Closure Rules for Bazel (αlpha)

JavaScript	Templating	Stylesheets	Miscellaneous
closure_js_library	closure_js_template_library	closure_css_library	closure_js_proto_library
closure_js_binary	closure_java_template_library	closure_css_binary	phantomjs_test
closure_js_deps	closure_py_template_library
closure_js_test

Overview

Closure Rules provides a polished JavaScript build system for Bazel that emphasizes type safety, strictness, testability, and optimization. These rules are built with the Closure Tools, which are what Google used to create websites like Google.com and Gmail. The goal of this project is to take the frontend development methodology that Google actually uses internally, and make it easily available to outside developers.

Closure Rules is an abstract build system. This is what sets it apart from Grunt, Gulp, Webpacker, Brunch, Broccoli, etc. These projects all provide a concrete framework for explaining how to build your project. Closure Rules instead provides a framework for declaring what your project is. Closure Rules is then able to use this abstract definition to infer an optimal build strategy.

Closure Rules is also an austere build system. The Closure Compiler doesn't play games. It enforces a type system that can be stricter than Java. From a stylistic perspective, Closure is verbose like Java; there's no cryptic symbols or implicit behavior; the code says exactly what it's doing. This sets Closure apart from traditional JavaScript development, where terseness was favored over readability, because minifiers weren't very good. Furthermore, the Closure Library and Templates help you follow security best practices which will keep your users safe.

What's Included

Closure Rules bundles the following tools and makes them "just work."

Bazel: The build system Google uses to manage a repository with petabytes of code.
Closure Compiler: Type-safe, null-safe, optimizing JavaScript compiler that transpiles ECMASCRIPT6 to minified ES3 JavaScript that can run in any browser.
Closure Library: Google's core JavaScript libraries.
Closure Templates: Type-safe HTML templating system that compiles to both JavaScript and Java. This is one of the most secure templating systems available. It's where Google has put the most thought into preventing things like XSS attacks. It also supports i18n and l10n.
Closure Stylesheets: CSS compiler supporting class name minification, variables, functions, conditionals, mixins, and bidirectional layout.
PhantomJS: Headless web browser used for automating JavaScript unit tests in a command line environment.
Protocol Buffers: Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data. This is used instead of untyped JSON.
Incremental DOM (experimental): Google's in-place DOM diffing library. This optional backend for Closure Templates builds DOM trees and updates them in-place when data changes.

Mailing Lists

Caveat Emptor

Closure Rules is production ready, but its design is not yet finalized. Breaking changes will be introduced. However they will be well-documented in the release notes.

Setup

First you must install Bazel ≥0.3.1. Then you must add the following to your WORKSPACE file:

http_archive(
    name = "io_bazel_rules_closure",
    strip_prefix = "rules_closure-0.4.1",
    sha256 = "ba5e2e10cdc4027702f96e9bdc536c6595decafa94847d08ae28c6cb48225124",
    url = "https://mirror.bazel.build/github.com/bazelbuild/rules_closure/archive/0.4.1.tar.gz",
)

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_repositories")

closure_repositories()

You are not required to install the Closure Tools, PhantomJS, or anything else for that matter; they will be fetched automatically by Bazel.

We also strongly recommend that you add the following to your ~/.bazelrc file:

build --strategy=Closure=worker

Overriding Dependency Versions

When you call closure_repositories() in your WORKSPACE file, it causes a few dozen external dependencies to be added to your project, e.g. Guava, Guice, JSR305, etc. You might need to customize this behavior.

To override the version of any dependency, modify your WORKSPACE file to pass omit_<dependency_name>=True to closure_repositories(). Next define your custom dependency version. A full list of dependencies is available from repositories.bzl. For example, to override the version of Guava:

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_repositories")
closure_repositories(omit_guava=True)

maven_jar(
    name = "guava",
    artifact = "...",
    sha1 = "...",
)

Examples

Please see the test directories within this project for concrete examples of usage:

Reference

closure_js_library

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_library")
closure_js_library(name, srcs, data, deps, language, exports, suppress,
                   convention, no_closure_library)

Defines a set of JavaScript sources.

