plugin-conditions

@putout/plugin-conditions

🐊Putout adds support of conditions transformations.

Install

npm i @putout/plugin-conditions -D

Rules

• ✅ add-return;
• ✅ apply-comparison-order;
• ✅ apply-consistent-blocks;
• ✅ apply-early-return;
• ✅ apply-equal;
• ✅ apply-if;
• ✅ convert-arrow-to-condition;
• ✅ convert-comparison-to-boolean;
• ✅ convert-equal-to-strict-equal;
• ✅ convert-switch-to-if;
• ✅ evaluate;
• ✅ merge-if-statements;
• ✅ merge-if-with-else;
• ✅ remove-boolean;
• ✅ remove-constant;
• ✅ remove-same-values-condition;
• ✅ remove-useless-else;
• ✅ remove-useless-loop-condition;
• ✅ remove-zero;
• ✅ reverse;
• ✅ simplify;
• ✅ wrap-with-block;

Config

{
    "rules": {
        "conditions/add-return": "on",
        "conditions/apply-comparison-order": "on",
        "conditions/apply-consistent-blocks": "on",
        
        "conditions/apply-equal": "on",
        "conditions/apply-if": "on",
        "conditions/apply-return-return": "on",
        
        "conditions/convert-arrow-to-condition": "on",
        "conditions/convert-comparison-to-boolean": "on",
        "conditions/convert-equal-to-strict-equal": "on",
        "conditions/convert-switch-to-if": "on",
        "conditions/evaluate": "on",
        
        "conditions/merge-if-statements": "on",
        "conditions/merge-if-with-else": "on",
        "conditions/remove-boolean": "on",
        "conditions/remove-constant": "on",
        
        "conditions/remove-same-values-condition": "on",
        "conditions/remove-useless-else": "on",
        "conditions/remove-useless-loop-condition": "on",
        "conditions/remove-zero": "on",
        "conditions/reverse": "on",
        
        "conditions/simplify": "on",
        "conditions/wrap-with-block": "on"
    }
}

add-return

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

if (a)
    false;

✅ Example of correct code

if (a)
    return false;

apply-comparison-order

The result of evaluating an equality operator is always of type boolean based on whether the comparison is true.

(c) MDN

Checkout it 🐊Putout Editor.

❌ Example of incorrect code

3 === a;
3 < b;

✅ Example of correct code

a === 3;
b > 3;

Comparison

Linter	Rule	Fix
🐊 Putout	conditions/apply-comparison-order	✅
⏣ ESLint	yoda	½

apply-consistent-blocks

A block statement is used to group zero or more statements. The block is delimited by a pair of braces ("curly braces") and contains a list of zero or more statements and declarations.

(c) MDN

Check out in 🐊Putout Editor:

• Replacer;
• Traverser;

❌ Example of incorrect code

if (a > 3) {
    m();
}

if (a > 3)
    b = 5;
else {
    b = 6;
}

if (a > 3)
    b = 5;
else {
    b = 6;
    fn();
}

✅ Example of correct code

if (a > 3)
    m();

if (a > 3)
    b = 5;
else
    b = 6;

if (a > 3) {
    b = 5;
} else {
    b = 6;
    fn();
}

apply-early-return

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

function notBlockNoNext() {
    if (a)
        x();
    else
        b();
}

✅ Example of correct code

function notBlockNoNext() {
    if (a) {
        x();
        return;
    }
    
    b();
}

apply-equal

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

return a.b = c;

✅ Example of correct code

return a.b === c;

apply-if

❌ Example of incorrect code

if (2 > 3)
    ;

alert();

✅ Example of correct code

if (2 > 3)
    alert();

convert-arrow-to-condition

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

if ((a) => b) {}

✅ Example of correct code

if (a <= b) {}

convert-comparison-to-boolean

Strict equality compares two values for equality. Neither value is implicitly converted to some other value before being compared. If the values have different types, the values are considered unequal.

(c) MDN

❌ Example of incorrect code

const t = 2 < 3;

✅ Example of correct code

const t = false;

convert-equal-to-strict-equal

The strict equality operator (===) checks whether its two operands are equal, returning a Boolean result. Unlike the equality operator (==), the strict equality operator always considers operands of different types to be different.

