android_build_config

An android_build_config() rule is used to generate a BuildConfig class with global configuration variables that other android_library() rules can compile against. Currently, the only variable exposed by BuildConfig is a global boolean named DEBUG, much like the BuildConfig.java generated by the official Android build tools based on Gradle.

Details

The fields in the generated BuildConfig class will be non-constant-expressions (see JLS 15.28). However, if BuildConfig is packaged into an APK, it will be replaced with a new version where:

• The fields will be set to literal values (i.e., constant expressions).
• The boolean BuildConfig.DEBUG field will correspond to that of the package_type argument to the android_binary() rule that is packaging it.

This transformation is done before ProGuard is applied (if applicable), so that it can propagate constants from BuildConfig and eliminate dead code.

Function Signature

def android_build_config(
    *,
    name: str,
    default_target_platform: None | str = None,
    target_compatible_with: list[str] = [],
    compatible_with: list[str] = [],
    exec_compatible_with: list[str] = [],
    visibility: list[str] = [],
    within_view: list[str] = ["PUBLIC"],
    metadata: OpaqueMetadata = {},
    tests: list[str] = [],
    modifiers: OpaqueMetadata = [],
    _android_toolchain: str = "gh_facebook_buck2_shims_meta//:android",
    _apple_platforms: dict[str, str] = {},
    _build_only_native_code: bool = select({"prelude//android/constraints:build_only_native_code": True, "DEFAULT": False}),
    _is_building_android_binary: bool = select({"prelude//os:building_android_binary": True, "DEFAULT": False}),
    _java_toolchain: str = "gh_facebook_buck2_shims_meta//:java_for_android",
    contacts: list[str] = [],
    default_host_platform: None | str = None,
    labels: list[str] = [],
    licenses: list[str] = [],
    package: str = "",
    uses_content_based_path_for_jar_snapshot: bool = select({"DEFAULT": False}),
    values: list[str] = [],
    values_file: None | str = None,
) -> None

Parameters

• name: (required)

  name of the target

• default_target_platform: (defaults to: None)

  specifies the default target platform, used when no platforms are specified on the command line

• target_compatible_with: (defaults to: [])

  a list of constraints that are required to be satisfied for this target to be compatible with a configuration

• compatible_with: (defaults to: [])

  a list of constraints that are required to be satisfied for this target to be compatible with a configuration

• exec_compatible_with: (defaults to: [])

  a list of constraints that are required to be satisfied for this target to be compatible with an execution platform

• visibility: (defaults to: [])

  a list of visibility patterns restricting what targets can depend on this one

• within_view: (defaults to: ["PUBLIC"])

  a list of visibility patterns restricting what this target can depend on

• metadata: (defaults to: {})

  a key-value map of metadata associated with this target

• tests: (defaults to: [])

  a list of targets that provide tests for this one

• modifiers: (defaults to: [])

  an array of modifiers associated with this target

• contacts: (defaults to: [])

  A list of organizational contacts for this rule. These could be individuals who you would contact in the event of a failure or other issue with the rule.

  contacts = [ 'Joe Sixpack', 'Erika Mustermann' ]

• labels: (defaults to: [])

  Set of arbitrary strings which allow you to annotate a build rule with tags that can be searched for over an entire dependency tree using buck query().

• licenses: (defaults to: [])

  Set of license files for this library. To get the list of license files for a given build rule and all of its dependencies, you can use buck query

• package: (defaults to: "")

  Name of the Java package to use in the generated BuildConfig.java file. Most developers set this to the application id declared in the manifest via <manifest package="APP_ID">. Example: com.facebook.orca.

• values: (defaults to: [])

  List of strings that defines additional fields (and values) that should be declared in the generated BuildConfig.java file. Like DEBUG, the values will be non-constant-expressions that evaluate to the value specified in the file at compilation time. To override the values in an APK, specify build_config_values or build_config_values_file in android_binary().

• values_file: (defaults to: None)

  Optional path to a file that defines additional fields (and values) that should be declared in the generated BuildConfig.java file. Like DEBUG, the values will be non-constant-expressions that evaluate to the value specified in the file at compilation time. To override the values in an APK, specify build_config_values or build_config_values_file in android_binary().

  Note that values_file can be a generated file, as can build_config_values_file as demonstrated in the example below.

Examples

Here is an example of an android_build_config() rule that is transitively included by both debug and release versions of an android_binary() rule. The value of com.example.pkg.BuildConfig.DEBUG will be different in each APK even though they both transitively depend on the same :build_config rule.

android_build_config(
  name = 'build_config',
  package = 'com.example.pkg',
  values = [
    'String COMMIT_ID = "0000000000000000000000000000000000000000"',
  ],
)

# The .java files in this library may contain references to the boolean
# com.example.pkg.BuildConfig.DEBUG because :build_config is in the deps.
# It could also reference BuildConfig.COMMIT_ID.
android_library(
  name = 'mylib',
  srcs = glob(['src/**/*.java']),
  deps = [
    ':build_config',
  ],
)

android_binary(
  name = 'debug',
  package_type = 'DEBUG',
  keystore =  '//keystores:debug',
  manifest = 'AndroidManifest.xml',
  target = 'Google Inc.:Google APIs:19',
  deps = [
    ':mylib',
  ],
)

# The contents of the file generated by this rule might be:
#
# String COMMIT_ID = "7bf804bdf71fdbfc99cce3b155b3643f022c6fa4"
#
# Note that the output of :build_config_release_values will be cached by Buck.
# Assuming that generate_release_build_config.py depends on state that is not
# expressed by its deps (which violates a fundamental invariant in Buck!), a
# workaround is to ensure that the inputs to :build_config_release_values are
# changed in some way before :release is built to ensure that the output from
# :build_config_release_values is not pulled from cache. For example:
#
# $ buck build :release
# $ uuidgen > dummy_state_file.txt
# $ buck build :release
#
# This makes sure that generate_release_build_config.py is re-run before
# :release is rebuilt. This is much cheaper than deleting your build cache
# before rebuilding.
genrule(
  name = 'build_config_release_values',
  srcs = [ 'generate_release_build_config.py', 'dummy_state_file.txt' ],
  bash = 'generate_release_build_config.py $OUT',
  out = 'build_config_release_values.txt',
)

android_binary(
  name = 'release',
  package_type = 'RELEASE',
  keystore =  '//keystores:release',
  manifest = 'AndroidManifest.xml',
  target = 'Google Inc.:Google APIs:19',
  build_config_values_file = ':build_config_release_values',
  deps = [
    ':mylib',
  ],
)