Fenced code block must be preceded by an empty line

[thallgren]

I'm using a PegDownProcessor created with Extensions.ALL as a replacement for ruby code that used the github-markdown gem. Most things work seamlessly but there's a difference in how fenced code blocks are handled. This text:

Code example

```ruby
a = b
```

formats OK using PegDown and the resulting html contains a <code class="ruby"> element. This text however:

Code example
```ruby
a = b
```

will instead yield <code>ruby e.g. the 'ruby' is no longer a class attribute, instead it becomes visible text in the output.

The only difference between the two examples is that an empty line precedes the fenced block in the first one.

[thallgren]

Some debugging shows that the gets FencedCodeBlock is eaten by the NonLinkInline rule that adds a Code rule.

[sirthias]

Yes, currently a fenced code block must be separated by other block elements with an empty line.

[thallgren]

Any chance that this may change?

[sirthias]

You could submit a PR with a fix... :)

[thallgren]

I know. I actually set out to do just that but realized that it wasn't trivial. First I need to learn new parser technology, then new build technology, and finally test technology that I haven't been using either. I can't motivate the time it would take to do that right now. Someone with the right skill-set can probably solve the problem in a faction of the time I'd need to spend.

[sirthias]

I see, no worries. This is what github is for. I'll keep this ticket open.

[takkuumi]

I want to know how to do it too,i meet the same with @thallgren 's problom

[takkuumi]

@thallgren @sirthias I have solved this problem,i just show my code here.

1.You should add a class in plugins package named CodeParser.java

package org.pegdown.plugins;

import org.parboiled.BaseParser;
import org.parboiled.Rule;
import org.parboiled.support.StringBuilderVar;
import org.pegdown.Parser;
import org.pegdown.ast.VerbatimNode;

/**
 * Created by ling on 2015/3/30.
 */
public class CodeParser extends Parser implements InlinePluginParser {
    private final String TAG = "```";

    public CodeParser() {
        super(ALL, 1000L, DefaultParseRunnerProvider);
    }

    @Override
    public Rule[] inlinePluginRules() {
        return new Rule[]{
                codeInline()
        };
    }

    public Rule codeInline() {
        StringBuilderVar language = new StringBuilderVar();
        StringBuilderVar code = new StringBuilderVar();
        return NodeSequence(
                Sequence(
                        TAG,
                        OneOrMore(
                                TestNot('\n'),
                                BaseParser.ANY,
                                language.append(matchedChar()
                                )
                        ),
                        push(language.getString().trim())
                ),
                Sequence(
                        OneOrMore(
                                TestNot(TAG),
                                BaseParser.ANY,
                                code.append(matchedChar())
                        ),
                        push(code.getString().trim())
                ),
                TAG,
                push(
                        new VerbatimNode(
                                (String) pop(),
                                (String) pop()
                        )
                )
        );
    }
}

2.You need to regist the CodeParser into the plugins.It look like this:

 private static PegDownPlugins plugins;
    private static PegDownProcessor processor;

    static {
        plugins = PegDownPlugins.builder().withPlugin(EmojiParser.class).withPlugin(CodeParser.class).build();
        processor = new PegDownProcessor(Extensions.ALL, plugins);
    }

this is my own main demo

import org.apache.commons.lang3.StringEscapeUtils;
import org.pegdown.Extensions;
import org.pegdown.PegDownProcessor;
import org.pegdown.plugins.CodeParser;
import org.pegdown.plugins.EmojiParser;
import org.pegdown.plugins.PegDownPlugins;

import java.io.UnsupportedEncodingException;

/**
 * Created by ling on 2015/3/26.
 */
public class Test {

    private static PegDownPlugins plugins;
    private static PegDownProcessor processor;

    static {
        plugins = PegDownPlugins.builder().withPlugin(EmojiParser.class).withPlugin(CodeParser.class).build();
        processor = new PegDownProcessor(Extensions.ALL, plugins);
    }

    /**
     * markdown to HTML
     *
     * @param content
     * @return
     */
    public static String markdownToHtml(String content) {
        try {
            content = StringEscapeUtils.unescapeHtml4(content);
            content = processor.markdownToHtml(content);
            return content;
        } catch (Exception e) {
            return content;
        }
    }

    public static void main(String[] args) throws UnsupportedEncodingException {
        String md = "1111111111111\n" +
                "``` c\n" +
                "int main(){\n" +
                "   return 0;\n" +
                "}\n" +
                "```";
        System.out.println(StringEscapeUtils.unescapeHtml4(markdownToHtml(new String(md))));
    }
}

[sirthias]

Closing as suggested by @vsch in #181.