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69 lines
3.0 KiB
Markdown
69 lines
3.0 KiB
Markdown
# About Psalm
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Psalm is a static analysis tool that attempts to dig into your program and find as many type-related bugs as possible.
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It has a few features that go further than other similar tools:
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- **Mixed type warnings**<br />
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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.
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- **Intelligent logic checks**<br />
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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 ($a) {}`.
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- **Property initialisation checks**<br />
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Psalm checks that all properties of a given object have values after the constructor is called.
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Psalm also has a few features to make it perform as well as possible on large codebases:
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- **Multi-threaded mode**<br />
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Wherever possible Psalm will run its analysis in parallel to save time. Useful for large codebases, it has a massive impact on performance.
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- **Incremental checks**<br />
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When using the `--diff` command line option, Psalm will only analyse files that have changed *and* files that reference them.
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## Example output
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Given a file `implode_strings.php`:
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```php
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<?php
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$a = ['foo', 'bar'];
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echo implode($a, ' ');
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```
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```bash
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> ./vendor/bin/psalm implode_strings.php
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ERROR: InvalidArgument - somefile.php:3:14 - Argument 1 of implode expects `string`, `array` provided (see https://psalm.dev/004)
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```
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## Inspirations
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There are two main inspirations for Psalm:
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- Etsy's [Phan](https://github.com/etsy/phan), which uses nikic's [php-ast](https://github.com/nikic/php-ast) extension to create an abstract syntax tree
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- Facebook's [Hack](http://hacklang.org/), a PHP-like language that supports many advanced typing features natively, so docblocks aren't necessary.
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## Index
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- Running Psalm:
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- [Installation](running_psalm/installation.md)
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- [Configuration](running_psalm/configuration.md)
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- Plugins
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- [Using plugins](running_psalm/plugins/using_plugins.md)
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- [Authoring plugins](running_psalm/plugins/authoring_plugins.md)
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- [How Psalm represents types](running_psalm/plugins/plugins_type_system.md)
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- [Command line usage](running_psalm/command_line_usage.md)
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- [IDE support](running_psalm/language_server.md)
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- Handling errors:
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- [Dealing with code issues](running_psalm/dealing_with_code_issues.md)
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- [Issue Types](running_psalm/issues.md)
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- [Checking non-PHP files](running_psalm/checking_non_php_files.md)
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- Annotating code:
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- [Typing in Psalm](annotating_code/typing_in_psalm.md)
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- [Supported Annotations](annotating_code/supported_annotations.md)
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- [Template Annotations](annotating_code/templated_annotations.md)
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- Manipulating code:
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- [Fixing code](manipulating_code/fixing.md)
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- [Refactoring code](manipulating_code/refactoring.md)
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