解析降价缩进的代码块 [英] Parse markdown indented code block
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问题描述
我正在尝试使用Parslet编写的语法来解析Markdown.但是，我无法克服缩进的代码块，因为到目前为止我尝试过的所有事情都陷入了递归之中.他们看起来像这样:
I am trying to parse Markdown using a grammar written with Parslet. However, I cannot get past indented code blocks because everything I tried so far got stuck in recursion. They look like this:
This is a indented code block.
Second line.
Code block continues after blank line.
There can be any number of chunks,
separated by not more than one blank line.
为了解决这个问题，我写了一个最小的示例，该示例用a替换行(包括\n)，并用空格替换空白行(\n\n)，例如:a aaa aa.
In order to solve this I wrote a minimal example wich replaces the lines (including \n) with a and blank lines (\n\n) with spaces, eg: a aaa aa.
# recurring_group_parser.rb
require 'parslet'
require 'rspec'
require 'parslet/rig/rspec'
class RecurringGroupParser < Parslet::Parser
root(:block)
rule :block do
chunk.repeat(1,3)
end
rule :chunk do
str('a').repeat(1,3) >> space
end
rule :space do
str(' ') | chunk.absent?
end
end
describe RecurringGroupParser do
it 'should parse a' do
is_expected.to parse "a"
end
it 'should parse aa' do
is_expected.to parse "aa"
end
it 'should parse aaa' do
is_expected.to parse "aaa"
end
it 'should parse a a' do
is_expected.to parse "a a"
end
it 'should parse aa a' do
is_expected.to parse "aa a"
end
it 'should parse aaa a' do
is_expected.to parse "aaa a"
end
it 'should parse a aa' do
is_expected.to parse "a aa"
end
it 'should parse a aaa' do
is_expected.to parse "a aaa"
end
it 'should parse aa a' do
is_expected.to parse "aa a"
end
it 'should parse aa aa' do
is_expected.to parse "aa aa"
end
it 'should parse aa aaa' do
is_expected.to parse "aa aaa"
end
it 'should parse aaa aa' do
is_expected.to parse "aaa aa"
end
it 'should parse aaa aaa' do
is_expected.to parse "aaa aaa"
end
it 'should parse a a a' do
is_expected.to parse "a a a"
end
it 'should parse aa a a' do
is_expected.to parse "aa a a"
end
it 'should parse aaa a a' do
is_expected.to parse "aaa a a"
end
it 'should parse a aa a' do
is_expected.to parse "a aa a"
end
it 'should parse aa aa a' do
is_expected.to parse "aa aa a"
end
it 'should parse aaa aa a' do
is_expected.to parse "aaa aa a"
end
it 'should parse a aaa a' do
is_expected.to parse "a aaa a"
end
it 'should parse aa aaa a' do
is_expected.to parse "aa aaa a"
end
it 'should parse aaa aaa a' do
is_expected.to parse "aaa aaa a"
end
it 'should parse a a aa' do
is_expected.to parse "a a aa"
end
it 'should parse aa a aa' do
is_expected.to parse "aa a aa"
end
it 'should parse aaa a aa' do
is_expected.to parse "aaa a aa"
end
it 'should parse a aa aa' do
is_expected.to parse "a aa aa"
end
it 'should parse aa aa aa' do
is_expected.to parse "aa aa aa"
end
it 'should parse aaa aa aa' do
is_expected.to parse "aaa aa aa"
end
it 'should parse a aaa aa' do
is_expected.to parse "a aaa aa"
end
it 'should parse aa aaa aa' do
is_expected.to parse "aa aaa aa"
end
it 'should parse aaa aaa aa' do
is_expected.to parse "aaa aaa aa"
end
it 'should parse a a aaa' do
is_expected.to parse "a a aaa"
end
it 'should parse aa a aaa' do
is_expected.to parse "aa a aaa"
end
it 'should parse aaa a aaa' do
is_expected.to parse "aaa a aaa"
end
it 'should parse a aa aaa' do
is_expected.to parse "a aa aaa"
end
it 'should parse aa aa aaa' do
is_expected.to parse "aa aa aaa"
end
it 'should parse aaa aa aaa' do
is_expected.to parse "aaa aa aaa"
end
it 'should parse a aaa aaa' do
is_expected.to parse "a aaa aaa"
end
it 'should parse aa aaa aaa' do
is_expected.to parse "aa aaa aaa"
end
it 'should parse aaa aaa aaa' do
is_expected.to parse "aaa aaa aaa"
end
end
运行rspec recurring_group_parser.rb可以正常工作.只有当我将换行符放回去时，它才会停顿:
Running rspec recurring_group_parser.rb works fine. Only when I put the newlines back in, it stalls:
# recurring_group_parser.rb
require 'parslet'
require 'rspec'
require 'parslet/rig/rspec'
class RecurringGroupParser < Parslet::Parser
root(:block)
rule :block do
chunk.repeat(1,3)
end
rule :chunk do
line.repeat(1,3) >> blank_line
end
rule :line do
str('a') >> newline
end
rule :blank_line do
newline.repeat(2) | chunk.absent?
