markdown writer appends blank line at end of file

[aaren]

pandoc 1.13.1 adds a blank line to the end of text that does not already end in a blank line, i.e.

$ echo -ne "some text\n"
some text
$ echo -ne "some text\n" | pandoc --to markdown
some text

$

$ echo -ne "some text\n\n" | pandoc --to markdown
some text

$

Compared to the behaviour in e.g. 1.11.1, which is to strip all blank lines:

$ echo -ne "some text\n" | pandoc-1.11.1 --to markdown
some text
$

$ echo "some text\n\n" | pandoc-1.11.1 --to markdown
some text
$

I would like pandoc to respect my input and not add or remove blank lines.

[jgm]

Blank lines aren't represented at all in the internal document model.
They are significant in indicating breaks between paragraphs, etc., but
otherwise ignored. So, for example, if you put two blank lines instead
of one between paragraphs, you'll get output with one blank line. That
won't change.

What I could probably do is ensure that, if the output already ends with a
newline, an extra newline isn't inserted. Currently, when generating a
fragment, we just slap a newline onto the output of the writer, since
some of the writers don't produce output that ends in a newline. We
could instead check first to see if the output ends in a newline.
This would have a small performance cost.

+++ aaren [Oct 20 14 12:16 ]:

pandoc 1.13.1 adds a blank line to the end of text that does not already end in a blank line, i.e.

$ echo -ne "some text\n"
some text
$ echo -ne "some text\n" | pandoc --to markdown
some text

$

$ echo -ne "some text\n\n" | pandoc --to markdown
some text

$

Compared to the behaviour in e.g. 1.11.1, which is to strip all blank lines:

$ echo -ne "some text\n" | pandoc-1.11.1 --to markdown
some text

$ echo "some text\n\n" | pandoc-1.11.1 --to markdown
some text

I would like pandoc to respect my input and not add or remove blank lines.

---

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#1705

[aaren]

Right, so the markdown writer is just adding a blank line after each Para. If you end the text with some other block element then this doesn't occur, e.g.

$ echo -ne 'some text\n\n```{.code}\ncode\n```\n\n\n' | pandoc --to markdown
some text

``` {.code}
code
```
$

But yes, checking for the existence of a finishing newline before adding one is the way to go I think.

[jgm]

It's actually a bit more subtle than that. We use a custom
prettyprinter to add the blank lines after the paragraphs, and
it is smart enough not to add one at the end. So if you use
the library,

writeMarkdown def (Pandoc nullMeta [Para [Str "hi"]])

you'll get the output

"hi\n"

The extra newline is appended in pandoc.hs, since not all writers
behave this well.

+++ aaren [Oct 20 14 13:15 ]:

Right, so the markdown writer is just adding a blank line after each Para. If you end the text with some other block element then this doesn't occur, e.g.

$ echo -ne 'some text\n\n{.code}\ncode\n\n\n\n' | pandoc --to markdown
some text

   code

$

But yes, checking for the existence of a finishing newline before adding one is the way to go I think.

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#1705 (comment)

[aaren]

I'm not sure I understand then. If the prettyprinter isn't adding the blank line then where is it coming from? If it is added by pandoc.hs then shouldn't text that ends with a CodeBlock also end up with a blank line added at the end?

[jgm]

You raise a good point. I think I see what is going on here, but it
will need to wait til I can find time to look into it further.

+++ aaren [Oct 20 14 13:58 ]:

I'm not sure I understand then. If the prettyprinter isn't adding the blank line then where is it coming from? If it is added by pandoc.hs then shouldn't text that ends with a CodeBlock also end up with a blank line added at the end?

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#1705 (comment)

[aaren]

Works for me, in that the old behaviour is recovered and pandoc no longer leaves a blank line at the end of the file.