fix(whl_library): remove --no-index and add --no-build-isolation when build sdist

CHANGELOG.md

@@ -28,6 +28,9 @@ A brief description of the categories of changes:
 * (gazelle): Update error messages when unable to resolve a dependency to be more human-friendly.
 
 ### Fixed
+* (whl_library): Remove `--no-index` and add `--no-build-isolation` to the
+  `pip install` command when installing a wheel from a local file, which happens
+  when `experimental_index_url` flag is used.
 * (bzlmod) get the path to the host python interpreter in a way that results in
   platform non-dependent hashes in the lock file when the requirement markers need
   to be evaluated.

python/private/pypi/whl_library.bzl

@@ -227,8 +227,10 @@ def _whl_library_impl(rctx):
             whl_path = rctx.path(rctx.attr.filename)
         else:
             # It is an sdist and we need to tell PyPI to use a file in this directory
-            # and not use any indexes.
-            extra_pip_args.extend(["--no-index", "--find-links", "."])
+            # and, allow getting build dependencies from PYTHONPATH, which we
+            # setup in this repository rule, but still download any necessary
+            # build deps from PyPI (e.g. `flit_core`) if they are missing.
+            extra_pip_args.extend(["--no-build-isolation", "--find-links", "."])
 
     args = _parse_optional_attrs(rctx, args, extra_pip_args)
 

tests/pypi/integration/BUILD.bazel

@@ -0,0 +1,20 @@
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("@dev_pip//:requirements.bzl", "all_requirements")
+load(":transitions.bzl", "transition_rule")
+
+build_test(
+    name = "all_requirements_build_test",
+    targets = all_requirements,
+)
+
+# Rule that transitions dependencies to be built from sdist
+transition_rule(
+    name = "all_requirements_from_sdist",
+    testonly = True,
+    deps = all_requirements,
+)
+
+build_test(
+    name = "all_requirements_from_sdist_build_test",
+    targets = ["all_requirements_from_sdist"],
+)

tests/pypi/integration/transitions.bzl

@@ -0,0 +1,24 @@
+""" Define a custom transition that sets the pip_whl flag to no """
+
+def _flag_transition_impl(_settings, _ctx):
+    return {"//python/config_settings:pip_whl": "no"}
+
+flag_transition = transition(
+    implementation = _flag_transition_impl,
+    inputs = [],
+    outputs = ["//python/config_settings:pip_whl"],
+)
+
+# Define a rule that applies the transition to dependencies
+def _transition_rule_impl(_ctx):
+    return [DefaultInfo()]
+
+transition_rule = rule(
+    implementation = _transition_rule_impl,
+    attrs = {
+        "deps": attr.label_list(cfg = flag_transition),
+        "_allowlist_function_transition": attr.label(
+            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+        ),
+    },
+)