Site, page and nav variables

When a markdown file (or other supported content) is rendered, the Mako template receives a number of context variables as partly described above. A few of these variables, such as MDTEMPLATES and DATADIR set directly by wmk (see above). Others are user-configured either (1) in wmk_config.yaml (the contents of the site object and potentially additional “global” varaibles in template_context); or (2) the cascade of index.yaml files in the content directory and its subdirectories along with the YAML frontmatter of the markdown file itself, the result of which is placed in the page object.

When gathering the content of the page variable, wmk will start by looking for index.yaml files in each parent directory of the markdown file in question, starting at the root of the content directory and moving upwards, at each step extending and potentially overriding the data gathered at previous stages. Only then will the YAML in the frontmatter of the file itself be parsed and added to the page data.

The file-specific frontmatter may be in the content file itself, or it may be in a separate YAML file with the same name as the content file but with an extra .yaml extension. For instance, if the content filename is important.md, then the YAML file would be named important.md.yaml. If both in-file and external frontmatter is present, the two will be merged, with the in-file values “winning” in case of conflict.

At any point, a data source in this cascade may specify an extra YAML file using the special LOAD variable. This file will then be loaded as well and subsequently treated as if the data in it had been specified directly at the start of the file containing the LOAD directive.

Which variables are defined and used by templates is very much up the user, although a few of them have a predefined meaning to wmk itself. For making it easier to switch between different themes it is however suggested to stick to the following meaning of some of the variables:

The variables site and page are dicts with a thin convenience layer on top which makes it possible to reference subkeys belonging to them in templates using dot notation rather than subscripts. For instance, if page has a dict variable named foo, then a template could contain a fragment such as ${ page.foo.bar or 'splat' } – even if the foo dict does not contain a key named bar. Without this syntactic sugar you would have to write something much more defensive and long-winded such as ${ page.foo.bar if page.foo and 'bar' in page.foo else 'splat' }.

The `nav` variable

The nav key in the wmk_config.yaml file, if present, will be treated as a navigation tree for the site and represented as a tree-like Nav object.

A typical nav setting looks something like this:

nav:
    - Home: /
    - User Guide:
        - Lorem:
            - Ipsum: /guide/ipsum/
            - Eu fuit: /guide/mageisse/
        - Dolor sit amet: /guide/concupescit/
    - Resources:
        - Community: 'https://example.com/'
        - Source code: 'https://github.com/example/com/'
    - About:
        - License: /about/license/
        - History: /about/history/

In templates, this will be available as the nav variable.

There are two types of entries in the nav: links and sections. A link is just a title and an URL. A section has a title and a list of links or sections (possibly nested).

Each item has a parent (with the nav itself as the top level parent) and a level (starting from 0 for the immediate children of the nav). The nav has a homepage attribute which by default is the first local link in the nav. Each local link has previous and next attributes. Each section has children. There are other attributes but these are the basics.

The nav variable is relatively new (as of version 1.2.x, May 2023) and not really supported by themes yet. It is especially intended for sites with a hierarchical structure but neither very many pages nor deeply nested, such as a typical documentation site.

The `TOC` variable

When a page is rendered, the generated HTML is examined and a simple table of contents object constructed, which will be available to templates as TOC. It contains a list of the top-level headings (i.e. H1 headings, or H2 headings if no H1 headings are present, etc.), with lower-level headings hierarchically arranged in its children. Other attributes are url and title. TOC.item_count contains the heading count (regardless of nesting).

The TOC variable can e.g. be used by the page template to show a table of contents elsewhere on the page.

The table of contents object is not constructed unless each heading has an id attribute. When using the default python-markdown, this means that the toc extension must be active.

System variables

The following frontmatter variables affect the operation of wmk itself, rather than being exclusively handled by Mako templates.

Templates

Note that a variable called something like page.foo below is referenced as such in Mako templates but specified in YAML frontmatter simply as foo: somevalue.

page.template specifies the Mako template which will render the content.
page.layout is used by several other static site generators. For compatibility with them, this variable is supported as a fallback synonym with template. It has no effect unless template has not been specified explicitly anywhere in the cascade of frontmatter data sources.

