OneTimeUseVariables

warning on by default quick-fix

Group: Control flow · PhpStorm name: OneTimeUseVariablesInspection

A local variable that is assigned in one statement and consumed exactly once in the very next return, throw or destructuring statement adds a name without adding meaning. The value can be used directly at the consumption site.

Example

Before

<?php
$total = 40 + 2;
return $total;

function makeUser() {
    $user = new User();
    return $user->name;
}

function failWith($why) {
    $err = new DomainError($why);
    throw $err;
}

function split2() {
    $parts = explode(':', 'a:b');
    [$head, $tail] = $parts;
    return $head . $tail;
}

function pick($a, $b) {
    $chosen = $a ?: $b;
    return $chosen->label;
}

function copyOf($proto) {
    $dup = clone $proto;
    return $dup->fresh();
}

function &byRef() {
    $slot = null;
    return $slot;
}

function twice() {
    $n = compute();
    $n = $n * 2;
    return $n;
}

function readAgain() {
    $cfg = load();
    [$k] = $cfg;
    return $cfg ? $k : null;
}

function annotated() {
    /** @var Gadget $g */
    $g = factory();
    return $g;
}

function staticAccess() {
    $cls = whichClass();
    return $cls::build();
}

function compound($v) {
    $v .= '!';
    return $v;
}

$fn = function () use (&$acc) {
    $acc = 5;
    return $acc;
};

function refParam(&$out) {
    $out = 1;
    return $out;
}

After fix

<?php
return 40 + 2;

function makeUser() {
    return (new User())->name;
}

function failWith($why) {
    throw new DomainError($why);
}

function split2() {
    [$head, $tail] = explode(':', 'a:b');
    return $head . $tail;
}

function pick($a, $b) {
    return ($a ?: $b)->label;
}

function copyOf($proto) {
    return (clone $proto)->fresh();
}

function &byRef() {
    $slot = null;
    return $slot;
}

function twice() {
    $n = compute();
    $n = $n * 2;
    return $n;
}

function readAgain() {
    $cfg = load();
    [$k] = $cfg;
    return $cfg ? $k : null;
}

function annotated() {
    /** @var Gadget $g */
    $g = factory();
    return $g;
}

function staticAccess() {
    $cls = whichClass();
    return $cls::build();
}

function compound($v) {
    $v .= '!';
    return $v;
}

$fn = function () use (&$acc) {
    $acc = 5;
    return $acc;
};

function refParam(&$out) {
    $out = 1;
    return $out;
}

Reported:

• line 2: Variable $total is used only once; inline its value.
• line 6: Variable $user is used only once; inline its value.
• line 11: Variable $err is used only once; inline its value.
• line 16: Variable $parts is used only once; inline its value.
• line 22: Variable $chosen is used only once; inline its value.
• line 27: Variable $dup is used only once; inline its value.

Options

Option	Type	Default	Effect
ALLOW_LONG_STATEMENTS	bool	false	When false, assignments whose text exceeds 80 characters are left alone (a long expression may deserve a name). When true, length is ignored.
ANALYZE_RETURN_STATEMENTS	bool	true	Inspect return consumers (D1).
ANALYZE_THROW_STATEMENTS	bool	true	Inspect throw consumers (D2).
ANALYZE_ARRAY_DESTRUCTURING	bool	true	Inspect list()/[] destructuring consumers (D3).

Configure

In custos.json:

{
  "rules": {
    "OneTimeUseVariables": {
      "enabled": false,
      "options": {
        "ALLOW_LONG_STATEMENTS": false,
        "ANALYZE_RETURN_STATEMENTS": true,
        "ANALYZE_THROW_STATEMENTS": true,
        "ANALYZE_ARRAY_DESTRUCTURING": true
      }
    }
  }
}

Suppress

Before the statement or declaration (or the first statement of the file), either of:

// @custos-ignore OneTimeUseVariables

/**
 * @noinspection OneTimeUseVariablesInspection
 */