eyeglass

Getting some npm in your Sass

Eyeglass is a sass (github) extension manager built on top of npm. Using eyeglass, you can bring the power of node modules to your Sass files.

Eyeglass works with node-sass as well as dart-sass. Eyeglass has no direct dependency on a sass implementation and it will use whichever sass implementation that you have installed in your project. If necessary, you can pass a sass implementation to eyeglass using the eyeglass.engines.sass option.

Installing eyeglass

npm install --save-dev eyeglass

Additionally, you must install a compatible Sass implementation.

If you want to use node-sass:

npm install --save-dev node-sass

If you want to use dart-sass:

npm install --save-dev sass

Additionally, if you use sass.renderSync() and have eyeglass modules that export functions that are asynchronous, you should also add the deasync library to your project:

npm install --save-dev deasync

Note: If your project uses yarn, the above commands should replace npm install --save-dev with yarn add --dev.

Adding eyeglass modules to your project

eyeglass modules are regular npm modules. Install them into your project just like any other item.

npm install my_eyeglass_module --save-dev

Once installed via npm, an eyeglass module can:

• Make stylesheets in the npm module accessible to the project via Sass's @import or @use directives.
• Expose custom functions and importers written in javascript to the Sass compiler.

If your build-tool is eyeglass-aware, you can reference the eyeglass module with standard Sass import syntax: @import "my_eyeglass_module/file";. The my_eyeglass_module will be resolved to the correct directory in your node modules, and the file will then resolve using the standard import rules for Sass.

Transitive dependencies

Eyeglass modules can depend on other eyeglass modules. By default Eyeglass will only allow modules with a direct dependency on another eyeglass module to import files from that module.

Setting eyeglass.disableStrictDependencyCheck to true will allow any module in the dependency tree to be imported from any other file in the dependency tree (note: setting this option is discouraged and should not be necessary in most situations).

Unlike node, Sass has a global namespace. There are situations where npm will happily install multiple instances of the same node package within the package hierarchy, even spanning major versions. Eyeglass always creates a global resolution of all the different versions of an eyeglass module by picking the instance with the highest version. If multiple major versions of the same package are found, eyeglass will warn you by default. If you set eyeglass.strictModuleVersions to true, eyeglass will produce a hard error. If you set eyeglass.strictModuleVersions to false it will silently ignore these version conflicts (this is not recommended).

Manually adding modules

Eyeglass will transitively auto-discover npm installed modules that are listed in your package.json files. (Just using npm link is not enough to use modules on your local filesystem). In some cases, you might need to use an eyeglass module that isn't distributed as an npm package, or adapt a sass library that doesn't expose itself as an eyeglass module. In these situation, you can manually add modules to your project.

To add modules that are not part of the npm ecosystem, you can manually add modules via the eyeglass options:

var sass = require("node-sass");
var eyeglass = require("eyeglass");
var options = {
  eyeglass: {
    modules: [
      // add module by path (must have a valid package.json)
      {
        path: "/path/to/your/module"
      },
      // add module by Object
      {
        name: "my-module-name",
        main: function(eyeglass, sass) {
          return {
            sassDir: ...,
            functions: ...,
            ...
          }
        },
        eyeglass: {
          needs: "...",
          ...
        }
      }
    ],

    engines: {
      sass: sass
    }
  }
};
sass.render(eyeglass(options)));

When adding a module by object, the object has the same format as the object in an eyeglass module's package.json that would normally be assigned to top-level eyeglass property. However, it supports one additional property: main. The main object is a function as would be returned by requiring the eyeglass exports file. In this way, it is possible to expose any arbitrary Sass project as an eyeglass module without that module being required to "become an eyeglass" module. This also enables the use of bower packages with Eyeglass.

Manually added eyeglass modules will only be able to be imported by the main application's sass files. Dependencies between such manual modules are not currently supported.

Module Caching

By default, eyeglass uses a global module cache to help improve the performance of module discovery. This should be safe for almost all use cases, but if you modify your node_modules directory and/or package.json dependencies during build time, this may cause issues. You can opt-out of the by passing the eyeglass option useGlobalModuleCache: false.

eyeglass({
  // sass options
  // ...
  eyeglass: {
    // eyeglass options
    // ...
    useGlobalModuleCache: false
  }
});

You can programmatically purge the global caches in Eyeglass using Eyeglass.resetGlobalCaches().

