Block must not be padded by blank lines. Open
export default class TopicView extends Component {
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require or disallow padding within blocks (padded-blocks)
Some style guides require block statements to start and end with blank lines. The goal is to improve readability by visually separating the block content and the surrounding code.
if (a) {
b();
}
Since it's good to have a consistent code style, you should either always write padded blocks or never do it.
Rule Details
This rule enforces consistent empty line padding within blocks.
Options
This rule has one option, which can be a string option or an object option.
String option:
-
"always"
(default) requires empty lines at the beginning and ending of block statements (exceptswitch
statements and classes) -
"never"
disallows empty lines at the beginning and ending of block statements (exceptswitch
statements and classes)
Object option:
-
"blocks"
require or disallow padding within block statements -
"classes"
require or disallow padding within classes -
"switches"
require or disallow padding withinswitch
statements
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint padded-blocks: ["error", "always"]*/
if (a) {
b();
}
if (a) { b(); }
if (a)
{
b();
}
if (a) {
b();
}
if (a) {
b();
}
if (a) {
// comment
b();
}
Examples of correct code for this rule with the default "always"
option:
/*eslint padded-blocks: ["error", "always"]*/
if (a) {
b();
}
if (a)
{
b();
}
if (a) {
// comment
b();
}
never
Examples of incorrect code for this rule with the "never"
option:
/*eslint padded-blocks: ["error", "never"]*/
if (a) {
b();
}
if (a)
{
b();
}
if (a) {
b();
}
if (a) {
b();
}
Examples of correct code for this rule with the "never"
option:
/*eslint padded-blocks: ["error", "never"]*/
if (a) {
b();
}
if (a)
{
b();
}
blocks
Examples of incorrect code for this rule with the { "blocks": "always" }
option:
/*eslint padded-blocks: ["error", { "blocks": "always" }]*/
if (a) {
b();
}
if (a) { b(); }
if (a)
{
b();
}
if (a) {
b();
}
if (a) {
b();
}
if (a) {
// comment
b();
}
Examples of correct code for this rule with the { "blocks": "always" }
option:
/*eslint padded-blocks: ["error", { "blocks": "always" }]*/
if (a) {
b();
}
if (a)
{
b();
}
if (a) {
// comment
b();
}
Examples of incorrect code for this rule with the { "blocks": "never" }
option:
/*eslint padded-blocks: ["error", { "blocks": "never" }]*/
if (a) {
b();
}
if (a)
{
b();
}
if (a) {
b();
}
if (a) {
b();
}
Examples of correct code for this rule with the { "blocks": "never" }
option:
/*eslint padded-blocks: ["error", { "blocks": "never" }]*/
if (a) {
b();
}
if (a)
{
b();
}
classes
Examples of incorrect code for this rule with the { "classes": "always" }
option:
/*eslint padded-blocks: ["error", { "classes": "always" }]*/
class A {
constructor(){
}
}
Examples of correct code for this rule with the { "classes": "always" }
option:
/*eslint padded-blocks: ["error", { "classes": "always" }]*/
class A {
constructor(){
}
}
Examples of incorrect code for this rule with the { "classes": "never" }
option:
/*eslint padded-blocks: ["error", { "classes": "never" }]*/
class A {
constructor(){
}
}
Examples of correct code for this rule with the { "classes": "never" }
option:
/*eslint padded-blocks: ["error", { "classes": "never" }]*/
class A {
constructor(){
}
}
switches
Examples of incorrect code for this rule with the { "switches": "always" }
option:
/*eslint padded-blocks: ["error", { "switches": "always" }]*/
switch (a) {
case 0: foo();
}
Examples of correct code for this rule with the { "switches": "always" }
option:
/*eslint padded-blocks: ["error", { "switches": "always" }]*/
switch (a) {
case 0: foo();
}
if (a) {
b();
}
Examples of incorrect code for this rule with the { "switches": "never" }
option:
/*eslint padded-blocks: ["error", { "switches": "never" }]*/
switch (a) {
case 0: foo();
}
Examples of correct code for this rule with the { "switches": "never" }
option:
/*eslint padded-blocks: ["error", { "switches": "never" }]*/
switch (a) {
case 0: foo();
}
if (a) {
b();
}
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of padding within blocks. Source: http://eslint.org/docs/rules/
Closing curly brace does not appear on the same line as the subsequent block. Open
}
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Require Brace Style (brace-style)
Brace style is closely related to indent style in programming and describes the placement of braces relative to their control statement and body. There are probably a dozen, if not more, brace styles in the world.
