MDon

Stupid simple inline markdown fields used by the Polyestr application framework.

Features

• Hackable, zero-dependency, fast, lightweight (so nothing new).
• Auto-inject content from package.json.
• Include content from other files.
• Familiar syntax that is mostly template literal like.
• Embedded annotations without the need for source files.
• First-class opt-in support for using raw "source" files.
• Simple but elegant fault-tolerance to prevent malformed output.
• Doesn't mess with your YAML frontmatter!
• Works like a swiss-army knife instead of a shop - 3 concepts to get started.

Note: MDon is still highly experimental and is not yet cross-platform enabled, so if you managed to use it on Windows or Linux or worked-out quirks, please submit an issue, not a PR at this point, but feel free to gist.

Stay up-to-date by checking the changelog.

Installation

» yarn add mdon

CLI

MDon provides a CLI which is intended for use with scripts defined in your local package.json (assuming you follow the recommended practice of installing tools like MDon locally inside your projects). When MDon is installed locally, you can call the CLI by prefixing it with ./node_modules/.bin/ (or the equivalent relative to your local node_modules folder path).

To process README.md in the current directory simply execute:

» mdon

You can also list one or more markdown files to process them:

» mdon README.md OTHER.md

Additional (less-safe) Arguments

There are some other CLI features which are not fully tested so please use with care.

Your system might support using globs instead of listing each file:

» mdon *.md

You can specify a different package root as the first argument as long as the name of that folder doesn't look like a filename (aka no extension) but then you will have to prefix your markdown files (if any are supplied) with the same path prefix:

» mdon path/to/package path/to/package/*.md

The ./ in relative paths are optional:

» mdon relative/path/to/FILE.md
» mdon ./relative/path/to/FILE.md
» mdon /absolute/path/to/FILE.md

If you want to output to a different file you can only do so by appending a suffix to the name (before the extension) which must begin with a dot and include no spaces. So if you want README.md to be compiled to README.out.md you can do this:

» mdon .out

Important:

If any argument looks like a file extension MDon might treat it as a suffix argument so if your markdown files or package path "awkwardly" look like an extension, either rename them (pretty-please) or try preceeding such arguments with either -p or -m which is explained below.

Explicit Arguments

If you prefer to be more explicit about your arguments and marshal over some of the syntatic restrictions you can always use dash-styled markers:

» mdon -p path/to/package -m README.md OTHER.md -o .out
» mdon -p path/to/package -m README.md -o .out -m OTHER.md

But keep in mind that globs must always be relative to the current path. Also, you cannot specify a different projects or different suffixes so multiple -p or -o simply mean that the last one is used for all the markdown files.

Legacy Systems

If you get errors related to import/export then you might be running a NodeJS version that does not support ES modules. If that is the case consider using the CommonJS flavour of MDon:

» mdon~ …

This will execute and identical implementation which uses CJS-style require instead of ES module import/export.

Package Scripts

It is recommended when dealing with nested packages to always call MDon from the root of each package to prevent unintended outcomes.

If you need to call it from a different root follow this universal pattern:

» pushd path/to/package/root; mdon; popd;

Read more on pushd and popd on Wikipedia.

Also, avoid using globbs with ** which could match a markdown file in a nested package assuming it belongs to the top package, at which point it will simply use the top package's JSON fields in place of the nest one.

API

MDon is meant to be used from the command-line, however, you can still use it in your code through it's simple single-function interface which will process a single markdown file at a time (does not glob) and returns an object with the input and output strings.

  import mdon from 'mdon';

Or for legacy common-js:

  const mdon = require('mdon');

To process and write the file, mimicing the CLI's behavior:

  mdon('<path/to/package>', '<path/to/DOCUMENT.md>');

To capture the processed output after MDon writes the output:

  const {output} = mdon('<path/to/package>', '<path/to/DOCUMENT.md>');

To simply capture the processed output without writing the output:

  const {output} = mdon('<path/to/package>', '<path/to/DOCUMENT.md>', false);

To append a suffix to the name of the output file:

  mdon('<path/to/package>', '<path/to/DOCUMENT.md>', '.out');

To process the file and write the output to a different file (work in progress, use cautiously):

  mdon('<path/to/package>', '<path/to/DOCUMENT.md>', '<path/to/OUTPUT.md>');

Concepts

Fragments

Fragments are sections or regions that will be processed in the order by which they appear in markdown.

