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Supported docblock annotations
Psalm supports a wide range of docblock annotations.
PHPDoc tags
Psalm uses the following PHPDoc tags to understand your code:
@varUsed for specifying the types of properties and variables@@returnUsed for specifying the return types of functions, methods and closures@paramUsed for specifying types of parameters passed to functions, methods and closures@propertyUsed to specify what properties can be accessed on an object that uses__getand__set@property-readUsed to specify what properties can be read on object that uses__get@property-writeUsed to specify what properties can be written on object that uses__set@methodUsed to specify which magic methods are available on object that uses__call.@deprecatedUsed to mark functions, methods, classes and interfaces as being deprecated@internalused to mark classes, functions and properties that are internal to an application or library.
Off-label usage of the @var tag
The @var tag is supposed to only be used for properties. Psalm, taking a lead from PHPStorm and other static analysis tools, allows its use inline in the form @var Type [VariableReference].
If VariableReference is provided, it should be of the form $variable or $variable->property. If used above an assignment, Psalm checks whether the VariableReference matches the variable being assigned. If they differ, Psalm will assign the Type to VariableReference and use it in the expression below.
If no VariableReference is given, the annotation tells Psalm that the right hand side of the expression, whether an assignment or a return, is of type Type.
<?php
/** @var string */
$a = $_GET['foo'];
/** @var string $b */
$b = $_GET['bar'];
function bat(): string {
/** @var string */
return $_GET['bat'];
}
Psalm-specific tags
There are a number of custom tags that determine how Psalm treats your code.
@psalm-consistent-constructor
@psalm-consistent-templates
See UnsafeGenericInstantiation
@param-out, @psalm-param-out
This is used to specify that a by-ref type is different from the one that entered. In the function below the first param can be null, but once the function has executed the by-ref value is not null.
<?php
/**
* @param-out string $s
*/
function addFoo(?string &$s) : void {
if ($s === null) {
$s = "hello";
}
$s .= "foo";
}
@psalm-var, @psalm-param, @psalm-return, @psalm-property, @psalm-property-read, @psalm-property-write, @psalm-method
When specifying types in a format not supported by phpDocumentor (but supported by Psalm) you may wish to prepend @psalm- to the PHPDoc tag, so as to avoid confusing your IDE. If a @psalm-prefixed tag is given, Psalm will use it in place of its non-prefixed counterpart.
@psalm-ignore-var
This annotation is used to ignore the @var annotation written in the same docblock. Some IDEs don't fully understand complex types like generics. To take advantage of such IDE's auto-completion, you may sometimes want to use explicit @var annotations even when psalm can infer the type just fine. This weakens the effectiveness of type checking in many cases since the explicit @var annotation overrides the types inferred by psalm. As psalm ignores the @var annotation which is co-located with @psalm-ignore-var, IDEs can use the type specified by the @var for auto-completion, while psalm can still use its own inferred type for type checking.
<?php
/** @return iterable<array-key,\DateTime> $f */
function getTimes(int $n): iterable {
while ($n--) {
yield new \DateTime();
}
};
/**
* @var \Datetime[] $times
* @psalm-ignore-var
*/
$times = getTimes(3);
// this trace shows "iterable<array-key, DateTime>" instead of "array<array-key, Datetime>"
/** @psalm-trace $times */
foreach ($times as $time) {
echo $time->format('Y-m-d H:i:s.u') . PHP_EOL;
}
@psalm-suppress SomeIssueName
This annotation is used to suppress issues. It can be used in function docblocks, class docblocks and also inline, applying to the following statement.
Function docblock example:
<?php
/**
* @psalm-suppress PossiblyNullOperand
*/
function addString(?string $s) {
echo "hello " . $s;
}
Inline example:
<?php
function addString(?string $s) {
/** @psalm-suppress PossiblyNullOperand */
echo "hello " . $s;
}
@psalm-suppress all can be used to suppress all issues instead of listing them individually.
@psalm-assert, @psalm-assert-if-true and @psalm-assert-if-false
See Adding assertions.
