Build: Pin setuptools only when required

Ref #8659
Closes #10263

readthedocs/config/config.py

@@ -282,6 +282,14 @@ def is_using_conda(self):
             return self.python_interpreter in ("conda", "mamba")
         return self.conda is not None
 
+    @property
+    def is_using_setup_py_install(self):
+        """Check if this project is using `setup.py install` as installation method."""
+        for install in self.python.install:
+            if isinstance(install, PythonInstall) and install.method == SETUPTOOLS:
+                return True
+        return False
+
     @property
     def python_interpreter(self):
         if self.using_build_tools:

readthedocs/doc_builder/director.py

@@ -542,17 +542,22 @@ def install_build_tools(self):
                     self.data.config.python_interpreter not in ("conda", "mamba"),
                 ]
             ):
+                # We cap setuptools to avoid breakage of projects
+                # relying on setup.py invokations,
+                # see https://github.com/readthedocs/readthedocs.org/issues/8659
+                setuptools_version = (
+                    "setuptools<58.3.0"
+                    if self.data.config.is_using_setup_py_install
+                    else "setuptools"
+                )
                 # Install our own requirements if the version is compiled
                 cmd = [
                     "python",
                     "-mpip",
                     "install",
                     "-U",
                     "virtualenv",
-                    # We cap setuptools to avoid breakage of projects
-                    # relying on setup.py invokations,
-                    # see https://github.com/readthedocs/readthedocs.org/issues/8659
-                    "setuptools<58.3.0",
+                    setuptools_version,
                 ]
                 self.build_environment.run(
                     *cmd,

readthedocs/doc_builder/python_environments.py

@@ -171,7 +171,15 @@ def install_core_requirements(self):
             positive='pip<20.3',
             negative='pip',
         )
-        cmd = pip_install_cmd + [pip_version, 'setuptools<58.3.0']
+        # Installing a project with setup.py install is deprecated
+        # in new versions of setuptools, so we need to pin setuptools
+        # to a supported version if the project is using setup.py install.
+        setuptools_version = (
+            "setuptools<58.3.0"
+            if self.config.is_using_setup_py_install
+            else "setuptools"
+        )
+        cmd = pip_install_cmd + [pip_version, setuptools_version]
         self.build_env.run(
             *cmd,
             bin_path=self.venv_bin(),
@@ -248,7 +256,7 @@ def install_core_requirements(self):
         self.build_env.run(
             *cmd,
             bin_path=self.venv_bin(),
-            cwd=self.checkout_path  # noqa - no comma here in py27 :/
+            cwd=self.checkout_path,
         )
 
     def install_requirements_file(self, install):

readthedocs/projects/tests/test_build_tasks.py

@@ -708,7 +708,7 @@ def test_build_commands_executed(
                     "--upgrade",
                     "--no-cache-dir",
                     "pip",
-                    "setuptools<58.3.0",
+                    "setuptools",
                     bin_path=mock.ANY,
                     cwd=mock.ANY,
                 ),
@@ -981,7 +981,7 @@ def test_build_tools(self, load_yaml_config):
                     "install",
                     "-U",
                     "virtualenv",
-                    "setuptools<58.3.0",
+                    "setuptools",
                 ),
                 mock.call("asdf", "install", "nodejs", nodejs_version),
                 mock.call("asdf", "global", "nodejs", nodejs_version),
@@ -1138,7 +1138,7 @@ def test_build_commands(self, load_yaml_config):
                     "install",
                     "-U",
                     "virtualenv",
-                    "setuptools<58.3.0",
+                    "setuptools",
                 ),
                 # NOTE: when running commands from `build.jobs` or
                 # `build.commands` they are not split to allow multi-line

readthedocs/rtd_tests/tests/test_doc_building.py

@@ -418,7 +418,7 @@ def test_install_core_requirements_sphinx(self, checkout_path):
         self.assertEqual(self.build_env_mock.run.call_count, 2)
         calls = self.build_env_mock.run.call_args_list
 
-        core_args = self.pip_install_args + ['pip', 'setuptools<58.3.0']
+        core_args = self.pip_install_args + ["pip", "setuptools"]
         self.assertArgsStartsWith(core_args, calls[0])
 
         requirements = self.base_requirements + requirements_sphinx
@@ -457,7 +457,7 @@ def test_install_core_requirements_sphinx_system_packages_caps_setuptools(self,
         self.assertEqual(self.build_env_mock.run.call_count, 2)
         calls = self.build_env_mock.run.call_args_list
 
-        core_args = self.pip_install_args + ['pip', 'setuptools<58.3.0']
+        core_args = self.pip_install_args + ["pip", "setuptools"]
         self.assertArgsStartsWith(core_args, calls[0])
 
         requirements = self.base_requirements + requirements_sphinx
@@ -482,7 +482,7 @@ def test_install_core_requirements_mkdocs(self, checkout_path):
         self.assertEqual(self.build_env_mock.run.call_count, 2)
         calls = self.build_env_mock.run.call_args_list
 
-        core_args = self.pip_install_args + ['pip', 'setuptools<58.3.0']
+        core_args = self.pip_install_args + ["pip", "setuptools"]
         self.assertArgsStartsWith(core_args, calls[0])
 
         requirements = self.base_requirements + requirements_mkdocs