From 2a3c21645e5c303a71694c0ff68d0a56c2d734d5 Mon Sep 17 00:00:00 2001
From: Gleb Nikonorov <gleb.i.nikonorov@gmail.com>
Date: Sat, 6 Jun 2020 02:38:18 -0400
Subject: [PATCH] Commit solution thus far, needs to be polished up pre PR

---
 doc/en/reference.rst           | 10 +++++
 src/_pytest/config/__init__.py | 33 +++++++++++++---
 testing/test_config.py         | 71 ++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+), 6 deletions(-)

diff --git a/doc/en/reference.rst b/doc/en/reference.rst
index 7348636a2..d84d9d405 100644
--- a/doc/en/reference.rst
+++ b/doc/en/reference.rst
@@ -1604,3 +1604,13 @@ passed multiple times. The expected format is ``name=value``. For example::
 
         [pytest]
         xfail_strict = True
+
+
+.. confval:: required_plugins
+
+   A space seperated list of plugins that must be present for pytest to run
+
+   .. code-block:: ini
+
+       [pytest]
+       require_plugins = pluginA pluginB pluginC
diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 27083900d..83878a486 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -952,6 +952,12 @@ class Config:
         self._parser.extra_info["inifile"] = self.inifile
         self._parser.addini("addopts", "extra command line options", "args")
         self._parser.addini("minversion", "minimally required pytest version")
+        self._parser.addini(
+            "require_plugins",
+            "plugins that must be present for pytest to run",
+            type="args",
+            default=[],
+        )
         self._override_ini = ns.override_ini or ()
 
     def _consider_importhook(self, args: Sequence[str]) -> None:
@@ -1035,7 +1041,8 @@ class Config:
         self.known_args_namespace = ns = self._parser.parse_known_args(
             args, namespace=copy.copy(self.option)
         )
-        self._validatekeys()
+        self._validate_keys()
+        self._validate_plugins()
         if self.known_args_namespace.confcutdir is None and self.inifile:
             confcutdir = py.path.local(self.inifile).dirname
             self.known_args_namespace.confcutdir = confcutdir
@@ -1078,12 +1085,26 @@ class Config:
                     )
                 )
 
-    def _validatekeys(self):
+    def _validate_keys(self) -> None:
         for key in sorted(self._get_unknown_ini_keys()):
-            message = "Unknown config ini key: {}\n".format(key)
-            if self.known_args_namespace.strict_config:
-                fail(message, pytrace=False)
-            sys.stderr.write("WARNING: {}".format(message))
+            self._emit_warning_or_fail("Unknown config ini key: {}\n".format(key))
+
+    def _validate_plugins(self) -> None:
+        # so iterate over all required plugins and see if pluginmanager hasplugin
+        # NOTE: This also account for -p no:<plugin> ( e.g: -p no:celery )
+        # raise ValueError(self._parser._inidict['requiredplugins'])
+        # raise ValueError(self.getini("requiredplugins"))
+        # raise ValueError(self.pluginmanager.hasplugin('debugging'))
+        for plugin in self.getini("require_plugins"):
+            if not self.pluginmanager.hasplugin(plugin):
+                self._emit_warning_or_fail(
+                    "Missing required plugin: {}\n".format(plugin)
+                )
+
+    def _emit_warning_or_fail(self, message: str) -> None:
+        if self.known_args_namespace.strict_config:
+            fail(message, pytrace=False)
+        sys.stderr.write("WARNING: {}".format(message))
 
     def _get_unknown_ini_keys(self) -> List[str]:
         parser_inicfg = self._parser._inidict
diff --git a/testing/test_config.py b/testing/test_config.py
index 867012e93..f88a9a0ce 100644
--- a/testing/test_config.py
+++ b/testing/test_config.py
@@ -212,6 +212,77 @@ class TestParseIni:
             with pytest.raises(pytest.fail.Exception, match=exception_text):
                 testdir.runpytest("--strict-config")
 
+    @pytest.mark.parametrize(
+        "ini_file_text, stderr_output, exception_text",
+        [
+            (
+                """
+          [pytest]
+          require_plugins = fakePlugin1 fakePlugin2
+          """,
+                [
+                    "WARNING: Missing required plugin: fakePlugin1",
+                    "WARNING: Missing required plugin: fakePlugin2",
+                ],
+                "Missing required plugin: fakePlugin1",
+            ),
+            (
+                """
+          [pytest]
+          require_plugins = a monkeypatch z
+          """,
+                [
+                    "WARNING: Missing required plugin: a",
+                    "WARNING: Missing required plugin: z",
+                ],
+                "Missing required plugin: a",
+            ),
+            (
+                """
+          [pytest]
+          require_plugins = a monkeypatch z
+          addopts = -p no:monkeypatch
+          """,
+                [
+                    "WARNING: Missing required plugin: a",
+                    "WARNING: Missing required plugin: monkeypatch",
+                    "WARNING: Missing required plugin: z",
+                ],
+                "Missing required plugin: a",
+            ),
+            (
+                """
+          [some_other_header]
+          require_plugins = wont be triggered
+          [pytest]
+          minversion = 5.0.0
+          """,
+                [],
+                "",
+            ),
+            (
+                """
+          [pytest]
+          minversion = 5.0.0
+          """,
+                [],
+                "",
+            ),
+        ],
+    )
+    def test_missing_required_plugins(
+        self, testdir, ini_file_text, stderr_output, exception_text
+    ):
+        testdir.tmpdir.join("pytest.ini").write(textwrap.dedent(ini_file_text))
+        testdir.parseconfig()
+
+        result = testdir.runpytest()
+        result.stderr.fnmatch_lines(stderr_output)
+
+        if stderr_output:
+            with pytest.raises(pytest.fail.Exception, match=exception_text):
+                testdir.runpytest("--strict-config")
+
 
 class TestConfigCmdlineParsing:
     def test_parsing_again_fails(self, testdir):