Merge pull request 'lexer: introduce Error{}' (#6)

Reviewed-on: #6

lexer/error.go

@@ -0,0 +1,45 @@
+package lexer
+
+import (
+	"fmt"
+	"strings"
+)
+
+var (
+	_ error = (*Error)(nil)
+)
+
+// Error represents a generic parsing error
+type Error struct {
+	Filename string
+	Line     int
+	Column   int
+
+	Content string
+	Err     error
+}
+
+func (err Error) Error() string {
+	var s []string
+
+	switch {
+	case err.Line > 0 || err.Column > 0:
+		s = append(s, fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column))
+	case err.Filename != "":
+		s = append(s, err.Filename)
+	}
+
+	if err.Err != nil {
+		s = append(s, err.Err.Error())
+	}
+
+	if err.Content != "" {
+		s = append(s, fmt.Sprintf("%q", err.Content))
+	}
+
+	return strings.Join(s, ": ")
+}
+
+func (err Error) Unwrap() error {
+	return err.Err
+}

readcloser.go

@@ -0,0 +1,64 @@
+package core
+
+import (
+	"bytes"
+	"io"
+	"io/fs"
+	"strings"
+)
+
+// ReadCloser adds a Close() to Readers without one
+type ReadCloser struct {
+	r io.Reader
+}
+
+// Read passes the Read() call to the underlying [io.Reader]
+// and fail if it was Closed()
+func (rc *ReadCloser) Read(b []byte) (int, error) {
+	switch {
+	case rc.r != nil:
+		return rc.r.Read(b)
+	default:
+		return 0, fs.ErrClosed
+	}
+}
+
+// Close attempts to Close the underlying [io.Reader], or
+// remove it if it doesn't support Close() and fail
+// if closed twice
+func (rc *ReadCloser) Close() error {
+	switch {
+	case rc.r != nil:
+		rc.r = nil
+		return nil
+	default:
+		return fs.ErrClosed
+	}
+}
+
+// NewReadCloser wraps a [io.Reader] to satisfy
+// [io.ReadCloser] if needed
+func NewReadCloser(r io.Reader) io.ReadCloser {
+	switch p := r.(type) {
+	case io.ReadCloser:
+		return p
+	case nil:
+		return nil
+	default:
+		return &ReadCloser{
+			r: r,
+		}
+	}
+}
+
+// NewReadCloserBytes wraps a bytes slice to implement
+// a [io.ReadCloser]
+func NewReadCloserBytes(b []byte) io.ReadCloser {
+	return NewReadCloser(bytes.NewReader(b))
+}
+
+// NewReadCloserString wraps a string to implement
+// a [io.ReadCloser]
+func NewReadCloserString(s string) io.ReadCloser {
+	return NewReadCloser(strings.NewReader(s))
+}