lexer: introduce Error{}

Signed-off-by: Alejandro Mery <amery@jpi.io>

README.md

@@ -1,78 +1 @@
 # asciigoat's core library
-
-[![Go Reference][godoc-badge]][godoc]
-[![Go Report Card][goreport-badge]][goreport]
-
-This package contains the basics for writing simple parsers of
-text languages heavily inspired by
-[Rob Pike](https://en.wikipedia.org/wiki/Rob_Pike)'s talk on
-[Lexical Scanning in Go](https://go.dev/talks/2011/lex.slide#1) in 2011 which
-you can [watch online](https://www.youtube.com/watch?v=HxaD_trXwRE) to get
-better understanding of the ideas behind **asciigoat**.
-
-**asciigoat** is [MIT](https://opensource.org/license/mit/) licensed.
-
-[godoc]: https://pkg.go.dev/asciigoat.org/core
-[godoc-badge]: https://pkg.go.dev/badge/asciigoat.org/core.svg
-[goreport]: https://goreportcard.com/report/asciigoat.org/core
-[goreport-badge]: https://goreportcard.com/badge/asciigoat.org/core
-
-[godoc-lexer-reader]: https://pkg.go.dev/asciigoat.org/core/lexer#Reader
-[godoc-readcloser]: https://pkg.go.dev/asciigoat.org/core#ReadCloser
-
-## Lexer
-
-### lexer.Reader
-
-The lexer package provides [`lexer.Reader`][godoc-lexer-reader] which is
-actually an [`io.RuneScanner`](https://pkg.go.dev/io#RuneScanner)
-that buffers accepted runes until you are ready to
-[emit](https://pkg.go.dev/asciigoat.org/core/lexer#Reader.Emit) or
-[discard](https://pkg.go.dev/asciigoat.org/core/lexer#Reader.Discard).
-
-### lexer.Position
-
-[`lexer.Position`](https://pkg.go.dev/asciigoat.org/core/lexer#Position)
-is a `(Line, Column)` pair with methods to facilitate tracking
-your position on the source [Reader](https://pkg.go.dev/io#Reader).
-
-### lexer.Error
-
-[`lexer.Error`](https://pkg.go.dev/asciigoat.org/core/lexer#Error)
-is an [unwrappable](https://pkg.go.dev/errors#Unwrap) error with a
-token position and hint attached.
-
-### lexer.StateFn
-
-At the heart of **asciigoat** we have _state functions_ as proposed on [Rob Pike's famous talk](https://www.youtube.com/watch?v=HxaD_trXwRE) which return the next _state function_ parsing is done.
-Additionally there is a [`Run()`](https://pkg.go.dev/asciigoat.org/lexer#Run) helper that implements the loop.
-
-### rune checkers
-
-_Rune checkers_ are simple functions that tell if a rune is of a class or it's not.
-Fundamental checkers are provided by the [`unicode` package](https://pkg.go.dev/unicode).
-
-Our [`lexer.Reader`][godoc-lexer-reader] uses them on its `Accept()` and `AcceptAll()` methods to
-make it easier to consume the _source_ document.
-
-To facilitate the declaration of _rune classes_ in the context of **asciigoat** powered parsers we include
-a series of rune checker factories.
-
-* `NewIsIn(string)`
-* `NewIsInRunes(...rune)`
-* `NewIsNot(checker)`
-* `NewIsOneOf(...checker)`
-
-## Others
-
-### ReadCloser
-
-[ReadCloser][godoc-readcloser] assists in providing a
-[io.Closer](https://pkg.go.dev/io#Closer) to Readers or buffers without on,
-or unearthing one if available so
-[io.ReadCloser](https://pkg.go.dev/io#ReadCloser) can be fulfilled.
-
-## See also
-
-* [asciigoat.org/ini](https://asciigoat.org/ini)
-* [oss.jpi.io](https://oss.jpi.io)

go.mod

@@ -2,22 +2,20 @@ module asciigoat.org/core
 
 go 1.19
 
-require (
-	github.com/fatih/structtag v1.2.0
-	github.com/mgechev/revive v1.3.3
-	github.com/pkg/errors v0.9.1
-)
+require github.com/mgechev/revive v1.3.3
 
