Bazel 2.0

_posts/2019-12-20-bazel-2.0.md

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+---
+layout: posts
+title: "Bazel 2.0"
+authors:
+  - aehlig
+---
+
+A new major version of Bazel,
+[Bazel 2.0](https://github.com/bazelbuild/bazel/releases/tag/2.0.0) has just
+been released. In particular, it brings some important flag flips that did
+not make it into
+[Bazel 1.0](https://blog.bazel.build/2019/10/10/bazel-1.0.html).
+
+## Incompatible changes
+Bazel 2.0 is a new major release and brings the following incompatible changes.
+
+* [`--incompatible_remap_main_repo`](https://github.com/bazelbuild/bazel/issues/7130)
+  is enabled by default. Both ways of addressing the main repository (by its
+  name and by '@') are now considered referring to the same repository.
+
+* [`--incompatible_disallow_dict_lookup_unhashable_keys`](https://github.com/bazelbuild/bazel/issues/9184)
+  is enabled by default.
+
+* [`--incompatible_remove_native_maven_jar`](https://github.com/bazelbuild/bazel/issues/6799)
+  is now enabled by default and the flag removed.
+
+* [`--incompatible_prohibit_aapt1`](https://github.com/bazelbuild/bazel/issues/10000)
+  is enabled by default.
+
+## Aquery
+
+* Proto v2 for aquery proto output formats, which reduces the output size
+  compared to v1, guarded behind the flag
+  [`--incompatible_proto_output_v2`](https://github.com/bazelbuild/bazel/issues/10358).
+  This proto format is still experimental and subject to further changes.
+
+## Platforms
+
+* New incompatible flag, [`--incompatible_remove_enabled_toolchain_types`](https://github.com/bazelbuild/bazel/issues/10262),
+  which allows removing the `PlatformConfiguration.enabled_toolchain_types`
+  field.
+
+## Other important changes
+
+* Package loading now consistently fails if package loading had a glob
+  evaluation that encountered a symlink cycle or symlink infinite
+  expansion. Previously, such package loading with such glob evaluations would
+  fail only in some cases.
+
+
+* The `--disk_cache` flag can now also be used together with the gRPC remote
+  cache.
+
+* An action's discover inputs runtime metrics is now categorized as parse time
+  on the CriticalPathComponent.
+
+* Bazel's Debian package and the binary installer now include an improved
+  wrapper that understands `<WORKSPACE>/.bazelversion` files and the
+  `$USE_BAZEL_VERSION` environment variable. This is similar to [what Bazelisk
+  offers](https://github.com/bazelbuild/bazelisk#how-does-bazelisk-know-which-bazel-version-to-run-and-where-to-get-it-from),
+  except that it works offline and integrates with apt-get.
+
+* We are planning to deprecate the runfiles manifest files, which aren't safe in
+  the presence of whitespace, and also unnecessarily require local CPU when
+  remote execution is used. This release adds
+  `--experimental_skip_runfiles_manifests` to disable the generation of the
+  input manifests (rule.manifest files) in most cases. This can be used for
+  initial testing, but the exact semantics are still subject to change; let us
+  know if this is causing problems. Note that this flag has no effect on Windows
+  by default or if `--experimental_enable_runfiles` is explicitly set to false.
+
+## Community
+
+This release contains contributions from many people at Google, as well as
+aldersondrive, Benjamin Peterson, Bor Kae Hwang, David Ostrovsky, John Millikin,
+Keith Smiley, Lauri Peltonen, nikola-sh, Peter Mounce, Tony Hsu.