Code Style Checker

Wed, 31 Mar 2021 19:51:41 +0200

author
Detlev Offenbach <detlev@die-offenbachs.de>
date
Wed, 31 Mar 2021 19:51:41 +0200
changeset 8186
655b658aa7ee
parent 8185
c9acf46b54ce
child 8187
7bfee4d12551

Code Style Checker
- started to implement a checker for potential code simplifications

eric6.epj file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/CodeStyleChecker.py file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/CodeStyleCheckerDialog.py file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/SimplifyChecker.py file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/__init__.py file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/ast_unparse.py file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/translations.py file | annotate | diff | comparison | revisions
eric6/Plugins/CheckerPlugins/CodeStyleChecker/translations.py file | annotate | diff | comparison | revisions
--- a/eric6.epj	Tue Mar 30 19:59:24 2021 +0200
+++ b/eric6.epj	Wed Mar 31 19:51:41 2021 +0200
@@ -48,7 +48,7 @@
         "CopyrightMinFileSize": 0,
         "DocstringType": "eric",
         "EnabledCheckerCategories": "C, D, E, M, N, W",
-        "ExcludeFiles": "*/ThirdParty/*, */coverage/*, */Ui_*.py, */Examples/*, */*_rc.py,*/pycodestyle.py,*/pyflakes/checker.py,*/mccabe.py,*/eradicate.py",
+        "ExcludeFiles": "*/ThirdParty/*, */coverage/*, */Ui_*.py, */Examples/*, */*_rc.py,*/pycodestyle.py,*/pyflakes/checker.py,*/mccabe.py,*/eradicate.py,*/ast_unparse.py",
         "ExcludeMessages": "C101,E265,E266,E305,E402,M201,M301,M302,M303,M304,M305,M306,M307,M308,M311,M312,M313,M314,M315,M321,M701,M702,M811,M834,N802,N803,N807,N808,N821,W293,W504",
         "FixCodes": "",
         "FixIssues": false,
@@ -2573,7 +2573,11 @@
       "eric6/Plugins/CheckerPlugins/CodeStyleChecker/PathLib/PathlibChecker.py",
       "eric6/Plugins/CheckerPlugins/CodeStyleChecker/PathLib/translations.py",
       "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Miscellaneous/eradicate.py",
-      "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Complexity/mccabe.py"
+      "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Complexity/mccabe.py",
+      "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/__init__.py",
+      "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/ast_unparse.py",
+      "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/SimplifyChecker.py",
+      "eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/translations.py"
     ],
     "SPELLEXCLUDES": "Dictionaries/excludes.dic",
     "SPELLLANGUAGE": "en_US",
--- a/eric6/Plugins/CheckerPlugins/CodeStyleChecker/CodeStyleChecker.py	Tue Mar 30 19:59:24 2021 +0200
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/CodeStyleChecker.py	Wed Mar 31 19:51:41 2021 +0200
@@ -23,6 +23,7 @@
 from Complexity.ComplexityChecker import ComplexityChecker
 from Security.SecurityChecker import SecurityChecker
 from PathLib.PathlibChecker import PathlibChecker
+from Simplify.SimplifyChecker import SimplifyChecker
 
 
 def initService():
@@ -427,6 +428,7 @@
                 stats.update(annotationsChecker.counters)
                 errors += annotationsChecker.errors
             
+            # check for security issues
             securityChecker = SecurityChecker(
                 source, filename, select, ignore, [], repeatMessages,
                 securityArgs)
@@ -434,11 +436,19 @@
             stats.update(securityChecker.counters)
             errors += securityChecker.errors
             
+            # check for pathlib usage
             pathlibChecker = PathlibChecker(
                 source, filename, select, ignore, [], repeatMessages)
             pathlibChecker.run()
             stats.update(pathlibChecker.counters)
             errors += pathlibChecker.errors
+            
+            # check for code simplifications
+            simplifyChecker =SimplifyChecker(
+                source, filename, select, ignore, [], repeatMessages)
+            simplifyChecker.run()
+            stats.update(simplifyChecker.counters)
+            errors += simplifyChecker.errors
     
     errorsDict = {}
     for error in errors:
--- a/eric6/Plugins/CheckerPlugins/CodeStyleChecker/CodeStyleCheckerDialog.py	Tue Mar 30 19:59:24 2021 +0200
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/CodeStyleCheckerDialog.py	Wed Mar 31 19:51:41 2021 +0200
@@ -91,6 +91,9 @@
         "W": QCoreApplication.translate(
             "CheckerCategories",
             "Warnings"),
+        "Y": QCoreApplication.translate(
+            "CheckerCategories",
+            "Simplify Code"),
     }
     
     noResults = 0
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/SimplifyChecker.py	Wed Mar 31 19:51:41 2021 +0200
@@ -0,0 +1,249 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2021 Detlev Offenbach <detlev@die-offenbachs.de>
+#
+
+"""
+Module implementing the checker for simplifying Python code.
+"""
+
+import ast
+import collections
+import sys
+
+try:
+    from ast import unparse
+except AttributeError:
+    # Python < 3.9
+    from .ast_unparse import unparse
+
+
+class SimplifyChecker(object):
+    """
+    Class implementing a checker for to help simplifying Python code.
