feat: Introduce variable_case fixer

[jmkoni]

The project that I am working in has a rule that variables should all be in camelCase. However, we don't have any way to currently lint or automatically fix. Since we are using PHPCSFixer, I wanted to add a fixer that would automatically make that change.

[GrahamCampbell]

This fixer should be marked as risky. It will break compact/require/include.

[GrahamCampbell]

Also, we are missing test cases with string variable interpolation?

[jmkoni]

@GrahamCampbell do you mean a test like this:

[
     '<?php $testVariable = 2; echo "hi $testVariable!"; ',
     '<?php $test_variable = 2; echo "hi $test_variable!"',
]

It will break compact/require/include
Is there something I can do to make sure it is not risky? New-ish to PHP.

[GrahamCampbell]

Yes, and "${testVariable}" and "{$testVariable}". Both cases tokenize differently, and need handling.

[julienfalque]

Is there something I can do to make sure it is not risky? New-ish to PHP.

Sadly no. PHP CS Fixer works on one file at a time and isn't able to detect that a change in that file will have any impact on other files. Users have to check for breaking changes after running risky rules.

You may even have cases where a break is introduced inside the same file:

$some_variable = 'foo';
$name = 'some_variable';
echo $$name; // prints "foo"

would become:

$someVariable = 'foo';
$name = 'some_variable';
echo $$name; // Undefined variable $some_variable

PHP CS Fixer does not really have advanced analysis capabilities and detecting this would be too much complicated to implement here IMO. Maybe tools like PHPStan or Psalm can detect it anyway.

[GrahamCampbell]

Even then, this kind of fixer is inherently risky, like I said earlier. It cannot fix the following correctly:

function f($bar_baz, $file)
{
    require $file;
}

[jmkoni]

I updated this, marked it as risky, added some more tests.

[spawnia]

Thanks @jmkoni for your work on this PR. We are trying to add this as a custom rule via mll-lab/php-cs-fixer-config#3 and stumbled upon some edge cases:

$_ = 2;
var_dump($_ENV);

Thus, i modified the camel case fixer to preserve leading underscores and exclude globals.

    private function camelCase(string $string): string
    {
        $leadingDollar = '';
        if ('$' === $string[0]) {
            $string = substr($string, 1);
            $leadingDollar = '$';
        }

        // Preserve leading underscores
        $leadingUnderscoreMatches = [];
        Preg::match('/^_*/', $string, $leadingUnderscoreMatches);
        $leadingUnderscores = $leadingUnderscoreMatches[0] ?? '';

        if (array_key_exists($string, $GLOBALS)) {
            return $leadingDollar . $string;
        }

        $string = Preg::replace('/[$_]/i', ' ', $string);
        $string = trim($string);
        // uppercase the first character of each word
        $string = ucwords($string);
        $string = str_replace(' ', '', $string);

        return $leadingDollar . $leadingUnderscores . lcfirst($string);
    }

[muglug]

This also converts property names, which may not be desired. To avoid that I changed the applyFix method locally:

    /**
     * {@inheritdoc}
     */
    protected function applyFix(\SplFileInfo $file, Tokens $tokens)
    {
        foreach ($tokens as $index => $token) {
            if ((T_VARIABLE === $token->getId()) || (T_STRING_VARNAME === $token->getId())) {
                $prev_index = $tokens->getPrevMeaningfulToken($index);
                $prev_token = $tokens[$prev_index];

                if ($prev_token->getId() === T_STATIC) {
                    $prev_index = $tokens->getPrevMeaningfulToken($prev_index);
                    $prev_token = $tokens[$prev_index];
                }

                if ($prev_token->getId() === T_PROTECTED
                    || $prev_token->getId() === T_PUBLIC
                    || $prev_token->getId() === T_PRIVATE
                    || $prev_token->getId() === T_VAR
                    || $prev_token->getId() === T_DOUBLE_COLON
                ) {
                    continue;
                }

                $tokens[$index] = new Token([$token->getId(), $this->updateVariableCasing($token->getContent())]);
            }
        }
    }

[shakaran]

@jmkoni could you rerun

php dev-tools/doc.php

For update README.rst and resolve the conflict, so it would look RTM for maintainers? Thanks

[Wirone]

I've added failing test cases for class' properties to address @muglug's comment - will fix it after initial agreement that we want this fixer.

[Wirone]

@keradus we need decision whether we want to continue to work on this (see this comment).