pipe_tables seems to have broken syntax depending on the table size in input

[cderv]

Full context of how this was found at quarto-dev/quarto-cli#8332

For a long pipe tables like this (in file test.md for example)

|V1 |V2 |V3 |V4 |V5 |V6 |V7 |V8 |V9 |V10 |V11 |V12 |V13 |V14 |V15 |V16 |V17 |V18 |V19 |V20 |V21 |V22 |V23 |V24 |V25 |V26 |V27 |V28 |V29 |V30 |V31 |V32 |V33 |V34 |V35 |V36 |V37 |V38 |V39 |V40 |V41 |V42 |V43 |V44 |V45 |V46 |V47 |V48 |V49 |V50 |V51 |V52 |V53 |V54 |V55 |V56 |V57 |V58 |V59 |V60 |V61 |V62 |V63 |V64 |V65 |V66 |V67 |V68 |V69 |V70 |V71 |V72 |
|:--|:--|:--|:--|:--|:--|:--|:--|:--|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|
|1  |2  |3  |4  |5  |6  |7  |8  |9  |10  |11  |12  |13  |14  |15  |16  |17  |18  |19  |20  |21  |22  |23  |24  |25  |26  |27  |28  |29  |30  |31  |32  |33  |34  |35  |36  |37  |38  |39  |40  |41  |42  |43  |44  |45  |46  |47  |48  |49  |50  |51  |52  |53  |54  |55  |56  |57  |58  |59  |60  |61  |62  |63  |64  |65  |66  |67  |68  |69  |70  |71  |72  |

It will produce a pipe table with no - and only :

$ pandoc -f markdown -t markdown_strict+pipe_tables test.md
| V1  | V2  | V3  | V4  | V5  | V6  | V7  | V8  | V9  | V10 | V11 | V12 | V13 | V14 | V15 | V16 | V17 | V18 | V19 | V20 | V21 | V22 | V23 | V24 | V25 | V26 | V27 | V28 | V29 | V30 | V31 | V32 | V33 | V34 | V35 | V36 | V37 | V38 | V39 | V40 | V41 | V42 | V43 | V44 | V45 | V46 | V47 | V48 | V49 | V50 | V51 | V52 | V53 | V54 | V55 | V56 | V57 | V58 | V59 | V60 | V61 | V62 | V63 | V64 | V65 | V66 | V67 | V68 | V69 | V70 | V71 | V72 |
|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|:|
| 1   | 2   | 3   | 4   | 5   | 6   | 7   | 8   | 9   | 10  | 11  | 12  | 13  | 14  | 15  | 16  | 17  | 18  | 19  | 20  | 21  | 22  | 23  | 24  | 25  | 26  | 27  | 28  | 29  | 30  | 31  | 32  | 33  | 34  | 35  | 36  | 37  | 38  | 39  | 40  | 41  | 42  | 43  | 44  | 45  | 46  | 47  | 48  | 49  | 50  | 51  | 52  | 53  | 54  | 55  | 56  | 57  | 58  | 59  | 60  | 61  | 62  | 63  | 64  | 65  | 66  | 67  | 68  | 69  | 70  | 71  | 72  |

This seems to be broken syntax as even Pandoc can't read it as Table

$ pandoc -f markdown -t markdown_strict+pipe_tables test.md | pandoc -t native -f markdown_strict+pipe_tables | head -10
[ Para
    [ Str "|"
    , Space
    , Str "V1"
    , Space
    , Str "|"
    , Space
    , Str "V2"
    , Space
    , Str "|"

while the original can be read

$ pandoc -t native -f markdown_strict+pipe_tables test.md | head -10
[ Table
    ( "" , [] , [] )
    (Caption Nothing [])
    [ ( AlignLeft , ColWidth 1.0752688172043e-2 )
    , ( AlignLeft , ColWidth 1.0752688172043e-2 )
    , ( AlignLeft , ColWidth 1.0752688172043e-2 )
    , ( AlignLeft , ColWidth 1.0752688172043e-2 )
    , ( AlignLeft , ColWidth 1.0752688172043e-2 )
    , ( AlignLeft , ColWidth 1.0752688172043e-2 )
    , ( AlignLeft , ColWidth 1.0752688172043e-2 )

This happens only after a certain number of column in the table. Removing only one in the above (71 instead of 72) produces some -

$ pandoc -f markdown -t markdown_strict+pipe_tables test.md
| V1  | V2  | V3  | V4  | V5  | V6  | V7  | V8  | V9  | V10 | V11 | V12 | V13 | V14 | V15 | V16 | V17 | V18 | V19 | V20 | V21 | V22 | V23 | V24 | V25 | V26 | V27 | V28 | V29 | V30 | V31 | V32 | V33 | V34 | V35 | V36 | V37 | V38 | V39 | V40 | V41 | V42 | V43 | V44 | V45 | V46 | V47 | V48 | V49 | V50 | V51 | V52 | V53 | V54 | V55 | V56 | V57 | V58 | V59 | V60 | V61 | V62 | V63 | V64 | V65 | V66 | V67 | V68 | V69 | V70 | V71 |
|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|:-|
| 1   | 2   | 3   | 4   | 5   | 6   | 7   | 8   | 9   | 10  | 11  | 12  | 13  | 14  | 15  | 16  | 17  | 18  | 19  | 20  | 21  | 22  | 23  | 24  | 25  | 26  | 27  | 28  | 29  | 30  | 31  | 32  | 33  | 34  | 35  | 36  | 37  | 38  | 39  | 40  | 41  | 42  | 43  | 44  | 45  | 46  | 47  | 48  | 49  | 50  | 51  | 52  | 53  | 54  | 55  | 56  | 57  | 58  | 59  | 60  | 61  | 62  | 63  | 64  | 65  | 66  | 67  | 68  | 69  | 70  | 71  |

and it can be read

$ pandoc -f markdown -t markdown_strict+pipe_tables test.md | pandoc -t native -f markdown_strict+pipe_tables | head -10
[ Table
    ( "" , [] , [] )
    (Caption Nothing [])
    [ ( AlignLeft , ColWidth 1.4084507042253521e-2 )
    , ( AlignLeft , ColWidth 1.4084507042253521e-2 )
    , ( AlignLeft , ColWidth 1.4084507042253521e-2 )
    , ( AlignLeft , ColWidth 1.4084507042253521e-2 )
    , ( AlignLeft , ColWidth 1.4084507042253521e-2 )
    , ( AlignLeft , ColWidth 1.4084507042253521e-2 )
    , ( AlignLeft , ColWidth 1.4084507042253521e-2 )

I did not found the pipe tables specs, but the syntax without the - works in some only markdown table previewer, but other tools like Pandoc does not recognize it as a table (docusaurus MDX in our case)

[jgm]

Relevant code: https://github.com/jgm/pandoc/blob/main/src/Text/Pandoc/Writers/Markdown/Table.hs#L49-L72

[jgm]

                          AlignLeft    -> ":" <> T.replicate (w + 1) "-"

For this to happen, one of the pipeWidths would have to be negative.

[jgm]

So if colwidth is 72, and the number of columns is 72, then

                            (floor . (* fromIntegral (colwidth - (numcols +1))))

is negative. We can add code that ensures that this value is >= 1.

[jgm]

A workaround for now would be to specify a larger value with --columns.