Bazel installer stopped working after d3f8efc, if project has .bazelversion file

[davido]

After installing of bazel 2.0.0rc3 I am seeing this:

  $ cd gerrit
  $ cat .bazelversion
  2.0.0rc3
  bazelisk build :gerrit
  019/12/02 21:55:13 Downloading https://releases.bazel.build/2.0.0/rc3/bazel-2.0.0rc3-linux-x86_64...
Starting local Bazel server and connecting to it...
INFO: Invocation ID: 893fd804-3bed-41d5-8b7c-dda793e67520
INFO: Analyzed target //:release (419 packages loaded, 8377 targets configured).
INFO: Found 1 target...
INFO: Deleting stale sandbox base /home/davido/.cache/bazel/_bazel_davido/5c01f4f713b675540b8b424c5c647f63/sandbox
INFO: From Compiling 656 JavaScript files to polygerrit-ui/app/polygerrit_ui_closure_bin.js:
WARNING - Failed to resolve sourcemap at bazel-out/k8-fastbuild/bin/polygerrit-ui/app/custom-style-interface.min.js.map: bazel-out/k8-fastbuild/bin/polygerrit-ui/app/custom-style-interface.min.js.map
  Codes: SOURCEMAP_RESOLVE_FAILED

0 error(s), 1 warning(s)

Target //:release up-to-date:
  bazel-bin/release.war
INFO: Elapsed time: 154.755s, Critical Path: 99.96s
INFO: 435 processes: 3 remote cache hit, 330 linux-sandbox, 8 local, 94 worker.
INFO: Build completed successfully, 457 total actions

As expected, bazel was downloaded by the bazelisk:

  $ ls -all ~/.cache/bazelisk/bin/bazelbuild/bazel-2.0.0rc3-linux-x86_64
-rwxr-xr-x 1 davido users 43780359 Dec  2 21:55 /home/davido/.cache/bazelisk/bin/bazelbuild/bazel-2.0.0rc3-linux-x86_64

Now, if I try to build with bazel directly, bypassing bazelisk, it is failing:

  $ bazel build :gerrit
ERROR: The project you're trying to build requires Bazel 2.0.0rc3 (specified in /home/davido/projects/gerrit2/.bazelversion), but it wasn't found in /home/davido/.bazel/bin.

Bazel binaries for all official releaeses can be downloaded from here:
  https://github.com/bazelbuild/bazel/releases

You can download the required version directly using this command:
  (cd "/home/davido/.bazel/bin" && curl -LO https://releases.bazel.build/2.0.0rc3/release/bazel-2.0.0rc3-linux-x86_64 && chmod +x bazel-2.0.0rc3-linux-x86_64)

Now, I have to fetch bazel twice? It also doesn't change if I install Bazel locally, I still see the same breakage, even though bazel-2.0.0rc3 was installed:

  $ bash bazel-2.0.0rc3-installer-linux-x86_64.sh --user
  [...]
  Uncompressing.......

Bazel is now installed!

Make sure you have "/home/davido/bin" in your path. You can also activate bash
completion by adding the following line to your :
  source /home/davido/.bazel/bin/bazel-complete.bash

See http://bazel.build/docs/getting-started.html to start a new project!

And bazel still doesn't work:

  $ bazel version
  Build label: 2.0.0rc3
  $ cd gerrit

  $ bazel build :gerrit
ERROR: The project you're trying to build requires Bazel 2.0.0rc3 (specified in /home/davido/projects/gerrit2/.bazelversion), but it wasn't found in /home/davido/.bazel/bin.

Bazel binaries for all official releaeses can be downloaded from here:
  https://github.com/bazelbuild/bazel/releases

You can download the required version directly using this command:
  (cd "/home/davido/.bazel/bin" && curl -LO https://releases.bazel.build/2.0.0rc3/release/bazel-2.0.0rc3-linux-x86_64 && chmod +x bazel-2.0.0rc3-linux-x86_64)

[meisterT]

cc @meteorcloudy @philwo

[meteorcloudy]

This is caused by d3f8efc

@philwo
Looks like this is not only affecting users installing Bazel through APT repo, but also with bash bazel-2.0.0rc3-installer-linux-x86_64.sh --user. Maybe we should add a feature to check the current installed Bazel already matches the given version in .bazelversion? So that users don't run into the having to install Bazel twice problem.

[meteorcloudy]

Maybe we can package the version.txt file into the debian package and installer, then make the shell script check the Bazel version here?

[davido]

Interestingly, bazel project itself is not affected, and:

  $ cd bazel
  $ bazel build src:bazel-bin-dev

just works. However, all projects that have .bazelversion stopped working after d3f8efc.

So the workaround for now is to remove .bazelversion file from the tree.

Also, I would have expected, that higher version number semantic is still preserved. If .bazelversion file has "1.0.0" version, and I have installed bazel version 3.2.1, then it should just work. And not telling me that the .bazelversion has version 1.0.0, but currently higher version 3.2.1 is installed. The only reason to refuse running bazel, if the installed version is lower than the one referenced in .bazelversion file.

[dslomov]

Is this a release blocker for 2.0?

[philwo]

@dslomov Yes. I'm looking into this now.

[philwo]

So, here are some thoughts on this:

If a project has a .bazelversion file, it means it "should" be built with that exact Bazel version. Because the .bazelversion file is used to basically "version your build tool with your source code", I do not want to implement fuzzy matching like "as long as it's the same major version, it's fine". It will use and require the exact version, so this is working as intended.

Let's assume you have a project with a .bazelversion file that specifies "1.1.0" as the required Bazel version, then here's what happens:

• If you use Bazelisk, it will automatically and transparently use the correct version.
• If you installed Bazel via apt-get and you don't have the bazel-1.1.0 package installed, it will suggest to run the command to install that package.
• If you install Bazel via the installer, it will suggest the command to download Bazel 1.1.0 and put it into the correct place.
• If you use a plain Bazel binary (no wrapper script), it will ignore the .bazelversion file and just use whatever Bazel version you have.

I think this behavior makes sense and is pretty user friendly?

However, I agree that there's one optimization we should add: If the .bazelversion asks for Bazel X.Y and the Bazel version that was installed via apt-get install bazel or the installer script is already Bazel X.Y, then we do not need to download the same version once again. (Basically what Yun suggested.)

I'll think of some logic for the wrapper script that supports this, then we can do a cherry-pick and it should be fine.

[philwo]

Also, I don't understand this reasoning:

However, all projects that have .bazelversion stopped working after d3f8efc.
So the workaround for now is to remove .bazelversion file from the tree.

No, of course not - the workaround is not to remove the .bazelversion file, the "workaround" is to simply do what the (IMHO pretty helpful) error message suggests - install the required Bazel version :) I don't see how this is "broken" or how "Bazel stopped working".

Edit: @davido Sorry, to be clear, I totally understand why having to download the same Bazel version twice (once as the "latest" Bazel and once as the "specifically versioned package" Bazel) is weird and not a good UX. I'll fix this before we release Bazel 2.0. The general behavior should be fine and an improvement, though, or what do you think?