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Barney Laurance 7ed5e32840
Update docs on @psalm-internal as @internal no-longer has to be used at same time (#3911) 
See #42ad366dc8ccaf34
2020-07-30 14:09:14 -04:00
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annotating_code Update docs on @psalm-internal as @internal no-longer has to be used at same time (#3911) 2020-07-30 14:09:14 -04:00
manipulating_code Fix documentation 2020-07-30 12:11:28 -04:00
running_psalm Put RedundantIdentityWithTrue behind a flag cc @greg0ire 2020-07-30 10:25:59 -04:00
security_analysis Clarifying taint analysis usage documentation (#3834) 2020-07-17 10:10:35 -04:00
how_psalm_works.md add and correct links to how-psalm-works (#3523) 2020-06-04 15:32:18 -04:00
README.md Fix typos (#3255) 2020-04-28 09:17:31 -04:00
what_makes_psalm_complicated.md stripping trailing whitespace 2019-02-11 18:39:19 -05:00

README.md

About Psalm

Psalm is a static analysis tool that attempts to dig into your program and find as many type-related bugs as possible.

It has a few features that go further than other similar tools:

  • Mixed type warnings
    If Psalm cannot infer a type for an expression then it uses a mixed placeholder type. mixed types can sometimes mask bugs, so keeping track of them helps you avoid a number of common pitfalls.

  • Intelligent logic checks
    Psalm keeps track of logical assertions made about your code, so if ($a && $a) {} and if ($a && !$a) {} are both treated as issues. Psalm also keeps track of logical assertions made in prior code paths, preventing issues like if ($a) {} elseif ($a) {}.

  • Property initialisation checks
    Psalm checks that all properties of a given object have values after the constructor is called.

Psalm also has a few features to make it perform as well as possible on large codebases:

  • Multi-threaded mode
    Wherever possible Psalm will run its analysis in parallel to save time. Useful for large codebases, it has a massive impact on performance.

  • Incremental checks
    When using the --diff command line option, Psalm will only analyse files that have changed and files that reference them.

Example output

Given a file implode_strings.php:

<?php
$a = ['foo', 'bar'];
echo implode($a, ' ');

> ./vendor/bin/psalm implode_strings.php
ERROR: InvalidArgument - somefile.php:3:14 - Argument 1 of implode expects `string`, `array` provided (see https://psalm.dev/004)

Inspirations

There are two main inspirations for Psalm:

  • Etsy's Phan, which uses nikic's php-ast extension to create an abstract syntax tree
  • Facebook's Hack, a PHP-like language that supports many advanced typing features natively, so docblocks aren't necessary.

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