(c) MDN

❌ Example of incorrect code

if (a == b) {}

✅ Example of correct code

if (a === b) {}

convert-switch-to-if

The switch statement evaluates an expression, matching the expression's value against a series of case clauses, and executes statements after the first case clause with a matching value, until a break statement is encountered.

(c) MDN

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

function report(path) {
    switch(path.node.type) {
    case 'ImportFinding':
        return 'remove unused import: ' + path.node.path;
    }
    
    return 'remove unused variable';
}

✅ Example of correct code

function report(path) {
    if (path.node.type === 'ImportFinding')
        return 'remove unused import: ' + path.node.path;
    
    return 'remove unused variable';
}

evaluate

The if statement executes a statement if a specified condition is truthy. If the condition is falsy, another statement can be executed.

(c) MDN

❌ Example of incorrect code

const a = [];
const c = a;

if (a)
    console.log(a);

✅ Example of correct code

const a = [];
const c = a;

console.log(a);

merge-if-statements

Multiple if...else statements can be nested to create an else if clause

(c) MDN

❌ Example of incorrect code

if (a > b)
    if (b < c)
        console.log('hello');

✅ Example of correct code

if (a > b && b < c)
    console.log('hello');

merge-if-with-else

The if statement executes a statement if a specified condition is truthy.

(c) MDN

Checkout in Putout Editor.

❌ Example of incorrect code

if (!matchFn)
    fix(from, to, path);
else if (matchFn(options))
    fix(from, to, path);

✅ Example of correct code

if (!matchFn || matchFn(options))
    fix(from, to, path);

remove-boolean

❌ Example of incorrect code

if (a === true)
    alert();

✅ Example of correct code

if (a)
    alert();

remove-constant

❌ Example of incorrect code

function hi(a) {
    if (2 < 3) {
        console.log('hello');
        console.log('world');
    }
}

✅ Example of correct code

function hi(b) {
    console.log('hello');
    console.log('world');
}

remove-same-values-condition

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

for (const [i, el] of entries(elements)) {
    if (el !== path)
        continue;
    
    if (!Number(i) && n) {
        path.parentPath.node.elements[i] = null;
        break;
    }
    
    if (el === path) {
        remove(path);
        break;
    }
}

✅ Example of correct code

for (const [i, el] of entries(elements)) {
    if (el !== path)
        continue;
    
    if (!Number(i) && n) {
        path.parentPath.node.elements[i] = null;
        break;
    }
    
    remove(path);
}

remove-useless-else

You can skip the else block if your if block always executes a return statement, it makes code a lot easier to read.

(c) no else return

Remove useless else before:

• return;
• continue;
• break;

❌ Example of incorrect code

if (x)
    return;
else
    console.log();

✅ Example of correct code

if (x)
    return;

console.log();

Comparison

Linter	Rule	Fix
🐊 Putout	conditions/remove-useless-else	✅
⏣ ESLint	no-else-return	✅

remove-useless-loop-condition

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

while (currentDirPath = getParentDirectory(currentDirPath)) {
    if (!currentDirPath)
        break;
}

✅ Example of correct code

while (currentDirPath = getParentDirectory(currentDirPath)) {}

remove-zero

❌ Example of incorrect code

if (b === 0) {}

if (b !== 0) {}

✅ Example of correct code

if (!b) {}

if (b) {}

reverse

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❌ Example of incorrect code

const check = (references) => !(references > 3);

return !(nextNode.type !== 'text' || nextNode.value !== ' ');

✅ Example of correct code

const check = (references) => references <= 3;

return nextNode.type === 'text' && nextNode.value === ' ';

simplify

❌ Example of incorrect code

if (zone?.tooltipCallback)
    zone.tooltipCallback(e);

if (a)
    alert('hello');
else
    alert('hello');

✅ Example of correct code

zone?.tooltipCallback(e);

alert('hello');

wrap-with-block

If you use a declaration instead of a statement, it would be a SyntaxError. For example, a let declaration is not a statement, so you can't use it in its bare form as the body of an if statement.

(c) MDN

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❌ Example of incorrect code

if (a)
   const b = 5;

✅ Example of correct code

if (a) {
    const b = 5;
}

License

MIT