The purpose of this rule is to define an abstract graph of JavaScript sources. It must be used in conjunction with closure_js_binary to output a minified file.

This rule will perform syntax checking and linting on your files. This can be tuned with the suppress attribute. To learn more about what the linter wants, read the Google JavaScript Style Guide.

Strict dependency checking is performed on the sources listed in each library target. See the documentation of the deps attribute for further information.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will always be empty and data will contain all transitive JS sources and data.

Arguments

name: (Name; required) A unique name for this rule. The standard convention is that this be the same name as the Bazel package with srcs = glob(['*.js']). If it contains a subset of the .js srcs in the package, then convention states that the _lib suffix should be used.
srcs: (List of labels; optional) The list of .js source files that represent this library. This can include files marked as @externs or @nocompile. This attribute is required unless the exports attribute is being defined.
data: (List of labels; optional) Runfiles directly referenced by JS sources in this rule. For example, if the JS generated injected an img tag into the page with a hard coded image named foo.png, then you might want to list that image here, so it ends up in the webserver runfiles.
deps: (List of labels; optional) Direct dependency list. These can point to closure_js_library, closure_js_template_library, closure_css_library and closure_js_proto_library rules.
language: (String; optional; default is "ECMASCRIPT5_STRICT") Variant of JavaScript in which srcs are written. The following are valid options:
- ECMASCRIPT6_STRICT: Nitpicky, shiny new JavaScript.
- ECMASCRIPT5_STRICT: Nitpicky, traditional JavaScript.
- ECMASCRIPT6: Shiny new JavaScript.
- ECMASCRIPT5: Traditional JavaScript.
- ECMASCRIPT3: 90's JavaScript.
- ANY: Indicates sources are compatible with any variant of JavaScript.
Maintaining this attribute for your library rules is important because closure_js_binary checks the language attribute of dependencies to determine if it's a legal combination that's safe to compile.

Combinations that traverse a red line cause strictness to decay and a warning will be emitted. For example, if just one library is unstrict, then strictness will be removed for your entire binary. Therefore we strongly recommend that you use strict variants.

ProTip: You are not required to put "use strict" at the tops of your files. The Closure Compiler generates that in the output for you.

The default language is ECMASCRIPT5_STRICT for three reasons. First, we want to make the most conservative recommendation possible. Some ES6 features have not yet been implemented in the Closure Compiler. We're working on that. Secondly, it upgrades easily into ECMASCRIPT6_STRICT, should you choose to use it later. Thirdly, PhantomJS only supports ECMASCRIPT5_STRICT, so your unit tests will be able to run lightning fast in raw sources mode if you write your code exclusively in that language. (XXX: Unfortunately a bug in PhantomJS is blocking this at the moment.)
exports: (List of labels; optional) Listing dependencies here will cause them to become direct dependencies in parent rules. This functions similarly to java_library.exports. This can be used to create aliases for rules in another package. It can also be also be used to export private targets within the package. Another use is to roll up a bunch of fine-grained libraries into a single big one.
suppress (List of String; optional; default is []) List of codes the linter should ignore. Warning and error messages that are allowed to be suppressed, will display the codes for disabling it. For example, if the linter says:
```
foo.js:123: WARNING lintChecks JSC_MUST_BE_PRIVATE - Property bar_ must be marked @private
```
Then the diagnostic code "JSC_MUST_BE_PRIVATE" can be used in the suppress list. It is also possible to use the group code "lintChecks" to disable all diagnostic codes associated with linting.

