executing $(location my_tool) in a genrule doesn't work if it's in the same folder

[bsilver8192]

$(location a_tool) in the cmd of a genrule doesn't add a leading ./ if the tool is in the same package, which means it doesn't work. Whether a_tool is a target or a source file doesn't seem to matter.

Example BUILD (test_tool is an empty shell script):

genrule(
  name = 'my_genrule',
  tools = [
    'test_tool',
  ],
  outs = [
    'test_output',
  ],
  cmd = '$(location test_tool) > $(location test_output)',
)

I end up with this error:

$ bazel build ... --verbose_failures
INFO: Found 1 target...
INFO: From Executing genrule //:my_genrule:
/bin/bash: test_tool: command not found
ERROR: /tmp/tool_test_workspace/BUILD:1:1: Executing genrule //:my_genrule failed: bash failed: error executing command 
  (cd /home/brian/.cache/bazel/_bazel_brian/421f2e8b7d7f6adfe83f902fa91a62f0/tool_test_workspace && \
  exec env - \
    PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games \
  /bin/bash -c 'source tools/genrule/genrule-setup.sh; test_tool > bazel-out/local_linux-fastbuild/genfiles/test_output'): com.google.devtools.build.lib.shell.BadExitStatusException: Process exited with status 127: bash failed: error executing command 
  (cd /home/brian/.cache/bazel/_bazel_brian/421f2e8b7d7f6adfe83f902fa91a62f0/tool_test_workspace && \
  exec env - \
    PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games \
  /bin/bash -c 'source tools/genrule/genrule-setup.sh; test_tool > bazel-out/local_linux-fastbuild/genfiles/test_output'): com.google.devtools.build.lib.shell.BadExitStatusException: Process exited with status 127.
Target //:my_genrule failed to build
INFO: Elapsed time: 0.096s, Critical Path: 0.01s

Moving the tool to another folder (whether that's another package or not) fixes this example.

[damienmg]

Wow that's because you are in the root package it's missing the leading ./.

We should add the leading ./ when in the root package.

[ulfjack]

I just ran into this when trying to port an existing project to bazel, which contains a shell script in the root package that I want to run.

[jmmv]

Rather than prefixing only files in the root package with ./, maybe we should prefix all relative paths with ./? It shouldn't hurt, and it's nice to be explicit and consistent — though I'm unaware of the consequences at this point.

[bsilver8192]

I'm pretty sure f50e669 fixed this. It definitely works with current master.