Managing the Bazel lockfile#

The Bazel lockfile (MODULE.bazel.lock) is checked into the Pigweed repository. Some changes to the Bazel build (especially changes to the MODULE.bazel file) may require regenerating the lockfile. This document describes how to do this.

Simple case: automatic updates#

In the simplest case, Bazel will automatically update the lockfile in the course of your development work, as you execute commands like bazel build. You just need to commit the changes as part of your CL.

Complex case: platform-dependency#

Occasionally, some (transitive) dependency added to the build will be platform-dependent. An example of this are Rust crates added using the crates.from_specs module extension. If this happens, you will see errors like the following in CQ builders running on platforms different from the one you developed on:

ERROR: The module extension 'ModuleExtensionId{bzlFileLabel=@@rules_rust+//crate_universe:extension.bzl, extensionName=crate, isolationKey=Optional.empty}' for platform os:osx,arch:x86_64 does not exist in the lockfile.

What’s going on here is that the exact versions of external dependencies that enter the build vary depending on the OS or CPU architecture of the system Bazel is running on.

Fortunately, we have some builders meant to help you in this situation.

What do I do?#

  1. Upload your change to Gerrit.

  2. Use the “CHOOSE TRYJOBS” dialog to run the “pigweed-linux-bazel-lockfile” tryjob.

  3. If the job fails, the result will include the diff that you need to apply to your CL (via git apply) to update the Bazel lockfile for Linux. (You can find it under “lockfile_check” > “logs” > “git_diff.txt”.) Apply the patch and upload a new patchset to Gerrit. If the job passes, the lockfile is already up to date on this host platform and no patching is necessary!

    Here’s an example tryjob: http://ci.chromium.org/b/8728814798922152993.

  4. Run the “pigweed-mac-arm-bazel-lockfile” tryjob, and apply the patch it generates.

  5. Run the “pigweed-mac-x86-bazel-lockfile” tryjob, and apply the patch it generates.

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