The one true brace style is one of the most common brace styles in JavaScript, in which the opening brace of a block is placed on the same line as its corresponding statement or declaration. For example:
if (foo) {
bar();
} else {
baz();
}
One common variant of one true brace style is called Stroustrup, in which the else
statements in an if-else
construct, as well as catch
and finally
, must be on its own line after the preceding closing brace. For example:
if (foo) {
bar();
}
else {
baz();
}
Another style is called Allman, in which all the braces are expected to be on their own lines without any extra indentation. For example:
if (foo)
{
bar();
}
else
{
baz();
}
While no style is considered better than the other, most developers agree that having a consistent style throughout a project is important for its long-term maintainability.
Rule Details
This rule enforces consistent brace style for blocks.
Options
This rule has a string option:
-
"1tbs"
(default) enforces one true brace style -
"stroustrup"
enforces Stroustrup style -
"allman"
enforces Allman style
This rule has an object option for an exception:
-
"allowSingleLine": true
(defaultfalse
) allows the opening and closing braces for a block to be on the same line
1tbs
Examples of incorrect code for this rule with the default "1tbs"
option:
/*eslint brace-style: "error"*/
function foo()
{
return true;
}
if (foo)
{
bar();
}
try
{
somethingRisky();
} catch(e)
{
handleError();
}
if (foo) {
bar();
}
else {
baz();
}
Examples of correct code for this rule with the default "1tbs"
option:
/*eslint brace-style: "error"*/
function foo() {
return true;
}
if (foo) {
bar();
}
if (foo) {
bar();
} else {
baz();
}
try {
somethingRisky();
} catch(e) {
handleError();
}
// when there are no braces, there are no problems
if (foo) bar();
else if (baz) boom();
Examples of correct code for this rule with the "1tbs", { "allowSingleLine": true }
options:
/*eslint brace-style: ["error", "1tbs", { "allowSingleLine": true }]*/
function nop() { return; }
if (foo) { bar(); }
if (foo) { bar(); } else { baz(); }
try { somethingRisky(); } catch(e) { handleError(); }
stroustrup
Examples of incorrect code for this rule with the "stroustrup"
option:
/*eslint brace-style: ["error", "stroustrup"]*/
function foo()
{
return true;
}
if (foo)
{
bar();
}
try
{
somethingRisky();
} catch(e)
{
handleError();
}
if (foo) {
bar();
} else {
baz();
}
Examples of correct code for this rule with the "stroustrup"
option:
/*eslint brace-style: ["error", "stroustrup"]*/
function foo() {
return true;
}
if (foo) {
bar();
}
if (foo) {
bar();
}
else {
baz();
}
try {
somethingRisky();
}
catch(e) {
handleError();
}
// when there are no braces, there are no problems
if (foo) bar();
else if (baz) boom();
Examples of correct code for this rule with the "stroustrup", { "allowSingleLine": true }
options:
/*eslint brace-style: ["error", "stroustrup", { "allowSingleLine": true }]*/
function nop() { return; }
if (foo) { bar(); }
if (foo) { bar(); }
else { baz(); }
try { somethingRisky(); }
catch(e) { handleError(); }
allman
Examples of incorrect code for this rule with the "allman"
option:
/*eslint brace-style: ["error", "allman"]*/
function foo() {
return true;
}
if (foo)
{
bar(); }
try
{
somethingRisky();
} catch(e)
{
handleError();
}
if (foo) {
bar();
} else {
baz();
}
Examples of correct code for this rule with the "allman"
option:
/*eslint brace-style: ["error", "allman"]*/
function foo()
{
return true;
}
if (foo)
{
bar();
}
if (foo)
{
bar();
}
else
{
baz();
}
try
{
somethingRisky();
}
catch(e)
{
handleError();
}
// when there are no braces, there are no problems
if (foo) bar();
else if (baz) boom();
Examples of correct code for this rule with the "allman", { "allowSingleLine": true }
options:
/*eslint brace-style: ["error", "allman", { "allowSingleLine": true }]*/
function nop() { return; }
if (foo) { bar(); }
if (foo) { bar(); }
else { baz(); }
try { somethingRisky(); }
catch(e) { handleError(); }
When Not To Use It
If you don't want to enforce a particular brace style, don't enable this rule.
Further Reading
Arrow function should not return assignment. Open
<UpperOptions ref={x => this.upperOptions = x}
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Disallow Assignment in return Statement (no-return-assign)
One of the interesting, and sometimes confusing, aspects of JavaScript is that assignment can happen at almost any point. Because of this, an errant equals sign can end up causing assignment when the true intent was to do a comparison. This is especially true when using a return
statement. For example:
function doSomething() {
return foo = bar + 2;
}
It is difficult to tell the intent of the return
statement here. It's possible that the function is meant to return the result of bar + 2
, but then why is it assigning to foo
? It's also possible that the intent was to use a comparison operator such as ==
and that this code is an error.
