Fallback to editable-legacy if the build backend does not have build_editable

docs/changelog/2567.bugfix.rst

@@ -0,0 +1,2 @@
+Fallback to ``editable-legacy`` if package target is ``editable`` but the build backend does not have ``build_editable``
+hook - by :user:`gaborbernat`.

pyproject.toml

@@ -27,7 +27,7 @@ dependencies = [
   "packaging>=21.3",
   "platformdirs>=2.5.4",
   "pluggy>=1",
-  "pyproject-api>=1.1.2",
+  "pyproject-api>=1.2.1",
   'tomli>=2.0.1; python_version < "3.11"',
   "virtualenv>=20.17",
   'importlib-metadata>=5.1; python_version < "3.8"',
@@ -46,7 +46,7 @@ optional-dependencies.docs = [
 optional-dependencies.testing = [
   "build[virtualenv]>=0.9",
   "covdefaults>=2.2.2",
-  "devpi-process>=0.2",
+  "devpi-process>=0.3",
   "diff-cover>=7.2",
   "distlib>=0.3.6",
   "filelock>=3.8",

src/tox/tox_env/python/virtual_env/api.py

@@ -118,7 +118,8 @@ def virtualenv_env_vars(self) -> dict[str, str]:
         env["VIRTUALENV_COPIES"] = str(getattr(self.options, "always_copy", False) or self.conf["always_copy"])
         env["VIRTUALENV_DOWNLOAD"] = str(self.conf["download"])
         env["VIRTUALENV_PYTHON"] = "\n".join(base_python)
-        env["VIRTUALENV_TRY_FIRST_WITH"] = os.pathsep.join(self.options.discover)
+        if hasattr(self.options, "discover"):
+            env["VIRTUALENV_TRY_FIRST_WITH"] = os.pathsep.join(self.options.discover)
         return env
 
     @property

src/tox/tox_env/python/virtual_env/package/pyproject.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import logging
 import os
 import sys
 from contextlib import contextmanager
@@ -61,6 +62,10 @@ def __init__(self, backend_failed: BackendFailed) -> None:
         )
 
 
+class BuildEditableNotSupported(RuntimeError):
+    """raised when build editable is not supported"""
+
+
 class ToxCmdStatus(CmdStatus):
     def __init__(self, execute_status: ExecuteStatus) -> None:
         self._execute_status = execute_status
@@ -136,6 +141,8 @@ def register_run_env(self, run_env: RunToxEnv) -> Generator[tuple[str, str], Pac
     def _setup_env(self) -> None:
         super()._setup_env()
         if "editable" in self.builds:
+            if not self._frontend.optional_hooks["build_editable"]:
+                raise BuildEditableNotSupported
             build_requires = self._frontend.get_requires_for_build_editable().requires
             self.installer.install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_editable")
         if "wheel" in self.builds:
@@ -159,7 +166,17 @@ def _teardown(self) -> None:
 
     def perform_packaging(self, for_env: EnvConfigSet) -> list[Package]:
         """build the package to install"""
-        deps = self._load_deps(for_env)
+        try:
+            deps = self._load_deps(for_env)
+        except BuildEditableNotSupported:
+            logging.error(
+                f"package config for {for_env.env_name} is editable, however the build backend {self._frontend.backend}"
+                f" does not support PEP-660, falling back to editable-legacy - change your configuration to it",
+            )
+            self.builds.remove("editable")
+            self.builds.add("editable-legacy")
+            for_env._defined["package"].value = "editable-legacy"  # type: ignore
+            deps = self._load_deps(for_env)
         of_type: str = for_env["package"]
         if of_type == "editable-legacy":
             self.setup()
@@ -176,8 +193,8 @@ def perform_packaging(self, for_env: EnvConfigSet) -> list[Package]:
                     return w_env.perform_packaging(for_env)
             else:
                 self.setup()
+                method = "build_editable" if of_type == "editable" else "build_wheel"
                 with self._pkg_lock:
-                    method = "build_editable" if of_type == "editable" else "build_wheel"
                     path = getattr(self._frontend, method)(
                         wheel_directory=self.pkg_dir,
                         metadata_directory=self.meta_folder,
@@ -293,12 +310,7 @@ def _send(self, cmd: str, **kwargs: Any) -> tuple[Any, str, str]:
             if cmd in ("prepare_metadata_for_build_wheel", "prepare_metadata_for_build_editable"):
                 # given we'll build a wheel we might skip the prepare step
                 if "wheel" in self._tox_env.builds or "editable" in self._tox_env.builds:
-                    result = {
-                        "code": 1,
-                        "exc_type": "AvoidRedundant",
-                        "exc_msg": "will need to build wheel either way, avoid prepare",
-                    }
-                    raise BackendFailed(result, "", "")
+                    return None, "", ""  # will need to build wheel either way, avoid prepare
             return super()._send(cmd, **kwargs)
         except BackendFailed as exception:
             raise exception if isinstance(exception, ToxBackendFailed) else ToxBackendFailed(exception) from exception