If a code is used that isn't necessary, an error is raised. Therefore the use of fine-grained suppression codes is maintainable.
convention (String; optional; default is "CLOSURE") Specifies the coding convention which affects how the linter operates. This can be the following values:
- NONE: Don't take any special practices into consideration.
- CLOSURE: Take Closure coding conventions into consideration when linting. See the Google JavaScript Style Guide for more information.
- GOOGLE: Take Google coding conventions into consideration when linting. See the Google JavaScript Style Guide for more information.
no_closure_library (Boolean; optional; default is False) Do not link Closure Library base.js. If this flag is used, an error will be raised if any deps do not also specify this flag.

All closure_js_library rules with nonempty srcs have an implicit dependency on @closure_library//:closure/goog/base.js. This is a lightweight file that boostraps very important functions, e.g. goog.provide. Linking this file by default is important because:
1. It is logically impossible to say goog.require('goog').
2. The Closure Compiler will sometimes generate synthetic code that calls these functions. For example, the ProcessEs6Modules compiler pass turns ES6 module directives into goog.provide / goog.require statements.
The only tradeoff is that when compiling in WHITESPACE_ONLY mode, this code will show up in the resulting binary. Therefore this flag provides the option to remove it.

closure_js_binary

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_binary")
closure_js_binary(name, deps, css, pedantic, debug, language, entry_points,
                  dependency_mode, compilation_level, formatting,
                  output_wrapper, property_renaming_report, defs)

Turns JavaScript libraries into a minified optimized blob of code.

This rule must be used in conjunction with closure_js_library.

Implicit Output Targets

name.js: A minified JavaScript file containing all transitive sources.
name.js.map: Sourcemap file mapping compiled sources to their raw sources. This file can be loaded into browsers such as Chrome and Firefox to view a stacktrace when an error is thrown by compiled sources.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the .js and .js.map output files and data will contain those files in addition to all transitive JS sources and data.
closure_js_library: srcs will be the .js output file, language will be the output language, deps will be empty, data will contain all transitive data, and no_closure_library will be True.

Arguments

name: (Name; required) A unique name for this rule. Convention states that such rules be named foo_bin or foo_dbg if debug = True.
deps: (List of labels; required) Direct dependency list. This attribute has the same meaning as it does in closure_js_library. These can point to closure_js_library and closure_js_template_library rules.
css: (Label; optional) CSS class renaming target, which must point to a closure_css_binary rule. This causes the CSS name mapping file generated by the CSS compiler to be included in the compiled JavaScript. This tells Closure Compiler how to minify CSS class names.

This attribute is required if any of JavaScript or template sources depend on a closure_css_library. This rule will check that all the referenced CSS libraries are present in the CSS binary.
pedantic: (Boolean; optional; default is False) Setting this flag to True will turn on every single warning, and treat warnings as errors. Your reward is that type-based optimizations becomes enabled.

This flag is recommended for greenfield projects, however caveat emptor applies. Some of the checks that get enabled aren't yet mature. The Closure Compiler might do something crazy like generate synthetic code that doesn't validate. If that happens, please file an issue.