+    """
+    Codes = [
+        "Y101", 
+    ]
+    
+    def __init__(self, source, filename, selected, ignored, expected, repeat):
+        """
+        Constructor
+        
+        @param source source code to be checked
+        @type list of str
+        @param filename name of the source file
+        @type str
+        @param selected list of selected codes
+        @type list of str
+        @param ignored list of codes to be ignored
+        @type list of str
+        @param expected list of expected codes
+        @type list of str
+        @param repeat flag indicating to report each occurrence of a code
+        @type bool
+        """
+        self.__select = tuple(selected)
+        self.__ignore = ('',) if selected else tuple(ignored)
+        self.__expected = expected[:]
+        self.__repeat = repeat
+        self.__filename = filename
+        self.__source = source[:]
+        
+        # statistics counters
+        self.counters = {}
+        
+        # collection of detected errors
+        self.errors = []
+        
+        self.__checkCodes = (code for code in self.Codes
+                             if not self.__ignoreCode(code))
+    
+    def __ignoreCode(self, code):
+        """
+        Private method to check if the message code should be ignored.
+
+        @param code message code to check for
+        @type str
+        @return flag indicating to ignore the given code
+        @rtype bool
+        """
+        return (code.startswith(self.__ignore) and
+                not code.startswith(self.__select))
+    
+    def __error(self, lineNumber, offset, code, *args):
+        """
+        Private method to record an issue.
+        
+        @param lineNumber line number of the issue
+        @type int
+        @param offset position within line of the issue
+        @type int
+        @param code message code
+        @type str
+        @param args arguments for the message
+        @type list
+        """
+        if self.__ignoreCode(code):
+            return
+        
+        if code in self.counters:
+            self.counters[code] += 1
+        else:
+            self.counters[code] = 1
+        
+        # Don't care about expected codes
+        if code in self.__expected:
+            return
+        
+        if code and (self.counters[code] == 1 or self.__repeat):
+            # record the issue with one based line number
+            self.errors.append(
+                {
+                    "file": self.__filename,
+                    "line": lineNumber + 1,
+                    "offset": offset,
+                    "code": code,
+                    "args": args,
+                }
+            )
+    
+    def __reportInvalidSyntax(self):
+        """
+        Private method to report a syntax error.
+        """
+        exc_type, exc = sys.exc_info()[:2]
+        if len(exc.args) > 1:
+            offset = exc.args[1]
+            if len(offset) > 2:
+                offset = offset[1:3]
+        else:
+            offset = (1, 0)
+        self.__error(offset[0] - 1, offset[1] or 0,
+                     'M901', exc_type.__name__, exc.args[0])
+    
+    def __generateTree(self):
+        """
+        Private method to generate an AST for our source.
+        
+        @return generated AST
+        @rtype ast.AST
+        """
+        return ast.parse("".join(self.__source), self.__filename)
+    
+    def run(self):
+        """
+        Public method to check the given source against functions
+        to be replaced by 'pathlib' equivalents.
+        """
+        if not self.__filename:
+            # don't do anything, if essential data is missing
+            return
+        
+        if not self.__checkCodes:
+            # don't do anything, if no codes were selected
+            return
+        
+        try:
+            self.__tree = self.__generateTree()
+        except (SyntaxError, TypeError):
+            self.__reportInvalidSyntax()
+            return
+        
+        visitor = SimplifyVisitor(self.__error)
+        visitor.visit(self.__tree)
+
+######################################################################
+## The following code is derived from the flake8-simplify package.
+##
+## Original License:
+##
+## MIT License
+##
+## Copyright (c) 2020 Martin Thoma
+##
+## Permission is hereby granted, free of charge, to any person obtaining a copy
+## of this software and associated documentation files (the "Software"), to
+## deal in the Software without restriction, including without limitation the
+## rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+## sell copies of the Software, and to permit persons to whom the Software is
+## furnished to do so, subject to the following conditions:
+##
+## The above copyright notice and this permission notice shall be included in
+## all copies or substantial portions of the Software.
+##
+## THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+## IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+## FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+## AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+## LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+## FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+## IN THE SOFTWARE.
+######################################################################
+
+
+class SimplifyVisitor(ast.NodeVisitor):
+    """
+    Class to traverse the AST node tree and check for code that can be
+    simplified.
+    """
+    def __init__(self, errorCallback):
+        """
+        Constructor
+        
+        @param checkCallback callback function taking a reference to the
+            AST node and the resolved name
+        @type func
+        """
+        super(SimplifyVisitor, self).__init__()
+        
+        self.__error = errorCallback
+    
+    def visit_BoolOp(self, node):
+        """
+        Public method to process a BoolOp node.
+        
+        @param node reference to the BoolOp node
+        @type ast.BoolOp
+        """
+        self.__check101(node)
+    
+    #############################################################
+    ## Methods to check for possible code simplifications below
+    #############################################################
+    
+    def __getDuplicatedIsinstanceCall(self, node):
+        """
+        Private method to get a list of isinstance arguments which could
+        be combined.
+        
+        @param node reference to the AST node to be inspected
+        @type ast.BoolOp
+        """
+        counter = collections.defaultdict(int)
+        
+        for call in node.values:
+            # Ensure this is a call of the built-in isinstance() function.
+            if not isinstance(call,  ast.Call) or len(call.args) != 2:
+                continue
+            functionName = call.func.id
+            if functionName != "isinstance":
+                continue
+            
+            arg0Name = unparse(call.args[0])
+            counter[arg0Name] += 1
+        
+        return [name for name, count in counter.items() if count > 1]
+    
+    def __check101(self, node):
+        """
+        Private method to check for duplicate isinstance() calls.
