Gerrit failing with Bazel@HEAD

[davido]

On most recent Bazel version (b2fac74) and Gerrit@HEAD (039faeaa58e70d8adc5e81c37c02253529efd52b) the build is failing:

$ b10 build :release
INFO: Invocation ID: 82712434-7693-4d6a-8beb-299577ac363b
DEBUG: /home/davido/.cache/bazel/_bazel_davido/5c01f4f713b675540b8b424c5c647f63/external/bazel_toolchains/rules/version_check.bzl:45:9: 
Current running Bazel is not a release version and one was not defined explicitly in rbe_autoconfig target. Falling back to '0.25.2'
DEBUG: /home/davido/.cache/bazel/_bazel_davido/5c01f4f713b675540b8b424c5c647f63/external/bazel_toolchains/rules/version_check.bzl:45:9: 
Current running Bazel is not a release version and one was not defined explicitly in rbe_autoconfig target. Falling back to '0.25.2'
DEBUG: /home/davido/.cache/bazel/_bazel_davido/5c01f4f713b675540b8b424c5c647f63/external/bazel_skylib/lib/versions.bzl:96:13: Current Bazel is not a release version; cannot check for compatibility. Make sure that you are running at least Bazel 0.25.0.
INFO: Call stack for the definition of repository 'webcomponentsjs' which is a bower_archive (rule definition at /home/davido/projects/gerrit2/tools/bzl/js.bzl:120:17):
 - /home/davido/projects/gerrit2/lib/js/bower_archives.bzl:166:5
 - /home/davido/projects/gerrit2/WORKSPACE:1349:1
ERROR: An error occurred during the fetch of repository 'webcomponentsjs':
   Traceback (most recent call last):
	File "/home/davido/projects/gerrit2/tools/bzl/js.bzl", line 67
		_run_npm_binary_str(ctx, ctx.attr._bower_archive, [])
	File "/home/davido/projects/gerrit2/tools/bzl/js.bzl", line 51, in _run_npm_binary_str
		" ".join(([python_bin, ctx.path(ctx.attr....))
sequence element must be a string (got 'path')
ERROR: /home/davido/projects/gerrit2/polygerrit-ui/app/BUILD:7:1: no such package '@webcomponentsjs//': Traceback (most recent call last):
	File "/home/davido/projects/gerrit2/tools/bzl/js.bzl", line 67
		_run_npm_binary_str(ctx, ctx.attr._bower_archive, [])
	File "/home/davido/projects/gerrit2/tools/bzl/js.bzl", line 51, in _run_npm_binary_str
		" ".join(([python_bin, ctx.path(ctx.attr....))
sequence element must be a string (got 'path') and referenced by '//polygerrit-ui/app:polygerrit_ui'
ERROR: Analysis of target '//:release' failed; build aborted: no such package '@webcomponentsjs//': Traceback (most recent call last):
	File "/home/davido/projects/gerrit2/tools/bzl/js.bzl", line 67
		_run_npm_binary_str(ctx, ctx.attr._bower_archive, [])
	File "/home/davido/projects/gerrit2/tools/bzl/js.bzl", line 51, in _run_npm_binary_str
		" ".join(([python_bin, ctx.path(ctx.attr....))
sequence element must be a string (got 'path')
INFO: Elapsed time: 0.475s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (27 packages loaded, 126 targets configured)

The culprit seems to be this method in js.bzl:

# for use in repo rules.
def _run_npm_binary_str(ctx, tarball, args):
    python_bin = ctx.which("python")
    return " ".join([
        python_bin,
        ctx.path(ctx.attr._run_npm),
        ctx.path(tarball),
    ] + args)

To reproduce, clone recursively Gerrit Code Review and run: bazel-at-head build :release.

All is fine on Bazel 0.26.0.

@laurentlb, @philwo Any idea, why we have not noticed this breakage on Gerrit build on Bazel CI?

[laurentlb]

It looks like Gerrit build is failing: https://buildkite.com/bazel/gerrit/builds/2821#f1c9b046-3e7a-4277-acfb-a06ff95c8dfe

On the Bazelisk pipeline, there's no failure. I think this is because we test at the last green commit.

The error you see is caused by the flag incompatible_string_join_requires_strings.

[laurentlb]

fyi, we're going to improve the error message: #8507

[davido]

Thanks for the quick reply! It would be definitely helpful if the error message would reference the relevant flag.