One benefit of pedantic mode is null safety. ProTip: The Closure Compiler will take into consideration goog.asserts.assert statements and conditionals like if (foo != null).
debug: (Boolean; optional; default is False) Enables debug mode. Many types of properties and variable names will be renamed to include $ characters, to help you spot bugs when using ADVANCED compilation mode. Assert statements will not be stripped. Dependency directives will be removed.
language: (String; optional; default is "ECMASCRIPT3") Output language variant to which library sources are transpiled. The default is ES3 because it works in all browsers. The input language is calculated automatically based on the language attribute of closure_js_library dependencies.
entry_points: (List of String; optional; default is []) List of unreferenced namespaces that should not be pruned by the compiler. This should only be necessary when you want to invoke them from a <script> tag on your HTML page. See Exports and Entry Points to learn how this works with the @export feature. For further context, see the Closure Compiler documentation on managing dependencies.
dependency_mode: (String; optional; default is "LOOSE") In rare circumstances you may want to set this flag to "STRICT". See the Exports and Entry Points unit tests and the Closure Compiler's managing dependencies documentation for more information.
compilation_level: (String; optional; default is "ADVANCED") Specifies how minified you want your JavaScript binary to be. Valid options are:
- ADVANCED: Enables maximal minification and type checking. This is strongly recommended for production binaries. Warning: Properties that are accessed with dot notation will be renamed. Use quoted notation if this presents problems for you, e.g. foo['bar'], {'bar': ...}.
- SIMPLE: Tells the Closure Compiler to function more like a traditional JavaScript minifier. Type checking becomes disabled. Local variable names will be minified, but object properties and global names will not. Namespaces will be managed. Code that will never execute will be removed. Local functions and variables can be inlined, but globals can not.
- WHITESPACE_ONLY: Tells the Closure Compiler to strip whitespace and comments. Transpilation between languages will still work. Type checking becomes disabled. No symbols will not be renamed. Nothing will be inlined. Dependency statements will not be removed. ProTip: If you're using the Closure Library, you'll need to look into the CLOSURE_NO_DEPS and goog.ENABLE_DEBUG_LOADER options in order to execute the compiled output.)
formatting: (String; optional) Specifies what is passed to the --formatting flag of the Closure Compiler. The following options are valid:
- PRETTY_PRINT
- PRINT_INPUT_DELIMITER
- SINGLE_QUOTES
output_wrapper: (String; optional) Interpolate output into this string at the place denoted by the marker token %output%. Use the marker token %output|jsstring% to do JS string escaping on the output. The default behavior is to generate code that pollutes the global namespace. Many users will want to set this to "(function(){%output%}).call(this);" instead. See the Closure Compiler FAQ for more details.
property_renaming_report: (File; optional) Output file for property renaming report. It will contain lines in the form of old:new. This feature has some fringe use cases, such as minifying JSON messages. However it's recommended that you use protobuf instead.
defs: (List of strings; optional) Specifies additional flags to be passed to the Closure Compiler, e.g. "--hide_warnings_for=some/path/". To see what flags are available, run: bazel run @io_bazel_rules_closure//third_party/java/jscomp:main -- --help

Support for AngularJS

When compiling AngularJS applications, you need to pass custom flags to the Closure Compiler. This can be accomplished by adding the following to your closure_js_binary rule:

closure_js_binary(
    # ...
    defs = [
        "--angular_pass",
        "--export_local_property_definitions",
    ],
)

closure_js_test

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_test")
closure_js_test(name, srcs, data, deps, css, html, language, pedantic, suppress,
                compilation_level, entry_points, defs)

Runs JavaScript unit tests inside a headless web browser.

This is a build macro that composes closure_js_library, closure_js_binary, and phantomjs_test.

A test is defined as any function in the global namespace that begins with test, setUp, or tearDown. You are not required to @export these functions. If you don't have a global namespace, because you're using goog.module or goog.scope, then you must register your test functions with goog.testing.testSuite.

Each test file should require goog.testing.jsunit and goog.testing.asserts because they run the tests and provide useful testing functions such as assertEquals().

Any JavaScript file related to testing is strongly recommended to contain a goog.setTestOnly() statement in the file. However this is not required, because some projects might not want to directly reference Closure Library functions.

No Network Access

Your test will run within a hermetically sealed environment. You are not allowed to send HTTP requests to any external servers. It is expected that you'll use Closure Library mocks for things like XHR. However a local HTTP server is started up on a random port that allows to request runfiles under the /filez/WORKSPACE_NAME/ path.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the outputted executable, data will contain all transitive sources, data, and other runfiles.

Arguments

name: (Name; required) A unique name for this rule.
srcs: (List of labels; required) List of _test.js source files that register test functions.
deps: (List of labels; optional) Direct dependency list passed along to closure_js_library. This list will almost certainly need "@io_bazel_rules_closure//closure/library:testing".
data: (List of labels; optional) Passed to closure_js_library.
css: Passed to closure_js_binary.
html: Passed to phantomjs_test.
language: Passed to closure_js_binary.
compilation_level: Passed to closure_js_binary. Setting this to "WHITESPACE_ONLY" will cause tests to run significantly faster (at the expense of type checking.)
pedantic: Passed to closure_js_binary.
suppress: Passed to closure_js_library.
entry_points: Passed to closure_js_binary.
defs: Passed to closure_js_binary.

phantomjs_test

load("@io_bazel_rules_closure//closure:defs.bzl", "phantomjs_test")
phantomjs_test(name, data, deps, html, harness, runner)

Runs PhantomJS (QtWebKit) for unit testing purposes.

