Remove markdown wiki-link brackets during pandoc exports

remove_links.py

#!/usr/bin/env python3

from pandocfilters import toJSONFilter, Str
import re

def replace(key, value, format, meta):
    if key == 'Str':
        if '[[' in value:
            new_value = value.replace('[[', '')
            return Str(new_value)
        if ']]' in value:
            new_value = value.replace(']]', '')
            return Str(new_value)

if __name__ == '__main__':
    toJSONFilter(replace)

You can install it using pip, but I tried installing it with conda instead in an isolated environment just in case.

conda create -n pandoc
conda install -c conda-forge pandocfilteres
conda activate pandoc

Before any filtering is done, pandac parses markdown file into abstract syntax tree (AST). I took a look at what the tree looks like for a simple markdown with a single line: [[@citekey]]. The string is actually broken into three blocks: [, [@citekey], and ]. So there would be no string that contains [[ or ]], therefore this pandocfilter script didn't work. Similary for the lua filters, replacing [[ or ]] doesn't work.

Both pandocfilter and lua filter would work if we replace [ and ] with ''.

Here is what the AST looks like

List of 3
 |-pandoc-api-version:List of 4
 |  |-: int 1
 |  |-: int 22
 |  |-: int 2
 |  |-: int 1
 |-meta              : Named list()
 |-blocks            :List of 1
    |-:List of 2
       |-t: chr "Para"
       |-c:List of 3
          |-:List of 2
          |  |-t: chr "Str"
          |  |-c: chr "["
          |-:List of 2
          |  |-t: chr "Cite"
          |  |-c:List of 2
          |     |-:List of 1
          |     |  |-:List of 6
          |     |     |-citationId     : chr "citekey"
          |     |     |-citationPrefix : list()
          |     |     |-citationSuffix : list()
          |     |     |-citationMode   :List of 1
          |     |     |  |-t: chr "NormalCitation"
          |     |     |-citationNoteNum: int 1
          |     |     |-citationHash   : int 0
          |     |-:List of 1
          |        |-:List of 2
          |           |-t: chr "Str"
          |           |-c: chr "[@citekey]"
          |-:List of 2
             |-t: chr "Str"
             |-c: chr "]"

Thanks for this great insight @racng . I was able to make this change and get it work except I noticed that the back end of the link did not get filtered correctly.
It went from [[name]] to name] . I found it odd that it was able to replace [[ but only one of the ]

This is the modified code I am using,
#!/usr/bin/env python3

from pandocfilters import toJSONFilter, Str
import re

def replace(key, value, format, meta):
if key == 'Str':
if '[' in value:
new_value = value.replace('[', '')
return Str(new_value)
if ']' in value:
new_value = value.replace(']', '')
return Str(new_value)

if name == 'main':
toJSONFilter(replace)

Thanks for the original filter code @maybemkl! I was hitting the same problem as @aravindk100 in that the filter would not find the closing ]] characters, so I modified the script to take advantage of some newer Python 3.8 features which also greatly simplifies the code. Here's my version:

#!/usr/bin/env python3

from pandocfilters import toJSONFilter, Str
import re

def replace(key, value, format, meta):
    if key == 'Str':
        if match := re.search('\[\[(.+)\]\]',value,re.IGNORECASE):
           new_value = match.group(1)
           return Str(new_value)

if __name__ == '__main__':
    toJSONFilter(replace)

Thank you all, this is really helpful, especially when exporting linked notes from Obsidian through pandoc!

Apparently there seemed to be an invalid escape sequence. The regex pattern '\[\[(.+)\]\]' contains backslashes (\). In Python strings, \[ and \] could be misinterpreted as escape sequences. A raw string (r"") tells Python to ignore escape sequences, so \[ and \] are treated as literal brackets instead of escape sequences.

This is the improved version (with help of ChatGTP):

#!/usr/bin/env python3

from pandocfilters import toJSONFilter, Str
import re

def replace(key, value, format, meta):
    if key == 'Str':
        if match := re.search(r'\[\[(.+)\]\]', value, re.IGNORECASE):
            new_value = match.group(1)
            return Str(new_value)

if __name__ == '__main__':
    toJSONFilter(replace)