+        
+        @param node reference to the AST node to be checked
+        @type ast.BoolOp
+        """
+        if not isinstance(node.op, ast.Or):
+            return
+        
+        for variable in self.__getDuplicatedIsinstanceCall(node):
+            self.__error(node.lineno - 1, node.col_offset, "Y101", variable)
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/__init__.py	Wed Mar 31 19:51:41 2021 +0200
@@ -0,0 +1,8 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2021 Detlev Offenbach <detlev@die-offenbachs.de>
+#
+
+"""
+Package implementing a checker to help simplifying the code.
+"""
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/ast_unparse.py	Wed Mar 31 19:51:41 2021 +0200
@@ -0,0 +1,959 @@
+"""
+    ast_unparse
+    ~~~~~~~~~~~
+
+    This module is a backport of the unparse function of the Python 3.9
+    ast module.
+
+    Original ast module code is
+    :copyright: Copyright 2008 by Armin Ronacher.
+    :license: Python License.
+"""
+
+import ast
+import sys
+from enum import IntEnum, auto
+from contextlib import contextmanager, nullcontext
+
+# Large float and imaginary literals get turned into infinities in the AST.
+# We unparse those infinities to INFSTR.
+_INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)
+
+class _Precedence(IntEnum):
+    """Precedence table that originated from python grammar."""
+
+    TUPLE = auto()
+    YIELD = auto()           # 'yield', 'yield from'
+    TEST = auto()            # 'if'-'else', 'lambda'
+    OR = auto()              # 'or'
+    AND = auto()             # 'and'
+    NOT = auto()             # 'not'
+    CMP = auto()             # '<', '>', '==', '>=', '<=', '!=',
+                             # 'in', 'not in', 'is', 'is not'
+    EXPR = auto()
+    BOR = EXPR               # '|'
+    BXOR = auto()            # '^'
+    BAND = auto()            # '&'
+    SHIFT = auto()           # '<<', '>>'
+    ARITH = auto()           # '+', '-'
+    TERM = auto()            # '*', '@', '/', '%', '//'
+    FACTOR = auto()          # unary '+', '-', '~'
+    POWER = auto()           # '**'
+    AWAIT = auto()           # 'await'
+    ATOM = auto()
+
+    def next(self):
+        try:
+            return self.__class__(self + 1)
+        except ValueError:
+            return self
+
+
+_SINGLE_QUOTES = ("'", '"')
+_MULTI_QUOTES = ('"""', "'''")
+_ALL_QUOTES = (*_SINGLE_QUOTES, *_MULTI_QUOTES)
+
+class _Unparser(ast.NodeVisitor):
+    """Methods in this class recursively traverse an AST and
+    output source code for the abstract syntax; original formatting
+    is disregarded."""
+
+    def __init__(self, *, _avoid_backslashes=False):
+        self._source = []
+        self._buffer = []
+        self._precedences = {}
+        self._type_ignores = {}
+        self._indent = 0
+        self._avoid_backslashes = _avoid_backslashes
+
+    def interleave(self, inter, f, seq):
+        """Call f on each item in seq, calling inter() in between."""
+        seq = iter(seq)
+        try:
+            f(next(seq))
+        except StopIteration:
+            pass
+        else:
+            for x in seq:
+                inter()
+                f(x)
+
+    def items_view(self, traverser, items):
+        """Traverse and separate the given *items* with a comma and append it to
+        the buffer. If *items* is a single item sequence, a trailing comma
+        will be added."""
+        if len(items) == 1:
+            traverser(items[0])
+            self.write(",")
+        else:
+            self.interleave(lambda: self.write(", "), traverser, items)
+
+    def maybe_newline(self):
+        """Adds a newline if it isn't the start of generated source"""
+        if self._source:
+            self.write("\n")
+
+    def fill(self, text=""):
+        """Indent a piece of text and append it, according to the current
+        indentation level"""
+        self.maybe_newline()
+        self.write("    " * self._indent + text)
+
+    def write(self, text):
+        """Append a piece of text"""
+        self._source.append(text)
+
+    def buffer_writer(self, text):
+        self._buffer.append(text)
+
+    @property
+    def buffer(self):
+        value = "".join(self._buffer)
+        self._buffer.clear()
+        return value
+
+    @contextmanager
+    def block(self, *, extra = None):
+        """A context manager for preparing the source for blocks. It adds
+        the character':', increases the indentation on enter and decreases
+        the indentation on exit. If *extra* is given, it will be directly
+        appended after the colon character.
+        """
+        self.write(":")
+        if extra:
+            self.write(extra)
+        self._indent += 1
+        yield
+        self._indent -= 1
+
+    @contextmanager
+    def delimit(self, start, end):
+        """A context manager for preparing the source for expressions. It adds
+        *start* to the buffer and enters, after exit it adds *end*."""
+
+        self.write(start)
+        yield
+        self.write(end)
+
+    def delimit_if(self, start, end, condition):
+        if condition:
+            return self.delimit(start, end)
+        else:
+            return nullcontext()
+
+    def require_parens(self, precedence, node):
+        """Shortcut to adding precedence related parens"""
+        return self.delimit_if("(", ")", self.get_precedence(node) > precedence)
+
+    def get_precedence(self, node):
+        return self._precedences.get(node, _Precedence.TEST)
+
+    def set_precedence(self, precedence, *nodes):
+        for node in nodes:
+            self._precedences[node] = precedence
+
+    def get_raw_docstring(self, node):
+        """If a docstring node is found in the body of the *node* parameter,
+        return that docstring node, None otherwise.
+
+        Logic mirrored from ``_PyAST_GetDocString``."""
