Can read setup.cfg and pyproject.toml files

Closes #617

8 files changed, 166 insertions, 34 deletions

diff --git a/ChangeLog b/ChangeLog
index 409dfec8f..a22e2ce6f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,10 @@ What's New in Pylint 2.5.0?
 
 Release date: TBA
 
+* Can read config from a setup.cfg or pyproject.toml file.
+
+  Close #617
+
 
 What's New in Pylint 2.4.3?
 ===========================
@@ -22,6 +26,7 @@ Release date: TBA
 
   Close #3175
 
+
 What's New in Pylint 2.4.2?
 ===========================
 
diff --git a/doc/user_guide/run.rst b/doc/user_guide/run.rst
index 338a07064..d8268c36d 100644
--- a/doc/user_guide/run.rst
+++ b/doc/user_guide/run.rst
@@ -89,6 +89,10 @@ configuration file in the following order and uses the first one it finds:
 
 #. ``pylintrc`` in the current working directory
 #. ``.pylintrc`` in the current working directory
+#. ``pyproject.toml`` in the current working directory,
+   providing it has at least one ``tool.pylint.`` section.
+#. ``setup.cfg`` in the current working directory,
+   providing it has at least one ``pylint.`` section
 #. If the current working directory is in a Python module, Pylint searches \
    up the hierarchy of Python modules until it finds a ``pylintrc`` file. \
    This allows you to specify coding standards on a module-by-module \
diff --git a/doc/whatsnew/2.5.rst b/doc/whatsnew/2.5.rst
new file mode 100644
index 000000000..a1d97fb6c
--- /dev/null
+++ b/doc/whatsnew/2.5.rst
@@ -0,0 +1,27 @@
+**************************
+ What's New in Pylint 2.5
+**************************
+
+:Release: 2.5
+:Date: TBC
+
+
+Summary -- Release highlights
+=============================
+
+
+New checkers
+============
+
+
+Other Changes
+=============
+
+* Configuration can be read from a setup.cfg or pyproject.toml file
+  in the current directory.
+  A setup.cfg must prepend pylintrc section names with ``pylint.``,
+  for example ``[pylint.MESSAGES CONTROL]``.
+  A pyproject.toml file must prepend section names with ``tool.pylint.``,
+  for example ``[tool.pylint.'MESSAGES CONTROL']``.
+  These files can also be passed in on the command line.
+
diff --git a/doc/whatsnew/index.rst b/doc/whatsnew/index.rst
index e7faa7cc7..542b9743b 100644
--- a/doc/whatsnew/index.rst
+++ b/doc/whatsnew/index.rst
@@ -9,6 +9,7 @@ High level descriptions of the most important changes between major Pylint versi
 .. toctree::
    :maxdepth: 1
 
+   2.5.rst
    2.4.rst
    2.3.rst
    2.2.rst
diff --git a/pylint/__pkginfo__.py b/pylint/__pkginfo__.py
index bfca25d80..cc3c14a1a 100644
--- a/pylint/__pkginfo__.py
+++ b/pylint/__pkginfo__.py
@@ -29,7 +29,12 @@ version = ".".join(str(num) for num in numversion)
 if dev_version is not None:
     version += "-dev" + str(dev_version)
 
-install_requires = ["astroid>=2.3.0,<2.4", "isort>=4.2.5,<5", "mccabe>=0.6,<0.7"]
+install_requires = [
+    "astroid>=2.3.0,<2.4",
+    "isort>=4.2.5,<5",
+    "mccabe>=0.6,<0.7",
+    "toml>=0.7.1",
+]
 
 dependency_links = []  # type: ignore
 
diff --git a/pylint/config.py b/pylint/config.py
index 0925575b4..219bc6b78 100644
--- a/pylint/config.py
+++ b/pylint/config.py
@@ -46,6 +46,8 @@ import sys
 import time
 from typing import Any, Dict, Tuple
 
+import toml
+
 from pylint import utils
 
 USER_HOME = os.path.expanduser("~")
@@ -87,38 +89,70 @@ def save_results(results, base):
         print("Unable to create file %s: %s" % (data_file, ex), file=sys.stderr)
 
