bazelversion without trailing newline is an error (?)

[justinsb]

Description of the problem / feature request:

After upgrading to bazel 2.0, bazel silently failed to launch. All bazel commands exited very quickly. I had a .bazelversion file with no newline at the end.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

Create a .bazelversion file with "1.2.0" but no trailing newline; try running bazel, observe that it exits immediately.

What operating system are you running Bazel on?

Linux (I'm a googler if you want to contact me directly)

What's the output of bazel info release?

With .bazelversion of 1.2.0 without a newline it outputs nothing; with a newline it outputs:

bazel info release
INFO: Invocation ID: ee1bab32-42c3-400a-98cb-1293e0659e59
release 1.2.0

Not sure how helpful that is though! dpkg -l bazel tells me I am running the bazel package version 2.0.0.

Any other information, logs, or outputs that you want to share?

I believe the issue is that I have a .bazelversion file without a trailing newline. Adding a newline fixed the problem. (Proposed fix is in kubernetes/kops#8161)

The line in question (based on bash -x -v /usr/bin/bazel) seems to be this one:

bazel/scripts/packages/bazel.sh

Line 114 in d5ae460

read -r bazel_version < "${workspace_dir}/.bazelversion"

I did confirm that read -r foo < .bazelversion; echo $? gives 1 without the trailing newline, and 0 with a trailing newline, so this seems to match.

[jin]

@meteorcloudy @philwo

[philwo]

Ahh, good catch and sorry for the breakage. I will fix this and add a test case for it!

[konste]

@philwo But why Bazel even read .bazelversion file? I thought it is only used by Bazelisk.

[philwo]

@konste Bazel itself doesn't read the .bazelversion file, but the bazel shell script that's installed as /usr/bin/bazel if you install Bazel using apt-get or a similar package manager does - this is intended to help people build projects with the correct Bazel version. Projects like TensorFlow had lots of issues with people trying to build it with a too old or too new version, because they weren't aware that you need a specific Bazel version.

[konste]

Thank you, @philwo!