move intersection with project python constraint

src/poetry/packages/locker.py

@@ -32,6 +32,7 @@
 
 
 if TYPE_CHECKING:
+    from poetry.core.semver.version_constraint import VersionConstraint
     from poetry.core.version.markers import BaseMarker
     from tomlkit.items import InlineTable
     from tomlkit.toml_document import TOMLDocument
@@ -315,9 +316,19 @@ def get_project_dependencies(
     def get_project_dependency_packages(
         self,
         project_requires: list[Dependency],
+        project_python_marker: VersionConstraint | None = None,
         dev: bool = False,
         extras: bool | Sequence[str] | None = None,
     ) -> Iterator[DependencyPackage]:
+        # Apply the project python marker to all requirements.
+        if project_python_marker is not None:
+            marked_requires: list[Dependency] = []
+            for require in project_requires:
+                require = deepcopy(require)
+                require.marker = require.marker.intersect(project_python_marker)
+                marked_requires.append(require)
+            project_requires = marked_requires
+
         repository = self.locked_repository(with_dev_reqs=dev)
 
         # Build a set of all packages required by our selected extras

src/poetry/utils/exporter.py

@@ -2,7 +2,6 @@
 
 import urllib.parse
 
-from copy import deepcopy
 from typing import TYPE_CHECKING
 from typing import Sequence
 
@@ -70,17 +69,13 @@ def _export_requirements_txt(
         content = ""
         dependency_lines = set()
 
-        # Get project dependencies, and add the project-wide marker to them.
+        # Get project dependencies.
         groups = ["dev"] if dev else []
         root_package = self._poetry.package.with_dependency_groups(groups)
-        project_requires = []
-        for require in root_package.all_requires:
-            require = deepcopy(require)
-            require.marker = require.marker.intersect(root_package.python_marker)
-            project_requires.append(require)
 
         for dependency_package in self._poetry.locker.get_project_dependency_packages(
-            project_requires=project_requires,
+            project_requires=root_package.all_requires,
+            project_python_marker=root_package.python_marker,
             dev=dev,
             extras=extras,
         ):