@psalm-ignore-nullable-return
This can be used to tell Psalm not to worry if a function/method returns null. It’s a bit of a hack, but occasionally useful for scenarios where you either have a very high confidence of a non-null value, or some other function guarantees a non-null value for that particular code path.
<?php
class Foo {}
function takesFoo(Foo $f): void {}
/** @psalm-ignore-nullable-return */
function getFoo(): ?Foo {
return rand(0, 10000) > 1 ? new Foo() : null;
}
takesFoo(getFoo());
@psalm-ignore-falsable-return
This provides the same, but for false. Psalm uses this internally for functions like preg_replace, which can return false if the given input has encoding errors, but where 99.9% of the time the function operates as expected.
@psalm-seal-properties
If you have a magic property getter/setter, you can use @psalm-seal-properties to instruct Psalm to disallow getting and setting any properties not contained in a list of @property (or @property-read/@property-write) annotations.
<?php
/**
* @property string $foo
* @psalm-seal-properties
*/
class A {
public function __get(string $name): ?string {
if ($name === "foo") {
return "hello";
}
}
public function __set(string $name, $value): void {}
}
$a = new A();
$a->bar = 5; // this call fails
@psalm-internal
Used to mark a class, property or function as internal to a given namespace. Psalm treats this slightly differently to
the PHPDoc @internal tag. For @internal, an issue is raised if the calling code is in a namespace completely
unrelated to the namespace of the calling code, i.e. not sharing the first element of the namespace.
In contrast for @psalm-internal, the docbloc line must specify a namespace. An issue is raised if the calling code
is not within the given namespace.
<?php
namespace A\B {
/**
* @internal
* @psalm-internal A\B
*/
class Foo { }
}
namespace A\B\C {
class Bat {
public function batBat(): void {
$a = new \A\B\Foo(); // this is fine
}
}
}
namespace A\C {
class Bat {
public function batBat(): void {
$a = new \A\B\Foo(); // error
}
}
}
@psalm-readonly and @readonly
Used to annotate a property that can only be written to in its defining class's constructor.
<?php
class B {
/** @readonly */
public string $s;
public function __construct(string $s) {
$this->s = $s;
}
}
$b = new B("hello");
echo $b->s;
$b->s = "boo"; // disallowed
@psalm-mutation-free
Used to annotate a class method that does not mutate state, either internally or externally of the class's scope.
<?php
class D {
private string $s;
public function __construct(string $s) {
$this->s = $s;
}
/**
* @psalm-mutation-free
*/
public function getShort() : string {
return substr($this->s, 0, 5);
}
/**
* @psalm-mutation-free
*/
public function getShortMutating() : string {
$this->s .= "hello"; // this is a bug
return substr($this->s, 0, 5);
}
}
@psalm-external-mutation-free
Used to annotate a class method that does not mutate state externally of the class's scope.
<?php
class E {
private string $s;
public function __construct(string $s) {
$this->s = $s;
}
/**
* @psalm-external-mutation-free
*/
public function getShortMutating() : string {
$this->s .= "hello"; // this is fine
return substr($this->s, 0, 5);
}
/**
* @psalm-external-mutation-free
*/
public function save() : void {
file_put_contents("foo.txt", $this->s); // this is a bug
}
}
@psalm-immutable
Used to annotate a class where every property is treated by consumers as @psalm-readonly and every instance method is treated as @psalm-mutation-free.
<?php
/**
* @psalm-immutable
*/
abstract class Foo
{
public string $baz;
abstract public function bar(): int;
}
/**
* @psalm-immutable
*/
final class ChildClass extends Foo
{
public function __construct(string $baz)
{
$this->baz = $baz;
}
public function bar(): int
{
return 0;
}
}
$anonymous = new /** @psalm-immutable */ class extends Foo
{
public string $baz = "B";
public function bar(): int
{
return 1;
}
};
@psalm-pure
Used to annotate a pure function - one whose output is just a function of its input.