For both template and layout, the .mhtml extension of the template may be omitted. If the template value appears to have no extension, .mhtml is assumed; but if the intended template file has a different extension, then it of course cannot be omitted.

Likewise, a leading base/ directory may be omitted when specifying template or layout. For instance, a layout value of post would find the template file base/post.mhtml unless a post.mhtml file exists in the template root somewhere in the template search path.

If neither template nor layout has been specified and no default_template setting is found in wmk_config.yaml, the default template name for markdown files is md_base.mhtml.

Affects rendering

page.slug: If the value of slug is nonempty and consists exclusively of lowercase alphanumeric characters, underscores and hyphens (i.e. matches the regular expression ^[a-z0-9_-]+$), then this will be used instead of the basename of the markdown file to determine where to write the output. If a slug variable is missing, one will be automatically added by wmk based on the basename of the current markdown file. Templates should therefore be able to depend upon slugs always being present. Note that slugs are not guaranteed to be unique, although that is good practice.
page.pretty_path: If this is true, the basename of the markdown filename (or the slug) will become a directory name and the HTML output will be written to index.html inside that directory. By default it is false for files named index.md or index.html and true for all other files. If the filename contains symbols that do not match the character class [\w.,=-], then it will be “slugified” before final processing (although this only works for languages using the Latin alphabet).
page.do_not_render: Tells wmk not to write the output of this template to a file in htdocs. All other processing will be done, so the gathered information can be used by templates for various purposes. (This is similar to the headless setting in Hugo).
page.draft: If this is true, it prevents further processing of the markdown file unless render_drafts has been set to true in the config file.
page.no_cache: If this is true, the rendering cache will not be used for this file. (See also the use_cache setting in the configuration file).
page.markdown_extensions, page.markdown_extension_configs, page.pandoc, page.pandoc_filters, page.pandoc_options, page.pandoc_input_format, page.pandoc_output_format: See the description of these options in the section on the configuration file, above.
page.POSTPROCESS: This contains a list of processing instructions which are called on the rendered HTML just before writing it to the output directory. Each instruction is either a function (placed into POSTPROCESS by a shortcode) or a string (possibly specified in the frontmatter). If the latter, it points to a function entry in the autoload dict imported from either the project’s py/wmk_autoload.py file or the theme’s py/wmk_theme_autoload.py file. In either case, the function receives the html as the first argument while the rest of the arguments constitute the template context. It should return the processed html.
page.PREPROCESS: This is analogous to page.POSTPROCESS, except that the instructions in the list are applied to the markdown (or other content document) just before converting it to HTML. The function receives two arguments: the document text and the page object. It should return the altered document source. Note that this happens before shortcodes have been expanded, so (unlike page.POSTPROCESS) such actions cannot be added via shortcode.

Note that if two files in the same directory have the same slug, they may both be rendered to the same output file; it is unpredictable which of them will go last (and thus “win the race”). The same kind of conflict may arise between a slug and a filename or even between two filenames containing non-ascii characters. It is up to the content author to take care to avoid this; wmk does nothing to prevent it.

Standard variables and their recommended meaning

The following variables are not used directly by wmk but affect templates in different ways. It is a list of recommendations rather than something which must be necessarily followed.

Typical site variables

Site variables are the keys-value pairs under site: in wmk_config.yaml.

site.title: Name or title of the site.
site.lang: Language code, e.g. ‘en’ or ‘en-us’. Used e.g. for translations by some themes.
site.locale: Locale code, e.g. ‘en_US.utf8’. Used when sorting MDCONTENT by name or title.
site.tagline: Subtitle or slogan.
site.description: Site description.
site.author: Main author/proprietor of the site. Depending on the site templates (or the theme), may be a string or a dict with keys such as “name”, “email”, etc.
site.base_url: The protocol and hostname of the site (perhaps followed by a directory path if site.leading_path is not being used). Normally without a trailing slash.
site.leading_path: If the web pages built by wmk are not at the root of the website but in a subdirectory, this is the appropriate prefix path. Normally without a trailing slash.
site.build_time: This is automatically added to the site variable by wmk. It is a datetime object indicating when the rendering phase of the current run started.
site.lunr_search: A boolean automatically added to the site variable. It is true when lunr_index is true in the configuration file.

