cquery --output=files is not useful for external dependencies

[jscheid-ventana]

Description of the feature request:

With #15979 cquery --output=files provides a relative path to the output or source file. The feature request is to make the output as readily usable when the target is from an external dependency.

Bazel 6.0.0

% cat WORKSPACE
workspace(name = "com_example")
load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
% touch BUILD
% bazel cquery --output=files @bazel_tools//tools/build_defs/repo:git.bzl
Starting local Bazel server and connecting to it...
INFO: Analyzed target @bazel_tools//tools/build_defs/repo:git.bzl (1 packages loaded, 1 target configured).
INFO: Found 1 target...
external/bazel_tools/tools/build_defs/repo/git.bzl
INFO: Elapsed time: 3.607s, Critical Path: 0.00s
INFO: 0 processes.
INFO: Build completed successfully, 0 total actions

There is no WORKSPACE-relative "external" directory.

I happen to know that I can currently use $(bazel info output_path)/.. to get the parent directory to "external", but that's arcane knowledge and isn't directly provided by the cquery feature.

What underlying problem are you trying to solve with this feature?

Have cquery --output=files behave consistently for all files known to bazel.

Which operating system are you running Bazel on?

Linux

What is the output of bazel info release?

release 6.0.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

Linked issues and PRs associated with #15979

Any other information, logs, or outputs that you want to share?

No response

[fmeum]

There are pros and cons to emitting relative paths: They are hermetic (don't differ between developer machines), but at the same slightly harder to use (require prefixing with $(bazel info execution_root) to be resolvable in general).

@jscheid-ventana What do you think, would prominently documenting the fact that the paths emitted by --output=files may have to be (and can always) be resolved relative to $(bazel info execution_root) resolve the issue for you?

[jscheid-ventana]

would prominently documenting the fact that the paths emitted by --output=files may have to be (and can always) be resolved relative to $(bazel info execution_root) resolve the issue for you

Yes. Documentation would help clarify context for usage of output (versus some assumption that the bazel-out prefixes are relative to the helper symlinks, etc.) and seems to solve my problem: scripts can use a consistent path base for source, external, and output files.