Working with assets

It's quite common to need to refer to assets from within your stylesheets. Eyeglass provides core support for exposing assets to your stylesheets for your application or from an eyeglass module and generating urls to those assets as well as making sure only those assets that you actually use end up in your built application.

Exposing assets

In your application

The addSource method on eyeglass.assets is how you add assets to your application. The path passed to asset-url() is going to be relative to the directory that you pass to addSource.

Given the following assets directory structure:

myproject/
└── assets/
    ├── images/
    │   ├── foo/
    │   │   └── image1.png
    │   └── unused.gif
    ├── js/
    │   └── app.js
    └── scss/
        └── app.scss

The simplest way to expose your assets to eyeglass is to add your assets directory as an eyeglass asset source. Using a simple node script we can compile a Sass file.

#!/usr/bin/env node
var path = require("path");
var sass = require("node-sass");
var eyeglass = require("eyeglass");
var rootDir = __dirname;
var assetsDir = path.join(rootDir, "assets");

var options = { ... node-sass options ... };


options.eyeglass = {
  // specifying root lets the script run from any directory instead of having to be in the same directory.
  root: rootDir,

  // where assets are installed by eyeglass to expose them according to their output url.
  // If not provided, assets are not installed unless you provide a custom installer.
  buildDir: path.join(rootDir, "dist"),

  assets: {
    // prefix to give assets for their output url.
    httpPrefix: "assets",

    // Add assets except for js and sass files
    // The url passed to asset-url should be
    // relative to the assets directory specified.
    sources: [
      {directory: assetsDir, globOpts: { ignore: ["**/*.js", "**/*.scss"] }}
    ]
  },

  engines: {
    sass: sass
  }
}

// Standard node-sass rendering of a single file.
sass.render(eyeglass(options), function(err, result) {
  // handle results
});

In the module

In function that you export from your eyeglass-exports.js, you have the eyeglass as the first parameter. It has assets property, and it has the method export that accepts the same arguments as addSource and returns a new instance of assets list with the given path already included in the list with provided options.

To expose it, you need to set it as assets property on the object you return from exported function:

module.exports = function(eyeglass, sass) {
  return {
    assets: eyeglass.assets.export('some/path/here'),
  };
};

See the Examples section below for more details.

Examples

Let's say your module has structure like this:

mymodule/
└── assets/
    ├── images/
    │   ├── foo/
    │   │   └── image1.png
    │   └── unused.gif
    ├── fonts/
    │   └── coolfont.ttf
    └── scss/
        └── app.scss

If you don't require per-path options or fine-grained control of what can be imported from SASS, you can use just one path:

var path = require('path');

var assets_path = path.join(__dirname, 'assets');

module.exports = function(eyeglass, sass) {
  return {
    sassDir: path.join(assets_path, 'scss'),
    assets: eyeglass.assets.export(assets_path, {
      globOpts: {
        ignore: [ '**/*.scss', '**/*.js' ]
      }
    });
  }
};

But if you want more fine-grained control, you can save the result of assets.export() to the variable and call addSource on it any amount of times:

var path = require('path');

var assets_path = path.join(__dirname, 'assets');
var images_path = path.join(assets_path, 'images');
var fonts_path = path.join(assets_path, 'fonts');

var images_options = { ... images-related options ... };
var fonts_options = { ... fonts-related options ... };

module.exports = function(eyeglass, sass) {
  // Create new list of assets with at least one path
  var module_assets = eyeglass.assets.export(images_path, images_options);

  // You can add more paths like this
  module_assets.addSource(fonts_path, fonts_options);

  return {
    sassDir: path.join(assets_path, 'stylesheets'),
    assets: module_assets
  }
};

Note that in this case, given the name of the module is mymodule, the coolfont.ttf and foo/image1.png will be avilable as mymodule/coolfont.ttf and mymodule/foot/image1.png accordingly.

Referencing Assets

To reference an asset in your application or within your own module you can simply @import "assets". To reference assets that are in a module that you have a direct dependency on, you can @import "<module>/assets". For example: @import "my-theme/assets" would import the assets from the my-theme eyeglass module.

Importing assets for an application or module returns an automatically generated Sass file that registers asset information with the eyeglass assets Sass module.

Then you can refer to that asset using the fully qualified source url of the asset. This url must include the module prefix when referencing the asset. For example background: asset-url("images/foo.png") would import a file images/foo.png that is relative to the assetsDir.