Templates or themes may be configurable through various site variables, e.g. site.paginate for number of items per page in listings or site.mainfont for configuring the font family.

Classic meta tags

These variables mostly relate to the text content and affect the metadata section of the <head> of the HTML page.

page.title: The title of the page, typically placed in the <title> tag in the <head> and used as a heading on the page. Normally the title should not be repeated as a header in the body of the markdown file. Most markdown documents should have a title. If it is not explicitly specified, the title will be generated automatically from the filename.
page.slug: See above. If it is missing, the slug is created from the title.
page.id: This is guaranteed to be unique at rendering time. If it is present but not unique, then “-1”, “-2”, etc., will be appended as necessary. If it is not explicitly specified, then it is generated by slugifying the full path to the source markdown file (relative to the content directory). For instance, blog/2022/09/The letter Þ in Old English.md will become the ID blog-2022-09-the-letter-th-in-old-english.
page.description: Affects the <meta name="description" ...> tag in the <head> of the page. The variable summary (see later) may also be used as fallback here.
page.keywords: Affects the <meta name="keywords" ...> tag in the <head> of the page. This may be either a list or a string (where items are separated with commas).
page.robots: Instructions for Google and other search engines relating to this content (e.g. noindex, nofollow) should be placed in this variable.
page.author: The name of the author (if there is only one). May lead to <meta name="keywords" ...> tag in the <head> as well as appear in the body of the rendered HTML file. Some themes may expect this to be a dict with keys such as name, email, image, etc.
page.authors: If there are many authors they may be specified here as a list. It is up to the template how to handle it if both author and authors are specified, but one way is to add the author to the authors unless already present in the list.
page.summary: This may affect the <meta name="description" ...> tag as a fallback if no description is provided, but its main purpose is for list pages with article teasers and similar content.

Note that this is by no means an exhaustive list of variables likely to affect the <head> of the page. Notably, several other variables may affect meta tags used for sharing on social media. The most common is probably page.image (described below). In any case, the implementation itself is up to the theme or template author.

Dates

Dates and datetimes should normally be in a format conformant with or similar to ISO 8601, e.g. 2021-09-19 and 2021-09-19T09:19:21+00:00. The T may be replaced with a space and the time zone may be omitted (localtime is assumed). If the datetime string contains hours it should also contain minutes, but seconds may be omitted. If these rules are followed, the following variables are converted to date or datetime objects (depending on the length of the string) before they are passed on to templates.

page.date: A generic date or datetime associated with the document.
page.pubdate: The date/datetime when first published. Currently wmk does not skip files with pubdate in the future, but it may do so in a later version.
page.modified_date: The last-modified date/datetime. Note that wmk will also add the variable MTIME, which is the modification time of the file containing the markdown source, so this information can be inferred from that if this variable is not explicitly specified.
page.created_date: The date the document was first created.
page.expire_date: The date from which the document should no longer be published. Similarly to pubdate, this currently has no direct effect on wmk but may do so in a later version.

See also the description of the DATE and MTIME context variables above.

Media content

page.image: The main image associated with the document. Affects the og:image meta tag in HTML output and may be used for both teasers and content rendering.
page.images: A list of images associated with the document. If image is not specified, the main image will be taken to be the first in the list.
page.audio: A list of audio files/urls associated with this document.
page.videos: A list of video files/urls associated with this document.
page.attachments: A list of attachments (e.g. PDF files) associated with this document.

Taxonomy

page.section: One of a quite small number of sections on the site, often corresponding to the leading subdirectory in content. E.g. “blog”, “docs”, “products”.
page.categories: A list of broad categories the page belongs to. E.g. “Art”, “Science”, “Food”. The first-named category may be regarded as the primary one.
page.tags: A list of tags relevant to the content of the page. E.g. “quantum physics”, “knitting”, “Italian food”.
page.weight: A measure of importance attached to a page and used as an ordering key for a list of pages. This should be a positive integer. The list is normally ascending, i.e. with the lower numbers at the top. (Pages may of course be ordered by other criteria, e.g. by pubdate).

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Site, page and nav variables