The Bazel team is happy to announce a new version of Bazel, Bazel 0.18.

Here are the major changes since Bazel 0.17.

General changes

• New bazelrc file list. If you need to keep both the old and new lists of .rc files active concurrently to support multiple versions of Bazel, you can import the old file location into the new list using try-import. This imports a file if it exists and silently exits if it does not. You can use this method to account for a user file that may or may not exist

• .bazelignore is now fully functional.

• The startup flag --host_javabase has been renamed to --server_javabase to avoid confusion with the build flag --host_javabase.

Android

• The Android resource processing pipeline now supports persistence via worker processes. Enable it with --persistent_android_resource_processor. We have observed a 50% increase in build speed for clean local builds and up to 150% increase in build speed for incremental local builds.

C++

• In-memory package //tools/defaults has been removed (controlled by --incompatible_disable_tools_defaults_package flag). Please see migration instructions and migrate soon, the flag will be flipped in Bazel 0.19, and the legacy behavior will be removed in Bazel 0.20.

• Late bound option defaults (typical example was the --compiler flag, when it was not specified, it’s value was computed using the CROSSTOOL) are removed (controlled by --incompatible_disable_late_bound_option_defaults flag). Please see migration instructions and migrate soon, the flag will be flipped in Bazel 0.19, and the legacy behavior will be removed in Bazel 0.20.

• Depsets are no longer accepted in user_compile_flags and user_link_flags in the C++ toolchain API (controlled by --incompatible_disable_depset_in_cc_user_flags flag) affects C++ users. Please see migration instructions and migrate soon, the flag will be flipped in Bazel 0.19, and the legacy behavior will be removed in Bazel 0.20.

• CROSSTOOL is no longer consulted when selecting C++ toolchain (controlled by --incompatible_disable_cc_toolchain_label_from_crosstool_proto flag). Please see migration instructions and migrate soon, the flag will be flipped in Bazel 0.19, and the legacy behavior will be removed in Bazel 0.20.

• You can now use toolchain_identifier attribute on cc_toolchain to pair it with CROSSTOOL toolchain.

• C++ specific Make variables are no longer passed from the CppConfiguration, but from the C++ toolchain (controlled by --incompatible_disable_cc_configuration_make_variables flag). Please see migration instructions and migrate soon, the flag will be flipped in Bazel 0.19, and the legacy behavior will be removed in Bazel 0.20.

• Starlark api accessing C++ toolchain in ctx.fragments.cpp is removed (controlled by --incompatible_disable_legacy_cpp_toolchain_skylark_api flag). Please migrate soon, the flag will be flipped in Bazel 0.19, and the legacy behavior will be removed in Bazel 0.20.

• cc_binary link action no longer hardcodes -static-libgcc for toolchains that support embedded runtimes (guarded by --experimental_dont_emit_static_libgcc temporarily). Proper deprecation using --incompatible flags will follow.

Java

• Future versions of Bazel will require a locally installed JDK for Java development. Previously Bazel would fall back to using the embedded --server_javabase if no JDK as available. Pass --incompatible_never_use_embedded_jdk_for_javabase to disable the legacy behaviour.

• --javacopt= no longer affects compilations of tools that are executed during the build; use --host_javacopt= to change javac flags in the host configuration.

Objective C

• objc_library now supports the module_name attribute.

Starlark

• Adds --incompatible_expand_directories to automatically expand directories in Starlark command lines. Design doc: https://docs.google.com/document/d/11agWFiOUiz2htBLj6swPTob5z78TrCxm8DQE4uJLOwM

• Support fileset expansion in ctx.actions.args(). Controlled by --incompatible_expand_directories.

Windows

• --windows_exe_launcher is deprecated, this flag will be removed soon. Please make sure you are not using it.

• Bazel now supports the symlink runfiles tree on Windows with --experimental_enable_runfiles flag. For more details, see this doc.

Other Changes

• A new experimental option --experimental_ui_deduplicate has been added. It causes the UI to attempt to deduplicate messages from actions to keep the console output cleaner.

• Add --modify_execution_info, a flag to customize action execution info.

• Add ExecutionInfo to aquery output for ExecutionInfoSpecifier actions.

• When computing --instrumentation_filter, end filter patterns with "[/:]" to match non-top-level packages exactly and treat top-level targets consistently.

• Added the bazel info server_log command, which obtains the main Bazel server log file path. This can help debug Bazel issues.

• aapt shrink resources now properly respect filter configurations.

Thank you to our contributors!

This release contains contributions from many people at Google, as well as Andreas Hippler, Arielle Albon, Benjamin Peterson, Eran Shalom, Geoff Maddox, Igal Tabachnik, Iancu, Jared Neil, Jason Gavris, Li-Wen Hsu, Loo Rong Jie, microjixl, Oscar Bonilla, Philip Patsch, Taras Tsugrii, XindaH, and Yannic Bonenberger.

Thank you to everyone who contributed to this release!