To refer to an asset in your module, include the module name as a directory prefix when invoking asset-url. For example asset-url("my-theme/icons/party.png") would import the file icons/party.png that is exposed by the my-theme module. Even within the my-theme module, this prefix must be used when referring to the assets of that module.

Astute readers will have noted that there is a possible namespace collision if you have a directory in your application with the same name as a module. This is on purpose: it lets you replace module assets with your own assets if you need to do so by overriding them in your own application.

Asset URL Manipulation

By default, eyeglass will namespace module asset urls according to their eyeglass module name and both application and module assets urls will be placed within folder specified by the assetsHttpPrefix option. However, an application or framework can chose to override the url scheme for assets by defining an asset resolver.

Example: Adding a modification timestamp to assets as a query parameter.

  eyeglass.assets.resolver(function(assetFile, assetUri, oldResolver, done) {
    var fs = require("fs");
    var mtime = fs.statSync(assetFile).mtime.getTime();
    done(null, {
      path: assetUri,
      query: mtime.toString()
    });
  });

Example: hashing assets by md5sum.

eyeglass.assets.resolver(function(assetFile, assetUri, oldResolver, done) {
  var path = require("path");
  var fs = require("fs");
  var md5 = require("MD5");
  var prefix = "/" + eyeglass.options.assetsHttpPrefix + "/";
  fs.readFile(assetFile, function(err, buffer) {
    if (err) {
      done(err);
    } else {
      done(null, {
        path: prefix + md5(buffer) + path.extname(assetFile)
      });
    }
  });
});

Asset Installation

By using Eyeglass's asset installation system, you can ensure that only those assets that are referenced in your stylesheets will be part of your application when it is built.

Once an asset's url is fully resolved, the asset probably needs to be installed into a location from where it can be served as that url. The simplest way to do this is to specify the buildDir option to eyeglass. Once that is specified the resolved url will be used to copy the file to a location relative to the build directory.

In order to allow for asset pipeline integration (E.g. writing to a Vinyl file) and more complex application needs, it's possible to chain or override the default eyeglass asset installer.

Installer Example: Logging installed assets:

eyeglass.assets.installer(function(assetFile, assetUri, oldInstaller, cb) {
  // oldInstaller is the standard eyeglass installer in this case.
  // We proxy to it for logging purposes.
  oldInstaller(assetFile, assetUri, function(err, result) {
    if (err) {
      console.log("Error installing '" + assetFile + "': " + err.toString());
    } else {
      console.log("Installed Asset '" + assetFile + "' => '" + result + "'");
    }
    cb(err, result);
  });
});

More on Assets

The code samples here are actually derived from a simple eyeglass project. You can view the actual code as a gist.

Assets are complex and the asset configuration of Eyeglass is very flexible. For more documentation see the asset documentation.

Writing an eyeglass module with Sass files

To create an eyeglass module with Sass files, place the files inside of a sass directory in your npm module.

|- /
  |- eyeglass-exports.js
  |- package.json
  |- sass
    |- index.scss (or .sass)

eyeglass will automatically map the first directory of @import statements to the correct node-module directory if there is a eyeglass module with that eyeglass name. Because Sass uses a global namespace, it's recommended that you namespace-prefix any mixins you create in order to avoid collisions.

In keeping with node's conventions, eyeglass modules can create an index.scss file in any folder instead of defining a file of the same name as a folder in order to be the main entry point for a sass module having submodules.

Building sass files with eyeglass support

The easiest way to use eyeglass is to use an eyeglass-aware build-tool plugin. The following plugins are available:

• broccoli-eyeglass
• ember-cli-eyeglass

Integrating with other build systems

Eyeglass is designed to be easy to use with any node-sass based compilation system.

var eyeglass = require("eyeglass");
var sass = require("node-sass")
var sassOptions = { ... } ; // options for node-sass

// eyeglass specific options are passed via the `eyeglass` key in the sass options.
sassOptions.eyeglass {
  assets: {
    sources: [
      // Expose images in the assets/images directory as /images on the
      // website by putting the images we reference with asset-url()
      // into the public/images directory.
      {directory: "assets", {pattern: "images/**/*"}},

      // Expose fonts in the assets/fonts directory as /fonts on the
      // website by putting the fonts we reference with asset-url()
      // into the public/fonts directory.
      {directory: "assets", {pattern: "fonts/**/*"}}
    ]
  }
}

// These options are processed and returned as options that can be passed to any build tool
// that passes options through to node-sass.
sass.render(eyeglass(sassOptions), function(error, result) {
  if (error) {
    //handle the compilation error
  } else {
    // write the result.css output to a file.
  }
});

Example: integration with grunt and grunt-sass

...
var eyeglass = require("eyeglass");
...
sass: {
    options: eyeglass({sourceMap: true}),
    dist: {
        files: {
            'public/css/main.css': 'sass/main.scss'
        }
    }
}
...

