"Execute an input binary" Skylark cookbook example fails

[dfabulich]

Consider this git repository: https://github.com/dfabulich/bazel-tempfile-example

It's a copy and paste from the "Execute an input binary" sample from the Skylark cookbook. http://bazel.io/docs/skylark/cookbook.html

I expected it to succeed, but it failed.

dfab: /tp/tempfiles $ bazel build --verbose_failures //:e
INFO: Found 1 target...
ERROR: /private/tmp/tp/tempfiles/BUILD:3:1: Executing a.sh failed: a.sh failed: error executing command
  (cd /private/var/tmp/_bazel_dfabulich/cddaf6252bd073c3ed3cc32458593a42/tempfiles && \
  exec env - \
  a.sh bazel-out/local_darwin-fastbuild/bin/hello bazel-out/local_darwin-fastbuild/bin/foo): com.google.devtools.build.lib.shell.BadExitStatusException: Process exited with status 1: a.sh failed: error executing command
  (cd /private/var/tmp/_bazel_dfabulich/cddaf6252bd073c3ed3cc32458593a42/tempfiles && \
  exec env - \
  a.sh bazel-out/local_darwin-fastbuild/bin/hello bazel-out/local_darwin-fastbuild/bin/foo): com.google.devtools.build.lib.shell.BadExitStatusException: Process exited with status 1.
process-wrapper: execvp("a.sh", ...): No such file or directory
Target //:e failed to build
INFO: Elapsed time: 0.066s, Critical Path: 0.01s
dfab: /tp/tempfiles $ ls -l bazel-tempfiles/a.sh
lrwxr-xr-x  1 dfabulich  wheel  30 Feb 29 23:33 bazel-tempfiles/a.sh -> /private/tmp/tp/tempfiles/a.sh

a.sh is definitely there in the bazel-tempfiles directory, but since it's not being invoked with ./a.sh, it's not on the path, so the script isn't executed. You can run a.sh by hand like this:

bazel-tempfiles/a.sh bazel-out/local_darwin-fastbuild/bin/hello bazel-out/local_darwin-fastbuild/bin/foo

How is this example supposed to work?

[dfabulich]

$ bazel version
Build label: 0.2.0-homebrew
Build target: bazel-out/local_darwin-fastbuild/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Tue Feb 23 14:12:29 2016 (1456236749)
Build timestamp: 1456236749
Build timestamp as int: 1456236749

[kchodorow]

We should update the example to prefix a.sh with "./". Thanks for the report!

[dfabulich]

I don't think that's possible. In the example, "a.sh" is a file label. If you change it to "./a.sh" it fails with this error:

ERROR: /private/tmp/tp/tempfiles/BUILD:3:1: //:e: invalid label './a.sh' in attribute 'binary' in 'execute' rule: invalid target name './a.sh': target names may not contain '.' as a path segment.

And since a.sh is being provided as the executable of a ctx.action call, there's no place to add ./ anywhere in the Skylark code, either.

I think the only way to fix this code is to to move a.sh into a subdirectory.

Which is to say, I think there's an actual bug in Bazel, because running an executable in the WORKSPACE root directory really ought to work.

[kchodorow]

Ah, good point. Perhaps the skylark action code needs to change.

[kchodorow]

Assigning to @jmmv, since you just did #958.

[jmmv]

This actually looks like #347.

I very much doubt #958 had to do anything with this: the default path modified in that bug should have never come into play because it's very hard to imagine a realistic scenario in which PATH is unset in the environment. If a user's rules worked when invoking a binary from the top-level directory, they most likely did so because the user's own PATH included the current directory in it.

I think the examples in the documentation are correct, but those examples are not specific to any BUILD file: if you put them in a subdirectory, they would work; but if you put them in the top-level directory they do not.

[laurentlb]

Obsolete.

Examples are now here: https://github.com/bazelbuild/examples