 require (
 	github.com/BurntSushi/toml v1.3.2 // indirect
 	github.com/chavacava/garif v0.0.0-20230608123814-4bd63c2919ab // indirect
 	github.com/fatih/color v1.15.0 // indirect
+	github.com/fatih/structtag v1.2.0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.17 // indirect
 	github.com/mattn/go-runewidth v0.0.9 // indirect
 	github.com/mgechev/dots v0.0.0-20210922191527-e955255bf517 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/olekukonko/tablewriter v0.0.5 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	golang.org/x/sys v0.11.0 // indirect
 	golang.org/x/tools v0.12.0 // indirect
 )

lexer/error.go

@@ -1,7 +1,6 @@
 package lexer
 
 import (
-	"errors"
 	"fmt"
 	"strings"
 )
@@ -10,14 +9,6 @@ var (
 	_ error = (*Error)(nil)
 )
 
-var (
-	// ErrUnacceptableRune indicates the read rune isn't acceptable in the context
-	ErrUnacceptableRune = errors.New("rune not acceptable in context")
-
-	// ErrNotImplemented indicates something hasn't been implemented yet
-	ErrNotImplemented = errors.New("not implemented")
-)
-
 // Error represents a generic parsing error
 type Error struct {
 	Filename string
@@ -25,29 +16,17 @@ type Error struct {
 	Column   int
 
 	Content string
-	Hint    string
 	Err     error
 }
 
-func (err Error) prefix() string {
-	switch {
-	case err.Line > 0 || err.Column > 0:
-		if err.Filename != "" {
-			return fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column)
-		}
-
-		return fmt.Sprintf("%v:%v", err.Line, err.Column)
-	default:
-		return err.Filename
-	}
-}
-
 func (err Error) Error() string {
 	var s []string
 
-	prefix := err.prefix()
-	if prefix != "" {
-		s = append(s, prefix)
+	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 {
@@ -58,10 +37,6 @@ func (err Error) Error() string {
 		s = append(s, fmt.Sprintf("%q", err.Content))
 	}
 
-	if err.Hint != "" {
-		s = append(s, err.Hint)
-	}
-
 	return strings.Join(s, ": ")
 }
 

lexer/lexer.go

@@ -1,31 +1,17 @@
 // Package lexer provides basic helpers to implement parsers
 package lexer
 
-import (
-	"errors"
-	"io"
-)
-
 // StateFn is a State Function of the parser
 type StateFn func() (StateFn, error)
 
 // Run runs a state machine until the state function either
 // returns nil or an error
 func Run(fn StateFn) error {
-	for fn != nil {
-		var err error
+	var err error
 
+	for fn != nil && err == nil {
 		fn, err = fn()
-		switch {
-		case errors.Is(err, io.EOF):
-			// EOF
-			return nil
-		case err != nil:
-			// failed
-			return err
-		}
 	}
 
-	// ended
-	return nil
+	return err
 }

lexer/position.go

@@ -41,26 +41,28 @@ func (p *Position) Step() {
 	p.Column++
 }
 
-// StepN moves the column N places forward
-func (p *Position) StepN(n int) {
+// Next returns a new Position one rune forward
+// on the line
+func (p Position) Next() Position {
 	if p.Line == 0 {
 		p.Reset()
 	}
 
-	switch {
-	case n > 0:
-		p.Column += n
-	default:
-		panic(fmt.Errorf("invalid %v increment", n))
+	return Position{
+		Line:   p.Line,
+		Column: p.Column + 1,
 	}
 }
 
-// StepLine moves position to the start of the next line
-func (p *Position) StepLine() {
+// NextLine returns a new Position at the begining of the next
+// line.
+func (p Position) NextLine() Position {
 	if p.Line == 0 {
 		p.Reset()
 	}
 
