
 
 		c := compiler.NewCompiler(srcFile, symbolTable, constants, nil, nil)
 		if err := c.Compile(file); err != nil {
-			_, _ = fmt.Fprintf(out, "Compilation error:\n %s\n", err.Error())
+			_, _ = fmt.Fprintln(out, err.Error())
 			continue
 		}
 
 		bytecode := c.Bytecode()
 
 		machine := runtime.NewVM(bytecode, globals, nil)
-		if err != nil {
-			_, _ = fmt.Fprintf(out, "VM error:\n %s\n", err.Error())
-			continue
-		}
 		if err := machine.Run(); err != nil {
-			_, _ = fmt.Fprintf(out, "Execution error:\n %s\n", err.Error())
+			_, _ = fmt.Fprintln(out, err.Error())
 			continue
 		}
 

compiler/compiler_error_report_test.go

@@ -3,15 +3,15 @@ package compiler_test
 import "testing"
 
 func TestCompilerErrorReport(t *testing.T) {
-	expectError(t, `import("user1")`, "test:1:1: module file read error: open user1.tengo: no such file or directory")
+	expectError(t, `import("user1")`, "Compile Error: module file read error: open user1.tengo: no such file or directory\n\tat test:1:1")
 
-	expectError(t, `a = 1`, "test:1:1: unresolved reference 'a'")
-	expectError(t, `a, b := 1, 2`, "test:1:1: tuple assignment not allowed")
+	expectError(t, `a = 1`, "Compile Error: unresolved reference 'a'\n\tat test:1:1")
+	expectError(t, `a, b := 1, 2`, "Compile Error: tuple assignment not allowed\n\tat test:1:1")
 	expectError(t, `a.b := 1`, "not allowed with selector")
-	expectError(t, `a:=1; a:=3`, "test:1:7: 'a' redeclared in this block")
+	expectError(t, `a:=1; a:=3`, "Compile Error: 'a' redeclared in this block\n\tat test:1:7")
 
-	expectError(t, `return 5`, "test:1:1: return not allowed outside function")
-	expectError(t, `func() { break }`, "test:1:10: break not allowed outside loop")
-	expectError(t, `func() { continue }`, "test:1:10: continue not allowed outside loop")
-	expectError(t, `func() { export 5 }`, "test:1:10: export not allowed inside function")
+	expectError(t, `return 5`, "Compile Error: return not allowed outside function\n\tat test:1:1")
+	expectError(t, `func() { break }`, "Compile Error: break not allowed outside loop\n\tat test:1:10")
+	expectError(t, `func() { continue }`, "Compile Error: continue not allowed outside loop\n\tat test:1:10")
+	expectError(t, `func() { export 5 }`, "Compile Error: export not allowed inside function\n\tat test:1:10")
 }

compiler/error.go

@@ -16,5 +16,5 @@ type Error struct {
 
 func (e *Error) Error() string {
 	filePos := e.fileSet.Position(e.node.Pos())
-	return fmt.Sprintf("%s: %s", filePos, e.error.Error())
+	return fmt.Sprintf("Compile Error: %s\n\tat %s", e.error.Error(), filePos)
 }

compiler/parser/error.go

@@ -1,6 +1,10 @@
 package parser
 
-import "github.com/d5/tengo/compiler/source"
+import (
+	"fmt"
+
+	"github.com/d5/tengo/compiler/source"
+)
 
 // Error represents a parser error.
 type Error struct {
@@ -10,8 +14,8 @@ type Error struct {
 
 func (e Error) Error() string {
 	if e.Pos.Filename != "" || e.Pos.IsValid() {
-		return e.Pos.String() + ": " + e.Msg
+		return fmt.Sprintf("Parse Error: %s\n\tat %s", e.Msg, e.Pos)
 	}
 
-	return e.Msg
+	return fmt.Sprintf("Parse Error: %s", e.Msg)
 }

compiler/parser/error_list_test.go

@@ -14,5 +14,5 @@ func TestErrorList_Sort(t *testing.T) {
 	list.Add(source.FilePos{Offset: 30, Line: 3, Column: 10}, "error 3")
 	list.Add(source.FilePos{Offset: 10, Line: 1, Column: 10}, "error 1")
 	list.Sort()
-	assert.Equal(t, "1:10: error 1 (and 2 more errors)", list.Error())
+	assert.Equal(t, "Parse Error: error 1\n\tat 1:10 (and 2 more errors)", list.Error())
 }

compiler/parser/error_test.go

@@ -10,5 +10,5 @@ import (
 
 func TestError_Error(t *testing.T) {
 	err := &parser.Error{Pos: source.FilePos{Offset: 10, Line: 1, Column: 10}, Msg: "test"}
-	assert.Equal(t, "1:10: test", err.Error())
+	assert.Equal(t, "Parse Error: test\n\tat 1:10", err.Error())
 }