refactor: unnested _py_package_impl logic

Signed-off-by: Thulio Ferraz Assis <3149049+f0rmiga@users.noreply.github.com>

python/private/py_package.bzl

diff --git a/python/private/py_package.bzl b/python/private/py_package.bzl
index 7975a8d..ec8126b 100644
--- a/python/private/py_package.bzl
+++ b/python/private/py_package.bzl
@@ -41,26 +41,12 @@
         filtered_inputs = input_files
         imports = [dep[PyInfo].imports for dep in ctx.attr.deps]
     else:
+        input_files_list = input_files.to_list()
         filtered_files = []
         for dep in ctx.attr.deps:
-            add_imports = False
-
-            # TODO: flattening depset to list gives poor performance,
-            for input_file in input_files.to_list():
-                path_inside_wheel = _path_inside_wheel(input_file)
-                for package in packages:
-                    if path_inside_wheel.startswith(package) and not exclude:
-                        filtered_files.append(input_file)
-                        if path_inside_wheel.endswith(".py"):
-                            add_imports = True
-                    else:
-                        for excluded in exclude:
-                            if path_inside_wheel.startswith(package) and not path_inside_wheel.startswith(excluded):
-                                filtered_files.append(input_file)
-                                if path_inside_wheel.endswith(".py"):
-                                    add_imports = True
-            if add_imports:
-                imports.append(dep[PyInfo].imports)
+            (dep_imports, dep_filtered_files) = _py_package_add_imports(dep, input_files_list, packages, exclude)
+            imports.append(dep_imports)
+            filtered_files.extend(dep_filtered_files)
         filtered_inputs = depset(direct = filtered_files)
 
     return [
@@ -73,6 +59,46 @@
         ),
     ]
 
+def _py_package_add_imports(dep, input_files, packages, exclude):
+    """Returns the imports and filtered files for the given dep based on the packages and exclude list.
+
+    Args:
+        dep: Dependency to add imports for.
+        input_files: List of input files.
+        packages: List of packages to include.
+        exclude: List of packages to exclude.
+    """
+    filtered_files = []
+    add_imports = False
+
+    for input_file in input_files:
+        path_inside_wheel = _path_inside_wheel(input_file)
+        for package in packages:
+            if _py_package_should_include_file(path_inside_wheel, package, exclude):
+                filtered_files.append(input_file)
+                add_imports = add_imports or path_inside_wheel.endswith(".py")
+
+    if add_imports:
+        return (dep[PyInfo].imports, filtered_files)
+
+    return ([], filtered_files)
+
+def _py_package_should_include_file(path_inside_wheel, package, exclude):
+    """Returns true if the file should be included in the wheel based on the package and exclude list.
+
+    Args:
+        path_inside_wheel: Path of the file inside the wheel.
+        package: Package name to include.
+        exclude: List of packages to exclude.
+    """
+    if path_inside_wheel.startswith(package):
+        if not exclude:
+            return True
+        for excluded in exclude:
+            if not path_inside_wheel.startswith(excluded):
+                return True
+    return False
+
 py_package_lib = struct(
     implementation = _py_package_impl,
     attrs = {