<?php
class Arithmetic {
/** @psalm-pure */
public static function add(int $left, int $right) : int {
return $left + $right;
}
/** @psalm-pure - this is wrong */
public static function addCumulative(int $left) : int {
/** @var int */
static $i = 0; // this is a side effect, and thus a bug
$i += $left;
return $i;
}
}
echo Arithmetic::add(40, 2);
echo Arithmetic::add(40, 2); // same value is emitted
echo Arithmetic::addCumulative(3); // outputs 3
echo Arithmetic::addCumulative(3); // outputs 6
On the other hand, pure-callable can be used to denote a callable which needs to be pure.
/**
* @param pure-callable(mixed): int $callback
*/
function foo(callable $callback) {...}
// this fails since random_int is not pure
foo(
/** @param mixed $p */
fn($p) => random_int(1, 2)
);
@psalm-allow-private-mutation
Used to annotate readonly properties that can be mutated in a private context. With this, public properties can be read from another class but only be mutated within a method of its own class.
<?php
class Counter {
/**
* @readonly
* @psalm-allow-private-mutation
*/
public int $count = 0;
public function increment() : void {
$this->count++;
}
}
$counter = new Counter();
echo $counter->count; // outputs 0
$counter->increment(); // Method can mutate property
echo $counter->count; // outputs 1
$counter->count = 5; // This will fail, as it's mutating a property directly
@psalm-readonly-allow-private-mutation
This is a shorthand for the property annotations @readonly and @psalm-allow-private-mutation.
<?php
class Counter {
/**
* @psalm-readonly-allow-private-mutation
*/
public int $count = 0;
public function increment() : void {
$this->count++;
}
}
$counter = new Counter();
echo $counter->count; // outputs 0
$counter->increment(); // Method can mutate property
echo $counter->count; // outputs 1
$counter->count = 5; // This will fail, as it's mutating a property directly
@psalm-trace
You can use this annotation to trace inferred type (applied to the next statement).
<?php
/** @psalm-trace $username */
$username = $_GET['username']; // prints something like "test.php:4 $username: mixed"
Note: it throws special low-level issue, so you have to set errorLevel to 1, override it in config or invoke Psalm with --show-info=true.
@psalm-taint-*
See Security Analysis annotations.
@psalm-type
This allows you to define an alias for another type.
<?php
/**
* @psalm-type PhoneType = array{phone: string}
*/
class Phone {
/**
* @psalm-return PhoneType
*/
public function toArray(): array {
return ["phone" => "Nokia"];
}
}
@psalm-import-type
You can use this annotation to import a type defined with @psalm-type if it was defined somewhere else.
<?php
/**
* @psalm-import-type PhoneType from Phone
*/
class User {
/**
* @psalm-return PhoneType
*/
public function toArray(): array {
return array_merge([], (new Phone())->toArray());
}
}
You can also alias a type when you import it:
<?php
/**
* @psalm-import-type PhoneType from Phone as MyPhoneTypeAlias
*/
class User {
/**
* @psalm-return MyPhoneTypeAlias
*/
public function toArray(): array {
return array_merge([], (new Phone())->toArray());
}
}
@psalm-require-extends
The @psalm-require-extends annotation allows you to define a requirements that a trait imposes on the using class.
<?php
abstract class DatabaseModel {
// methods, properties, etc.
}
/**
* @psalm-require-extends DatabaseModel
*/
trait SoftDeletingTrait {
// useful but scoped functionality, that depends on methods/properties from DatabaseModel
}
class MyModel extends DatabaseModel {
// valid
use SoftDeletingTrait;
}
class NormalClass {
// triggers an error
use SoftDeletingTrait;
}
@psalm-require-implements
Behaves the same way as @psalm-require-extends, but for interfaces.
@no-named-arguments
This will prevent access to the function or method tagged with named parameters (by emitting a NamedArgumentNotAllowed issue).
Incidentally, it will change the inferred type for the following code:
<?php
function a(int ...$a){
var_dump($a);
}
The type of $a is array<array-key, int> without @no-named-arguments but becomes list<int> with it, because it exclude the case where the offset would be a string with the name of the parameter
Type Syntax
Psalm supports PHPDoc’s type syntax, and also the proposed PHPDoc PSR type syntax.
A detailed write-up is found in Typing in Psalm