WebDriver's Build System

• WebDriver 's Build System
• Target Names
• Short Target Names
• Implicit Targets
• Outputs
• Dependencies
• Browsers
• Build Targets
• Common Attributes
• java_library
• java_test
• js_deps
• js_binary
• js_fragment
• js_fragment_header
• js_test
• py_test
• rake_task
• gcc_library

WebDriver is a large project: if we tried to push everything into a single monolithic build file it eventually becomes unmanageable. We know this. We've tried it. So we broke the single Rakefile into a series of build.desc files. Each of these describe a part of the build.

Let's take a look at a build.desc file. This is part of the main test build.desc:

java_test(name = "single",
  srcs = [
    "SingleTestSuite.java",
  ],
  deps = [
    ":tests",
    "//java/server/src/org/openqa/selenium/server",
    "//java/client/test/org/openqa/selenium/v1:selenium-backed-webdriver-test",
    "//java/client/test/org/openqa/selenium/firefox:test",
  ]  ])

This highlights most of the key concepts. Firstly, it declares target, in this case there is a single java_test target. Each target has a name attribute.

Target Names

The combination of the location of the "build.desc" file and the name are used to derive the rake tasks that are generated. All task names are prefixed with "//" followed by the path to the directory containing the "build.desc" file relative to the Rakefile, followed by a ":" and then the name of the target within the "build.desc". An example makes this far clearer :)

The rake task generated by this example is //java/client/test/org/openqa/selenium:single

Short Target Names

As a shortcut, if a target is named after the directory containing the "build.desc" file, you can omit the part of the rake task name after the colon. In our example: //java/server/src/org/openqa/selenium/server is the same as //java/server/src/org/openqa/selenium/server:server.

Implicit Targets

Some build rules supply implicit targets, and provide related extensions to a normal build target. Examples include generating archives of source code, or running tests. These are declared by appending a further colon and the name of the implicit target to the full name of a build rule. In our example, you could run the tests using "//java/client/test/org/openqa/selenium:single:run"

Each of the rules described below have a list of implicit targets that are associated with them.

Outputs

Each target specified in a "build.desc" file produces one and only one output. This is important. Keep it in mind. Generally, all output files are placed in the "build" directory, relative to the rake task name. In our example, the output of "//java/org/openqa/selenium/server" would be found in "build/java/org/openqa/selenium/server.jar". Build rules should output the names and locations of any files that they generate.

Dependencies

Take a look at the "deps" section of the "single" target above. The ":tests" is a reference to a target in the current "build.desc" file, in this case, it's a "java_library" target immediately above. You'll also see that there's a reference to several full paths. For example "//java/server/src/org/openqa/selenium/server" This refers to another target defined in a crazy fun build.desc file.

Browsers

The py_test and js_test rules have special handling for running the same tests in multiple browsers. Relevant browser-specific meta-data is held in rake-tasks/browsers.rb. The general way to use this is to append _browsername to the target name; without the _browsername suffix, the tests will be run for all browsers.

As an example, if we had a js_test rule //foo/bar, we would run its tests in firefox by running the target //foo/bar_ff:run or we would run in all available browsers by running the target //foo/bar:run

Build Targets

Being a brief description of the available targets that you can use.

Common Attributes

The following attributes are required for all build targets:

The following attributes are commonly used:

java_library

• Output: JAR file named after the "name" attribute if the "srcs" attribute is set.
• Implicit Targets: run (if "main" attribute specifiec), project, project-srcs, uber, zip
• Required Attributes: "name" and at least one of "srcs" or "deps".

java_test

• Output: JAR file named after the "name" attribute if the "srcs" attribute is set.
• Implicit Targets: run, project, project-srcs, uber, zip
• Required Attributes: "name" and at least one of "srcs" or "deps".

js_deps

• Output: Marker file to indicate task is up to date.
• Implicit Targets: None
• Required Attributes: "name" and "srcs"

js_binary

• Output: A monolithic JS file containing all dependencies and sources compiled using the closure compiler without optimizations.
• Implicit Targets: None
• Required Attributes: At least one of srcs or deps.

js_fragment

• Output: Source of an anonymous function representing the exported function, compiled by the closure compiler with all optimizations turned on.
• Implicit Targets: None
• Required Attributes: name, module, function, deps

js_fragment_header

• Output: A C header file with all js_fragment dependencies declared as constants.
• Implicit Targets: None
• Required Attributes: name, deps

js_test

• Output:
• Implicit Targets: _BROWSER:run, run
• Required Attributes: None.

Assuming browsers = ['ff', 'chrome'], for target //foo, the implicit targets: //foo_ff:run and //foo_chrome:run will be generated, which run the tests in each of those browsers, and the implicit target //foo:run will be generated, which runs the tests in both ff and chrome.

py_test

• Output: Creates the directory structure required to run the listed python tests.
• Implicit Targets: _BROWSER:run, run
• Required Attributes: name.

Note: Every py_test invocation is performed in a new virtualenv.

rake_task

• Output: A crazy fun build rule that can be referred to "blow the escape" hatch and use ordinary rake targets.
• Implicit Targets: None
• Required Attributes: name, task_name, out.

gcc_library

• Output: Shared library file named after the "name" attribute if the "srcs" attribute is set.
• Implicit Targets: None.
• Required Attributes: "name" and "srcs".

Note: When building a new library for the first time, the build will succeed but copying to pre-built will fail with a similar message:

cp build/cpp/amd64/libimetesthandler64.so 
go aborted!
can't convert nil into String

Solution: Copy the just-built library to the appropriate prebuilt folder (cpp/prebuilt/arch/).