refactor: don't load repo-phase objects from build-phase (bazel-contrib#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).

Author: rickeylev

python/private/pypi/deps.bzl

@@ -123,10 +123,7 @@ py_library(
 """
 
 # 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

@@ -20,7 +20,6 @@ make it possible to have multiple tools inside the `pypi` directory
 """
 
 load("//python:defs.bzl", _py_binary = "py_binary", _py_test = "py_test")
-load(":deps.bzl", "requirement")
 
 def pip_compile(
         name,
@@ -115,19 +114,19 @@ def pip_compile(
     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

@@ -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 @@ py_library(
         "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 @@ py_binary(
 filegroup(
     name = "distribution",
     srcs = glob(["*"]),
-    visibility = ["//python/private/pypi:__subpackages__"],
+    visibility = ["//:__subpackages__"],
 )

python/private/pypi/whl_library.bzl

@@ -21,7 +21,7 @@ load("//python/private:envsubst.bzl", "envsubst")
 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 @@ attr makes `extra_pip_args` and `download_only` ignored.""",
         ] + [
             # Includes all the external dependencies from repositories.bzl
             Label("@" + repo + "//:BUILD.bazel")
-            for repo in all_requirements
+            for repo in all_repo_names
         ],
     ),
 }, **ATTRS)