Sass Rules for Bazel

Rules

sass_binary
sass_library
multi_sass_binary

Overview

These build rules are used for building Sass projects with Bazel.

Setup

To use the Sass rules, add the following to your WORKSPACE file to add the external repositories for Sass, making sure to use the latest published versions:

http_archive(
    name = "io_bazel_rules_sass",
    # Make sure to check for the latest version when you install
    url = "https://github.com/bazelbuild/rules_sass/archive/1.26.3.zip",
    strip_prefix = "rules_sass-1.26.3",
    sha256 = "9dcfba04e4af896626f4760d866f895ea4291bc30bf7287887cefcf4707b6a62",
)

# Fetch required transitive dependencies. This is an optional step because you
# can always fetch the required NodeJS transitive dependency on your own.
load("@io_bazel_rules_sass//:package.bzl", "rules_sass_dependencies")
rules_sass_dependencies()

# Setup repositories which are needed for the Sass rules.
load("@io_bazel_rules_sass//:defs.bzl", "sass_repositories")
sass_repositories()

Basic Example

Suppose you have the following directory structure for a simple Sass project:

[workspace]/
    WORKSPACE
    hello_world/
        BUILD
        main.scss
    shared/
        BUILD
        _fonts.scss
        _colors.scss

shared/_fonts.scss

$default-font-stack: Cambria, "Hoefler Text", serif;
$modern-font-stack: Constantia, "Lucida Bright", serif;

shared/_colors.scss

$example-blue: #0000ff;
$example-red: #ff0000;

shared/BUILD

package(default_visibility = ["//visibility:public"])

load("@io_bazel_rules_sass//:defs.bzl", "sass_library")

sass_library(
    name = "colors",
    srcs = ["_colors.scss"],
)

sass_library(
    name = "fonts",
    srcs = ["_fonts.scss"],
)

hello_world/main.scss:

@import "shared/fonts";
@import "shared/colors";

html {
  body {
    font-family: $default-font-stack;
    h1 {
      font-family: $modern-font-stack;
      color: $example-red;
    }
  }
}

hello_world/BUILD:

package(default_visibility = ["//visibility:public"])

load("@io_bazel_rules_sass//:defs.bzl", "sass_binary")

sass_binary(
    name = "hello_world",
    src = "main.scss",
    deps = [
         "//shared:colors",
         "//shared:fonts",
    ],
)

Build the binary:

$ bazel build //hello_world
INFO: Found 1 target...
Target //hello_world:hello_world up-to-date:
  bazel-bin/hello_world/hello_world.css
  bazel-bin/hello_world/hello_world.css.map
INFO: Elapsed time: 1.911s, Critical Path: 0.01s

Build Rule Reference

sass_binary

sass_binary(name, src, deps=[], include_paths=[], output_dir=".", output_name=<src_filename.css>, output_style="compressed", sourcemap=True)

sass_binary compiles a single CSS output from a single Sass entry-point file. The entry-point file may have dependencies (sass_library rules, see below).

Implicit output targets

Label	Description
output_name	The generated CSS output
output_name.map	The source map that can be used to debug the Sass source in-browser

Attribute	Description
`name`	Unique name for this rule (required)
`src`	Sass compilation entry-point (required).
`deps`	List of dependencies for the `src`. Each dependency is a `sass_library`
`include_paths`	Additional directories to search when resolving imports
`output_dir`	Output directory, relative to this package
`output_name`	Output file name, including .css extension. Defaults to `<src_name>.css`
`output_style`	Output style for the generated CSS.
`sourcemap`	Whether to generate sourcemaps for the generated CSS. Defaults to True.

sass_library

sass_library(name, srcs, deps=[])

Defines a collection of Sass files that can be depended on by a sass_binary. Does not generate any outputs.

Attribute	Description
`name`	Unique name for this rule (required)
`srcs`	Sass files included in this library. Each file should start with an underscore
`deps`	Dependencies for the `srcs`. Each dependency is a `sass_library`

multi_sass_binary

multi_sass_binary(name, srcs=[], output_style="compressed", sourcemap=True)

multi_sass_binary compiles a list of Sass files and outputs the corresponding CSS files and optional sourcemaps. Output is omitted for filenames that start with underscore "_".

⚠️ WARNING: This rule does a global compilation, and thus any change in the sources will trigger a build for all files. It is inefficient. Always prefer sass_binary and provide strict dependencies for most efficient compilation. This rule is also not used internally at Google.

Output targets

The following pair of files is generated for each file in srcs.

Label	Description
.css	The generated CSS output
.css.map	The source map that can be used to debug the Sass source in-browser

Attribute	Description
`name`	Unique name for this rule (required)
`srcs`	A list of Sass files (required).
`output_style`	Output style for the generated CSS.
`sourcemap`	Whether to generate sourcemaps for the generated CSS. Defaults to True.

davidmorgan/rules_sass