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

@@ -6,17 +6,16 @@ require github.com/mgechev/revive v1.3.3
 
 require (
 	github.com/BurntSushi/toml v1.3.2 // indirect
-	github.com/chavacava/garif v0.1.0 // 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 v0.0.19 // indirect
-	github.com/mattn/go-runewidth v0.0.15 // 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
-	github.com/rivo/uniseg v0.4.4 // indirect
 	golang.org/x/sys v0.11.0 // indirect
 	golang.org/x/tools v0.12.0 // indirect
 )

go.sum

@@ -1,7 +1,7 @@
 github.com/BurntSushi/toml v1.3.2 h1:o7IhLm0Msx3BaB+n3Ag7L8EVlByGnpq14C4YWiu/gL8=
 github.com/BurntSushi/toml v1.3.2/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
-github.com/chavacava/garif v0.1.0 h1:2JHa3hbYf5D9dsgseMKAmc/MZ109otzgNFk5s87H9Pc=
-github.com/chavacava/garif v0.1.0/go.mod h1:XMyYCkEL58DF0oyW4qDjjnPWONs2HBqYKI+UIPD+Gww=
+github.com/chavacava/garif v0.0.0-20230608123814-4bd63c2919ab h1:5JxePczlyGAtj6R1MUEFZ/UFud6FfsOejq7xLC2ZIb0=
+github.com/chavacava/garif v0.0.0-20230608123814-4bd63c2919ab/go.mod h1:XMyYCkEL58DF0oyW4qDjjnPWONs2HBqYKI+UIPD+Gww=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -12,11 +12,10 @@ github.com/fatih/structtag v1.2.0/go.mod h1:mBJUNpUnHmRKrKlQQlmCrh5PuhftFbNv8Ys4
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
 github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
-github.com/mattn/go-isatty v0.0.19 h1:JITubQf0MOLdlGRuRq+jtsDlekdYPia9ZFsB8h/APPA=
-github.com/mattn/go-isatty v0.0.19/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-isatty v0.0.17 h1:BTarxUcIeDqL27Mc+vyvdWYSL28zpIhv3RoTdsLMPng=
+github.com/mattn/go-isatty v0.0.17/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-runewidth v0.0.9 h1:Lm995f3rfxdpd6TSmuVCHVb/QhupuXlYr8sCI/QdE+0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
-github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZgg3U=
-github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
 github.com/mgechev/dots v0.0.0-20210922191527-e955255bf517 h1:zpIH83+oKzcpryru8ceC6BxnoG8TBrhgAvRg8obzup0=
 github.com/mgechev/dots v0.0.0-20210922191527-e955255bf517/go.mod h1:KQ7+USdGKfpPjXk4Ga+5XxQM4Lm4e3gAogrreFAYpOg=
 github.com/mgechev/revive v1.3.3 h1:GUWzV3g185agbHN4ZdaQvR6zrLVYTUSA2ktvIinivK0=
@@ -29,9 +28,6 @@ github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
-github.com/rivo/uniseg v0.4.4 h1:8TfxU8dW6PdqD27gjM8MVNuicgxIjxpm4K7x4jp8sis=
-github.com/rivo/uniseg v0.4.4/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
@@ -41,7 +37,6 @@ github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcU
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
 golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/tools v0.12.0 h1:YW6HUoUmYBpwSgyaGaZq1fHjrBjX1rlpZ54T6mu2kss=

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

@@ -41,46 +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
-}
-
-// Add adds a relative position considering
-// potential new lines
-func (p *Position) Add(rel Position) {
-	if p.Line == 0 {
-		p.Reset()
-	}
-
-	switch {
-	case rel.Line == 0:
-		// nothing
-	case rel.Line > 1:
-		// includes new lines
-		p.Line += rel.Line - 1
-		p.Column = rel.Column
-	default:
-		// same line
-		p.Column += rel.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)
-}