Add support for relative requirements in pip_install

.bazelrc

@@ -3,7 +3,7 @@
 # This lets us glob() up all the files inside the examples to make them inputs to tests
 # (Note, we cannot use `common --deleted_packages` because the bazel version command doesn't support it)
 # To update these lines, run tools/bazel_integration_test/update_deleted_packages.sh
-build --deleted_packages=examples/legacy_pip_import/boto,examples/legacy_pip_import/extras,examples/legacy_pip_import/helloworld,examples/pip_install,examples/pip_parse,examples/py_import
-query --deleted_packages=examples/legacy_pip_import/boto,examples/legacy_pip_import/extras,examples/legacy_pip_import/helloworld,examples/pip_install,examples/pip_parse,examples/py_import
+build --deleted_packages=examples/legacy_pip_import/boto,examples/legacy_pip_import/extras,examples/legacy_pip_import/helloworld,examples/pip_install,examples/pip_parse,examples/py_import,examples/relative_requirements
+query --deleted_packages=examples/legacy_pip_import/boto,examples/legacy_pip_import/extras,examples/legacy_pip_import/helloworld,examples/pip_install,examples/pip_parse,examples/py_import,examples/relative_requirements
 
 test --test_output=errors

examples/BUILD

@@ -36,3 +36,8 @@ bazel_integration_test(
     name = "py_import_example",
     timeout = "long",
 )
+
+bazel_integration_test(
+    name = "relative_requirements_example",
+    timeout = "long",
+)

examples/relative_requirements/BUILD

@@ -0,0 +1,10 @@
+load("@pip//:requirements.bzl", "requirement")
+load("@rules_python//python:defs.bzl", "py_test")
+
+py_test(
+    name = "main",
+    srcs = ["main.py"],
+    deps = [
+        requirement("relative_package_name"),
+    ],
+)

examples/relative_requirements/README.md

@@ -0,0 +1,4 @@
+# relative_requirements example
+
+This example shows how to use pip to fetch relative dependencies from a requirements.txt file,
+then use them in BUILD files as dependencies of Bazel targets.

examples/relative_requirements/WORKSPACE

@@ -0,0 +1,15 @@
+workspace(name = "example_repo")
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "rules_python",
+    sha256 = "b6d46438523a3ec0f3cead544190ee13223a52f6a6765a29eae7b7cc24cc83a0",
+    url = "https://github.com/bazelbuild/rules_python/releases/download/0.1.0/rules_python-0.1.0.tar.gz",
+)
+
+load("@rules_python//python:pip.bzl", "pip_install")
+
+pip_install(
+    requirements = "//:requirements.txt",
+)

examples/relative_requirements/main.py

@@ -0,0 +1,5 @@
+import relative_package_name
+
+if __name__ == "__main__":
+    # Run a function from the relative package
+    print(relative_package_name.test())

examples/relative_requirements/relative_package/relative_package_name/__init__.py

@@ -0,0 +1,2 @@
+def test():
+    return True

examples/relative_requirements/relative_package/setup.py

@@ -0,0 +1,7 @@
+from setuptools import setup
+
+setup(
+    name='relative_package_name',
+    version='1.0.0',
+    packages=['relative_package_name'],
+)

examples/relative_requirements/requirements.txt

@@ -0,0 +1 @@
+./relative_package

python/pip_install/extract_wheels/__init__.py

@@ -8,6 +8,7 @@
 import argparse
 import glob
 import os
+import pathlib
 import subprocess
 import sys
 import json
@@ -63,17 +64,22 @@ def main() -> None:
     deserialized_args = dict(vars(args))
     arguments.deserialize_structured_args(deserialized_args)
 
+    # Pip is run with the working directory changed to the folder containing the requirements.txt file, to allow for
+    # relative requirements to be correctly resolved. The --wheel-dir is therefore required to be repointed back to the
+    # current calling working directory (the repo root in .../external/name), where the wheel files should be written to
     pip_args = (
         [sys.executable, "-m", "pip"] + 
         (["--isolated"] if args.isolated else []) + 
         ["wheel", "-r", args.requirements] +
+        ["--wheel-dir", os.getcwd()] +
         deserialized_args["extra_pip_args"]
     )
 
     env = os.environ.copy()
     env.update(deserialized_args["environment"])
+
     # Assumes any errors are logged by pip so do nothing. This command will fail if pip fails
-    subprocess.run(pip_args, check=True, env=env)
+    subprocess.run(pip_args, check=True, env=env, cwd=str(pathlib.Path(args.requirements).parent.resolve()))
 
     extras = requirements.parse_extras(args.requirements)