Writing an Eyeglass Module

node-sass allows you to register custom functions for advanced functionality. Eyeglass allows any node modules that are tagged with eyeglass-module to be automatically loaded into eyeglass and makes your module discoverable on NPM. To tag your module as an eyeglass module, add the eyeglass-module keyword to your package.json.

{
  ...
  "keywords": ["eyeglass-module", "sass", ...],
  "eyeglass": {
    "sassDir": "sass",
    "exports": "eyeglass-exports.js",
    "name": "greetings",
    "needs": "^0.6.0"
  },
  ...
}

In the "eyeglass" option block in your package.json, you will declare the eyeglass exports file and the semver dependency that your module has on eyeglass itself using the "needs" option. Failure to provide this option will give your users a warning since eyeglass has no way to check if your module is compatible with the currect eyeglass version.

Eyeglass Exports File

If your eyeglass module needs to define Sass functions in javascript, you will need to make an eyeglass exports file. It is convention to name this file eyeglass-exports.js but any file name is allowed.

Below is an example eyeglass exports file:

"use strict";

var path = require("path");

module.exports = function(eyeglass, sass) {
  return {
    functions: {
      "greetings-hello($name: 'World')": function(name, done) {
        done(new sass.types.String("Hello, " + name.getValue()));
      }
    }
  }
};

If the eyeglass.exports option is not found in package.json eyeglass will fall back to using the npm standard main file declared in your package.json. If your npm module has a main file meant to be used generally by javascript, but no eyeglass exports file, then you can simply set eyeglass.exports option to false in your package.json.

Since all functions declared from javascript are global, it is best practice to scope your function names to avoid naming conflicts. Then, to simplify the naming of your functions for the normal case, provide a sass file that when imported, unscopes the function names by wrapping them.

// index.scss
@function hello($args...) {
  @return greetings-hello($args...);
}

Specifying a name for @import that is different from your npm package name

If you need the top level import to be named differently than the name of your npm module then you can specify a name attribute for the eyeglass object in your package.json. The following example would allow @import "foo"; to import index.scss from your package's sass directory.

{
  ...
  "name": "eyeglass-foo",
  "eyeglass": {
    "name": "foo"
  }
  ...
}

Import-Once

Any sass files imported from your node modules will only ever be imported once per CSS output file. Note that Sass files imported from the Sass load path will have the standard Sass @import behavior.

To disable the import-once behavior, you need to set the enableImportOnce option to false:

var sass = require("node-sass");
var eyeglass = require("eyeglass");
var sassOptions = {
  eyeglass: {
    enableImportOnce: false
  }
};

sass.render(eyeglass(sassOptions, sass));

URI path normalization

By default, eyeglass will normalize path separators for interoperability between different platforms (Windows, Unix, etc). While we don't anticipate any issues with this feature, you can opt-out of this feature if you do encounter issues. Please do report any such issues so we may investigate. If you disable this feature, eyeglass will not work on Windows platforms.

Opt-Out via Environment Variable

Setting an environment variable EYEGLASS_NORMALIZE_PATHS=false

Opt-Out via Config Option

Explicitly via eyeglass options:

var sass = require("node-sass");
var eyeglass = require("eyeglass");
var options = {
  eyeglass: {
    engines: {
      sass: sass
    },
    normalizePaths: false
  }
};
sass.render(eyeglass(options)));

asset-uri/asset-url string literals are not normalized

When using the asset-uri and asset-url, the URI string passed are not normalized. This is to ensure that the URI always uses valid web path separators (/) rather than file system path separators. That is asset-uri('path/to/file.png) will resolve the correct file asset on any platform, but asset-url('foo\\bar.png') will expect to find a file with a literal \ in it's name (foo\\bar.png), not a file located at foo/bar.png. We encourage you not to use backslashes in your file names, as this means your code cannot easily be ported to Windows platforms.