+        if not isinstance(
+            node, (ast.AsyncFunctionDef, ast.FunctionDef, ast.ClassDef,
+                   ast.Module)
+        ) or len(node.body) < 1:
+            return None
+        node = node.body[0]
+        if not isinstance(node, ast.Expr):
+            return None
+        node = node.value
+        if isinstance(node, ast.Constant) and isinstance(node.value, str):
+            return node
+
+    def get_type_comment(self, node):
+        comment = self._type_ignores.get(node.lineno) or node.type_comment
+        if comment is not None:
+            return f" # type: {comment}"
+
+    def traverse(self, node):
+        if isinstance(node, list):
+            for item in node:
+                self.traverse(item)
+        else:
+            super().visit(node)
+
+    def visit(self, node):
+        """Outputs a source code string that, if converted back to an ast
+        (using ast.parse) will generate an AST equivalent to *node*"""
+        self._source = []
+        self.traverse(node)
+        return "".join(self._source)
+
+    def _write_docstring_and_traverse_body(self, node):
+        if (docstring := self.get_raw_docstring(node)):
+            self._write_docstring(docstring)
+            self.traverse(node.body[1:])
+        else:
+            self.traverse(node.body)
+
+    def visit_Module(self, node):
+        self._type_ignores = {
+            ignore.lineno: f"ignore{ignore.tag}"
+            for ignore in node.type_ignores
+        }
+        self._write_docstring_and_traverse_body(node)
+        self._type_ignores.clear()
+
+    def visit_FunctionType(self, node):
+        with self.delimit("(", ")"):
+            self.interleave(
+                lambda: self.write(", "), self.traverse, node.argtypes
+            )
+
+        self.write(" -> ")
+        self.traverse(node.returns)
+
+    def visit_Expr(self, node):
+        self.fill()
+        self.set_precedence(_Precedence.YIELD, node.value)
+        self.traverse(node.value)
+
+    def visit_NamedExpr(self, node):
+        with self.require_parens(_Precedence.TUPLE, node):
+            self.set_precedence(_Precedence.ATOM, node.target, node.value)
+            self.traverse(node.target)
+            self.write(" := ")
+            self.traverse(node.value)
+
+    def visit_Import(self, node):
+        self.fill("import ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.names)
+
+    def visit_ImportFrom(self, node):
+        self.fill("from ")
+        self.write("." * node.level)
+        if node.module:
+            self.write(node.module)
+        self.write(" import ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.names)
+
+    def visit_Assign(self, node):
+        self.fill()
+        for target in node.targets:
+            self.traverse(target)
+            self.write(" = ")
+        self.traverse(node.value)
+        if type_comment := self.get_type_comment(node):
+            self.write(type_comment)
+
+    def visit_AugAssign(self, node):
+        self.fill()
+        self.traverse(node.target)
+        self.write(" " + self.binop[node.op.__class__.__name__] + "= ")
+        self.traverse(node.value)
+
+    def visit_AnnAssign(self, node):
+        self.fill()
+        with self.delimit_if("(", ")", not node.simple and isinstance(node.target, ast.Name)):
+            self.traverse(node.target)
+        self.write(": ")
+        self.traverse(node.annotation)
+        if node.value:
+            self.write(" = ")
+            self.traverse(node.value)
+
+    def visit_Return(self, node):
+        self.fill("return")
+        if node.value:
+            self.write(" ")
+            self.traverse(node.value)
+
+    def visit_Pass(self, node):
+        self.fill("pass")
+
+    def visit_Break(self, node):
+        self.fill("break")
+
+    def visit_Continue(self, node):
+        self.fill("continue")
+
+    def visit_Delete(self, node):
+        self.fill("del ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.targets)
+
+    def visit_Assert(self, node):
+        self.fill("assert ")
+        self.traverse(node.test)
+        if node.msg:
+            self.write(", ")
+            self.traverse(node.msg)
+
+    def visit_Global(self, node):
+        self.fill("global ")
+        self.interleave(lambda: self.write(", "), self.write, node.names)
+
+    def visit_Nonlocal(self, node):
+        self.fill("nonlocal ")
+        self.interleave(lambda: self.write(", "), self.write, node.names)
+
+    def visit_Await(self, node):
+        with self.require_parens(_Precedence.AWAIT, node):
+            self.write("await")
+            if node.value:
+                self.write(" ")
+                self.set_precedence(_Precedence.ATOM, node.value)
+                self.traverse(node.value)
+
+    def visit_Yield(self, node):
+        with self.require_parens(_Precedence.YIELD, node):
+            self.write("yield")
+            if node.value:
+                self.write(" ")
+                self.set_precedence(_Precedence.ATOM, node.value)
+                self.traverse(node.value)
+
+    def visit_YieldFrom(self, node):
+        with self.require_parens(_Precedence.YIELD, node):
+            self.write("yield from ")
+            if not node.value:
+                raise ValueError("Node can't be used without a value attribute.")
+            self.set_precedence(_Precedence.ATOM, node.value)
+            self.traverse(node.value)
+
+    def visit_Raise(self, node):
+        self.fill("raise")
+        if not node.exc:
+            if node.cause:
+                raise ValueError("Node can't use cause without an exception.")