This is a low level rule. Please use the closure_js_test macro if possible.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the outputted executable, data will contain all transitive sources, data, and other runfiles.

Arguments

name: (Name; required) Unique name for this rule.
data: (List of labels; optional) Additional runfiles for the local HTTP server to serve, under the /filez/ + repository path. This attribute should not be necessary, because the transitive runfile data is already collected from dependencies.
deps: (List of labels; required) Labels of Skylark rules exporting transitive_js_srcs. Each source will be inserted into the webpage in its own <script> tag based on a depth-first preordering.
html: (Label; optional; default is "@io_bazel_rules_closure//closure/testing:empty.html") HTML file containing DOM structure of virtual web page before <script> tags are automatically inserted. Do not include a doctype in this file.
harness: (Label; required; default is "@io_bazel_rules_closure//closure/testing:phantomjs_harness") JS binary or library exporting a single source file, to be used as the PhantomJS outer script.
runner: (Label; optional; default is "@io_bazel_rules_closure//closure/testing:phantomjs_jsunit_runner") Same as deps but guaranteed to be loaded inside the virtual web page last. This should run whatever tests got loaded by deps and then invoke callPhantom to report the result to the harness.

closure_js_deps

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_deps")
closure_js_deps(name, deps)

Generates a dependency file, for an application using the Closure Library.

Generating this file is necessary for running an application in raw sources mode, because it tells the Closure Library how to load namespaces from the web server that are requested by goog.require().

For example, if you've made your source runfiles available under a protected admin-only path named /filez/, then raw source mode could be used as follows:

<script src="/filez/external/closure_library/closure/goog/base.js"></script>
<script src="/filez/myapp/deps.js"></script>
<script>goog.require('myapp.main');</script>
<script>myapp.main();</script>

Implicit Output Targets

name.js: A JavaScript source file containing goog.addDependency() statements which map Closure Library namespaces to JavaScript source paths. Each path is expressed relative to the location of the Closure Library base.js file.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the deps.js output files and data will contain that file in addition to all transitive JS sources and data.

Arguments

name: (Name; required) A unique name for this rule. Convention states that this be "deps".
deps: (List of labels; required) List of closure_js_library and closure_js_template_library targets which define all JavaScript sources in your application.

closure_js_template_library

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_template_library")
closure_js_template_library(name, srcs, data, deps, globals, plugin_modules,
                            should_generate_js_doc,
                            should_provide_require_soy_namespaces,
                            should_generate_soy_msg_defs,
                            soy_msgs_are_external, incremental_dom)

Compiles Closure templates to JavaScript source files.

This rule is necessary in order to render Closure templates from within JavaScript code.

This rule pulls in a transitive dependency on the Closure Library.

The documentation on using Closure Templates can be found here.

For additional help on using some of these attributes, please see the output of the following:

bazel run @io_bazel_rules_closure//third_party/java/soy:SoyToJsSrcCompiler -- --help
bazel run @io_bazel_rules_closure//third_party/java/soy:SoyToIncrementalDomSrcCompiler -- --help

Implicit Output Targets

src.js: A separate JavaScript source file is generated for each file listed under srcs. The filename will be the same as the template with a .js suffix. For example foo.soy would become foo.soy.js.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the generated JS output files and data will contain all transitive JS sources and data.
closure_js_library: srcs will be the generated JS output files, data will contain the transitive data, language will be ECMASCRIPT5_STRICT, deps will contain necessary libraries, and no_closure_library will be False.

