compile_pip_requirements fails if the output file `requirements.txt` does not already exist

[diazona]

🐞 bug report

Affected Rule

The issue is caused by the rule: compile_pip_requirements

Is this a regression?

Not as far as I can tell. I'm not aware of any version of rules_python in which this works (although I haven't exhaustively checked).

Description

I'm trying to use compile_pip_requirements to create requirements_lock.txt for the first time from requirements.in. This is exactly the same issue as #1129 (now closed), except that I encountered it on Linux whereas the other report was on Windows. (I would guess the issue is platform-independent.) I wasn't sure of the right protocol for "reactivating" an issue that was closed for inactivity, but if I was wrong to post this, feel free to reopen the original issue instead.

🔬 Minimal Reproduction

WORKSPACE

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "rules_python",
    sha256 = "8844347f050932fb339f8bce78ac3bd0f0dc118d347ce4d2dcc39490f2954941",
    strip_prefix = "rules_python-76f1c76f60ccb536d3b3e2c9f023d8063f40bcd5",
    url = "https://github.com/bazelbuild/rules_python/archive/76f1c76f60ccb536d3b3e2c9f023d8063f40bcd5.tar.gz",
)

load("@rules_python//python:repositories.bzl", "py_repositories")

py_repositories()

BUILD

load("@rules_python//python:pip.bzl", "compile_pip_requirements")

compile_pip_requirements(
    name = "requirements",
    src = "//:requirements.in",
    visibility = ["//visibility:public"],
)

requirements.in

python-dummy==0.1

I pushed a repository with these files as well: https://github.com/diazona/bazel-python-error

🔥 Exception or Error

$ bazelisk run //:requirements.update
INFO: Analyzed target //:requirements.update (1 packages loaded, 4 targets configured).
ERROR: /home/diazona/tmp/bazel-python-error/BUILD:3:25: Middleman _middlemen/requirements.update-runfiles failed: missing input file '//:requirements.txt'
ERROR: /home/diazona/tmp/bazel-python-error/BUILD:3:25: Middleman _middlemen/requirements.update-runfiles failed: 1 input file(s) do not exist
Target //:requirements.update failed to build
Use --verbose_failures to see the command lines of failed build steps.
ERROR: /home/diazona/tmp/bazel-python-error/BUILD:3:25 Middleman _middlemen/requirements.update-runfiles failed: 1 input file(s) do not exist
INFO: Elapsed time: 0.285s, Critical Path: 0.01s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully
ERROR: Build failed. Not running target

🌍 Your Environment

Operating System:

Gentoo Linux

$ uname -a
Linux acetylene09 6.7.0-gentoo #1 SMP PREEMPT_DYNAMIC Sun Jan 14 21:02:35 PST 2024 x86_64 AMD Ryzen 7 2700X Eight-Core Processor AuthenticAMD GNU/Linux

Output of bazel version:

$ bazelisk version
Bazelisk version: development
Build label: 7.0.2
Build target: @@//src/main/java/com/google/devtools/build/lib/bazel:BazelServer
Build time: Thu Jan 25 16:13:35 2024 (1706199215)
Build timestamp: 1706199215
Build timestamp as int: 1706199215

I also tried versions 6.5.0, 6.3.1, and 5.4.1 (all through Bazelisk, by setting USE_BAZEL_VERSION), with the same results.

Rules_python version:

Commit 76f1c76f60ccb536d3b3e2c9f023d8063f40bcd5, which is the current head of main as I'm writing this

Anything else relevant?

If I create requirements.txt manually, regardless of what I put in it, the update command seems to work as expected: it replaces the content of requirements.txt with a list of requirements.

And I might very well be misunderstanding what compile_pip_requirements is supposed to do. If the existing behavior (fail if the output file doesn't exist) is expected, then consider this a request to improve the clarity of the documentation. (I'd be happy to offer a PR in that case.)

[brunobely]

This example says it was generated by running bazel run //:requirements.update. I wonder if that must be (or can be) depended on?

[diazona]

If I understand correctly, I don't think so, because the error I'm reporting happens when building //:requirements.update. Depending on it would just trigger the same error whenever its dependent target gets built.

[aignas]

I am not sure if this is a doc issue where we just ask the users to create an empty file. At the end of the day this is something that gets passed to a target definition and the error happens within bazel itself, not within the code that is owned by rules python.