分词正在报告意外的标记。

huangapple
go评论123阅读模式
英文:

Participle is stating Unexpected Token

问题

我正在玩一个分词器来学习解析，但我无法确定为什么会出现这种意外情况。

  1. // nolint: golint, dupl
  2. package main
  4. import (
  5. 	"fmt"
  6. 	"io"
  8. 	"github.com/alecthomas/participle/v2"
  9. 	"github.com/alecthomas/participle/v2/lexer"
  10. )
  12. var htaccessLexer = lexer.MustSimple([]lexer.SimpleRule{
  13. 	{"Comment", `^#[^\n]*`},
  14. 	{"Ident", `^\w+`},
  15. 	{"Int", `\d+`},
  16. 	{"String", `("(\\\"|[^"])*"|\S+)`},
  17. 	{"EOL", `[\n\r]+`},
  18. 	{"whitespace", `[ \t]+`},
  19. })
  21. type HTACCESS struct {
  22. 	Directives []*Directive `@@*`
  23. }
  25. type Directive struct {
  26. 	Pos lexer.Position
  28. 	ErrorDocument *ErrorDocument `@@`
  29. }
  31. type ErrorDocument struct {
  32. 	Code int    `"ErrorDocument" @Int`
  33. 	Path string `@String`
  34. }
  36. var htaccessParser = participle.MustBuild(&HTACCESS{},
  37. 	participle.Lexer(htaccessLexer),
  38. 	participle.CaseInsensitive("Ident"),
  39. 	participle.Unquote("String"),
  40. 	participle.Elide("whitespace"),
  41. )
  43. func Parse(r io.Reader) (*HTACCESS, error) {
  44. 	program := &HTACCESS{}
  45. 	err := htaccessParser.Parse("", r, program)
  46. 	if err != nil {
  47. 		return nil, err
  48. 	}
  50. 	return program, nil
  51. }
  53. func main() {
  54. 	v, err := htaccessParser.ParseString("", `ErrorDocument 403 test`)
  56. 	if err != nil {
  57. 		panic(err)
  58. 	}
  60. 	fmt.Println(v)
  61. }

据我所知，这似乎是正确的，我期望403在那里，但我不确定为什么它无法识别它。

编辑：
我将我的分词器更改为以下内容：

  1. var htaccessLexer = lexer.MustSimple([]lexer.SimpleRule{
  2. 	{"dir", `^\w+`},
  3. 	{"int", `\d+`},
  4. 	{"str", `("(\\\"|[^"])*"|\S+)`},
  5. 	{"EOL", `[\n\r]+`},
  6. 	{"whitespace", `\s+`},
  7. })

错误消失了，但它仍然打印一个空数组，不确定为什么。我也不确定为什么使用不同的分词器值会修复它。

英文:

I am playing with a participle to learn how to parse and I cannot determine why this is unexpected.

  1. // nolint: golint, dupl
  2. package main
  4. import (
  5. 	"fmt"
  6. 	"io"
  8. 	"github.com/alecthomas/participle/v2"
  9. 	"github.com/alecthomas/participle/v2/lexer"
  10. )
  12. var htaccessLexer = lexer.MustSimple([]lexer.SimpleRule{
  13. 	{"Comment", `^#[^\n]*`},
  14. 	{"Ident", `^\w+`},
  15. 	{"Int", `\d+`},
  16. 	{"String", `("(\\"|[^"])*"|\S+)`},
  17. 	{"EOL", `[\n\r]+`},
  18. 	{"whitespace", `[ \t]+`},
  19. })
  21. type HTACCESS struct {
  22. 	Directives []*Directive `@@*`
  23. }
  25. type Directive struct {
  26. 	Pos lexer.Position
  28. 	ErrorDocument *ErrorDocument `@@`
  29. }
  31. type ErrorDocument struct {
  32. 	Code int    `"ErrorDocument" @Int`
  33. 	Path string `@String`
  34. }
  36. var htaccessParser = participle.MustBuild[HTACCESS](
  37. 	participle.Lexer(htaccessLexer),
  38. 	participle.CaseInsensitive("Ident"),
  39. 	participle.Unquote("String"),
  40. 	participle.Elide("whitespace"),
  41. )
  43. func Parse(r io.Reader) (*HTACCESS, error) {
  44. 	program, err := htaccessParser.Parse("", r)
  45. 	if err != nil {
  46. 		return nil, err
  47. 	}
  49. 	return program, nil
  50. }
  52. func main() {
  53. 	v, err := htaccessParser.ParseString("", `ErrorDocument 403 test`)
  55. 	if err != nil {
  56. 		panic(err)
  57. 	}
  59. 	fmt.Println(v)
  60. }

