metalsmith-metafiles

A Metalsmith plugin to read file metadata from separate files (as an alternative to frontmatter).

For example, when using this plugin you could add metadata to a file named index.html by creating a file named index.html.meta.json and putting your metadata in that file.

Why choose this method over frontmatter? While frontmatter is a convenient way to set metadata in your files, it can cause problems with syntax highlighters, linters, and other tools which expect your source files to contain only valid syntax from the language they are written in. (Frontmatter isn't valid CSS, HTML, JavaScript, etc.) Putting your metadata in separate files eliminates these problems.

Currently, metalsmith-metafiles supports the JSON, YAML, CSON, and TOML formats, among others. (See the parsers section below for details.)

Installation

npm install --save metalsmith-metafiles

CLI Usage

After installing metalsmith-metafiles, simply add the metalsmith-metafiles key to the plugins in your metalsmith.json file. Be sure to include it before any plugins which need to use the metadata in your metadata files. Generally speaking, this means that metalsmith-metafiles should be the first plugin in the list.

{
  "frontmatter": false, // Optionally disable frontmatter parsing
  "plugins": {
    "metalsmith-metafiles": {
      // Options here
    },
    // Other plugins...
  }
}

JavaScript Usage

After installing metalsmith-metafiles, you can require metalsmith-metafiles in your code, then call the exported value to initialize the plugin and pass the result to Metalsmith.use (just as you would with any other Metalsmith plugin). Again, be sure to use metalsmith-metafiles before any plugins which need to use the metadata defined your metadata files. Generally speaking, this means that metalsmith-metafiles should be the first plugin in the list.

var metafiles = require('metalsmith-metafiles');
 
Metalsmith(__dirname)
  .frontmatter(false) // Optionally disable frontmatter parsing
  .use(metafiles({
    // Options here
  }))
  .use(/* Other plugins... */)
  .build(function(err) {
    if (err) throw err;
  });

Options

metalsmith-metafiles supports the following configuration options:

deleteMetaFiles

Type: Boolean

Default: true

Determines whether metadata files are removed from the generated site.

For example, setting this option to false would result in your .meta.json files being put in your destination directory when you build the site. (Unless of course they're removed by some other plugin.)

postfix

Type: String

Default: .meta

The postfix added to filenames to indicate they are metadata files. This doesn't include the file extension, only the extra text before the extension.

For example, setting this option to .m would allow you to use *.m.json files to store file metadata instead of *.meta.json files. Values without a . in them are also allowed. For example, meta would result in *meta.json being used to store metadata.

prefix

Type: String

Default: ""

The prefix added to filenames to indicate they are metadata files.

For example, setting this option to "m-", in combination with the default postfix value of ".meta", would result in m-*.meta.json files being used to store metadata.

onMissingMainFile

Type: String

Default: "throw"

Controls what happens when metalsmith-metafiles encounters a metadata file with no corresponding main file. (E.g. when a.meta.json exists, but not a.)

The possible values are:

• "throw" - Throws an error when a metadata file with no corresponding main file is encountered (default)
• "ignore" - Silently ignores metadata files with no corresponding main file
• "delete" - Deletes metadata files with no corresponding main file

parsers

Type: Object

Default: {".json": true}

An object containing configuration details for the parsers used for different metadata formats.

Each key should be an extension used by a parser (including the leading '.'), with a value of either a boolean, a string, a function, or an object.

If you use a boolean (true or false) as the value, that simply determines whether or not you want the default parser for that extension to be enabled. (E.g. {".yaml": true} enables the js-yaml parser for *.meta.yaml files, and {".json": false} disables parsing JSON metadata files.)

If you use a string for the value, you can also choose a specific built-in parsers to be assigned to the given file extension. The string must correspond to the name of the built-in parser. (E.g. {".custom-yaml": 'js-yaml', '.j': 'JSON.parse'})

Using a function for the value (which can only be done using the JavaScript API, not the CLI) allows you to assign a custom parser to a file extension. The function is passed the contents of the file (as a Buffer) as its first argument, and an object with a path property assigned to the path of the file as its second argument. The function should return an object containing the metadata properties contained within the metadata file it was passed.

Using an object for the value allows for fine-grained control over the config settings used for the given parser. The object can contain any of the config options for metalsmith-metafiles mentioned above (except for parsers of course), and overrides the global settings for the given parser. Additionally, the object can contain (or must in the case of a file extension without a default parser) a parser property, which may be either a named parser or a function (both of which work as described in the paragraphs above).

Currently, the following named parsers are supported:

• "JSON.parse" - Exactly what it sounds like
• "js-yaml" - An npm package which parses YAML formatted data files. To use this, you must have js-yaml installed. (Preferably as a dependency of your project.)
• "eval" - Executes the file as JavaScript and returns the result of the last expression
• "eval-wrapped" - Like eval, but wraps the file's code in an object before evaluating it. (E.g. (function() {return {...}; })())
• "require" - Requires the file as a Node module and returns the module's exports
• "coffee-script" - Executes the file as CoffeeScript using the coffee-script package, and returns the result of the last expression. To use this, you must have coffee-script installed. (Preferably as a dependency of your project.)
• "toml" - Parses TOML formatted data files using the toml npm package. To use this, you must have toml installed. (Preferably as a dependency of your project.)

The following file extensions are assigned default parsers when you enable them with {".extension": true} (only .json is enabled by default):

• .json - Uses "JSON.parse" (enabled by default)
• .yaml - Uses "js-yaml"
• .yml - Uses "js-yaml"
• .js - Uses "require"
• .coffee - Uses "coffee-script"
• .cson - Uses "coffee-script"
• .toml - Uses "toml"

CLI config example:

{
  "frontmatter": false,
  "plugins": {
    "metalsmith-metafiles": {
      "parsers": {
        ".json": false, // Disable using JSON metadata files
        ".yaml": true, // Enable using YAML metadata files
        ".y": "js-yaml", // Treat *.meta.y files as YAML metadata
        '.custom': {
          parser: "js-yaml",
          prefix: 'm-',
        }
      }
    },
    // Other plugins...
  }
}

JavaScript example:

var metafiles = require('metalsmith-metafiles');
 
Metalsmith(__dirname)
  .frontmatter(false)
  .use(metafiles({
    parsers: {
      ".json": false, // Disable using JSON metadata files
      ".yaml": true, // Enable using YAML metadata files
      ".y": "js-yaml", // Treat *.meta.y files as YAML metadata
      ".js": function(content, options) { // Custom parser
        // Print the path to the file
        console.log("Parsing file: " + options.path + "!");
 
        // Execute the file and return the result
        return eval(content.toString());
      },
      '.custom': {
        parser: "js-yaml",
        prefix: 'm-',
      },
    }
  }))
  .use(/* Other plugins... */)
  .build(function(err) {
    if (err) throw err;
  });

License

MIT (See LICENSE file)