tests/session/cmd/test_sequential.py

@@ -83,6 +83,7 @@ def test_result_json_sequential(
 
     assert packaging_setup == [
         (0, "install_requires"),
+        (None, "_optional_hooks"),
         (None, "get_requires_for_build_wheel"),
         (0, "install_requires_for_build_wheel"),
         (0, "freeze"),
@@ -284,6 +285,7 @@ def test_skip_develop_mode(tox_project: ToxProjectCreator, demo_pkg_setuptools:
     calls = [(i[0][0].conf.name, i[0][3].run_id) for i in execute_calls.call_args_list]
     expected = [
         (".pkg", "install_requires"),
+        (".pkg", "_optional_hooks"),
         (".pkg", "get_requires_for_build_editable"),
         (".pkg", "install_requires_for_build_editable"),
         (".pkg", "build_editable"),

tests/tox_env/python/pip/test_pip_install.py

@@ -143,6 +143,7 @@ def test_pkg_dep_remove_recreate(tox_project: ToxProjectCreator, demo_pkg_inline
     result_first.assert_success()
     run_ids = [i[0][3].run_id for i in execute_calls.call_args_list]
     assert run_ids == [
+        "_optional_hooks",
         "get_requires_for_build_wheel",
         "build_wheel",
         "install_package_deps",
@@ -156,7 +157,7 @@ def test_pkg_dep_remove_recreate(tox_project: ToxProjectCreator, demo_pkg_inline
     result_second.assert_success()
     assert "py: recreate env because dependencies removed: wheel" in result_second.out, result_second.out
     run_ids = [i[0][3].run_id for i in execute_calls.call_args_list]
-    assert run_ids == ["get_requires_for_build_wheel", "build_wheel", "install_package", "_exit"]
+    assert run_ids == ["_optional_hooks", "get_requires_for_build_wheel", "build_wheel", "install_package", "_exit"]
 
 
 def test_pkg_env_dep_remove_recreate(tox_project: ToxProjectCreator, demo_pkg_inline: Path) -> None:
@@ -172,15 +173,22 @@ def test_pkg_env_dep_remove_recreate(tox_project: ToxProjectCreator, demo_pkg_in
     result_first = proj.run("r")
     result_first.assert_success()
     run_ids = [i[0][3].run_id for i in execute_calls.call_args_list]
-    assert run_ids == ["install_requires", "get_requires_for_build_wheel", "build_wheel", "install_package", "_exit"]
+    assert run_ids == [
+        "install_requires",
+        "_optional_hooks",
+        "get_requires_for_build_wheel",
+        "build_wheel",
+        "install_package",
+        "_exit",
+    ]
     execute_calls.reset_mock()
 
     (proj.path / "pyproject.toml").write_text(toml)
     result_second = proj.run("r")
     result_second.assert_success()
     assert ".pkg: recreate env because dependencies removed: setuptools" in result_second.out, result_second.out
     run_ids = [i[0][3].run_id for i in execute_calls.call_args_list]
-    assert run_ids == ["get_requires_for_build_wheel", "build_wheel", "install_package", "_exit"]
+    assert run_ids == ["_optional_hooks", "get_requires_for_build_wheel", "build_wheel", "install_package", "_exit"]
 
 
 def test_pip_install_requirements_file_deps(tox_project: ToxProjectCreator) -> None:

tests/tox_env/python/test_python_api.py

@@ -52,6 +52,7 @@ def test_build_wheel_in_non_base_pkg_env(
     result.assert_success()
     calls = [(i[0][0].conf.name, i[0][3].run_id) for i in execute_calls.call_args_list]
     assert calls == [
+        (f".pkg-{impl}{prev_ver}", "_optional_hooks"),
         (f".pkg-{impl}{prev_ver}", "get_requires_for_build_wheel"),
         (f".pkg-{impl}{prev_ver}", "build_wheel"),
         (f"py{prev_ver}", "install_package"),

tests/tox_env/python/virtual_env/package/test_package_cmd_builder.py

@@ -52,6 +52,7 @@ def test_tox_install_pkg_sdist(tox_project: ToxProjectCreator, pkg_with_extras_p
     deps = ["black>=3", "colorama>=0.4.3", "flake8", "platformdirs>=2.1", "sphinx-rtd-theme<1,>=0.4.3", "sphinx>=3"]
     assert calls == [
         (".pkg_external_sdist_meta", "install_requires", ["setuptools", "wheel"]),
+        (".pkg_external_sdist_meta", "_optional_hooks", []),
         (".pkg_external_sdist_meta", "get_requires_for_build_sdist", []),
         (".pkg_external_sdist_meta", "prepare_metadata_for_build_wheel", []),
         ("py", "install_package_deps", deps),

tests/tox_env/python/virtual_env/package/test_package_pyproject.py

@@ -107,7 +107,7 @@ def test_pyproject_deps_from_static(
     result = proj.run("r", "--notest")
     result.assert_success()
 
-    expected_calls = [(".pkg", "get_requires_for_build_sdist"), (".pkg", "build_sdist")]
+    expected_calls = [(".pkg", "_optional_hooks"), (".pkg", "get_requires_for_build_sdist"), (".pkg", "build_sdist")]
     if deps:
         expected_calls.append(("py", "install_package_deps"))
     expected_calls.extend((("py", "install_package"), (".pkg", "_exit")))
@@ -157,8 +157,8 @@ def test_pyproject_deps_static_with_dynamic(
     result.assert_success()
 
     expected_calls = [
+        (".pkg", "_optional_hooks"),
         (".pkg", "get_requires_for_build_sdist"),
-        (".pkg", "prepare_metadata_for_build_wheel"),
         (".pkg", "build_wheel"),
         (".pkg", "build_sdist"),
         ("py", "install_package_deps"),
@@ -170,3 +170,25 @@ def test_pyproject_deps_static_with_dynamic(
 
     args = execute_calls.call_args_list[-3][0][3].cmd
     assert args == ["python", "-I", "-m", "pip", "install", *deps]
+
+
+def test_pyproject_no_build_editable_fallback(tox_project: ToxProjectCreator, demo_pkg_inline: Path) -> None:
+    proj = tox_project({"tox.ini": ""}, base=demo_pkg_inline)
+    execute_calls = proj.patch_execute(lambda r: 0 if "install" in r.run_id else None)
+    result = proj.run("r", "--notest", "--develop")
+    result.assert_success()
+    warning = (
+        ".pkg: package config for py is editable, however the build backend build does not support PEP-660, "
+        "falling back to editable-legacy - change your configuration to it"
+    )
+    assert warning in result.out.splitlines()
+
+    expected_calls = [
+        (".pkg", "_optional_hooks"),
+        (".pkg", "build_wheel"),
+        (".pkg", "get_requires_for_build_sdist"),
+        ("py", "install_package"),
+        (".pkg", "_exit"),
+    ]
+    found_calls = [(i[0][0].conf.name, i[0][3].run_id) for i in execute_calls.call_args_list]
+    assert found_calls == expected_calls

tests/tox_env/python/virtual_env/test_setuptools.py

@@ -48,5 +48,5 @@ def test_setuptools_package(
     assert len(py_messages) == 5, "\n".join(py_messages)  # 1 install wheel + 3 command + 1 final report
 
     package_messages = [i for i in result if ".pkg: " in i]
-    # 1 install requires + 1 build requires + 1 build meta + 1 build isolated + 1 exit
-    assert len(package_messages) == 5, "\n".join(package_messages)
+    # 1 optional hooks + 1 install requires + 1 build requires + 1 build meta + 1 build isolated + 1 exit
+    assert len(package_messages) == 6, "\n".join(package_messages)