1. Fragments begin with a variant of an opening <?[ directive ]?> tag immediately at the start of a new line (no spaces).

2. This is followed by an optional body which ends with the closing <?!> tag also on a new line without spaces.

3. If it is not in a well-formed fragment it will come back to haunt you.

Directives

Directives are either a marker or a template literal expression enclosed between the <? and ?> of an opening tag.

1. Static tags starting with <? ?> make MDon hands-off till <?!>.

2. Generated tags starting with <?!?> make everything till <?!> sleep with the fishes (those are MDons business not yours).

3. Template tags starting with <? `MDon will obey your ${[interpolations]}` ?> make up everything that will take over till <?!>.

Interpolations

Template expressions follow standard javascript interpolations for the most part but they are evaluated in a sandboxed environment to prevent malicious or unintended mishaps.

1. ${displayName}: Any field in your package.json (only single property names or property paths are supported, not statements).

2. ${@<operation>( … args )}: MDon will, at least:

   a. Either ${@exists(path/to/file)} finds the file relative to the root of the package or it throws and you get nothing out.

   b. You can borrow ${@include(…/file)} from other files in your package.

   c. With ${@alias(<relative-or-absolute-url>)} you get [title][alias] instead of [title](<relative-or-absolute-url>), this means that you also will get see a line that looks like [alias]: <relative-or-absolute-url> at the end of the file, it's just how aliases work in markdown.

3. `${ {{displayName}} + ' ' + {{version}} }` is MDon's way of taking care of business if you decide that programming should be be something the MDon takes care of anyway, but honestly is `${displayName} ${version}` not good enought already… MDon always asks himself that question.

Latest Perks

Experimental Relative Paths:

Starting from v1.0.0-alpha.6 you may use relative paths to any operation which will be resolved relative to the path of the markdown file they appear in. So in stead of using absolute paths, you can now <?`${@include('./OTHER.md')}`?> to include it from the folder of the document your are authoring, similar to how relative ES modules and CSS imports work. Of course, unlike ES modules if your path does not begin with a './' it will actually be resolved relative to the root of your project not your node_modules!

Using Raw "Source" Paths:

A common and highly recommended structure when working with compiled files is to separate source files from compiled files, which is not a requirement for MDon since it can recompile from compiled files but may still be a more robust setup in case something goes wrong. To opt in to this behaviour the first line of the target file needs to be begin with <!--%path/to/source.md%-->.

So if you want your ./README.md to compile from ./docs/README.md then you can simply create a blank ./README.md and set the first line to <!--%docs/README.md%-->.

Safe Output by Default:

At the moment some package managers are working on fixes for misinterpretting syntax that should normally not be visible when rendering markdown content on their websites, so by default MDon will wrap fragments with <!--…--> in all files. In the future this will only be the default behaviour for files declaring a raw source like <!--%docs/README.md%-->.

Gotchas

1. If you don't match your <?…?> with a <?!> you'll be sorry, things tend to go missing so if you want static content that does not go swimming wrap those lines with the <? ?> on the line before and <?!> on the line after.

2. No plugins, so hack all you want, it's one file, copy it into your project and hack away, that's better than flooding your code with plugins.

3. MDon likes to put things in multiples of 3, you know, a-b-c, 1-2-3.

FAQ

Q: What could cause some markdown to show up as raw text or simply vanish instead of rendered HTML, when all fragments seem to be properly terminated?

A: If all your fragments are terminated correctly, then the likely cause of this behavior is that you did not wrap this section in a static fragment. It was a design choice to use <?!> as the terminator, knowing that for major markdown breaks as they expect such tags to look more like <?…?>. This meant that any thing that followed this closing tag can and will likely break when parsed. That's why static fragment wrapper is highly encouraged, as most parsers will overcome the side-effects of malformed <?!> once they hit a properly formed one.

Q: What can cause the body of a fragment that used to be processed correctly to suddenly disappear if the same directive used to work fine previously.

A: If any errors occur while parsing a directive, the entire fragment will be replaced by an HTML comment containing the message from the exception. This should provide some hint on what would have cause the directive to fail without bloating MDon's code with more complex debugging mechanism. If you can't figure out the reason from this message, you can try using your prefered node debugger.

Q: What could cause an entire fragment (directive and body) to always get dropped even after manually putting it back?

A: This is a good time to file an issue so we can figure out where MDon can evolve to meet your practical needs.

Last Updated: Monday, October 23, 2017, 9:52:10 PM UTC