further cleanup

python/pip_install/tools/wheel_installer/BUILD.bazel

@@ -54,10 +54,10 @@ py_test(
     srcs = [
         "wheel_test.py",
     ],
-    data = [
-        "//examples/wheel:minimal_with_py_package",
+    data = ["//examples/wheel:minimal_with_py_package"],
+    deps = [
+        ":lib",
     ],
-    deps = [":lib"],
 )
 
 py_test(

python/pip_install/tools/wheel_installer/wheel.py

@@ -247,9 +247,10 @@ def __init__(
         self.name: str = Deps._normalize(name)
         self._platforms: Set[Platform] = platforms or set()
 
-        # Sort so that the dictionary order in the final order is deterministic
-        # because Python retains insertion order. That way the build() method
-        # and unit-tests can be simpler.
+        # Sort so that the dictionary order in the FrozenDeps is deterministic
+        # without the final sort because Python retains insertion order. That way
+        # the sorting by platform is limited within the Platform class itself and
+        # the unit-tests for the Deps can be simpler.
         reqs = sorted(
             (Requirement(wheel_req) for wheel_req in requires_dist),
             key=lambda x: f"{x.name}:{sorted(x.extras)}",
@@ -266,8 +267,7 @@ def __init__(
     def _add(self, dep: str, platform: Optional[Platform]):
         dep = Deps._normalize(dep)
 
-        # Packages may create dependency cycles when specifying optional-dependencies / 'extras'.
-        # Example: github.com/google/etils/blob/a0b71032095db14acf6b33516bca6d885fe09e35/pyproject.toml#L32.
+        # Self-edges are processed in _resolve_extras
         if dep == self.name:
             return
 
@@ -278,11 +278,9 @@ def _add(self, dep: str, platform: Optional[Platform]):
         # Add the platform-specific dep
         self._select[platform].add(dep)
 
-        all_specializations = list(platform.all_specializations())
-
         # Add the dep to specializations of the given platform if they
         # exist in the select statement.
-        for p in all_specializations:
+        for p in platform.all_specializations():
             if p not in self._select:
                 continue
 
@@ -295,6 +293,7 @@ def _add(self, dep: str, platform: Optional[Platform]):
         # existing dependencies from less specialized platforms are propagated
         # to the newly added dependency set.
         for p, deps in self._select.items():
+            # Check if the existing platform overlaps with the given platform
             if p == platform or platform not in p.all_specializations():
                 continue
 
@@ -313,6 +312,8 @@ def _resolve_extras(
         `etils`, where we have one set of extras as aliases for other extras
         and we have an extra called 'all' that includes all other extras.
 
+        Example: github.com/google/etils/blob/a0b71032095db14acf6b33516bca6d885fe09e35/pyproject.toml#L32.
+
         When the `requirements.txt` is generated by `pip-tools`, then it is likely that
         this step is not needed, but for other `requirements.txt` files this may be useful.