+            return
+        self.write(" ")
+        self.traverse(node.exc)
+        if node.cause:
+            self.write(" from ")
+            self.traverse(node.cause)
+
+    def visit_Try(self, node):
+        self.fill("try")
+        with self.block():
+            self.traverse(node.body)
+        for ex in node.handlers:
+            self.traverse(ex)
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+        if node.finalbody:
+            self.fill("finally")
+            with self.block():
+                self.traverse(node.finalbody)
+
+    def visit_ExceptHandler(self, node):
+        self.fill("except")
+        if node.type:
+            self.write(" ")
+            self.traverse(node.type)
+        if node.name:
+            self.write(" as ")
+            self.write(node.name)
+        with self.block():
+            self.traverse(node.body)
+
+    def visit_ClassDef(self, node):
+        self.maybe_newline()
+        for deco in node.decorator_list:
+            self.fill("@")
+            self.traverse(deco)
+        self.fill("class " + node.name)
+        with self.delimit_if("(", ")", condition = node.bases or node.keywords):
+            comma = False
+            for e in node.bases:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+            for e in node.keywords:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+
+        with self.block():
+            self._write_docstring_and_traverse_body(node)
+
+    def visit_FunctionDef(self, node):
+        self._function_helper(node, "def")
+
+    def visit_AsyncFunctionDef(self, node):
+        self._function_helper(node, "async def")
+
+    def _function_helper(self, node, fill_suffix):
+        self.maybe_newline()
+        for deco in node.decorator_list:
+            self.fill("@")
+            self.traverse(deco)
+        def_str = fill_suffix + " " + node.name
+        self.fill(def_str)
+        with self.delimit("(", ")"):
+            self.traverse(node.args)
+        if node.returns:
+            self.write(" -> ")
+            self.traverse(node.returns)
+        with self.block(extra=self.get_type_comment(node)):
+            self._write_docstring_and_traverse_body(node)
+
+    def visit_For(self, node):
+        self._for_helper("for ", node)
+
+    def visit_AsyncFor(self, node):
+        self._for_helper("async for ", node)
+
+    def _for_helper(self, fill, node):
+        self.fill(fill)
+        self.traverse(node.target)
+        self.write(" in ")
+        self.traverse(node.iter)
+        with self.block(extra=self.get_type_comment(node)):
+            self.traverse(node.body)
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+
+    def visit_If(self, node):
+        self.fill("if ")
+        self.traverse(node.test)
+        with self.block():
+            self.traverse(node.body)
+        # collapse nested ifs into equivalent elifs.
+        while node.orelse and len(node.orelse) == 1 and isinstance(node.orelse[0], ast.If):
+            node = node.orelse[0]
+            self.fill("elif ")
+            self.traverse(node.test)
+            with self.block():
+                self.traverse(node.body)
+        # final else
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+
+    def visit_While(self, node):
+        self.fill("while ")
+        self.traverse(node.test)
+        with self.block():
+            self.traverse(node.body)
+        if node.orelse:
+            self.fill("else")
+            with self.block():
+                self.traverse(node.orelse)
+
+    def visit_With(self, node):
+        self.fill("with ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.items)
+        with self.block(extra=self.get_type_comment(node)):
+            self.traverse(node.body)
+
+    def visit_AsyncWith(self, node):
+        self.fill("async with ")
+        self.interleave(lambda: self.write(", "), self.traverse, node.items)
+        with self.block(extra=self.get_type_comment(node)):
+            self.traverse(node.body)
+
+    def _str_literal_helper(
+        self, string, *, quote_types=_ALL_QUOTES, escape_special_whitespace=False
+    ):
+        """Helper for writing string literals, minimizing escapes.
+        Returns the tuple (string literal to write, possible quote types).
+        """
+        def escape_char(c):
+            # \n and \t are non-printable, but we only escape them if
+            # escape_special_whitespace is True
+            if not escape_special_whitespace and c in "\n\t":
+                return c
+            # Always escape backslashes and other non-printable characters
+            if c == "\\" or not c.isprintable():
+                return c.encode("unicode_escape").decode("ascii")
+            return c
+
+        escaped_string = "".join(map(escape_char, string))
+        possible_quotes = quote_types
+        if "\n" in escaped_string:
+            possible_quotes = [q for q in possible_quotes if q in _MULTI_QUOTES]
+        possible_quotes = [q for q in possible_quotes if q not in escaped_string]
+        if not possible_quotes:
+            # If there aren't any possible_quotes, fallback to using repr
+            # on the original string. Try to use a quote from quote_types,
+            # e.g., so that we use triple quotes for docstrings.
+            string = repr(string)
+            quote = next((q for q in quote_types if string[0] in q), string[0])
+            return string[1:-1], [quote]
+        if escaped_string:
+            # Sort so that we prefer '''"''' over """\""""
+            possible_quotes.sort(key=lambda q: q[0] == escaped_string[-1])
+            # If we're using triple quotes and we'd need to escape a final
+            # quote, escape it
+            if possible_quotes[0][0] == escaped_string[-1]:
+                assert len(possible_quotes[0]) == 3
+                escaped_string = escaped_string[:-1] + "\\" + escaped_string[-1]
+        return escaped_string, possible_quotes
+
+    def _write_str_avoiding_backslashes(self, string, *, quote_types=_ALL_QUOTES):
+        """Write string literal value with a best effort attempt to avoid backslashes."""
+        string, quote_types = self._str_literal_helper(string, quote_types=quote_types)
+        quote_type = quote_types[0]
+        self.write(f"{quote_type}{string}{quote_type}")
+
+    def visit_JoinedStr(self, node):
+        self.write("f")
+        if self._avoid_backslashes:
+            self._fstring_JoinedStr(node, self.buffer_writer)
+            self._write_str_avoiding_backslashes(self.buffer)
+            return
+
+        # If we don't need to avoid backslashes globally (i.e., we only need
+        # to avoid them inside FormattedValues), it's cosmetically preferred
+        # to use escaped whitespace. That is, it's preferred to use backslashes
+        # for cases like: f"{x}\n". To accomplish this, we keep track of what
+        # in our buffer corresponds to FormattedValues and what corresponds to
+        # Constant parts of the f-string, and allow escapes accordingly.