Because of this ambiguity, it's considered a best practice to not use assignment in return
statements.
Rule Details
This rule aims to eliminate assignments from return
statements. As such, it will warn whenever an assignment is found as part of return
.
Options
The rule takes one option, a string, which must contain one of the following values:
-
except-parens
(default): Disallow assignments unless they are enclosed in parentheses. -
always
: Disallow all assignments.
except-parens
This is the default option. It disallows assignments unless they are enclosed in parentheses.
Examples of incorrect code for the default "except-parens"
option:
/*eslint no-return-assign: "error"*/
function doSomething() {
return foo = bar + 2;
}
function doSomething() {
return foo += 2;
}
Examples of correct code for the default "except-parens"
option:
/*eslint no-return-assign: "error"*/
function doSomething() {
return foo == bar + 2;
}
function doSomething() {
return foo === bar + 2;
}
function doSomething() {
return (foo = bar + 2);
}
always
This option disallows all assignments in return
statements.
All assignments are treated as problems.
Examples of incorrect code for the "always"
option:
/*eslint no-return-assign: ["error", "always"]*/
function doSomething() {
return foo = bar + 2;
}
function doSomething() {
return foo += 2;
}
function doSomething() {
return (foo = bar + 2);
}
Examples of correct code for the "always"
option:
/*eslint no-return-assign: ["error", "always"]*/
function doSomething() {
return foo == bar + 2;
}
function doSomething() {
return foo === bar + 2;
}
When Not To Use It
If you want to allow the use of assignment operators in a return
statement, then you can safely disable this rule.
Source: http://eslint.org/docs/rules/
'mobile' is assigned a value but never used. Open
const { mobile, topic, currentUser, allForFiltering, visibleForFiltering,
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Disallow Unused Variables (no-unused-vars)
Variables that are declared and not used anywhere in the code are most likely an error due to incomplete refactoring. Such variables take up space in the code and can lead to confusion by readers.
Rule Details
This rule is aimed at eliminating unused variables, functions, and parameters of functions.
A variable is considered to be used if any of the following are true:
- It represents a function that is called (
doSomething()
) - It is read (
var y = x
) - It is passed into a function as an argument (
doSomething(x)
) - It is read inside of a function that is passed to another function (
doSomething(function() { foo(); })
)
A variable is not considered to be used if it is only ever assigned to (var x = 5
) or declared.
Examples of incorrect code for this rule:
/*eslint no-unused-vars: "error"*/
/*global some_unused_var*/
// It checks variables you have defined as global
some_unused_var = 42;
var x;
// Write-only variables are not considered as used.
var y = 10;
y = 5;
// A read for a modification of itself is not considered as used.
var z = 0;
z = z + 1;
// By default, unused arguments cause warnings.
(function(foo) {
return 5;
})();
// Unused recursive functions also cause warnings.
function fact(n) {
if (n < 2) return 1;
return n * fact(n - 1);
}
// When a function definition destructures an array, unused entries from the array also cause warnings.
function getY([x, y]) {
return y;
}
Examples of correct code for this rule:
/*eslint no-unused-vars: "error"*/
var x = 10;
alert(x);
// foo is considered used here
myFunc(function foo() {
// ...
}.bind(this));
(function(foo) {
return foo;
})();
var myFunc;
myFunc = setTimeout(function() {
// myFunc is considered used
myFunc();
}, 50);
// Only the second argument from the descructured array is used.
function getY([, y]) {
return y;
}
exported
In environments outside of CommonJS or ECMAScript modules, you may use var
to create a global variable that may be used by other scripts. You can use the /* exported variableName */
comment block to indicate that this variable is being exported and therefore should not be considered unused.
Note that /* exported */
has no effect for any of the following:
- when the environment is
node
orcommonjs
- when
parserOptions.sourceType
ismodule
- when
ecmaFeatures.globalReturn
istrue
The line comment // exported variableName
will not work as exported
is not line-specific.
Examples of correct code for /* exported variableName */
operation:
/* exported global_var */
var global_var = 42;
Options
This rule takes one argument which can be a string or an object. The string settings are the same as those of the vars
property (explained below).
By default this rule is enabled with all
option for variables and after-used
for arguments.
{
"rules": {
"no-unused-vars": ["error", { "vars": "all", "args": "after-used", "ignoreRestSiblings": false }]
}
}
vars
The vars
option has two settings:
-
all
checks all variables for usage, including those in the global scope. This is the default setting. -
local
checks only that locally-declared variables are used but will allow global variables to be unused.
vars: local
Examples of correct code for the { "vars": "local" }
option:
/*eslint no-unused-vars: ["error", { "vars": "local" }]*/
/*global some_unused_var */
some_unused_var = 42;
varsIgnorePattern
The varsIgnorePattern
option specifies exceptions not to check for usage: variables whose names match a regexp pattern. For example, variables whose names contain ignored
or Ignored
.
