Added errors package

src/errors/FileError.go

@@ -0,0 +1,68 @@
+package errors
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"git.urbach.dev/cli/q/src/fs"
+	"git.urbach.dev/cli/q/src/token"
+)
+
+// FileError is an error inside a file at a given line and column.
+type FileError struct {
+	err      error
+	file     *fs.File
+	position token.Position
+	stack    string
+}
+
+// Error implements the error interface.
+func (e *FileError) Error() string {
+	path := e.Path()
+	line, column := e.LineColumn()
+	return fmt.Sprintf("%s:%d:%d: %s\n\n%s", path, line, column, e.err, e.stack)
+}
+
+// LineColumn returns the line and column of the error.
+func (e *FileError) LineColumn() (int, int) {
+	line := 1
+	column := 1
+	lineStart := -1
+
+	for _, t := range e.file.Tokens {
+		if t.Position >= e.position {
+			column = int(e.position) - lineStart
+			break
+		}
+
+		if t.Kind == token.NewLine {
+			lineStart = int(t.Position)
+			line++
+		}
+	}
+
+	return line, column
+}
+
+// Path returns the relative path of the file to shorten the error message.
+func (e *FileError) Path() string {
+	cwd, err := os.Getwd()
+
+	if err != nil {
+		return e.file.Path
+	}
+
+	relative, err := filepath.Rel(cwd, e.file.Path)
+
+	if err != nil {
+		return e.file.Path
+	}
+
+	return relative
+}
+
+// Unwrap returns the wrapped error.
+func (e *FileError) Unwrap() error {
+	return e.err
+}

src/errors/FileError_test.go

@@ -0,0 +1,49 @@
+package errors_test
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"git.urbach.dev/cli/q/src/errors"
+	"git.urbach.dev/cli/q/src/fs"
+	"git.urbach.dev/cli/q/src/token"
+	"git.urbach.dev/go/assert"
+)
+
+func TestAbsolutePath(t *testing.T) {
+	relPath := "../../examples/hello/hello.q"
+	absPath, abserr := filepath.Abs(relPath)
+	assert.Nil(t, abserr)
+	err := test(t, absPath)
+	assert.Equal(t, err.Path(), relPath)
+}
+
+func TestRelativePath(t *testing.T) {
+	relPath := "../../examples/hello/hello.q"
+	err := test(t, relPath)
+	assert.Equal(t, err.Path(), relPath)
+}
+
+func test(t *testing.T, path string) *errors.FileError {
+	contents, oserr := os.ReadFile(path)
+	assert.Nil(t, oserr)
+	tokens := token.Tokenize(contents)
+
+	file := &fs.File{
+		Path:   path,
+		Bytes:  contents,
+		Tokens: tokens,
+	}
+
+	err := errors.New(io.EOF, file, 11)
+	assert.NotNil(t, err)
+
+	line, column := err.LineColumn()
+	assert.Equal(t, line, 3)
+	assert.Equal(t, column, 1)
+	assert.Equal(t, err.Unwrap().Error(), "EOF")
+	assert.Contains(t, err.Error(), ":3:1: EOF")
+	return err
+}

src/errors/New.go

@@ -0,0 +1,18 @@
+package errors
+
+import (
+	"git.urbach.dev/cli/q/src/fs"
+	"git.urbach.dev/cli/q/src/token"
+)
+
+// New generates an error message at the current token position.
+// The error message is clickable in popular editors and leads you
+// directly to the faulty file at the given line and position.
+func New(err error, file *fs.File, position token.Position) *FileError {
+	return &FileError{
+		err:      err,
+		file:     file,
+		position: position,
+		stack:    stack(),
+	}
+}

src/errors/stack.go

@@ -0,0 +1,30 @@
+package errors
+
+import (
+	"runtime"
+	"strings"
+)
+
+// stack generates a stack trace.
+func stack() string {
+	var (
+		final  []string
+		buffer = make([]byte, 4096)
+		n      = runtime.Stack(buffer, false)
+		stack  = string(buffer[:n])
+		lines  = strings.Split(stack, "\n")
+	)
+
+	for i := 6; i < len(lines); i += 2 {
+		line := strings.TrimSpace(lines[i])
+		space := strings.LastIndex(line, " ")
+
+		if space != -1 {
+			line = line[:space]
+		}
+
+		final = append(final, line)
+	}
+
+	return strings.Join(final, "\n")
+}