1 files changed, 87 insertions, 0 deletions
diff --git a/pylint/message/message_definition.py b/pylint/message/message_definition.py
new file mode 100644
index 000000000..30dacb32f
--- /dev/null
+++ b/pylint/message/message_definition.py
@@ -0,0 +1,87 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+
+import sys
+from typing import List, Optional, Tuple
+
+from pylint.constants import MSG_TYPES
+from pylint.exceptions import InvalidMessageError
+from pylint.utils import normalize_text
+
+
+class MessageDefinition:
+    def __init__(
+        self,
+        checker,  # BaseChecker
+        msgid: str,
+        msg: str,
+        description: str,
+        symbol: str,
+        scope: str,
+        minversion: Optional[Tuple[int, int]] = None,
+        maxversion: Optional[Tuple[int, int]] = None,
+        old_names: List[Tuple[str, str]] = None,
+    ):
+        self.checker_name = checker.name
+        self.check_msgid(msgid)
+        self.msgid = msgid
+        self.symbol = symbol
+        self.msg = msg
+        self.description = description
+        self.scope = scope
+        self.minversion = minversion
+        self.maxversion = maxversion
+        self.old_names: List[Tuple[str, str]] = []
+        if old_names:
+            for old_msgid, old_symbol in old_names:
+                self.check_msgid(old_msgid)
+                self.old_names.append(
+                    (old_msgid, old_symbol),
+                )
+
+    @staticmethod
+    def check_msgid(msgid: str) -> None:
+        if len(msgid) != 5:
+            raise InvalidMessageError(f"Invalid message id {msgid!r}")
+        if msgid[0] not in MSG_TYPES:
+            raise InvalidMessageError(f"Bad message type {msgid[0]} in {msgid!r}")
+
+    def __repr__(self):
+        return f"MessageDefinition:{self.symbol} ({self.msgid})"
+
+    def __str__(self):
+        return f"{repr(self)}:\n{self.msg} {self.description}"
+
+    def may_be_emitted(self) -> bool:
+        """return True if message may be emitted using the current interpreter"""
+        if self.minversion is not None and self.minversion > sys.version_info:
+            return False
+        if self.maxversion is not None and self.maxversion <= sys.version_info:
+            return False
+        return True
+
+    def format_help(self, checkerref: bool = False) -> str:
+        """return the help string for the given message id"""
+        desc = self.description
+        if checkerref:
+            desc += f" This message belongs to the {self.checker_name} checker."
+        title = self.msg
+        if self.minversion or self.maxversion:
+            restr = []
+            if self.minversion:
+                restr.append(f"< {'.'.join(str(n) for n in self.minversion)}")
+            if self.maxversion:
+                restr.append(f">= {'.'.join(str(n) for n in self.maxversion)}")
+            restriction = " or ".join(restr)
+            if checkerref:
+                desc += f" It can't be emitted when using Python {restriction}."
+            else:
+                desc += (
+                    f" This message can't be emitted when using Python {restriction}."
+                )
+        msg_help = normalize_text(" ".join(desc.split()), indent="  ")
+        message_id = f"{self.symbol} ({self.msgid})"
+        if title != "%s":
+            title = title.splitlines()[0]
+            return f":{message_id}: *{title.rstrip(' ')}*\n{msg_help}"
+        return f":{message_id}:\n{msg_help}"