Examples of correct code for the { "varsIgnorePattern": "[iI]gnored" }
option:
/*eslint no-unused-vars: ["error", { "varsIgnorePattern": "[iI]gnored" }]*/
var firstVarIgnored = 1;
var secondVar = 2;
console.log(secondVar);
args
The args
option has three settings:
-
after-used
- only the last argument must be used. This allows you, for instance, to have two named parameters to a function and as long as you use the second argument, ESLint will not warn you about the first. This is the default setting. -
all
- all named arguments must be used. -
none
- do not check arguments.
args: after-used
Examples of incorrect code for the default { "args": "after-used" }
option:
/*eslint no-unused-vars: ["error", { "args": "after-used" }]*/
// 1 error
// "baz" is defined but never used
(function(foo, bar, baz) {
return bar;
})();
Examples of correct code for the default { "args": "after-used" }
option:
/*eslint no-unused-vars: ["error", {"args": "after-used"}]*/
(function(foo, bar, baz) {
return baz;
})();
args: all
Examples of incorrect code for the { "args": "all" }
option:
/*eslint no-unused-vars: ["error", { "args": "all" }]*/
// 2 errors
// "foo" is defined but never used
// "baz" is defined but never used
(function(foo, bar, baz) {
return bar;
})();
args: none
Examples of correct code for the { "args": "none" }
option:
/*eslint no-unused-vars: ["error", { "args": "none" }]*/
(function(foo, bar, baz) {
return bar;
})();
ignoreRestSiblings
The ignoreRestSiblings
option is a boolean (default: false
). Using a Rest Property it is possible to "omit" properties from an object, but by default the sibling properties are marked as "unused". With this option enabled the rest property's siblings are ignored.
Examples of correct code for the { "ignoreRestSiblings": true }
option:
/*eslint no-unused-vars: ["error", { "ignoreRestSiblings": true }]*/
// 'type' is ignored because it has a rest property sibling.
var { type, ...coords } = data;
argsIgnorePattern
The argsIgnorePattern
option specifies exceptions not to check for usage: arguments whose names match a regexp pattern. For example, variables whose names begin with an underscore.
Examples of correct code for the { "argsIgnorePattern": "^_" }
option:
/*eslint no-unused-vars: ["error", { "argsIgnorePattern": "^_" }]*/
function foo(x, _y) {
return x + 1;
}
foo();
caughtErrors
The caughtErrors
option is used for catch
block arguments validation.
It has two settings:
-
none
- do not check error objects. This is the default setting. -
all
- all named arguments must be used.
caughtErrors: none
Not specifying this rule is equivalent of assigning it to none
.
Examples of correct code for the { "caughtErrors": "none" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrors": "none" }]*/
try {
//...
} catch (err) {
console.error("errors");
}
caughtErrors: all
Examples of incorrect code for the { "caughtErrors": "all" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrors": "all" }]*/
// 1 error
// "err" is defined but never used
try {
//...
} catch (err) {
console.error("errors");
}
caughtErrorsIgnorePattern
The caughtErrorsIgnorePattern
option specifies exceptions not to check for usage: catch arguments whose names match a regexp pattern. For example, variables whose names begin with a string 'ignore'.
Examples of correct code for the { "caughtErrorsIgnorePattern": "^ignore" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrorsIgnorePattern": "^ignore" }]*/
try {
//...
} catch (ignoreErr) {
console.error("errors");
}
When Not To Use It
If you don't want to be notified about unused variables or function arguments, you can safely turn this rule off. Source: http://eslint.org/docs/rules/
TODO found Open
// TODO: stop using {...this.props} and make explicit
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Similar blocks of code found in 2 locations. Consider refactoring. Open
componentDidUpdate(prevProps) {
const oldTopicId = prevProps.topicId
const { topicId, launchNewTopic } = this.props
if (!oldTopicId && topicId) launchNewTopic(topicId)
else if (oldTopicId && topicId && oldTopicId !== topicId) {
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Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 117.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 2 locations. Consider refactoring. Open
const { mobile, topic, currentUser, allForFiltering, visibleForFiltering,
toggleMetacode, toggleMapper, toggleSynapse, filterAllMetacodes,
filterAllMappers, filterAllSynapses, filterData, forkMap,
openHelpLightbox, onZoomIn, onZoomOut, contextMenu } = this.props
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Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 96.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76