-	p.Line++
-	p.Column = 1
+	return Position{
+		Line:   p.Line + 1,
+		Column: 1,
+	}
 }

lexer/runes.go

@@ -1,47 +0,0 @@
-package lexer
-
-import (
-	"strings"
-	"unicode"
-)
-
-// NewIsNot generates a rune condition checker that reverses the
-// decision of the given checker.
-func NewIsNot(cond func(rune) bool) func(rune) bool {
-	return func(r rune) bool {
-		return !cond(r)
-	}
-}
-
-// NewIsIn generates a rune condition checker that accepts runes
-// contained on the provided string
-func NewIsIn(s string) func(rune) bool {
-	return func(r rune) bool {
-		return strings.ContainsRune(s, r)
-	}
-}
-
-// NewIsInRunes generates a rune condition checker that accepts
-// the runes specified
-func NewIsInRunes(s ...rune) func(rune) bool {
-	return NewIsIn(string(s))
-}
-
-// NewIsOneOf generates a run condition checker that accepts runes
-// accepted by any of the given checkers
-func NewIsOneOf(s ...func(rune) bool) func(rune) bool {
-	return func(r rune) bool {
-		for _, cond := range s {
-			if cond(r) {
-				return true
-			}
-		}
-		return false
-	}
-}
-
-// IsSpace reports whether the rune is a space character as
-// defined by Unicode's White Space property
-func IsSpace(r rune) bool {
-	return unicode.IsSpace(r)
-}

reflection/error.go

@@ -1,69 +0,0 @@
-package reflection
-
-import (
-	"bytes"
-	"fmt"
-	"reflect"
-)
-
-// An InvalidUnmarshalError describes an invalid argument passed to New.
-// (It must be a non-nil pointer.)
-type InvalidUnmarshalError struct {
-	Method string
-	Prefix string
-
-	reflect.Type
-}
-
-func (e *InvalidUnmarshalError) Error() string {
-	var buf bytes.Buffer
-
-	if e.Prefix != "" {
-		_, _ = fmt.Fprintf(&buf, "%s: ", e.Prefix)
-	}
-
-	method := e.Method
-	if method == "" {
-		method = "New"
-	}
-
-	_, _ = fmt.Fprintf(&buf, "%s(", method)
-
-	switch {
-	case e.Type == nil:
-		_, _ = buf.WriteString("nil")
-	case e.Type.Kind() != reflect.Pointer:
-		_, _ = fmt.Fprintf(&buf, "%s %s", "non-pointer", e.Type.String())
-	default:
-		_, _ = fmt.Fprintf(&buf, "%s %s", "nil", e.Type.String())
-	}
-
-	_, _ = buf.WriteString(")")
-
-	return buf.String()
-}
-
-// An UnmarshalTypeError tells something went wrong while processing
-// a type.
-type UnmarshalTypeError struct {
-	Prefix string
-	Err    error
-
-	reflect.Type
-}
-
-func (e UnmarshalTypeError) Unwrap() error {
-	return e.Err
-}
-
-func (e UnmarshalTypeError) Error() string {
-	var buf bytes.Buffer
-
-	if e.Prefix != "" {
-		_, _ = fmt.Fprintf(&buf, "%s: ", e.Prefix)
-	}
-
-	_, _ = fmt.Fprintf(&buf, "%s: %s", e.Type.String(), e.Err)
-
-	return buf.String()
-}

reflection/reflect_help.go

@@ -1,16 +0,0 @@
-package reflection
-
-import (
-	"fmt"
-	"reflect"
-)
-
-func structFieldName(sf reflect.StructField) string {
-	if sf.Anonymous {
-		idx := sf.Index[len(sf.Index)-1]
-
-		return fmt.Sprintf("%s-%v", "anonymous", idx)
-	}
-
-	return sf.Name
-}

reflection/reflection.go

@@ -1,40 +0,0 @@
-// Package reflection helps Marshalling/Unmarshalling data to structs
-package reflection
-
-import (
-	"reflect"
-)
-
-// Reflection provides Marshalling/Unmarshalling oriented view
-// of a value
-type Reflection struct {
-	v reflect.Value
-
-	types map[reflect.Type]TypeInfo
-}
-
-// Value returns the object it reflects
-func (r *Reflection) Value() any {
-	return r.v.Interface()
-}
-
-// New creates a Reflection of the given pointer
-func New(v any) (*Reflection, error) {
-	rv := reflect.ValueOf(v)
-
-	if rv.Kind() != reflect.Pointer || rv.IsNil() {
-		err := &InvalidUnmarshalError{Type: rv.Type()}
-		return nil, err
-	}
-
-	r := &Reflection{
-		v:     rv,
-		types: make(map[reflect.Type]TypeInfo),
-	}
-
-	if err := r.scan(); err != nil {
-		return nil, err
-	}
-
-	return r, nil
-}

