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49 lines
1.2 KiB
Markdown
49 lines
1.2 KiB
Markdown
# PossiblyNullArgument
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Emitted when calling a function with a value that’s possibly null when the function does not expect it
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```php
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<?php
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function foo(string $s): void {}
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foo(rand(0, 1) ? "hello" : null);
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```
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## Common Problem Cases
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### Using a Function Call inside `if`
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```php
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if (is_string($cat->getName()) {
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foo($cat->getName());
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}
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```
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This fails since it's not guaranteed that subsequent calls to `$cat->getName()` always give the same result.
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#### Possible Solutions
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* Use a variable:
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```php
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$catName = $cat->getName();
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if (is_string($catName) {
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foo($catName);
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}
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unset($catName);
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```
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* Add [`@psalm-mutation-free`](../../annotating_code/supported_annotations.md#psalm-mutation-free) to the declaration of the function
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### Calling Another Function After `if`
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```php
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if (is_string($cat->getName()) {
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changeCat();
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foo($cat->getName());
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}
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```
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This fails since psalm cannot know if `changeCat()` does actually modify `$cat`.
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#### Possible Solutions
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* Add [`@psalm-mutation-free`](../../annotating_code/supported_annotations.md#psalm-mutation-free) to the declaration of the other function (here: `changeCat()`) too
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* Use a variable: See above
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