+        buffer = []
+        for value in node.values:
+            meth = getattr(self, "_fstring_" + type(value).__name__)
+            meth(value, self.buffer_writer)
+            buffer.append((self.buffer, isinstance(value, ast.Constant)))
+        new_buffer = []
+        quote_types = _ALL_QUOTES
+        for value, is_constant in buffer:
+            # Repeatedly narrow down the list of possible quote_types
+            value, quote_types = self._str_literal_helper(
+                value, quote_types=quote_types,
+                escape_special_whitespace=is_constant
+            )
+            new_buffer.append(value)
+        value = "".join(new_buffer)
+        quote_type = quote_types[0]
+        self.write(f"{quote_type}{value}{quote_type}")
+
+    def visit_FormattedValue(self, node):
+        self.write("f")
+        self._fstring_FormattedValue(node, self.buffer_writer)
+        self._write_str_avoiding_backslashes(self.buffer)
+
+    def _fstring_JoinedStr(self, node, write):
+        for value in node.values:
+            meth = getattr(self, "_fstring_" + type(value).__name__)
+            meth(value, write)
+
+    def _fstring_Constant(self, node, write):
+        if not isinstance(node.value, str):
+            raise ValueError("Constants inside JoinedStr should be a string.")
+        value = node.value.replace("{", "{{").replace("}", "}}")
+        write(value)
+
+    def _fstring_FormattedValue(self, node, write):
+        write("{")
+        unparser = type(self)(_avoid_backslashes=True)
+        unparser.set_precedence(_Precedence.TEST.next(), node.value)
+        expr = unparser.visit(node.value)
+        if expr.startswith("{"):
+            write(" ")  # Separate pair of opening brackets as "{ {"
+        if "\\" in expr:
+            raise ValueError("Unable to avoid backslash in f-string expression part")
+        write(expr)
+        if node.conversion != -1:
+            conversion = chr(node.conversion)
+            if conversion not in "sra":
+                raise ValueError("Unknown f-string conversion.")
+            write(f"!{conversion}")
+        if node.format_spec:
+            write(":")
+            meth = getattr(self, "_fstring_" + type(node.format_spec).__name__)
+            meth(node.format_spec, write)
+        write("}")
+
+    def visit_Name(self, node):
+        self.write(node.id)
+
+    def _write_docstring(self, node):
+        self.fill()
+        if node.kind == "u":
+            self.write("u")
+        self._write_str_avoiding_backslashes(node.value, quote_types=_MULTI_QUOTES)
+
+    def _write_constant(self, value):
+        if isinstance(value, (float, complex)):
+            # Substitute overflowing decimal literal for AST infinities,
+            # and inf - inf for NaNs.
+            self.write(
+                repr(value)
+                .replace("inf", _INFSTR)
+                .replace("nan", f"({_INFSTR}-{_INFSTR})")
+            )
+        elif self._avoid_backslashes and isinstance(value, str):
+            self._write_str_avoiding_backslashes(value)
+        else:
+            self.write(repr(value))
+
+    def visit_Constant(self, node):
+        value = node.value
+        if isinstance(value, tuple):
+            with self.delimit("(", ")"):
+                self.items_view(self._write_constant, value)
+        elif value is ...:
+            self.write("...")
+        else:
+            if node.kind == "u":
+                self.write("u")
+            self._write_constant(node.value)
+
+    def visit_List(self, node):
+        with self.delimit("[", "]"):
+            self.interleave(lambda: self.write(", "), self.traverse, node.elts)
+
+    def visit_ListComp(self, node):
+        with self.delimit("[", "]"):
+            self.traverse(node.elt)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_GeneratorExp(self, node):
+        with self.delimit("(", ")"):
+            self.traverse(node.elt)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_SetComp(self, node):
+        with self.delimit("{", "}"):
+            self.traverse(node.elt)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_DictComp(self, node):
+        with self.delimit("{", "}"):
+            self.traverse(node.key)
+            self.write(": ")
+            self.traverse(node.value)
+            for gen in node.generators:
+                self.traverse(gen)
+
+    def visit_comprehension(self, node):
+        if node.is_async:
+            self.write(" async for ")
+        else:
+            self.write(" for ")
+        self.set_precedence(_Precedence.TUPLE, node.target)
+        self.traverse(node.target)
+        self.write(" in ")
+        self.set_precedence(_Precedence.TEST.next(), node.iter, *node.ifs)
+        self.traverse(node.iter)
+        for if_clause in node.ifs:
+            self.write(" if ")
+            self.traverse(if_clause)
+
+    def visit_IfExp(self, node):
+        with self.require_parens(_Precedence.TEST, node):
+            self.set_precedence(_Precedence.TEST.next(), node.body, node.test)
+            self.traverse(node.body)
+            self.write(" if ")
+            self.traverse(node.test)
+            self.write(" else ")
+            self.set_precedence(_Precedence.TEST, node.orelse)
+            self.traverse(node.orelse)
+
+    def visit_Set(self, node):
+        if node.elts:
+            with self.delimit("{", "}"):
+                self.interleave(lambda: self.write(", "), self.traverse, node.elts)
+        else:
+            # `{}` would be interpreted as a dictionary literal, and
+            # `set` might be shadowed. Thus:
+            self.write('{*()}')
+
+    def visit_Dict(self, node):
+        def write_key_value_pair(k, v):
+            self.traverse(k)
