fix: Handle single-file module pypi-deps in py_pex_binary (#392)

Addresses the bug in
#391.

Single-file modules such as `six` and `typing-extensions` does not work
with the current `py_pex_binary` rule, since it's assumed that there
exist a sub-directory within `site-packages` that is not dist-info.

An example of what a single-file module pypi-dep looks like: 
```
ls bazel-reppro_pex_err/external/rules_python~~pip~pypi_311_six/site-packages/
__init__.py  six-1.16.0.dist-info  six.py
```

Since `Distribution.load(..)` takes in the `site-packages` directory, we
only emit this part of the path, and let `uniquify=True` handle
deduplication after `_map_srcs` is applied.


---

### Changes are visible to end-users: no

### Test plan

<!-- Delete any which do not apply -->

- Manual testing; please provide instructions so we can reproduce:
Add `six` to requirements and `"@pypi_six//:pkg"` as a dep to the
py_pex_binary example; then import `six` in py_pex_binary's `say.py`.
Printing the module or `cowsay.cow(f"{six}")` shows that the previous
example and single-files modules now also work.

gazelle_python.yaml

@@ -2161,6 +2161,7 @@ manifest:
     numpy.lib.ufunclike: numpy
     numpy.lib.user_array: numpy
     numpy.lib.utils: numpy
+    numpy.libs.libopenblas64_p-r0-0cf96a72: numpy
     numpy.linalg: numpy
     numpy.linalg.lapack_lite: numpy
     numpy.linalg.linalg: numpy
@@ -3716,6 +3717,7 @@ manifest:
     past.types.olddict: future
     past.types.oldstr: future
     past.utils: future
+    pillow.libs.libopenjp2-05423b53: pillow
     pluggy: pluggy
     proxytypes: jsonref
     psutil: psutil
@@ -3986,4 +3988,4 @@ manifest:
     yaml.tokens: PyYAML
   pip_repository:
     name: pypi
-integrity: e0cc13413ec04d597469a3a5baa75d320d7c614017bbccd34aa3e356675dd984
+integrity: 2e0cbc780621ce75951013e6968f66d1aadd8d1ecb8b7c470883c998b169e733

py/private/py_pex_binary.bzl

@@ -56,26 +56,15 @@ def _map_srcs(f, workspace):
 
     site_packages_i = f.path.find("site-packages")
 
-    # if path contains `site-packages` and there is only two path segments
-    # after it, it will be treated as third party dep.
-    # Here are some examples of path we expect and use and ones we ignore.
-    #
-    # Match: `external/rules_python~~pip~pypi_39_rtoml/site-packages/rtoml-0.11.0.dist-info/INSTALLER`
-    # Reason: It has two `/` after first `site-packages` substring.
-    #
-    # No Match: `external/rules_python~~pip~pypi_39_rtoml/site-packages/rtoml-0.11.0/src/mod/parse.py`
-    # Reason: It has three `/` after first `site-packages` substring.
-    if site_packages_i != -1 and f.path.count("/", site_packages_i) == 2:
-        if f.path.find("dist-info", site_packages_i) != -1:
+    # If the path contains 'site-packages', treat it as a third party dep
+    if site_packages_i != -1:
+        if f.path.find("dist-info", site_packages_i) != -1 and f.path.count("/", site_packages_i) == 2:
             return ["--distinfo={}".format(f.dirname)]
-        return ["--dep={}".format(f.dirname)]
 
-    elif site_packages_i == -1:
-        # If the path does not have a `site-packages` in it, then put it into
-        # the standard runfiles tree.
-        return ["--source={}={}".format(f.path, dest_path)]
+        return ["--dep={}".format(f.path[:site_packages_i + len("site-packages")])]
 
-    return []
+    # If the path does not have a `site-packages` in it, then put it into the standard runfiles tree.
+    return ["--source={}={}".format(f.path, dest_path)]
 
 def _py_python_pex_impl(ctx):
     py_toolchain = _py_semantics.resolve_toolchain(ctx)

py/tests/py-pex-binary/BUILD.bazel

@@ -0,0 +1,34 @@
+load("@aspect_bazel_lib//lib:testing.bzl", "assert_contains")
+load("//py:defs.bzl", "py_binary", "py_pex_binary")
+
+# Test that both single-file modules (six) and multi-file modules (cowsay) work with py_pex_binary.
+py_binary(
+    name = "print_modules_bin",
+    srcs = ["print_modules.py"],
+    data = ["data.txt"],
+    deps = [
+        "@bazel_tools//tools/python/runfiles",
+        "@pypi_cowsay//:pkg",
+        "@pypi_six//:pkg",
+    ],
+)
+
+py_pex_binary(
+    name = "print_modules_pex",
+    binary = ":print_modules_bin",
+    python_interpreter_constraints = [],
+)
+
+# PEX_ROOT is set to avoid warning on default user PEX_ROOT not being writable
+genrule(
+    name = "run_print_modules_pex",
+    outs = ["print_modules_pex.out"],
+    cmd = "PEX_ROOT=.pex $(execpath print_modules_pex) >$@",
+    tools = ["print_modules_pex"],
+)
+
+assert_contains(
+    name = "test__print_modules_pex",
+    actual = "print_modules_pex.out",
+    expected = "Mooo!,cowsay-6.1/cowsay/__init__.py,six-1.16.0/six.py",
+)

py/tests/py-pex-binary/data.txt

@@ -0,0 +1 @@
+Mooo!

py/tests/py-pex-binary/print_modules.py

@@ -0,0 +1,15 @@
+import sys
+import cowsay
+import six
+from bazel_tools.tools.python.runfiles import runfiles
+
+
+r = runfiles.Create()
+data_path = r.Rlocation("aspect_rules_py/py/tests/py-pex-binary/data.txt")
+
+# strings on one line to test presence for all
+print(open(data_path).read()
+      + ","
+      + "/".join(cowsay.__file__.split("/")[-3:])
+      + ","
+      + "/".join(six.__file__.split("/")[-2:]))

py/tools/pex/main.py

@@ -159,7 +159,7 @@ def __call__(self, parser, namespace, value, option_str=None):
 ]
 
 for dep in options.dependencies:
-    dist = Distribution.load(dep + "/../")
+    dist = Distribution.load(dep)
 
     # TODO: explain which level of inferno is this!
     key = "%s-%s" % (dist.key, dist.version)

requirements.in

@@ -5,3 +5,4 @@ pytest
 cowsay
 ftfy==6.2.0
 neptune==1.10.2
+six

requirements.txt

@@ -770,6 +770,7 @@ six==1.16.0 \
     --hash=sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926 \
     --hash=sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254
     # via
+    #   -r requirements.in
     #   bravado
     #   bravado-core
     #   neptune