$(location) and $(locations) do not properly quote file paths

[ensonic]

Follow up on #3475

Description of the problem / feature request:

A genrul using $(locations) fails with 'unbounded shell variable'.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

filegroup(
  name = "files",
  srcs = glob(["dir/*"]),    # put files with special chars here, e.g. $data.json, @foo.bar, ...
)

genrule(
  name = "example",
  srcs = [":files"],
  outs = ["foo"],
  cmd = "echo FILES: $(locations //:files) | tee $@",
)

What operating system are you running Bazel on?

linux

What's the output of bazel info release?

release 0.13.0

Have you found anything relevant by searching the web?

#3475

[aehlig]

My suggested fix is https://bazel-review.googlesource.com/c/bazel/+/56250 But note that there is no "correct" quoting of `$(location)` as those `$(location)` arguments can occur in various places. To me, the following all seem correct uses of a genrule (where `script` is the GNU version of `script(1)`). ``` cmd = "$(location :tool) $(location :files)" ``` ``` cmd = "script -c '$(location :tool) $(location :files)' $(location :log)" ``` ``` cmd = 'script -c "$(location :tool) $(location :files)" $(location :log)' ```

…

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