 
-def find_pylintrc():
-    """search the pylint rc file and return its path if it find it, else None
-    """
-    # is there a pylint rc file in the current directory ?
-    if os.path.exists("pylintrc"):
-        return os.path.abspath("pylintrc")
-    if os.path.exists(".pylintrc"):
-        return os.path.abspath(".pylintrc")
+def _toml_has_config(path):
+    with open(path, "r") as toml_handle:
+        content = toml.load(toml_handle)
+        try:
+            content["tool"]["pylint"]
+        except KeyError:
+            return False
+
+    return True
+
+
+def _cfg_has_config(path):
+    parser = configparser.ConfigParser()
+    parser.read(path)
+    return any(section.startswith("pylint.") for section in parser.sections())
+
+
+def find_default_config_files():
+    """Find all possible config files."""
+    rc_names = ("pylintrc", ".pylintrc")
+    config_names = rc_names + ("pyproject.toml", "setup.cfg")
+    for config_name in config_names:
+        if os.path.isfile(config_name):
+            if config_name.endswith(".toml") and not _toml_has_config(config_name):
+                continue
+            if config_name.endswith(".cfg") and not _cfg_has_config(config_name):
+                continue
+
+            yield os.path.abspath(config_name)
+
     if os.path.isfile("__init__.py"):
         curdir = os.path.abspath(os.getcwd())
         while os.path.isfile(os.path.join(curdir, "__init__.py")):
             curdir = os.path.abspath(os.path.join(curdir, ".."))
-            if os.path.isfile(os.path.join(curdir, "pylintrc")):
-                return os.path.join(curdir, "pylintrc")
-            if os.path.isfile(os.path.join(curdir, ".pylintrc")):
-                return os.path.join(curdir, ".pylintrc")
+            for rc_name in rc_names:
+                rc_path = os.path.join(curdir, rc_name)
+                if os.path.isfile(rc_path):
+                    yield rc_path
+
     if "PYLINTRC" in os.environ and os.path.exists(os.environ["PYLINTRC"]):
-        pylintrc = os.environ["PYLINTRC"]
+        if os.path.isfile(os.environ["PYLINTRC"]):
+            yield os.environ["PYLINTRC"]
     else:
         user_home = os.path.expanduser("~")
-        if user_home in ("~", "/root"):
-            pylintrc = ".pylintrc"
-        else:
-            pylintrc = os.path.join(user_home, ".pylintrc")
-            if not os.path.isfile(pylintrc):
-                pylintrc = os.path.join(user_home, ".config", "pylintrc")
-    if not os.path.isfile(pylintrc):
-        if os.path.isfile("/etc/pylintrc"):
-            pylintrc = "/etc/pylintrc"
-        else:
-            pylintrc = None
-    return pylintrc
+        if user_home not in ("~", "/root"):
+            home_rc = os.path.join(user_home, ".pylintrc")
+            if os.path.isfile(home_rc):
+                yield home_rc
+            home_rc = os.path.join(user_home, ".config", "pylintrc")
+            if os.path.isfile(home_rc):
+                yield home_rc
+
+    if os.path.isfile("/etc/pylintrc"):
+        yield "/etc/pylintrc"
+
+
+def find_pylintrc():
+    """search the pylint rc file and return its path if it find it, else None
+    """
+    for config_file in find_default_config_files():
+        if config_file.endswith("pylintrc"):
+            return config_file
+
+    return None
 
 
 PYLINTRC = find_pylintrc()
@@ -707,14 +741,28 @@ class OptionsManagerMixIn:
         if use_config_file:
             parser = self.cfgfile_parser
 
-            # Use this encoding in order to strip the BOM marker, if any.
-            with io.open(config_file, "r", encoding="utf_8_sig") as fp:
-                parser.read_file(fp)
+            if config_file.endswith(".toml"):
+                with open(config_file, "r") as fp:
+                    content = toml.load(fp)
 
-            # normalize sections'title
-            for sect, values in list(parser._sections.items()):
-                if not sect.isupper() and values:
-                    parser._sections[sect.upper()] = values
+                try:
+                    sections_values = content["tool"]["pylint"]
+                except KeyError:
+                    pass
+                else:
+                    for section, values in sections_values.items():
+                        parser._sections[section.upper()] = values
+            else:
+                # Use this encoding in order to strip the BOM marker, if any.
+                with io.open(config_file, "r", encoding="utf_8_sig") as fp:
+                    parser.read_file(fp)
+
+                # normalize sections'title
+                for sect, values in list(parser._sections.items()):
+                    if sect.startswith("pylint."):
+                        sect = sect[len("pylint.") :]
+                    if not sect.isupper() and values:
+                        parser._sections[sect.upper()] = values
 
         if not verbose:
             return
diff --git a/pylint/lint.py b/pylint/lint.py
index a98970b78..095eb0e2b 100644
--- a/pylint/lint.py
+++ b/pylint/lint.py
@@ -620,7 +620,9 @@ class PyLinter(
         MessagesHandlerMixIn.__init__(self)
         reporters.ReportsHandlerMixIn.__init__(self)
         super(PyLinter, self).__init__(
-            usage=__doc__, version=full_version, config_file=pylintrc or config.PYLINTRC
+            usage=__doc__,
+            version=full_version,
+            config_file=pylintrc or next(config.find_default_config_files(), None),
         )
         checkers.BaseTokenChecker.__init__(self)
         # provided reports
diff --git a/tests/test_config.py b/tests/test_config.py
new file mode 100644
index 000000000..4d79a6a7f
--- /dev/null
+++ b/tests/test_config.py
@@ -0,0 +1,40 @@
+import unittest.mock
+
+import pylint.lint
+import pytest
+
+
+def test_can_read_toml(tmp_path):
+    config_file = tmp_path / "pyproject.toml"
+    config_file.write_text(
+        "[tool.pylint.'messages control']\n"
+        "disable='all'\n"
+        "enable='missing-module-docstring'\n"
+        "jobs=10\n"
+    )
+
+    linter = pylint.lint.PyLinter()
+    linter.global_set_option = unittest.mock.MagicMock()
+    linter.read_config_file(str(config_file))
+
+    assert linter.global_set_option.called_with("disable", "all")
+    assert linter.global_set_option.called_with("enable", "missing-module-docstring")
+    assert linter.global_set_option.called_with("jobs", 10)
+
+
+def test_can_read_setup_cfg(tmp_path):
+    config_file = tmp_path / "setup.cfg"
+    config_file.write_text(
+        "[pylint.messages control]\n"
+        "disable=all\n"
+        "enable=missing-module-docstring\n"
+        "jobs=10\n"
+    )
+
+    linter = pylint.lint.PyLinter()
+    linter.global_set_option = unittest.mock.MagicMock()
+    linter.read_config_file(str(config_file))
+
+    assert linter.global_set_option.called_with("disable", "all")
+    assert linter.global_set_option.called_with("enable", "missing-module-docstring")
+    assert linter.global_set_option.called_with("jobs", 10)