Pylint reporter cleanup (#5003)

* Create a file for pylint.reporters.BaseWritter

* Calculate visitor name only once in Reporter nodes

Remove dead code that was always failing and replace it by
an attribute directly.

Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>

4 files changed, 104 insertions, 110 deletions

diff --git a/pylint/reporters/ureports/__init__.py b/pylint/reporters/ureports/__init__.py
index f0651f98c..29bc85d89 100644
--- a/pylint/reporters/ureports/__init__.py
+++ b/pylint/reporters/ureports/__init__.py
@@ -1,98 +1,6 @@
-# Copyright (c) 2015-2016, 2018, 2020 Claudiu Popa <pcmanticore@gmail.com>
-# Copyright (c) 2018 ssolanki <sushobhitsolanki@gmail.com>
-# Copyright (c) 2018 Sushobhit <31987769+sushobhit27@users.noreply.github.com>
-# Copyright (c) 2018 Anthony Sottile <asottile@umich.edu>
-# Copyright (c) 2019, 2021 Pierre Sassoulas <pierre.sassoulas@gmail.com>
-# Copyright (c) 2020 hippo91 <guillaume.peillex@gmail.com>
-# Copyright (c) 2021 Nick Drozd <nicholasdrozd@gmail.com>
-# Copyright (c) 2021 Marc Mueller <30130371+cdce8p@users.noreply.github.com>
-
 # 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
 
-"""Universal report objects and some formatting drivers.
-
-A way to create simple reports using python objects, primarily designed to be
-formatted as text and html.
-"""
-import os
-import sys
-from io import StringIO
-from typing import Iterator, TextIO
-
-
-class BaseWriter:
-    """base class for ureport writers"""
-
-    def format(self, layout, stream: TextIO = sys.stdout, encoding=None) -> None:
-        """format and write the given layout into the stream object
-
-        unicode policy: unicode strings may be found in the layout;
-        try to call stream.write with it, but give it back encoded using
-        the given encoding if it fails
-        """
-        if not encoding:
-            encoding = getattr(stream, "encoding", "UTF-8")
-        self.encoding = encoding or "UTF-8"
-        self.out = stream
-        self.begin_format()
-        layout.accept(self)
-        self.end_format()
-
-    def format_children(self, layout):
-        """recurse on the layout children and call their accept method
-        (see the Visitor pattern)
-        """
-        for child in getattr(layout, "children", ()):
-            child.accept(self)
-
-    def writeln(self, string=""):
-        """write a line in the output buffer"""
-        self.write(string + os.linesep)
-
-    def write(self, string):
-        """write a string in the output buffer"""
-        self.out.write(string)
-
-    def begin_format(self):
-        """begin to format a layout"""
-        self.section = 0
-
-    def end_format(self):
-        """finished to format a layout"""
-
-    def get_table_content(self, table):
-        """trick to get table content without actually writing it
-
-        return an aligned list of lists containing table cells values as string
-        """
-        result = [[]]
-        cols = table.cols
-        for cell in self.compute_content(table):
-            if cols == 0:
-                result.append([])
-                cols = table.cols
-            cols -= 1
-            result[-1].append(cell)
-        # fill missing cells
-        result[-1] += [""] * (cols - len(result[-1]))
-        return result
-
-    def compute_content(self, layout) -> Iterator[str]:
-        """trick to compute the formatting of children layout before actually
-        writing it
+__all__ = ("BaseWriter",)
 
