Thank you. May I suggest you and the authors of the other 2 related PRs, @uri-canva and @rdnetto4 discuss this and try to reach consensus on how to move forward.

I will close my PR and create a new PR for darwin support after Bazel has been upgraded to 0.13.0. As @mboes notes my PR has bigger changes than strictly required for the upgrade because of that.

@GrahamcOfBorg build bazel

No attempt on x86_64-darwin (full log)

The following builds were skipped because they don't evaluate on x86_64-darwin: bazel

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

No attempt on aarch64-linux (full log)

The following builds were skipped because they don't evaluate on aarch64-linux: bazel

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnfree = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnfree = true; }
to ~/.config/nixpkgs/config.nix.

Failure on x86_64-linux (full log)

Attempted: bazel

[2,076 / 2,210] no action
INFO: Elapsed time: 217.383s, Critical Path: 53.88s
[2,076 / 2,210] no action
INFO: 1706 processes: 1488 local, 218 worker.
[2,076 / 2,210] no action
FAILED: Build did NOT complete successfully

ERROR: Could not build Bazel
builder for '/nix/store/ahjv8qhsacyd6difl940v9bxdgyd7h6v-bazel-0.13.0.drv' failed with exit code 1
error: build of '/nix/store/ahjv8qhsacyd6difl940v9bxdgyd7h6v-bazel-0.13.0.drv' failed

@mboes the /usr/bin/env replacement is still necessary. The build is currently failing with:

Executing genrule //src:embedded_tools; 0s local
/nix/store/xn5gv3lpfy91yvfy9b0i7klfcxh9xskz-bash-4.4-p19/bin/bash: bazel-out/host/bin/src/create_embedded_tools: /usr/bin/env: bad interpreter: No such file or directory

Note that is might not be the case on your local host if build sandboxing is turned off.

@GrahamcOfBorg build bazel

No attempt on aarch64-linux (full log)

The following builds were skipped because they don't evaluate on aarch64-linux: bazel

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnfree = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnfree = true; }
to ~/.config/nixpkgs/config.nix.

No attempt on x86_64-darwin (full log)

The following builds were skipped because they don't evaluate on x86_64-darwin: bazel

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

Success on x86_64-linux (full log)

Attempted: bazel

//examples/cpp:hello-success_test                                        PASSED in 0.1s
//examples/java-native/src/test/java/com/example/myproject:hello         PASSED in 0.2s

Executed 2 out of 2 tests: 2 tests pass.
There were tests whose specified size is too big. Use the --test_verbose_timeout_warnings command line option to see which ones these are.
installing
post-installation fixup
patching script interpreter paths in /nix/store/k9i0ana4jn3nd8sp50qjav42k4v4h7rr-bazel-0.13.0
checking for references to /tmp in /nix/store/k9i0ana4jn3nd8sp50qjav42k4v4h7rr-bazel-0.13.0...
/nix/store/k9i0ana4jn3nd8sp50qjav42k4v4h7rr-bazel-0.13.0

things failing with nox-review:

error: build of '/nix/store/3p39fs8ffx0ypb71nvxmvlz4bb08ihka-python2.7-tflearn-0.2.1.drv', '/nix/store/d16mya1nc0inxijjmxypkpx4p633vjpz-python3.6-tensorflow-1.5.0.drv', '/nix/store/d4qdhaaj9n6lfl67s52kvi8ng8s8mn40-python3.6-edward-1.3.5.drv', '/nix/store/k5r4bbbsn00kqjhnv1bxghfxhacpihw7-python3.6-tflearn-0.2.1.drv', '/nix/store/racll38b0qkg79yd0x06yvz75h04mp2j-python2.7-edward-1.3.5.drv', '/nix/store/xk47wvbmyzjalbdfadr70v841bax4nfa-python2.7-tensorflow-1.5.0.drv' failed

they all seem to be tensorflow-related

even on master, the CI seems to be installing bazel 0.11.0: https://github.com/tensorflow/tensorflow/blob/0bde713c06895b9ce2de61d6aea1bff5415ddcbc/tensorflow/tools/ci_build/install/install_bazel.sh#L18

Yes, this breaks the build of tensorflow and would require us to bump it to 1.8 according to discussion in #40205 . I'd rather wait for someone familiar with tensorflow to test if 1.8 really works before we merge this.

it would also be acceptable to keep version 0.12 around until tensorflow gets upgraded

So I tried giving building tensorflow 1.8 a go. But I either ran out of memory or hit what looks like a internal race condition within Bazel. The error goes something like this:

java.lang.RuntimeException: Unrecoverable error while evaluating node 'PACKAGE:tensorflow/core/kernels' (requested by nodes '//tensorflow:libtensorflow_framework.so com.google.devtools.build.lib.skyframe.BuildConfigurationValue$Key@edd564fa true (2067960961)', '//tensorflow:libtensorflow_framework.so com.google.devtools.build.lib.skyframe.BuildConfigurationValue$Key@71af1344 false (265845462)', '//tensorflow/core/grappler/costs:measuring_cost_estimator com.google.devtools.build.lib.skyframe.BuildConfigurationValue$Key@71af1344 false (2120862100)', '//tensorflow/core:core_cpu_internal com.google.devtools.build.lib.skyframe.BuildConfigurationValue$Key@71af1344 false (308542468)', '//tensorflow/core:framework_internal_headers_lib_gather com.google.devtools.build.lib.skyframe.BuildConfigurationValue$Key@71af1344 false (2112525397)', '//tensorflow/core:framework_internal_headers_lib_gather com.google.devtools.build.lib.skyframe.BuildConfigurationValue$Key@edd564fa true (824725492)')
        at com.google.devtools.build.skyframe.AbstractParallelEvaluator$Evaluate.run(AbstractParallelEvaluator.java:424)
        at com.google.devtools.build.lib.concurrent.AbstractQueueVisitor$WrappedRunnable.run(AbstractQueueVisitor.java:355)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalArgumentException: Invalid EvalException:
java.lang.InterruptedException
        at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:503)
        at com.google.common.util.concurrent.AbstractFuture$TrustedFuture.get(AbstractFuture.java:85)
        at com.google.common.util.concurrent.ForwardingFuture.get(ForwardingFuture.java:62)
        ...

Only related upstream issue I could find is bazelbuild/bazel#2423.

Upshot: let's try keeping 0.12 for Tensorflow then, until we can get to the bottom of this.

Or more likely, this issue: bazelbuild/bazel#5177.

@mboes thanks for investigating. Let's keep the old version as bazel_0_12 and pin tensorflow to it for the time being.

@xeji so I retried the build on another computer. It works fine. PR to upgrade Tensorflow submitted as #40689. I tested that Bazel 0.13 is able to build that version of Tensorflow on that other computer. While I did run into a known race condition on my laptop, provided @GrahamcOfBorg is happy then I think we should still upgrade, because I could not reproduce this race condition and for all we know the race condition was already there in Bazel 0.12.

@mboes this cannot be merged yet because the tensorflow update (#40689) doesn't build.
We can merge this if we keep the old version as bazel_0_12 and pin tensorflow to it.
Or we can let this wait until #40689 is fixed. What do you prefer?

cc @abbradar

@xeji looks like tensorflow is no longer a problem, because since #41259 Tensorflow is now built from a binary distribution. So I believe that blocker is now gone.

I have rebased the commits that were on this branch originally to current master, which has #41259 merged in.

@GrahamcOfBorg build bazel

No attempt on aarch64-linux (full log)

The following builds were skipped because they don't evaluate on aarch64-linux: bazel

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnfree = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnfree = true; }
to ~/.config/nixpkgs/config.nix.

Failure on x86_64-darwin (full log)

Attempted: bazel

./tools/test/collect_coverage.sh: interpreter directive changed from "/bin/bash -x" to "/nix/store/46y32j94pm0cz6ygywb3wxxj0fdbqj13-bash/bin/bash -x"
./tools/test/test-setup.sh: interpreter directive changed from "/bin/bash" to "/nix/store/46y32j94pm0cz6ygywb3wxxj0fdbqj13-bash/bin/bash"
configuring
no configure script, doing nothing
building
Building Bazel from scratch....../usr/bin/xcrun clang -fobjc-arc -framework CoreServices -framework Foundation -o /tmp/bazel_jHWExtEd/archive/_embedded_binaries/xcode-locator tools/osx/xcode_locator.m
xcode-select: error: no developer tools were found at '/Applications/Xcode.app', and no install could be requested (perhaps no UI is present), please install manually from 'developer.apple.com'.
/nix/store/7amnc2662p390bgzj6c0snylj19vxmj2-stdenv-darwin/setup: line 1291: ./output/bazel: No such file or directory
builder for '/nix/store/skpwcblpi077b7zw26mm0jqmlznsw8d9-bazel-0.13.0.drv' failed with exit code 127
�[31;1merror:�[0m build of '/nix/store/skpwcblpi077b7zw26mm0jqmlznsw8d9-bazel-0.13.0.drv' failed

Success on x86_64-linux (full log)

Attempted: bazel

//examples/cpp:hello-success_test                                        PASSED in 0.0s
//examples/java-native/src/test/java/com/example/myproject:hello         PASSED in 0.2s

Executed 2 out of 2 tests: 2 tests pass.
There were tests whose specified size is too big. Use the --test_verbose_timeout_warnings command line option to see which ones these are.
installing
post-installation fixup
patching script interpreter paths in /nix/store/jh7xc1qbf4by5cqnqxgiafvwfwqbyish-bazel-0.13.0
checking for references to /tmp in /nix/store/jh7xc1qbf4by5cqnqxgiafvwfwqbyish-bazel-0.13.0...
/nix/store/jh7xc1qbf4by5cqnqxgiafvwfwqbyish-bazel-0.13.0

Darwin build was broken before this PR despite #41911, which (according to its title) should have fixed it. cc @uri-canva

xcode-select: error: no developer tools were found at '/Applications/Xcode.app', and no install could be requested (perhaps no UI is present), please install manually from 'developer.apple.com'.

It seems Bazel cannot be built on CI without Xcode, and I'm not sure we can install Xcode from nix because of the license. A shim can be created, but that's a lot of work.

In the meantime I'll double check it's working on darwin on master, thanks for the heads up @xeji.