end
rule :newline do
str("\n") | any.absent?
end
end
describe RecurringGroupParser do
it 'should parse a' do
is_expected.to parse "a"
end
it 'should parse aa' do
is_expected.to parse "a\na"
end
it 'should parse aaa' do
is_expected.to parse "a\na\na"
end
it 'should parse a a' do
is_expected.to parse "a\n\na"
end
it 'should parse aa a' do
is_expected.to parse "a\na\n\na"
end
it 'should parse aaa a' do
is_expected.to parse "a\naa\n\na"
end
it 'should parse a aa' do
is_expected.to parse "a\n\na\na"
end
it 'should parse a aaa' do
is_expected.to parse "a\n\na\na\na"
end
it 'should parse aa a' do
is_expected.to parse "a\na\n\na"
end
it 'should parse aa aa' do
is_expected.to parse "a\na\n\na\na"
end
it 'should parse aa aaa' do
is_expected.to parse "a\na\n\na\na\na"
end
it 'should parse aaa aa' do
is_expected.to parse "a\naa\n\na\na"
end
it 'should parse aaa aaa' do
is_expected.to parse "a\naa\n\na\na\na"
end
it 'should parse a a a' do
is_expected.to parse "a\n\na\n\na"
end
it 'should parse aa a a' do
is_expected.to parse "a\na\n\na\n\na"
end
it 'should parse aaa a a' do
is_expected.to parse "a\naa\n\na\n\na"
end
it 'should parse a aa a' do
is_expected.to parse "a\n\na\na\n\na"
end
it 'should parse aa aa a' do
is_expected.to parse "a\na\n\na\na\n\na"
end
it 'should parse aaa aa a' do
is_expected.to parse "a\naa\n\na\na\n\na"
end
it 'should parse a aaa a' do
is_expected.to parse "a\n\na\naa\n\na"
end
it 'should parse aa aaa a' do
is_expected.to parse "a\na\n\na\naa\n\na"
end
it 'should parse aaa aaa a' do
is_expected.to parse "a\naa\n\na\naa\n\na"
end
it 'should parse a a aa' do
is_expected.to parse "a\n\na\n\na\na"
end
it 'should parse aa a aa' do
is_expected.to parse "a\na\n\na\n\na\na"
end
it 'should parse aaa a aa' do
is_expected.to parse "a\naa\n\na\n\na\na"
end
it 'should parse a aa aa' do
is_expected.to parse "a\n\na\na\n\na\na"
end
it 'should parse aa aa aa' do
is_expected.to parse "a\na\n\na\na\n\na\na"
end
it 'should parse aaa aa aa' do
is_expected.to parse "a\naa\n\na\na\n\na\na"
end
it 'should parse a aaa aa' do
is_expected.to parse "a\n\na\naa\n\na\na"
end
it 'should parse aa aaa aa' do
is_expected.to parse "a\na\n\na\naa\n\na\na"
end
it 'should parse aaa aaa aa' do
is_expected.to parse "a\naa\n\na\naa\n\na\na"
end
it 'should parse a a aaa' do
is_expected.to parse "a\n\na\n\na\na\na"
end
it 'should parse aa a aaa' do
is_expected.to parse "a\na\n\na\n\na\na\na"
end
it 'should parse aaa a aaa' do
is_expected.to parse "a\naa\n\na\n\na\na\na"
end
it 'should parse a aa aaa' do
is_expected.to parse "a\n\na\na\n\na\na\na"
end
it 'should parse aa aa aaa' do
is_expected.to parse "a\na\n\na\na\n\na\na\na"
end
it 'should parse aaa aa aaa' do
is_expected.to parse "a\naa\n\na\na\n\na\na\na"
end
it 'should parse a aaa aaa' do
is_expected.to parse "a\n\na\naa\n\na\na\na"
end
it 'should parse aa aaa aaa' do
is_expected.to parse "a\na\n\na\naa\n\na\na\na"
end
it 'should parse aaa aaa aaa' do
is_expected.to parse "a\naa\n\na\naa\n\na\na\na"
end
end
为简化此操作，行只能由单个a组成，不能缩进，但以后可以轻松更改，并且与完成解析失败无关.我也很确定rule :blank_line中的chunk.absent?和rule :newline中的any.absent?之间存在冲突，但是我不知道如何解决此问题并提供打破递归的条件.需要任何帮助！
To simplify this, lines can only consist of a single a and are not indented but that can easily be changed later and are not related to the failure to finish parsing. I am also pretty sure that there is a collision between chunk.absent? in rule :blank_line and any.absent? in rule :newline but I have no idea how to fix this and provide criteria to break the recursion. Any help wanted!
