feat(pypi): support isolated pip.parse

.bazelrc.deleted_packages

@@ -36,6 +36,7 @@ common --deleted_packages=tests/integration/custom_commands
 common --deleted_packages=tests/integration/local_toolchains
 common --deleted_packages=tests/integration/pip_parse
 common --deleted_packages=tests/integration/pip_parse/empty
+common --deleted_packages=tests/integration/pip_parse_isolated
 common --deleted_packages=tests/integration/py_cc_toolchain_registered
 common --deleted_packages=tests/modules/another_module
 common --deleted_packages=tests/modules/other

python/private/pypi/extension.bzl

@@ -123,6 +123,23 @@ def build_config(
                 # overrides, etc. Index overrides per platform could be also used here.
             )
 
+    # When no platforms are configured (e.g., in isolated mode where
+    # rules_python's pip.default tags are not visible), provide a minimal
+    # host platform default so that requirements files can still be parsed.
+    if not defaults["platforms"]:
+        os_name = repo_utils.get_platforms_os_name(module_ctx)
+        arch_name = repo_utils.get_platforms_cpu_name(module_ctx)
+        platform_name = "{}_{}".format(os_name, arch_name)
+        defaults["platforms"][platform_name] = {
+            "name": platform_name.replace("-", "_").lower(),
+            "arch_name": arch_name,
+            "os_name": os_name,
+            "config_settings": [
+                "@platforms//cpu:{}".format(arch_name),
+                "@platforms//os:{}".format(os_name),
+            ],
+        }
+
     return struct(
         auth_patterns = defaults.get("auth_patterns", {}),
         netrc = defaults.get("netrc", None),

tests/integration/BUILD.bazel

@@ -67,6 +67,10 @@ rules_python_integration_test(
     name = "pip_parse_test",
 )
 
+rules_python_integration_test(
+    name = "pip_parse_isolated_test",
+)
+
 rules_python_integration_test(
     name = "pip_parse_workspace_test",
     bzlmod = False,

tests/integration/pip_parse_isolated/.bazelrc

@@ -0,0 +1,8 @@
+# Bazel configuration flags
+
+build --enable_runfiles
+
+common --experimental_isolated_extension_usages
+
+# https://docs.bazel.build/versions/main/best-practices.html#using-the-bazelrc-file
+try-import %workspace%/user.bazelrc

tests/integration/pip_parse_isolated/BUILD.bazel

@@ -0,0 +1,7 @@
+load("@rules_python//python:py_test.bzl", "py_test")
+
+py_test(
+    name = "test_isolated",
+    srcs = ["test_isolated.py"],
+    deps = ["@pypi//six"],
+)

tests/integration/pip_parse_isolated/MODULE.bazel

@@ -0,0 +1,19 @@
+module(name = "pip_parse_isolated")
+
+bazel_dep(name = "rules_python")
+local_path_override(
+    module_name = "rules_python",
+    path = "../../..",
+)
+
+python = use_extension("@rules_python//python/extensions:python.bzl", "python")
+python.toolchain(python_version = "3.13")
+
+# This test module verifies that dependencies can be used with `isolate = True`.
+pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip", isolate = True)
+pip.parse(
+    hub_name = "pypi",
+    python_version = "3.13",
+    requirements_lock = "//:requirements_lock.txt",
+)
+use_repo(pip, "pypi")

tests/integration/pip_parse_isolated/requirements_lock.txt

@@ -0,0 +1,2 @@
+six==1.17.0 \
+    --hash=sha256:4721f391ed90541fddacab5acf947aa0d3dc7d27b2e1e8eda2be8970586c3274

tests/integration/pip_parse_isolated/test_isolated.py

@@ -0,0 +1,16 @@
+"""
+Verify that a dependency added using an isolated extension can be imported.
+See MODULE.bazel.
+"""
+
+import six
+import unittest
+
+
+class TestIsolated(unittest.TestCase):
+    def test_import(self):
+        self.assertTrue(hasattr(six, "PY3"))
+
+
+if __name__ == "__main__":
+    unittest.main()