config: Handle rich (non-string) types in TOML file

Fixes #3538

Before that, we had to use strings in a TOML configuration file, like
this:

    enable = "use-symbolic-message-instead,useless-suppression"
    jobs = "10"
    suggestion-mode = "no"

TOML supports rich types like list, integer and boolean. They make for
a more readable and less error-prone file. We can now express the same
configuration like this:

    enable = [
        "use-symbolic-message-instead",
        "useless-suppression",
    ]
    jobs = 10
    suggestion-mode = false

4 files changed, 100 insertions, 24 deletions

diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index 420c62417..350b7d1c0 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -381,3 +381,5 @@ contributors:
 * Yang Yang: contributor
 
 * Andrew J. Simmons (anjsimmo): contributor
+
+* Damien Baty: contributor
diff --git a/ChangeLog b/ChangeLog
index 465e372df..c18dd3f9a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -38,6 +38,15 @@ Release date: TBA
 
   Close #3604
 
+* In a TOML configuration file, it's now possible to use rich (non-string) types, such as list, integer or boolean instead of strings. For example, one can now define a *list* of message identifiers to enable like this::
+
+    enable = [
+        "use-symbolic-message-instead",
+        "useless-suppression",
+    ]
+
+  Close #3538
+
 
 What's New in Pylint 2.5.2?
 ===========================
diff --git a/pylint/config/option_manager_mixin.py b/pylint/config/option_manager_mixin.py
index fafc3fd7d..353e1c8bc 100644
--- a/pylint/config/option_manager_mixin.py
+++ b/pylint/config/option_manager_mixin.py
@@ -261,7 +261,7 @@ class OptionsManagerMixIn:
                 raise OSError("The config file {:s} doesn't exist!".format(config_file))
 
         use_config_file = config_file and os.path.exists(config_file)
-        if use_config_file:
+        if use_config_file:  # pylint: disable=too-many-nested-blocks
             parser = self.cfgfile_parser
 
             if config_file.endswith(".toml"):
@@ -274,6 +274,15 @@ class OptionsManagerMixIn:
                     pass
                 else:
                     for section, values in sections_values.items():
+                        # TOML has rich types, convert values to
+                        # strings as ConfigParser expects.
+                        for option, value in values.items():
+                            if isinstance(value, bool):
+                                values[option] = "yes" if value else "no"
+                            elif isinstance(value, int):
+                                values[option] = str(value)
+                            elif isinstance(value, list):
+                                values[option] = ",".join(value)
                         parser._sections[section.upper()] = values
             else:
                 # Use this encoding in order to strip the BOM marker, if any.
diff --git a/tests/test_config.py b/tests/test_config.py
index 8ea626d03..ecfac3328 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,37 +1,93 @@
+# pylint: disable=missing-module-docstring, missing-function-docstring, protected-access
 import unittest.mock
 
 import pylint.lint
 
 
-def test_can_read_toml(tmp_path):
-    config_file = tmp_path / "pyproject.toml"
+def check_configuration_file_reader(config_file):
+    """Initialize pylint with the given configuration file and check that
+    what we initialized the linter with what was expected.
+    """
+    args = ["--rcfile", str(config_file), __file__]
+    # If we used `pytest.raises(SystemExit)`, the `runner` variable
+    # would not be accessible outside the `with` block.
+    with unittest.mock.patch("sys.exit") as mocked_exit:
+        # Do not actually run checks, that could be slow. Do not mock
+        # `Pylinter.check`: it calls `Pylinter.initialize` which is
+        # needed to properly set up messages inclusion/exclusion
+        # in `_msg_states`, used by `is_message_enabled`.
+        with unittest.mock.patch("pylint.lint.pylinter.check_parallel"):
+            runner = pylint.lint.Run(args)
+
+    # "logging-not-lazy" and "logging-format-interpolation"
+    expected_disabled = {"W1201", "W1202"}
+    for msgid in expected_disabled:
+        assert not runner.linter.is_message_enabled(msgid)
+    assert runner.linter.config.jobs == 10
+    assert runner.linter.config.reports
+
+    mocked_exit.assert_called_once_with(0)
+    return runner
+
+
+def test_can_read_ini(tmp_path):
+    # Check that we can read the "regular" INI .pylintrc file
+    config_file = tmp_path / ".pylintrc"
     config_file.write_text(
-        "[tool.pylint.'messages control']\n"
-        "disable='all'\n"
-        "enable='missing-module-docstring'\n"
-        "jobs=10\n"
+        """
+[messages control]
+disable = logging-not-lazy,logging-format-interpolation
+jobs = 10
+reports = yes
+"""
     )
-    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)
+    check_configuration_file_reader(config_file)
 
 
 def test_can_read_setup_cfg(tmp_path):
+    # Check that we can read a setup.cfg (which is an INI file where
+    # section names are prefixed with "pylint."
     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"
+        """
+[pylint.messages control]
+disable = logging-not-lazy,logging-format-interpolation
+jobs = 10
+reports = yes
+"""
     )
-    linter = pylint.lint.PyLinter()
-    linter.global_set_option = unittest.mock.MagicMock()
-    linter.read_config_file(str(config_file))
+    check_configuration_file_reader(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_toml(tmp_path):
+    # Check that we can read a TOML file where lists and integers are
+    # expressed as strings.
+    config_file = tmp_path / "pyproject.toml"
+    config_file.write_text(
+        """
+[tool.pylint."messages control"]
+disable = "logging-not-lazy,logging-format-interpolation"
+jobs = "10"
+reports = "yes"
+"""
+    )
+    check_configuration_file_reader(config_file)
+
+
+def test_can_read_toml_rich_types(tmp_path):
+    # Check that we can read a TOML file where lists, integers and
+    # booleans are expressed as such (and not as strings), using TOML
+    # type system.
+    config_file = tmp_path / "pyproject.toml"
+    config_file.write_text(
+        """
+[tool.pylint."messages control"]
+disable = [
+    "logging-not-lazy",
+    "logging-format-interpolation",
+]
+jobs = 10
+reports = true
+"""
+    )
+    check_configuration_file_reader(config_file)