Revert "Error out if installing a pyproject.toml-style (PEP 517) project in editable mode."

This reverts commit cc2d299f76.

src/pip/_internal/pyproject.py

@@ -49,27 +49,11 @@ def read_pyproject_toml(path):
     return build_system
 
 
-def make_editable_error(req_name, reason):
-    """
-    :param req_name: the name of the requirement.
-    :param reason: the reason the requirement is being processed as
-        pyproject.toml-style.
-    """
-    message = (
-        'Error installing {!r}: editable mode is not supported for '
-        'pyproject.toml-style projects. This project is being processed '
-        'as pyproject.toml-style because {}. '
-        'See PEP 517 for the relevant specification.'
-    ).format(req_name, reason)
-    return InstallationError(message)
-
-
 def resolve_pyproject_toml(
-    build_system,  # type: Optional[Dict[str, Any]]
+    build_system,  # type: Optional[Dict[str, str]]
     has_pyproject,  # type: bool
     has_setup,  # type: bool
     use_pep517,  # type: Optional[bool]
-    editable,  # type: bool
     req_name,  # type: str
 ):
     # type: (...) -> Optional[Tuple[List[str], str, List[str]]]
@@ -83,7 +67,6 @@ def resolve_pyproject_toml(
     :param has_setup: whether the project has a setup.py file.
     :param use_pep517: whether the user requested PEP 517 processing.  None
         means the user didn't explicitly specify.
-    :param editable: whether editable mode was requested for the requirement.
     :param req_name: the name of the requirement we're processing (for
         error reporting).
     """
@@ -99,10 +82,6 @@ def resolve_pyproject_toml(
                 "Disabling PEP 517 processing is invalid: "
                 "project does not have a setup.py"
             )
-        if editable:
-            raise make_editable_error(
-                req_name, 'it has a pyproject.toml file and no setup.py'
-            )
         use_pep517 = True
     elif build_system and "build-backend" in build_system:
         if use_pep517 is not None and not use_pep517:
@@ -113,18 +92,7 @@ def resolve_pyproject_toml(
                     build_system["build-backend"]
                 )
             )
-        if editable:
-            reason = (
-                'it has a pyproject.toml file with a "build-backend" key '
-                'in the "build_system" value'
-            )
-            raise make_editable_error(req_name, reason)
         use_pep517 = True
-    elif use_pep517:
-        if editable:
-            raise make_editable_error(
-                req_name, 'PEP 517 processing was explicitly requested'
-            )
 
     # If we haven't worked out whether to use PEP 517 yet,
     # and the user hasn't explicitly stated a preference,
@@ -207,7 +175,6 @@ def resolve_pyproject_toml(
 
 def load_pyproject_toml(
     use_pep517,  # type: Optional[bool]
-    editable,  # type: bool
     pyproject_toml,  # type: str
     setup_py,  # type: str
     req_name  # type: str
@@ -218,7 +185,6 @@ def load_pyproject_toml(
     Parameters:
         use_pep517 - Has the user requested PEP 517 processing? None
                      means the user hasn't explicitly specified.
-        editable - Whether editable mode was requested for the requirement.
         pyproject_toml - Location of the project's pyproject.toml file
         setup_py - Location of the project's setup.py file
         req_name - The name of the requirement we're processing (for
@@ -246,6 +212,5 @@ def load_pyproject_toml(
         has_pyproject=has_pyproject,
         has_setup=has_setup,
         use_pep517=use_pep517,
-        editable=editable,
         req_name=req_name,
     )

src/pip/_internal/req/req_install.py

@@ -487,7 +487,6 @@ class InstallRequirement(object):
         """
         pep517_data = load_pyproject_toml(
             self.use_pep517,
-            self.editable,
             self.pyproject_toml,
             self.setup_py,
             str(self)

tests/unit/test_pep517.py

@@ -1,69 +1,9 @@
 import pytest
 
 from pip._internal.exceptions import InstallationError
-from pip._internal.pyproject import resolve_pyproject_toml
 from pip._internal.req import InstallRequirement
 
 
-@pytest.mark.parametrize('editable', [False, True])
-def test_resolve_pyproject_toml__pep_517_optional(editable):
-    """
-    Test resolve_pyproject_toml() when has_pyproject=True but the source
-    tree isn't pyproject.toml-style per PEP 517.
-    """
-    actual = resolve_pyproject_toml(
-        build_system=None,
-        has_pyproject=True,
-        has_setup=True,
-        use_pep517=None,
-        editable=editable,
-        req_name='my-package',
-    )
-    expected = (
-        ['setuptools>=40.8.0', 'wheel'],
-        'setuptools.build_meta:__legacy__',
-        [],
-    )
-    assert actual == expected
-
-
-@pytest.mark.parametrize(
-    'has_pyproject, has_setup, use_pep517, build_system, expected_err', [
-        # Test pyproject.toml with no setup.py.
-        (True, False, None, None, 'has a pyproject.toml file and no setup.py'),
-        # Test "build-backend" present.
-        (True, True, None, {'build-backend': 'foo'},
-         'has a pyproject.toml file with a "build-backend" key'),
-        # Test explicitly requesting PEP 517 processing.
-        (True, True, True, None,
-         'PEP 517 processing was explicitly requested'),
-    ]
-)
-def test_resolve_pyproject_toml__editable_and_pep_517_required(
-    has_pyproject, has_setup, use_pep517, build_system, expected_err,
-):
-    """
-    Test that passing editable=True raises an error if PEP 517 processing
-    is required.
-    """
-    with pytest.raises(InstallationError) as excinfo:
-        resolve_pyproject_toml(
-            build_system=build_system,
-            has_pyproject=has_pyproject,
-            has_setup=has_setup,
-            use_pep517=use_pep517,
-            editable=True,
-            req_name='my-package',
-        )
-    err_args = excinfo.value.args
-    assert len(err_args) == 1
-    msg = err_args[0]
-    assert msg.startswith(
-        "Error installing 'my-package': editable mode is not supported"
-    )
-    assert expected_err in msg, 'full message: {}'.format(msg)
-
-
 @pytest.mark.parametrize(('source', 'expected'), [
     ("pep517_setup_and_pyproject", True),
     ("pep517_setup_only", False),