Arguments

name: (Name; required) A unique name for this rule.
srcs: (List of labels; required) A list of .soy source files that represent this library.
data: (List of labels; optional) Runfiles directly referenced by Soy sources in this rule. For example, if the template has an <img src=foo.png> tag, then the data attribute of its rule should be set to ["foo.png"] so the image is available in the web server runfiles.
deps: (List of labels; optional) List of closure_js_library, closure_js_template_library and closure_js_proto_library targets which define symbols referenced by the template.
globals: (List of labels; optional) List of text files containing symbol definitions that are only considered at compile-time. For example, this file might look as follows:
```
com.foo.bar.Debug.PRODUCTION = 0
com.foo.bar.Debug.DEBUG = 1
com.foo.bar.Debug.RAW = 2
```
plugin_modules: (List of labels; optional; default is []) Passed along verbatim to the SoyToJsSrcCompiler above.
should_generate_js_doc: (Boolean; optional; default is True) Passed along verbatim to the SoyToJsSrcCompiler above. Does not apply when using Incremental DOM.
should_provide_require_soy_namespaces: (Boolean; optional; default is True) Passed along verbatim to the SoyToJsSrcCompiler above. Does not apply when using Incremental DOM.
should_generate_soy_msg_defs: (Boolean; optional; default is False) Passed along verbatim to the SoyToJsSrcCompiler above. Does not apply when using Incremental DOM.
soy_msgs_are_external: (Boolean; optional; default is False) Passed along verbatim to the SoyToJsSrcCompiler above. Does not apply when using Incremental DOM.
incremental_dom: (Boolean; optional; default is False; example; experimental) Generate Incremental DOM compatible templates.

Incremental DOM is a different algorithm for rendering templates. It updates DOM elements in-place, rather than destroying and recreating them. This makes a tradeoff of less memory for more CPU. It also carries practical benefits; for example, the entire page could re-rendered and an input field would not lose its focus.

Google is already using this feature for multiple production services. However it is marked experimental because it's a relatively recent development. The web frameworks team at Google is still battle testing this library internally.

closure_java_template_library

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_java_template_library")
closure_java_template_library(name, srcs, data, deps, java_package)

Compiles Closure templates to Java source files.

This rule is necessary in order to serve Closure templates from a Java backend.

Unlike closure_js_template_library, globals are not specified by this rule. They get added at runtime by your Java code when serving templates.

This rule pulls in a transitive dependency on Guava, Guice, and ICU4J.

The documentation on using Closure Templates can be found here.

For additional help on using some of these attributes, please see the output of the following:

bazel run @io_bazel_rules_closure//third_party/java/soy:SoyParseInfoGenerator -- --help

Implicit Output Targets

SrcSoyInfo.java: A separate Java source file is generated for each file listed under srcs. The filename will be the same as the template, converted to upper camel case, with a SoyInfo.java suffix. For example foo_bar.soy would become FooBarSoyInfo.java.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the compiled jar file and data will contain all transitive data.
java_library: srcs will be the generated Java source files, and data will contain the transitive data.

Arguments

name: (Name; required) A unique name for this rule.
srcs: (List of labels; required) A list of .soy source files that represent this library.
data: (List of labels; optional) Runfiles directly referenced by Soy sources in this rule. For example, if the template has an <img src=foo.png> tag, then the data attribute of its rule should be set to ["foo.png"] so the image is available in the web server runfiles.
deps: (List of labels; optional) Soy files to parse but not to generate outputs for.
java_package: (List of labels; required) The package for the Java files that are generated, e.g. "com.foo.soy".

closure_py_template_library

TODO

closure_css_library

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_css_library")
closure_css_library(name, srcs, data, deps)

Defines a set of CSS stylesheets.

This rule does not compile your stylesheets; it is used in conjunction with closure_css_binary which produces the minified CSS file.