推荐答案
在这种情况下，换行符可以是eof.在这种情况下，换行符. repeat(2)重复匹配eof.您需要"repeat(2,2)".您可以使这些错误易于发现:)...只需使用我的叉子即可.
In this case newline can be eof. In which case newline. repeat(2) repeatedly matches eof. You want "repeat(2,2)". You can made these bugs easy to find :)... Just use my fork.
您可以使用我的Parslet叉来检测其循环. 它捕获循环并告诉您正在发生的事情. 它比通常的parslet慢，因此请切换回生产分析.
You can detect how it's looping by using my fork of parslet. It catches loops and tells you what's happening. It's slower than the usual parslet, so switch back for production parsing.
使用此Gemfile:
Use this Gemfile:
source "https://rubygems.org"
gem "parslet" , :git => "https://github.com/NigelThorne/parslet.git"
gem 'rspec'
您会得到以下结果:
9:23:40.20 > bundle exec rspec parser.rb
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
Failures:
1) RecurringGroupParser should parse a
Failure/Error: is_expected.to parse "a"
RuntimeError:
Grammar contains an infinite loop applying 'NEWLINE{2, }' at char position 1
...a<-- here
# ./parser.rb:33:in `block (2 levels) in <top (required)>'
2) RecurringGroupParser should parse aa
Failure/Error: is_expected.to parse "a\na"
RuntimeError:
Grammar contains an infinite loop applying 'NEWLINE{2, }' at char position 3
...a
a<-- here
# ./parser.rb:37:in `block (2 levels) in <top (required)>'
3) RecurringGroupParser should parse aaa
Failure/Error: is_expected.to parse "a\na\na"
RuntimeError:
Grammar contains an infinite loop applying 'NEWLINE{2, }' at char position 5
...a
a
a<-- here
# ./parser.rb:41:in `block (2 levels) in <top (required)>'
4) RecurringGroupParser should parse a a
Failure/Error: is_expected.to parse "a\n\na"
expected BLOCK to be able to parse "a\n\na"
# ./parser.rb:45:in `block (2 levels) in <top (required)>'
5) RecurringGroupParser should parse aa a
Failure/Error: is_expected.to parse "a\na\n\na"
expected BLOCK to be able to parse "a\na\n\na"
# ./parser.rb:49:in `block (2 levels) in <top (required)>'
6) RecurringGroupParser should parse aaa a
Failure/Error: is_expected.to parse "a\naa\n\na"
expected BLOCK to be able to parse "a\naa\n\na"
# ./parser.rb:53:in `block (2 levels) in <top (required)>'
7) RecurringGroupParser should parse a aa
Failure/Error: is_expected.to parse "a\n\na\na"
expected BLOCK to be able to parse "a\n\na\na"
# ./parser.rb:57:in `block (2 levels) in <top (required)>'
8) RecurringGroupParser should parse a aaa
Failure/Error: is_expected.to parse "a\n\na\na\na"
expected BLOCK to be able to parse "a\n\na\na\na"
# ./parser.rb:61:in `block (2 levels) in <top (required)>'
9) RecurringGroupParser should parse aa a
Failure/Error: is_expected.to parse "a\na\n\na"
expected BLOCK to be able to parse "a\na\n\na"
# ./parser.rb:65:in `block (2 levels) in <top (required)>'
10) RecurringGroupParser should parse aa aa
Failure/Error: is_expected.to parse "a\na\n\na\na"
expected BLOCK to be able to parse "a\na\n\na\na"
# ./parser.rb:69:in `block (2 levels) in <top (required)>'
11) RecurringGroupParser should parse aa aaa
Failure/Error: is_expected.to parse "a\na\n\na\na\na"
expected BLOCK to be able to parse "a\na\n\na\na\na"
# ./parser.rb:73:in `block (2 levels) in <top (required)>'
12) RecurringGroupParser should parse aaa aa
Failure/Error: is_expected.to parse "a\naa\n\na\na"
expected BLOCK to be able to parse "a\naa\n\na\na"
