refactor: don't load repo-phase objects from build-phase (#2056)

As a general practice, the repo-phase and build-phase shouldn't load
code from one
another because they can't use each other's objects. It can also result
in confusing
behavior because the "starlark environment" is slightly different
between the two phases.

Additionally, Google's version of Bazel essentially disables repo-phase
objects, so
loading e.g. http_archive results in errors. This makes it more
difficult to import
rules_python into Google, as we have to maintain patches to cut out the
code (and thus
we spend more time trying to import the code than working on it).

python/private/pypi/deps.bzl

diff --git a/python/private/pypi/deps.bzl b/python/private/pypi/deps.bzl
index 81bef7a..e07d9aa 100644
--- a/python/private/pypi/deps.bzl
+++ b/python/private/pypi/deps.bzl
@@ -123,10 +123,7 @@
 """
 
 # Collate all the repository names so they can be easily consumed
-all_requirements = [name for (name, _, _) in _RULE_DEPS]
-
-def requirement(pkg):
-    return Label("@pypi__" + pkg + "//:lib")
+all_repo_names = [name for (name, _, _) in _RULE_DEPS]
 
 def pypi_deps():
     """

python/private/pypi/pip_compile.bzl

diff --git a/python/private/pypi/pip_compile.bzl b/python/private/pypi/pip_compile.bzl
index 7389e72..f284a00 100644
--- a/python/private/pypi/pip_compile.bzl
+++ b/python/private/pypi/pip_compile.bzl
@@ -20,7 +20,6 @@
 """
 
 load("//python:defs.bzl", _py_binary = "py_binary", _py_test = "py_test")
-load(":deps.bzl", "requirement")
 
 def pip_compile(
         name,
@@ -115,19 +114,19 @@
     args.extend(extra_args)
 
     deps = [
-        requirement("build"),
-        requirement("click"),
-        requirement("colorama"),
-        requirement("importlib_metadata"),
-        requirement("more_itertools"),
-        requirement("packaging"),
-        requirement("pep517"),
-        requirement("pip"),
-        requirement("pip_tools"),
-        requirement("pyproject_hooks"),
-        requirement("setuptools"),
-        requirement("tomli"),
-        requirement("zipp"),
+        Label("@pypi__build//:lib"),
+        Label("@pypi__click//:lib"),
+        Label("@pypi__colorama//:lib"),
+        Label("@pypi__importlib_metadata//:lib"),
+        Label("@pypi__more_itertools//:lib"),
+        Label("@pypi__packaging//:lib"),
+        Label("@pypi__pep517//:lib"),
+        Label("@pypi__pip//:lib"),
+        Label("@pypi__pip_tools//:lib"),
+        Label("@pypi__pyproject_hooks//:lib"),
+        Label("@pypi__setuptools//:lib"),
+        Label("@pypi__tomli//:lib"),
+        Label("@pypi__zipp//:lib"),
         Label("//python/runfiles:runfiles"),
     ] + extra_deps
 

python/private/pypi/whl_installer/BUILD.bazel

diff --git a/python/private/pypi/whl_installer/BUILD.bazel b/python/private/pypi/whl_installer/BUILD.bazel
index 58231ce..fc9c0e6 100644
--- a/python/private/pypi/whl_installer/BUILD.bazel
+++ b/python/private/pypi/whl_installer/BUILD.bazel
@@ -1,5 +1,4 @@
 load("//python:defs.bzl", "py_binary", "py_library")
-load("//python/private/pypi:deps.bzl", "requirement")
 
 py_library(
     name = "lib",
@@ -10,14 +9,13 @@
         "wheel_installer.py",
     ],
     visibility = [
-        "//tests:__subpackages__",
-        "//third_party/rules_pycross/pycross/private:__subpackages__",
+        "//:__subpackages__",
     ],
     deps = [
-        requirement("installer"),
-        requirement("pip"),
-        requirement("packaging"),
-        requirement("setuptools"),
+        "@pypi__installer//:lib",
+        "@pypi__packaging//:lib",
+        "@pypi__pip//:lib",
+        "@pypi__setuptools//:lib",
     ],
 )
 
@@ -32,5 +30,5 @@
 filegroup(
     name = "distribution",
     srcs = glob(["*"]),
-    visibility = ["//python/private/pypi:__subpackages__"],
+    visibility = ["//:__subpackages__"],
 )

python/private/pypi/whl_library.bzl

diff --git a/python/private/pypi/whl_library.bzl b/python/private/pypi/whl_library.bzl
index 77cbd4e..a3fa1d8 100644
--- a/python/private/pypi/whl_library.bzl
+++ b/python/private/pypi/whl_library.bzl
@@ -21,7 +21,7 @@
 load("//python/private:repo_utils.bzl", "REPO_DEBUG_ENV_VAR", "repo_utils")
 load("//python/private:toolchains_repo.bzl", "get_host_os_arch")
 load(":attrs.bzl", "ATTRS", "use_isolated")
-load(":deps.bzl", "all_requirements")
+load(":deps.bzl", "all_repo_names")
 load(":generate_whl_library_build_bazel.bzl", "generate_whl_library_build_bazel")
 load(":parse_whl_name.bzl", "parse_whl_name")
 load(":patch_whl.bzl", "patch_whl")
@@ -490,7 +490,7 @@
         ] + [
             # Includes all the external dependencies from repositories.bzl
             Label("@" + repo + "//:BUILD.bazel")
-            for repo in all_requirements
+            for repo in all_repo_names
         ],
     ),
 }, **ATTRS)