This rule should be referenced by any closure_js_library rule whose sources contain a goog.getCssName('foo') call if foo is a CSS class name defined by this rule. The same concept applies to closure_js_template_library rules that contain {css('foo')} expressions.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the generated JS output files and data will contain all transitive CSS/GSS sources and data.
closure_js_library: srcs is empty, data is the transitive CSS sources and data, language is ANY, and no_closure_library is True. However the closure_css_library rule does pass special information along when used as a dep in closure_js_library. See its documentation to learn more.

Arguments

name: (Name; required) A unique name for this rule. Convention states that this end with _lib.
srcs: (List of labels; required) A list of .gss or .css source files that represent this library.

The order of stylsheets is srcs is undefined. If a CSS file overrides definitions in another CSS file, then each file must be specified in separate closure_css_library targets. That way Bazel can order your CSS definitions based on the depth-first preordering of dependent rules.

It is strongly recommended you use @provide and @require statements in your stylesheets so the CSS compiler can assert that the ordering is accurate.
data: (List of labels; optional) Runfiles directly referenced by CSS sources in this rule. For example, if the CSS has a url(foo.png) then the data attribute of its rule should be set to ["foo.png"] so the image is available in the web server runfiles.
deps: (List of labels; optional) List of other closure_css_library targets on which the CSS files in srcs depend.
orientation: (String; optional; default is "LTR") Defines the text direction for which this CSS was designed. This value can be:
- LTR: Outputs a sheet suitable for left to right display.
- RTL: Outputs a sheet suitable for right to left display.
An error will be raised if any deps do not have the same orientation. CSS libraries with different orientations can be linked together by creating an intermediary closure_css_binary that flips its orientation.

closure_css_binary

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_css_binary")
closure_css_binary(name, deps, renaming, debug, defs)

Turns stylesheets defined by closure_css_library rules into a single minified CSS file.

Closure-specific syntax such as variables, functions, conditionals, and mixins will be evaluated and turned into normal CSS. The documentation on using these features can be found here.

Unlike most CSS minifiers, this will minify class names by default. So this rule can be referenced by the css flag of closure_js_binary, in order to let the Closure Compiler know how to substitute the minified class names. See the renaming documentation below for more information.

Implicit Output Targets

name.css: A minified CSS file defining the transitive closure of dependent stylesheets compiled in a depth-first preordering.
name.css.map: CSS sourcemap file. This tells browsers like Chrome and Firefox where your CSS definitions are located in their original source files.
name.css.js: JavaScript file containing a goog.setCssNameMapping() statement which tells the Closure Compiler and Library how to minify CSS class names. The use of this file is largely handled transparently by the build system. The user should only need to worry about this file when rendering Soy templates from Java code, because its contents will need to be parsed into a map using a regular expression, which is then passed to the Soy Tofu Java runtime.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be the generated .css, .css.map, and .css.js output files. data will contain all transitive CSS/GSS sources and data.
closure_css_library: srcs is the output .css file, data is the transitive CSS sources and data, and orientation is the output orientation.

Arguments

name: (Name; required) A unique name for this rule. Convention states that such rules be named foo_bin or foo_dbg if debug = True.
deps: (List of labels; required) List of closure_css_library rules to compile. All dependencies must have their orientation attribute set to the same value.
renaming: (Boolean; optional; default is True) Enables CSS class name minification. This is one of the most powerful features of the Closure Tools. By default, this will turn class names like .foo-bar into things like .a-b. If debug = True then it will be renamed .foo_-bar_.

In order for this to work, you must update your JavaScript code to use the goog.getCssName("foo-bar") when referencing class names. JavaScript library targets that reference CSS classes must add the appropriate CSS library to its deps attribute. The css attribute of the closure_js_binary also needs to be updated to point to this CSS binary target, so the build system can verify (at compile time) that your CSS and JS binaries are both being compiled in a harmonious way.

