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Hasp

Half-assed CSS preprocessor.

Motivation

Tired of all the slow and bloated preprocessors out there, I talked to @soveran about writing my own take, which would address only basic functionality:

  • Be very fast.
  • Support variables.
  • Support includes.
  • Implement media queries efficiently.

The last point is especially important to me. I want to define how a selector behaves on all breakpoints in a single place. On the other hand, producing n @media declarations is wasteful. So my solution would buffer all rules defined for a breakpoint, group them and print them at the end of the resulting file.

Michel suggested I look at M4, a macro processor you already have on your system.

The result is a 30-LOC minimal preprocessor. You know, "it's okay if it's half-assed as long as it's the right half of the ass".

Usage

Open styles.hcss (the extension doesn't matter, but you may want to name the file something other than .css):

set(PRIMARY_COLOR, `#f00')

body {
  background: PRIMARY_COLOR;
}

Compile:

$ hasp styles.hcss

As expected, the variable was replaced.

Now let's use breakpoints for mobile-first development:

breakpoint(TABLET, min-device-width: 768px)

selector(.site-header) {
  height: 1rem;

  on(TABLET)
    height: 3rem;
  end
}

selector(.main-content) {
  padding: 0;

  on(TABLET)
    padding: 5rem;
  end
}

The output:

.site-header {
  height: 1rem;
}

.main-content {
  padding: 0;
}

@media only screen and (min-device-width: 768px) {
  .site-header {
    height: 3rem;
  }

  .main-content {
    padding: 5rem;
  }
}

You'll see there's only one @media declaration. w00t!

But it's not a superset of CSS!

Who cares? Do you use XSLT to render your HTML templates?

OK, should I use this in production?

Yes, you can use it in production. If you do, please let me know.

If you're still not sold on the idea, and are using Less or Sass, make yourself a favor and switch to something better. Anyway, they all require Node.js, a huge dependency for this simple problem, in my opinion.

What about minification?

Hasp assumes you'll minify its output, so it doesn't make any effort in producing compressed (or pretty) output.

What about sourcemaps?

¯\_(ツ)_/¯

How do I watch and rebuild?

In general, all other solutions use very high-level languages with slow startup times, like Node.js or Java. So they need to support file-watching functionality in the same runtime, so as to avoid the slow startup.

M4 is so fast that there's no need to keep a runtime alive. Just use the beautiful entr:

$ while true; do find . -name '*.hcss' | entr -rd sh -c 'hasp styles.hcss'; done

Syntax reference

set(<name>, <value>)

Defines a variable. Per convention, variables names should be upper-case.

Example:

set(BACKGROUND, white)

body {
  background: BACKGROUND;
}

include(<file>)

Includes another Hasp file.

Example:

body {
  background: white;
}

include(path/to/other.hcss)

breakpoint(<name>, <expression>)

Defines a named breakpoint for later use.

Example:

breakpoint(TABLET,  min-device-width: 768px)
breakpoint(DESKTOP, min-device-width: 900px)

selector(<rule>) on(<breakpoint>)

Declares a rule that will be affected by breakpoints.

Example:

breakpoint(TABLET,  min-device-width: 768px)

selector(.main-content) {
  width: 10rem;

  on(TABLET)
    width: 20rem;
  end
}

Installation

Until Hasp becomes available in package managers, you can install it by copying bin/hasp somewhere in your $PATH:

$ wget https://raw.githubusercontent.com/djanowski/hasp/master/bin/hasp /usr/local/bin/hasp
$ chmod +x /usr/local/bin/hasp

You should check that M4 is available on your system, but it most likely is:

$ which m4
/usr/bin/m4

Examples

Check out the examples directory.