# ./parser.rb:77:in `block (2 levels) in <top (required)>'
13) RecurringGroupParser should parse aaa aaa
Failure/Error: is_expected.to parse "a\naa\n\na\na\na"
expected BLOCK to be able to parse "a\naa\n\na\na\na"
# ./parser.rb:81:in `block (2 levels) in <top (required)>'
14) RecurringGroupParser should parse a a a
Failure/Error: is_expected.to parse "a\n\na\n\na"
expected BLOCK to be able to parse "a\n\na\n\na"
# ./parser.rb:85:in `block (2 levels) in <top (required)>'
15) RecurringGroupParser should parse aa a a
Failure/Error: is_expected.to parse "a\na\n\na\n\na"
expected BLOCK to be able to parse "a\na\n\na\n\na"
# ./parser.rb:89:in `block (2 levels) in <top (required)>'
16) RecurringGroupParser should parse aaa a a
Failure/Error: is_expected.to parse "a\naa\n\na\n\na"
expected BLOCK to be able to parse "a\naa\n\na\n\na"
# ./parser.rb:93:in `block (2 levels) in <top (required)>'
17) RecurringGroupParser should parse a aa a
Failure/Error: is_expected.to parse "a\n\na\na\n\na"
expected BLOCK to be able to parse "a\n\na\na\n\na"
# ./parser.rb:97:in `block (2 levels) in <top (required)>'
18) RecurringGroupParser should parse aa aa a
Failure/Error: is_expected.to parse "a\na\n\na\na\n\na"
expected BLOCK to be able to parse "a\na\n\na\na\n\na"
# ./parser.rb:101:in `block (2 levels) in <top (required)>'
19) RecurringGroupParser should parse aaa aa a
Failure/Error: is_expected.to parse "a\naa\n\na\na\n\na"
expected BLOCK to be able to parse "a\naa\n\na\na\n\na"
# ./parser.rb:105:in `block (2 levels) in <top (required)>'
20) RecurringGroupParser should parse a aaa a
Failure/Error: is_expected.to parse "a\n\na\naa\n\na"
expected BLOCK to be able to parse "a\n\na\naa\n\na"
# ./parser.rb:109:in `block (2 levels) in <top (required)>'
21) RecurringGroupParser should parse aa aaa a
Failure/Error: is_expected.to parse "a\na\n\na\naa\n\na"
expected BLOCK to be able to parse "a\na\n\na\naa\n\na"
# ./parser.rb:113:in `block (2 levels) in <top (required)>'
22) RecurringGroupParser should parse aaa aaa a
Failure/Error: is_expected.to parse "a\naa\n\na\naa\n\na"
expected BLOCK to be able to parse "a\naa\n\na\naa\n\na"
# ./parser.rb:117:in `block (2 levels) in <top (required)>'
23) RecurringGroupParser should parse a a aa
Failure/Error: is_expected.to parse "a\n\na\n\na\na"
expected BLOCK to be able to parse "a\n\na\n\na\na"
# ./parser.rb:121:in `block (2 levels) in <top (required)>'
24) RecurringGroupParser should parse aa a aa
Failure/Error: is_expected.to parse "a\na\n\na\n\na\na"
expected BLOCK to be able to parse "a\na\n\na\n\na\na"
# ./parser.rb:125:in `block (2 levels) in <top (required)>'
25) RecurringGroupParser should parse aaa a aa
Failure/Error: is_expected.to parse "a\naa\n\na\n\na\na"
expected BLOCK to be able to parse "a\naa\n\na\n\na\na"
# ./parser.rb:129:in `block (2 levels) in <top (required)>'
26) RecurringGroupParser should parse a aa aa
Failure/Error: is_expected.to parse "a\n\na\na\n\na\na"
expected BLOCK to be able to parse "a\n\na\na\n\na\na"
# ./parser.rb:133:in `block (2 levels) in <top (required)>'
27) RecurringGroupParser should parse aa aa aa
Failure/Error: is_expected.to parse "a\na\n\na\na\n\na\na"
expected BLOCK to be able to parse "a\na\n\na\na\n\na\na"
