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Utils for converting headers to anchors for different backends

Project description


HeaderAnchors is a module which converts heading titles into IDs just like it is done by specific backends.

Module exports three main functions:

  • to_id which converts a title into an ID by the rules of specific backend,
  • make_unique which adds a digit to make duplicate heading ID unique, according to the rules of specific backend.
  • is_flat which determines whether backend uses flatten preprocessor or not.


All Foliant backends add anchors to each heading to make it possible to reference headings in URLs. The problem is that each backend has its own way to do that. For example, the heading My wife's birthday-party will get an ID my-wifes-birthday-party in Pandoc, header-my-wife’s-birthday-party in aglio and my-wife-39-s-birthday-party in slate.

Moreover, different backends have different ways to deal with duplicate IDs. Utils in this module help you cope with these problems.


To use functions from this module, first install it with command

pip3 install foliantcontrib.utils.header_anchors

Then import the main functions:

>>> from foliant.preprocessors.utils.header_anchors import to_id, make_unique, is_flat


Feed a header title to the to_id function to get the proper id for each backend:

>>> title = "My wife's birthday-party"
>>> to_id(title, 'pandoc')
>>> to_id(title, 'aglio')
>>> to_id(title, 'slate')

available backends:

param backend
'pandoc' Pandoc
'mdtopdf' MdToPdf
'aglio' Aglio
'mkdocs' MkDocs
'slate' Slate
'confluence' Confluence
'no_transform' no transformations, return string as is

If the name of the backend is not recognized, pandoc will be used as a fallback backend:

>>> to_id(title, 'nonexistent backend')


If some headers in the document have the same title or their IDs match, each backend transforms the ID for it to remain unique. Pandoc adds subsequent numbers with a hyphen, MkDocs — numbers with an unerscore.

make_unique function handles the proper transformations for you. Feed it an id, backend name and number of occurrences of this title in the document to get the proper unique id:

>>> make_unique('my-title', 3, 'pandoc')
>>> make_unique('my-title', 3, 'mkdocs')
>>> make_unique('my-title', 3, 'slate')

If the name of the backend is not recognized, pandoc will be used as a fallback backend:

>>> make_unique('my-title', 3, 'nonexistent backend')


is_flat function takes the backend name as parameter and returns True if backend uses flatten preprocessor to make a single file out of all chapters.

>>> is_flat('pandoc')
>>> is_flat('mkdocs')

IDGenerator class

IDGenerator is a class which helps generate unique anchors in seemless way. It records every call to generate an anchor from a title, and if the anchor repeats, it calls make_unique to make it unique.

Here's an example usage:

>>> from foliant.preprocessors.utils.header_anchors import IDGenerator
>>> idgen = IDGenerator('pandoc')
>>> idgen.generate('My title')
>>> idgen.generate('Another title!')
>>> idgen.generate('My title')

After generating id for My title for a second time generator had added a -1 to it. To reset the id count call the reset method:

>>> idgen.reset()
>>> idgen.generate('My title')

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