From what I can tell, this seems to be correct, I expect 403 to be there, but I am not sure why it doesn't recognize it.

Edit:
I changed my lexer to this:

  1. var htaccessLexer = lexer.MustSimple([]lexer.SimpleRule{
  2. {"dir", `^\w+`},
  3. {"int", `\d+`},
  4. {"str", `("(\\"|[^"])*"|\S+)`},
  5. {"EOL", `[\n\r]+`},
  6. {"whitespace", `\s+`},
  7. })

And the error is gone, but it is still printing an empty array, not sure why. I am also unsure why using different values for the lexer fixes it either.

答案1

得分: 2

我相信我找到了问题所在，问题出在顺序上。Ident通过\w标签在我的词法分析器中找到了数字，这导致我的整数被标记为ident。

我发现我必须将QuotedStrings和UnQuotedStrings分开，否则未引用的字符串会捕捉到整数。或者我可以确保它只捕捉非数字的值，但这样会错过像stringwithnum2这样的内容。

这是我的解决方案：

  1. var htaccessLexer = lexer.MustSimple([]lexer.SimpleRule{
  2. 	{"Comment", `(?i)#[^\n]*`},
  3. 	{"QuotedString", `"(\\"|[^"])*"`},
  4. 	{"Number", `[-+]?(\\d*\\.)?\\d+`},
  5. 	{"UnQuotedString", `[^ \t]+`},
  6. 	{"Ident", `^[a-zA-Z_]`},
  7. 	{"EOL", `[\n\r]+`},
  8. 	{"whitespace", `[ \t]+`},
  9. })
  1. type ErrorDocument struct {
  2. 	Pos lexer.Position
  4. 	Code int    `"ErrorDocument" @Number`
  5. 	Path string `(@QuotedString | @UnQuotedString)`
  6. }

这解决了我的问题，因为它现在先找到引用的字符串，然后查找数字，然后查找未引用的字符串。

英文:

I believe I found the issue, it is the order, Ident was finding numbers in my lexer via the \w tag, so this caused my integers to be marked as ident.

I found that I have to separate QuotedStrings and UnQuotedStrings otherwise unquoted strings was picking up integers. Alternatively I could ensure it only picks up non-numeric values, but that would miss things like stringwithnum2

Here is my solution

  1. var htaccessLexer = lexer.MustSimple([]lexer.SimpleRule{
  2. {"Comment", `(?i)#[^\n]*`},
  3. {"QuotedString", `"(\\"|[^"])*"`},
  4. {"Number", `[-+]?(\d*\.)?\d+`},
  5. {"UnQuotedString", `[^ \t]+`},
  6. {"Ident", `^[a-zA-Z_]`},
  7. {"EOL", `[\n\r]+`},
  8. {"whitespace", `[ \t]+`},
  9. })
  1. type ErrorDocument struct {
  2. Pos lexer.Position
  3. Code int    `"ErrorDocument" @Number`
  4. Path string `(@QuotedString | @UnQuotedString)`
  5. }

This fixed my issue, because it now finds quoted strings, then looks for Numbers, then looks for unquoted strings.

huangapple
  • 本文由 发表于 2023年2月19日 04:33:58
  • 转载请务必保留本文链接：https://go.coder-hub.com/75496233.html
  • go
  • lexer
  • parsing
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