+            self.write(": ")
+            self.traverse(v)
+
+        def write_item(item):
+            k, v = item
+            if k is None:
+                # for dictionary unpacking operator in dicts {**{'y': 2}}
+                # see PEP 448 for details
+                self.write("**")
+                self.set_precedence(_Precedence.EXPR, v)
+                self.traverse(v)
+            else:
+                write_key_value_pair(k, v)
+
+        with self.delimit("{", "}"):
+            self.interleave(
+                lambda: self.write(", "), write_item, zip(node.keys, node.values)
+            )
+
+    def visit_Tuple(self, node):
+        with self.delimit("(", ")"):
+            self.items_view(self.traverse, node.elts)
+
+    unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
+    unop_precedence = {
+        "not": _Precedence.NOT,
+        "~": _Precedence.FACTOR,
+        "+": _Precedence.FACTOR,
+        "-": _Precedence.FACTOR,
+    }
+
+    def visit_UnaryOp(self, node):
+        operator = self.unop[node.op.__class__.__name__]
+        operator_precedence = self.unop_precedence[operator]
+        with self.require_parens(operator_precedence, node):
+            self.write(operator)
+            # factor prefixes (+, -, ~) shouldn't be seperated
+            # from the value they belong, (e.g: +1 instead of + 1)
+            if operator_precedence is not _Precedence.FACTOR:
+                self.write(" ")
+            self.set_precedence(operator_precedence, node.operand)
+            self.traverse(node.operand)
+
+    binop = {
+        "Add": "+",
+        "Sub": "-",
+        "Mult": "*",
+        "MatMult": "@",
+        "Div": "/",
+        "Mod": "%",
+        "LShift": "<<",
+        "RShift": ">>",
+        "BitOr": "|",
+        "BitXor": "^",
+        "BitAnd": "&",
+        "FloorDiv": "//",
+        "Pow": "**",
+    }
+
+    binop_precedence = {
+        "+": _Precedence.ARITH,
+        "-": _Precedence.ARITH,
+        "*": _Precedence.TERM,
+        "@": _Precedence.TERM,
+        "/": _Precedence.TERM,
+        "%": _Precedence.TERM,
+        "<<": _Precedence.SHIFT,
+        ">>": _Precedence.SHIFT,
+        "|": _Precedence.BOR,
+        "^": _Precedence.BXOR,
+        "&": _Precedence.BAND,
+        "//": _Precedence.TERM,
+        "**": _Precedence.POWER,
+    }
+
+    binop_rassoc = frozenset(("**",))
+    def visit_BinOp(self, node):
+        operator = self.binop[node.op.__class__.__name__]
+        operator_precedence = self.binop_precedence[operator]
+        with self.require_parens(operator_precedence, node):
+            if operator in self.binop_rassoc:
+                left_precedence = operator_precedence.next()
+                right_precedence = operator_precedence
+            else:
+                left_precedence = operator_precedence
+                right_precedence = operator_precedence.next()
+
+            self.set_precedence(left_precedence, node.left)
+            self.traverse(node.left)
+            self.write(f" {operator} ")
+            self.set_precedence(right_precedence, node.right)
+            self.traverse(node.right)
+
+    cmpops = {
+        "Eq": "==",
+        "NotEq": "!=",
+        "Lt": "<",
+        "LtE": "<=",
+        "Gt": ">",
+        "GtE": ">=",
+        "Is": "is",
+        "IsNot": "is not",
+        "In": "in",
+        "NotIn": "not in",
+    }
+
+    def visit_Compare(self, node):
+        with self.require_parens(_Precedence.CMP, node):
+            self.set_precedence(_Precedence.CMP.next(), node.left, *node.comparators)
+            self.traverse(node.left)
+            for o, e in zip(node.ops, node.comparators):
+                self.write(" " + self.cmpops[o.__class__.__name__] + " ")
+                self.traverse(e)
+
+    boolops = {"And": "and", "Or": "or"}
+    boolop_precedence = {"and": _Precedence.AND, "or": _Precedence.OR}
+
+    def visit_BoolOp(self, node):
+        operator = self.boolops[node.op.__class__.__name__]
+        operator_precedence = self.boolop_precedence[operator]
+
+        def increasing_level_traverse(node):
+            nonlocal operator_precedence
+            operator_precedence = operator_precedence.next()
+            self.set_precedence(operator_precedence, node)
+            self.traverse(node)
+
+        with self.require_parens(operator_precedence, node):
+            s = f" {operator} "
+            self.interleave(lambda: self.write(s), increasing_level_traverse, node.values)
+
+    def visit_Attribute(self, node):
+        self.set_precedence(_Precedence.ATOM, node.value)
+        self.traverse(node.value)
+        # Special case: 3.__abs__() is a syntax error, so if node.value
+        # is an integer literal then we need to either parenthesize
+        # it or add an extra space to get 3 .__abs__().
+        if isinstance(node.value, ast.Constant) and isinstance(node.value.value, int):
+            self.write(" ")
+        self.write(".")
+        self.write(node.attr)
+
+    def visit_Call(self, node):
+        self.set_precedence(_Precedence.ATOM, node.func)
+        self.traverse(node.func)
+        with self.delimit("(", ")"):
+            comma = False
+            for e in node.args:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+            for e in node.keywords:
+                if comma:
+                    self.write(", ")
+                else:
+                    comma = True
+                self.traverse(e)
+
+    def visit_Subscript(self, node):
+        def is_simple_tuple(slice_value):
+            # when unparsing a non-empty tuple, the parantheses can be safely
+            # omitted if there aren't any elements that explicitly requires
+            # parantheses (such as starred expressions).
