Revert "Refactor out read_pyproject_toml() and resolve_pyproject_toml()."

This reverts commit f66c1f7639.

src/pip/_internal/pyproject.py

@@ -10,7 +10,7 @@ from pip._internal.exceptions import InstallationError
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import Any, Dict, List, Optional, Tuple
+    from typing import Any, Tuple, Optional, List
 
 
 def _is_list_of_str(obj):
@@ -32,44 +32,42 @@ def make_pyproject_path(setup_py_dir):
     return path
 
 
-def read_pyproject_toml(path):
-    # type: (str) -> Optional[Dict[str, str]]
-    """
-    Read a project's pyproject.toml file.
-
-    :param path: The path to the pyproject.toml file.
-
-    :return: The "build_system" value specified in the project's
-        pyproject.toml file.
-    """
-    with io.open(path, encoding="utf-8") as f:
-        pp_toml = pytoml.load(f)
-    build_system = pp_toml.get("build-system")
-
-    return build_system
-
-
-def resolve_pyproject_toml(
-    build_system,  # type: Optional[Dict[str, str]]
-    has_pyproject,  # type: bool
-    has_setup,  # type: bool
+def load_pyproject_toml(
     use_pep517,  # type: Optional[bool]
-    req_name,  # type: str
+    pyproject_toml,  # type: str
+    setup_py,  # type: str
+    req_name  # type: str
 ):
     # type: (...) -> Optional[Tuple[List[str], str, List[str]]]
-    """
-    Return how a pyproject.toml file's contents should be interpreted.
+    """Load the pyproject.toml file.
 
-    :param build_system: the "build_system" value specified in a project's
-        pyproject.toml file, or None if the project either doesn't have the
-        file or does but the file doesn't have a "build_system" value.
-    :param has_pyproject: whether the project has a pyproject.toml file.
-    :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 req_name: the name of the requirement we're processing (for
-        error reporting).
+    Parameters:
+        use_pep517 - Has the user requested PEP 517 processing? None
+                     means the user hasn't explicitly specified.
+        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
+                   error reporting)
+
+    Returns:
+        None if we should use the legacy code path, otherwise a tuple
+        (
+            requirements from pyproject.toml,
+            name of PEP 517 backend,
+            requirements we should check are installed after setting
+                up the build environment
+        )
     """
+    has_pyproject = os.path.isfile(pyproject_toml)
+    has_setup = os.path.isfile(setup_py)
+
+    if has_pyproject:
+        with io.open(pyproject_toml, encoding="utf-8") as f:
+            pp_toml = pytoml.load(f)
+        build_system = pp_toml.get("build-system")
+    else:
+        build_system = None
+
     # The following cases must use PEP 517
     # We check for use_pep517 being non-None and falsey because that means
     # the user explicitly requested --no-use-pep517.  The value 0 as
@@ -171,46 +169,3 @@ def resolve_pyproject_toml(
         check = ["setuptools>=40.8.0", "wheel"]
 
     return (requires, backend, check)
-
-
-def load_pyproject_toml(
-    use_pep517,  # type: Optional[bool]
-    pyproject_toml,  # type: str
-    setup_py,  # type: str
-    req_name  # type: str
-):
-    # type: (...) -> Optional[Tuple[List[str], str, List[str]]]
-    """Load the pyproject.toml file.
-
-    Parameters:
-        use_pep517 - Has the user requested PEP 517 processing? None
-                     means the user hasn't explicitly specified.
-        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
-                   error reporting)
-
-    Returns:
-        None if we should use the legacy code path, otherwise a tuple
-        (
-            requirements from pyproject.toml,
-            name of PEP 517 backend,
-            requirements we should check are installed after setting
-                up the build environment
-        )
-    """
-    has_pyproject = os.path.isfile(pyproject_toml)
-    has_setup = os.path.isfile(setup_py)
-
-    if has_pyproject:
-        build_system = read_pyproject_toml(pyproject_toml)
-    else:
-        build_system = None
-
-    return resolve_pyproject_toml(
-        build_system=build_system,
-        has_pyproject=has_pyproject,
-        has_setup=has_setup,
-        use_pep517=use_pep517,
-        req_name=req_name,
-    )