reflection/scan.go

@@ -1,37 +0,0 @@
-package reflection
-
-import (
-	"reflect"
-)
-
-func (r *Reflection) scanType(rt reflect.Type) error {
-	switch rt.Kind() {
-	case reflect.Pointer, reflect.Slice:
-		rt = rt.Elem()
-	}
-
-	if _, ok := r.types[rt]; ok {
-		// cached
-		return nil
-	}
-
-	ti, err := NewTypeInfo(rt)
-	if err != nil {
-		return &UnmarshalTypeError{Type: rt, Err: err}
-	}
-
-	r.types[rt] = ti
-
-	for i := range ti.fields {
-		err := r.scanType(ti.fields[i].sf.Type)
-		if err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
-func (r *Reflection) scan() error {
-	return r.scanType(r.v.Type())
-}

reflection/typeinfo.go

@@ -1,108 +0,0 @@
-package reflection
-
-import (
-	"log"
-	"reflect"
-
-	"github.com/fatih/structtag"
-	"github.com/pkg/errors"
-)
-
-// TypeInfo ...
-type TypeInfo struct {
-	rt reflect.Type
-
-	fields []TypeInfoField
-}
-
-// Type ...
-func (ti *TypeInfo) Type() reflect.Type {
-	return ti.rt
-}
-
-// Kind ...
-func (ti *TypeInfo) Kind() reflect.Kind {
-	return ti.rt.Kind()
-}
-
-// TypeInfoField ...
-type TypeInfoField struct {
-	sf   reflect.StructField
-	tags *structtag.Tags
-
-	Name string
-}
-
-// Type ...
-func (tif *TypeInfoField) Type() reflect.Type {
-	return tif.sf.Type
-}
-
-// Kind ...
-func (tif *TypeInfoField) Kind() reflect.Kind {
-	return tif.sf.Type.Kind()
-}
-
-// Tag ...
-func (tif *TypeInfoField) Tag(key string) (*structtag.Tag, bool) {
-	if tif.tags != nil {
-		tag, _ := tif.tags.Get(key)
-		if tag != nil {
-			return tag, true
-		}
-	}
-	return nil, false
-}
-
-// NewTypeInfo ...
-func NewTypeInfo(rt reflect.Type) (TypeInfo, error) {
-	log.Printf("%s.%s: %s (%s)", "reflection", "NewTypeInfo", rt, rt.Kind())
-
-	ti := TypeInfo{
-		rt: rt,
-	}
-
-	err := ti.init()
-	return ti, err
-}
-
-func (ti *TypeInfo) init() error {
-	switch ti.Kind() {
-	case reflect.Struct:
-		return ti.initStruct()
-	default:
-		return nil
-	}
-}
-
-func (ti *TypeInfo) initStruct() error {
-	// load fields
-	n := ti.rt.NumField()
-	fields := make([]TypeInfoField, 0, n)
-	for i := 0; i < n; i++ {
-		sf := ti.rt.Field(i)
-		tags, err := structtag.Parse(string(sf.Tag))
-
-		if err != nil {
-			// tag parse error
-			err = &UnmarshalTypeError{
-				Type: ti.rt,
-				Err:  errors.Wrap(err, structFieldName(sf)),
-			}
-			return err
-		}
-
-		if sf.IsExported() {
-			log.Printf("%s.%s:   [%v]: %q %s (%s)",
-				"reflection", "NewTypeInfo",
-				i, structFieldName(sf), sf.Type, sf.Type.Kind())
-
-			fields = append(fields, TypeInfoField{
-				sf:   sf,
-				tags: tags,
-			})
-		}
-	}
-	ti.fields = fields
-	return nil
-}