+            return (
+                isinstance(slice_value, ast.Tuple)
+                and slice_value.elts
+                and not any(isinstance(elt, ast.Starred) for elt in slice_value.elts)
+            )
+
+        self.set_precedence(_Precedence.ATOM, node.value)
+        self.traverse(node.value)
+        with self.delimit("[", "]"):
+            if is_simple_tuple(node.slice):
+                self.items_view(self.traverse, node.slice.elts)
+            else:
+                self.traverse(node.slice)
+
+    def visit_Starred(self, node):
+        self.write("*")
+        self.set_precedence(_Precedence.EXPR, node.value)
+        self.traverse(node.value)
+
+    def visit_Ellipsis(self, node):
+        self.write("...")
+
+    def visit_Slice(self, node):
+        if node.lower:
+            self.traverse(node.lower)
+        self.write(":")
+        if node.upper:
+            self.traverse(node.upper)
+        if node.step:
+            self.write(":")
+            self.traverse(node.step)
+
+    def visit_arg(self, node):
+        self.write(node.arg)
+        if node.annotation:
+            self.write(": ")
+            self.traverse(node.annotation)
+
+    def visit_arguments(self, node):
+        first = True
+        # normal arguments
+        all_args = node.posonlyargs + node.args
+        defaults = [None] * (len(all_args) - len(node.defaults)) + node.defaults
+        for index, elements in enumerate(zip(all_args, defaults), 1):
+            a, d = elements
+            if first:
+                first = False
+            else:
+                self.write(", ")
+            self.traverse(a)
+            if d:
+                self.write("=")
+                self.traverse(d)
+            if index == len(node.posonlyargs):
+                self.write(", /")
+
+        # varargs, or bare '*' if no varargs but keyword-only arguments present
+        if node.vararg or node.kwonlyargs:
+            if first:
+                first = False
+            else:
+                self.write(", ")
+            self.write("*")
+            if node.vararg:
+                self.write(node.vararg.arg)
+                if node.vararg.annotation:
+                    self.write(": ")
+                    self.traverse(node.vararg.annotation)
+
+        # keyword-only arguments
+        if node.kwonlyargs:
+            for a, d in zip(node.kwonlyargs, node.kw_defaults):
+                self.write(", ")
+                self.traverse(a)
+                if d:
+                    self.write("=")
+                    self.traverse(d)
+
+        # kwargs
+        if node.kwarg:
+            if first:
+                first = False
+            else:
+                self.write(", ")
+            self.write("**" + node.kwarg.arg)
+            if node.kwarg.annotation:
+                self.write(": ")
+                self.traverse(node.kwarg.annotation)
+
+    def visit_keyword(self, node):
+        if node.arg is None:
+            self.write("**")
+        else:
+            self.write(node.arg)
+            self.write("=")
+        self.traverse(node.value)
+
+    def visit_Lambda(self, node):
+        with self.require_parens(_Precedence.TEST, node):
+            self.write("lambda ")
+            self.traverse(node.args)
+            self.write(": ")
+            self.set_precedence(_Precedence.TEST, node.body)
+            self.traverse(node.body)
+
+    def visit_alias(self, node):
+        self.write(node.name)
+        if node.asname:
+            self.write(" as " + node.asname)
+
+    def visit_withitem(self, node):
+        self.traverse(node.context_expr)
+        if node.optional_vars:
+            self.write(" as ")
+            self.traverse(node.optional_vars)
+
+def unparse(ast_obj):
+    unparser = _Unparser()
+    return unparser.visit(ast_obj)
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/Simplify/translations.py	Wed Mar 31 19:51:41 2021 +0200
@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2020 - 2021 Detlev Offenbach <detlev@die-offenbachs.de>
+#
+
+
+"""
+Module implementing message translations for the code style plugin messages
+(miscellaneous part).
+"""
+
+from PyQt5.QtCore import QCoreApplication
+
+_simplifyMessages = {
+    "Y101": QCoreApplication.translate(
+        "SimplifyChecker",
+        "Multiple 'isinstance()' calls which can be merged into a single "
+        "call for variable '{0}'"),
+}
+
+_simplifyMessagesSampleArgs = {
+    "Y101": ["foo"],
+}
--- a/eric6/Plugins/CheckerPlugins/CodeStyleChecker/translations.py	Tue Mar 30 19:59:24 2021 +0200
+++ b/eric6/Plugins/CheckerPlugins/CodeStyleChecker/translations.py	Wed Mar 31 19:51:41 2021 +0200
@@ -28,6 +28,9 @@
 from .Security.translations import (
     _securityMessages, _securityMessagesSampleArgs
 )
+from .Simplify.translations import (
+    _simplifyMessages, _simplifyMessagesSampleArgs
+)
 
 ##################################################################
 ## pycodestyle error messages
@@ -256,6 +259,7 @@
         "pycodestyle",
         "{0}"),
 }
+# TODO: change all syntax error reports to report E901
 
 ##################################################################
 ## pycodestyle warning messages
@@ -504,6 +508,7 @@
     "P": _pathlibMessages,
     "S": _securityMessages,
     "W": _pycodestyleWarningMessages,
+    "Y": _simplifyMessages,
     
     "FIX": _fixMessages,
 }
@@ -516,6 +521,7 @@
     "M": _miscellaneousMessagesSampleArgs,
     "S": _securityMessagesSampleArgs,
     "W": _pycodestyleWarningMessagesSampleArgs,
+    "Y": _simplifyMessagesSampleArgs,
     
     "FIX": _fixMessagesSampleArgs,
 }

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