dovetailer

v0.7.10

Published

2 years ago

Convert Nunjucks and Sass to an optimized HTML email

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maxlapides

email html inline css

Dovetailer: HTML Email Generator

Features

HTML and text versions
Nunjucks support
Sass support
Markdown support
Reset styles
Responsive support
HTML minification
Development build for more efficient development and debugging
Automatic special character replacement
- In HTML version, converts special characters to HTML entities
- In text version, replace non-ASCII characters with ASCII equivalents (ex: smart "curly" quotes are replaced by dumb quotes)
CSS Transformations
HTML Transformations

Quick Start

The easiest way to get started is to fork the Dovetailer starter project:

git clone [email protected]:maxlapides/dovetailer-starter.git
cd dovetailer-starter
npm install
npm start

Installation

If you want to set up Dovetailer yourself, you can install it into a new repo:

npm install dovetailer --save-dev

Usage

Dovetailer comes with two methods out of the box:

compileDirectory compiles all of the emails in your templates directory, and saves them to the file system
compileEmail compiles only a single email template and returns the result without saving to the file system

`compileDirectory`

Parameters:

templatesPath (STRING, required): filepath to your email templates
options (OBJECT, optional):
- doctype (STRING): a custom doctype if the HTML4 doctype isn't sufficient
- whitelistSelectors (ARRAY): selectors to not automatically strip from the HTML. For more info, see here.

const compileDirectory = require('dovetailer')
return compileDirectory(templatesPath, options)

`compileEmail`

To compile a single email template, you can use the compileEmail method:

Parameters:

templatePath (STRING, required): filepath to email template
extraContext (OBJECT, optional): data to override context

Example:

const { compileEmail } = require('dovetailer')
compileEmail(pathToTemplate, { extra: 'context' })

Writing Your Own Emails

In the templates folder, add another folder for the new template you want to build. Name this folder whatever you want to call your email template.
In that folder, add the following files:

html.njk: your Nunjucks template for the HTML version
style.scss: your main Sass file (these styles will be automatically inlined)
text.njk: your Nunjucks template for the text version
context.json: the data file used by Nunjucks to compile your template

Optional files:

reset.scss: your Sass file for custom reset styles (see Reset Styles below)

You can also add additional files and folders in your template directory such as Sass partials. See the example template for, well, an example.

Development and Production Builds

The development and production versions of your email should always render exactly the same (see below) in the browser. There is no development build of the text version, only the HTML version.

The main difference between the development build and the production build is the development build references external stylesheets. The external stylesheets have sourcemaps that point back to the original Sass files. This makes it much easier to develop and debug your emails.

You should use the development build when you're working on coding an email and you're viewing it in a web browser. You should never try to actually send a development build, even just as a test to yourself. It definitely won't work at all.

Great, but...the development and production builds aren't rendering the same for me!

The production build moves the media queries into the head and groups the styles together by media query. Since CSS is order dependent, in some cases this can produce unexpected results. However, if you follow best practices and keep your Sass organized, you can avoid these issues.

Reset Styles

Including "reset" styles helps ensure that your emails render the same across all email clients. There are two different types of reset styles: reset styles that need to be included in the <head> of the email and reset styles that need to be inlined. Generally, <head> reset styles are client-specific hacks.

Accordingly, in the included common folder, there are two reset files named reset-head.scss and reset-inline.scss. These are the default sets of reset styles that are included automatically in every email. These files are the result of our research and have been thoroughly tested.

This requires no configuration, but if you want to specify your own set of reset styles for an individual email, you can do so by adding files named reset-head.scss and/or reset-inline.scss to your email's template folder.

Responsive Styles

If you want to build a responsive email, you're going to need to use media queries. Since it's impossible to inline media queries, your responsive styles will be injected into the <head> of your HTML.

No extra configuration required! Your media queries will automatically be extracted from your CSS and injected. Also, if you have multiple of the same media query in your stylesheet, the selectors will all be grouped together into a single media query.

CSS Transformations

`!important` directive

For styles in media queries to take any effect in HTML emails, they need to override the internal styles. So, the compiler automatically adds the !important directive to all styles in media queries.

Autoprefixer

All compiled Sass files are also run through Autoprefixer, which in most cases will actually act as a minifier by removing extraneous vendor-prefixed styles.

MQ Packer

Media query declarations in the same media query rule are packed into one media query rule using CSS MQPacker. This enables you to nest media queries inside of any style rule in Sass without having redundant media query rules in your compiled CSS.

HTML Transformations

tables

Tables (<table>) always get the following HTML attributes:

cellpadding="0"
cellspacing="0"
border="0"

Empty table cells (<td>) are automatically filled with a non-breaking space ( ). An "empty" table cell is defined to be any table cell that contains either no characters or whitespace only.

imgs

Images (<img>) always get the following HTML attributes:

border="0"

Any width and height styles are always applied to <img>s as width/height HTML attributes.

Dovetailer does its best to look up the dimensions of any <img> image. It will automatically inject those dimensions as width/height HTML attributes as well as width/height inline CSS styles. If the image name ends in @2x, it will assume the image is retina quality, and divide the dimensions in half. Similarly, @3x images will have dimensions divided by 3. If you specify width/height values for an <img> using CSS, the natural dimensions are overridden. Image dimensions are cached; if you want to invalidate the cache you can delete/modify cache/images.json.

Known Issues

If you rename a directory in the templates folder while Gulp is running, it will crash Gulp.
Adding a directory in the templates folder while Gulp is running causes an infinite loop?

Roadmap

Improve error handling of email compiles that result in undefined output
Improve caching mechanism for image dimensions
Support @import in CSS
Easy mechanism for dates in copyright statements
Strip font-family style from empty table cells
Replace attributes like ""blah"" with '"blah"'
Outlook margin support
Add command line flags:
- Beautifying production HTML
- Disabling development version
Automatically ensure that empty table cells have line-height: 1px and font-size: 1px
Resolve adding/renaming templates issues
table attributes ordered: width, height, cellpadding, cellspacing, border
Automatically convert responsive styles to use the [class="..."] syntax
Move common build folder elsewhere
BrowserSync - CSS injection on dev build
Automatic Gmail Promotions tab code generation
em/rem to px converter
Warnings:
- relative img references
- <link> tags
- <script> tags
- W3C validation