You'll also need update your templates to say {css('foo-bar')} in place of class names. The closure_js_template_library must also depend on the appropriate CSS library.
debug: (Boolean; optional; default is False) Enables debug mode, which causes the compiled stylesheet to be pretty printed. If renaming = True then class names will be renamed, but still readable to humans.
orientation: (String; optional; default is "NOCHANGE") Specify this option to perform automatic right to left conversion of the input. You can choose between:
- NOCHANGE: Uses same orientation as was specified in dependent libraries.
- LTR: Outputs a sheet suitable for left to right display.
- RTL: Outputs a sheet suitable for right to left display.
The input orientation is calculated from the orientation flag of all closure_css_library targets listed in deps. If the input orientation is different than the requested output orientation, then 'left' and 'right' values in direction sensitive style rules are flipped. If the input already has the desired orientation, this option effectively does nothing except for defining GSS_LTR and GSS_RTL, respectively.
vendor: (String; optional; default is None) Creates browser-vendor-specific output by stripping all proprietary browser-vendor properties from the output except for those associated with this vendor. Valid values are:
- WEBKIT
- MOZILLA
- MICROSOFT
- OPERA
- KONQUEROR
The default behavior is to not strip any browser-vendor properties.
defs: (List of strings; optional) Specifies additional flags to be passed to the Closure Stylesheets compiler. To see what flags are available, run: bazel run @io_bazel_rules_closure//third_party/java/csscomp:ClosureCommandLineCompiler

closure_js_proto_library

load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_proto_library")
closure_js_proto_library(name, srcs, add_require_for_enums, binary,
                         import_style)

Defines a set of Protocol Buffer files.

Documentation

Implicit Output Targets

name.js: A generated protocol buffer JavaScript library.
name.descriptor: A protoc FileDescriptorsSet representation of the .proto files.

Rule Polymorphism

This rule can be referenced as though it were the following:

filegroup: srcs will be empty and data will contain all transitive JS sources and data.
closure_js_library: srcs will be the generated JS output files, data will contain the transitive data, language will be ECMASCRIPT5_STRICT, and deps will contain necessary libraries.

Arguments

name: (Name; required) A unique name for this rule. Convention states that such rules be named foo_proto.
srcs: (List of labels; required) A list of .proto source files that represent this library.
add_require_for_enums: (Boolean; optional; default is False) Add a goog.require() call for each enum type used. If false, a forward declaration with goog.forwardDeclare is produced instead.
binary: (Boolean; optional; default is True) Enable binary-format support.
import_style: (String; optional; default is IMPORT_CLOSURE) Specifies the type of imports that should be used. Valid values are:
- IMPORT_CLOSURE // goog.require()
- IMPORT_COMMONJS // require()
- IMPORT_BROWSER // no import statements
- IMPORT_ES6 // import { member } from ''

Name		Name	Last commit message	Last commit date
Latest commit History 344 Commits
.bazelci		.bazelci
closure		closure
java		java
javatests		javatests
third_party		third_party
.gitignore		.gitignore
.travis.yml		.travis.yml
AUTHORS		AUTHORS
CONTRIBUTING.md		CONTRIBUTING.md
CONTRIBUTORS		CONTRIBUTORS
LICENSE		LICENSE
README.md		README.md
WORKSPACE		WORKSPACE

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Closure Rules for Bazel (αlpha)

Overview

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Caveat Emptor

Setup

Overriding Dependency Versions

Examples

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closure_js_library

Rule Polymorphism

Arguments

closure_js_binary

Implicit Output Targets

Rule Polymorphism

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Support for AngularJS

closure_js_test

No Network Access

Rule Polymorphism

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phantomjs_test

Rule Polymorphism

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closure_js_deps

Implicit Output Targets

Rule Polymorphism

Arguments

closure_js_template_library

Implicit Output Targets

Rule Polymorphism

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closure_java_template_library

Implicit Output Targets

Rule Polymorphism

Arguments

closure_py_template_library

closure_css_library

Rule Polymorphism

Arguments

closure_css_binary

Implicit Output Targets

Rule Polymorphism

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closure_js_proto_library

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