# ./parser.rb:137:in `block (2 levels) in <top (required)>'
28) RecurringGroupParser should parse aaa aa aa
Failure/Error: is_expected.to parse "a\naa\n\na\na\n\na\na"
expected BLOCK to be able to parse "a\naa\n\na\na\n\na\na"
# ./parser.rb:141:in `block (2 levels) in <top (required)>'
29) RecurringGroupParser should parse a aaa aa
Failure/Error: is_expected.to parse "a\n\na\naa\n\na\na"
expected BLOCK to be able to parse "a\n\na\naa\n\na\na"
# ./parser.rb:145:in `block (2 levels) in <top (required)>'
30) RecurringGroupParser should parse aa aaa aa
Failure/Error: is_expected.to parse "a\na\n\na\naa\n\na\na"
expected BLOCK to be able to parse "a\na\n\na\naa\n\na\na"
# ./parser.rb:149:in `block (2 levels) in <top (required)>'
31) RecurringGroupParser should parse aaa aaa aa
Failure/Error: is_expected.to parse "a\naa\n\na\naa\n\na\na"
expected BLOCK to be able to parse "a\naa\n\na\naa\n\na\na"
# ./parser.rb:153:in `block (2 levels) in <top (required)>'
32) RecurringGroupParser should parse a a aaa
Failure/Error: is_expected.to parse "a\n\na\n\na\na\na"
expected BLOCK to be able to parse "a\n\na\n\na\na\na"
# ./parser.rb:157:in `block (2 levels) in <top (required)>'
33) RecurringGroupParser should parse aa a aaa
Failure/Error: is_expected.to parse "a\na\n\na\n\na\na\na"
expected BLOCK to be able to parse "a\na\n\na\n\na\na\na"
# ./parser.rb:161:in `block (2 levels) in <top (required)>'
34) RecurringGroupParser should parse aaa a aaa
Failure/Error: is_expected.to parse "a\naa\n\na\n\na\na\na"
expected BLOCK to be able to parse "a\naa\n\na\n\na\na\na"
# ./parser.rb:165:in `block (2 levels) in <top (required)>'
35) RecurringGroupParser should parse a aa aaa
Failure/Error: is_expected.to parse "a\n\na\na\n\na\na\na"
expected BLOCK to be able to parse "a\n\na\na\n\na\na\na"
# ./parser.rb:169:in `block (2 levels) in <top (required)>'
36) RecurringGroupParser should parse aa aa aaa
Failure/Error: is_expected.to parse "a\na\n\na\na\n\na\na\na"
expected BLOCK to be able to parse "a\na\n\na\na\n\na\na\na"
# ./parser.rb:173:in `block (2 levels) in <top (required)>'
37) RecurringGroupParser should parse aaa aa aaa
Failure/Error: is_expected.to parse "a\naa\n\na\na\n\na\na\na"
expected BLOCK to be able to parse "a\naa\n\na\na\n\na\na\na"
# ./parser.rb:177:in `block (2 levels) in <top (required)>'
38) RecurringGroupParser should parse a aaa aaa
Failure/Error: is_expected.to parse "a\n\na\naa\n\na\na\na"
expected BLOCK to be able to parse "a\n\na\naa\n\na\na\na"
# ./parser.rb:181:in `block (2 levels) in <top (required)>'
39) RecurringGroupParser should parse aa aaa aaa
Failure/Error: is_expected.to parse "a\na\n\na\naa\n\na\na\na"
expected BLOCK to be able to parse "a\na\n\na\naa\n\na\na\na"
# ./parser.rb:185:in `block (2 levels) in <top (required)>'
40) RecurringGroupParser should parse aaa aaa aaa
Failure/Error: is_expected.to parse "a\naa\n\na\naa\n\na\na\na"
expected BLOCK to be able to parse "a\naa\n\na\naa\n\na\na\na"
# ./parser.rb:189:in `block (2 levels) in <top (required)>'
Finished in 0.01702 seconds (files took 0.26725 seconds to load)
40 examples, 40 failures
有关使用Parslet解析缩进的信息，请参见此问题.
see this question on parsing indentation with Parslet.
这篇关于解析降价缩进的代码块的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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