-        return an iterator on strings (one for each child element)
-        """
-        # Patch the underlying output stream with a fresh-generated stream,
-        # which is used to store a temporary representation of a child
-        # node.
-        out = self.out
-        try:
-            for child in layout.children:
-                stream = StringIO()
-                self.out = stream
-                child.accept(self)
-                yield stream.getvalue()
-        finally:
-            self.out = out
+from pylint.reporters.ureports.base_writer import BaseWriter
diff --git a/pylint/reporters/ureports/base_writer.py b/pylint/reporters/ureports/base_writer.py
new file mode 100644
index 000000000..f0651f98c
--- /dev/null
+++ b/pylint/reporters/ureports/base_writer.py
@@ -0,0 +1,98 @@
+# Copyright (c) 2015-2016, 2018, 2020 Claudiu Popa <pcmanticore@gmail.com>
+# Copyright (c) 2018 ssolanki <sushobhitsolanki@gmail.com>
+# Copyright (c) 2018 Sushobhit <31987769+sushobhit27@users.noreply.github.com>
+# Copyright (c) 2018 Anthony Sottile <asottile@umich.edu>
+# Copyright (c) 2019, 2021 Pierre Sassoulas <pierre.sassoulas@gmail.com>
+# Copyright (c) 2020 hippo91 <guillaume.peillex@gmail.com>
+# Copyright (c) 2021 Nick Drozd <nicholasdrozd@gmail.com>
+# Copyright (c) 2021 Marc Mueller <30130371+cdce8p@users.noreply.github.com>
+
+# 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
+
+"""Universal report objects and some formatting drivers.
+
+A way to create simple reports using python objects, primarily designed to be
+formatted as text and html.
+"""
+import os
+import sys
+from io import StringIO
+from typing import Iterator, TextIO
+
+
+class BaseWriter:
+    """base class for ureport writers"""
+
+    def format(self, layout, stream: TextIO = sys.stdout, encoding=None) -> None:
+        """format and write the given layout into the stream object
+
+        unicode policy: unicode strings may be found in the layout;
+        try to call stream.write with it, but give it back encoded using
+        the given encoding if it fails
+        """
+        if not encoding:
+            encoding = getattr(stream, "encoding", "UTF-8")
+        self.encoding = encoding or "UTF-8"
+        self.out = stream
+        self.begin_format()
+        layout.accept(self)
+        self.end_format()
+
+    def format_children(self, layout):
+        """recurse on the layout children and call their accept method
+        (see the Visitor pattern)
+        """
+        for child in getattr(layout, "children", ()):
+            child.accept(self)
+
+    def writeln(self, string=""):
+        """write a line in the output buffer"""
+        self.write(string + os.linesep)
+
+    def write(self, string):
+        """write a string in the output buffer"""
+        self.out.write(string)
+
+    def begin_format(self):
+        """begin to format a layout"""
+        self.section = 0
+
+    def end_format(self):
+        """finished to format a layout"""
+
+    def get_table_content(self, table):
+        """trick to get table content without actually writing it
+
+        return an aligned list of lists containing table cells values as string
+        """
+        result = [[]]
+        cols = table.cols
+        for cell in self.compute_content(table):
+            if cols == 0:
+                result.append([])
+                cols = table.cols
+            cols -= 1
+            result[-1].append(cell)
+        # fill missing cells
+        result[-1] += [""] * (cols - len(result[-1]))
+        return result
+
+    def compute_content(self, layout) -> Iterator[str]:
+        """trick to compute the formatting of children layout before actually
+        writing it
+
+        return an iterator on strings (one for each child element)
+        """
+        # Patch the underlying output stream with a fresh-generated stream,
+        # which is used to store a temporary representation of a child
+        # node.
+        out = self.out
+        try:
+            for child in layout.children:
+                stream = StringIO()
+                self.out = stream
+                child.accept(self)
+                yield stream.getvalue()
+        finally:
+            self.out = out
diff --git a/pylint/reporters/ureports/nodes.py b/pylint/reporters/ureports/nodes.py
index d359093b8..3f7842a18 100644
--- a/pylint/reporters/ureports/nodes.py
+++ b/pylint/reporters/ureports/nodes.py
@@ -22,6 +22,7 @@ class VNode:
         # navigation
         self.parent = None
         self.children = []
+        self.visitor_name = self.__class__.__name__.lower()
 
     def __iter__(self):
         return iter(self.children)
@@ -36,25 +37,12 @@ class VNode:
         self.children.insert(index, child)
         child.parent = self
 
-    def _get_visit_name(self):
-        """
-        return the visit name for the mixed class. When calling 'accept', the
-        method <'visit_' + name returned by this method> will be called on the
-        visitor
-        """
-        try:
-            # pylint: disable=no-member
-            return self.TYPE.replace("-", "_")
-        # pylint: disable=broad-except
-        except Exception:
-            return self.__class__.__name__.lower()
-
     def accept(self, visitor, *args, **kwargs):
-        func = getattr(visitor, f"visit_{self._get_visit_name()}")
+        func = getattr(visitor, f"visit_{self.visitor_name}")
         return func(self, *args, **kwargs)
 
     def leave(self, visitor, *args, **kwargs):
-        func = getattr(visitor, f"leave_{self._get_visit_name()}")
+        func = getattr(visitor, f"leave_{self.visitor_name}")
         return func(self, *args, **kwargs)
 
 
diff --git a/tests/pyreverse/test_writer.py b/tests/pyreverse/test_writer.py
index 28ed16046..9c847be29 100644
--- a/tests/pyreverse/test_writer.py
+++ b/tests/pyreverse/test_writer.py
@@ -28,7 +28,7 @@ from typing import Callable, Iterator, List
 from unittest.mock import Mock
 
 import pytest
-from conftest import PyreverseConfig  # type: ignore
+from conftest import PyreverseConfig  # type: ignore #pylint: disable=no-name-in-module
 
 from pylint.pyreverse.diadefslib import DefaultDiadefGenerator, DiadefsHandler
 from pylint.pyreverse.inspector import Linker, Project