Psalm 7

[danog]

Psalm 7

Announcing the release of Psalm 7!

Featuring a simply enormous number of new features and bug fixes, such as:

• security analysis on by default: fully refactored for 10x+ performance and much greater coverage, in the same run as type checking and dead code detection;
• much deeper security analysis taint tracking: NoSQL, LLM prompt and URL injection, new sources like php://input and uploaded file names, flows through closures, generators, traits and by-reference parameters, and ready-made stubs for Guzzle, PSR-7, Monolog, MongoDB and more.
• a new purity model based on Hack's capabilities: declare exactly which side effects a function may have (io, time, write-props...), with purity templates for classes, closures and automatically inferred annotations;
• graph-based dead code detection: If nothing reachable uses a class, function, method, constant, variable, etc, Psalm finds it, now properly handling unused cycles as well.
• Template defaults (@template TError of Throwable = RuntimeException) for classes, functions and methods: Result<int> just works, and libraries can add templates without breaking their users.
• PHP 8.5 and 8.6 support: Full support for Partial Function Application, the pipe operator, and much more!
• Daily releases. Features and fixes reach you the day they land, no more waiting on dev-master.
• Framework plugins in the box. The PHPUnit, Symfony, Laravel, Mockery and sabre/event plugins ship with Psalm and switch on by themselves. Zero setup.
• a bigger Psalm maintainer team: @alies-dev has joined the Psalm maintainer team, contributing many new useful features and bugfixes!
• An official Discord community!
• And so, so many other new features and bugfixes!

Psalm 7 runs on 64-bit PHP 8.2 to 8.6. Upgrading is simple for most projects: see Upgrading below.

Security analysis: faster, always on, in a single run

Taints are now stored as a bitmask, and the taint graph is resolved over compact summaries of each function. This makes security analysis up to 10x faster.

Combined analysis (#11384) runs type checking, security analysis and dead code detection together in one run, so taint analysis is now on by default (#11399).

Taint issues are reported with a SECURITY severity, and with a rank in SARIF reports (#12068, #11383). The results no longer change between runs or with the thread count (#11946, #11952, #11953).

Deeper taint tracking

<?php
$run = function (string $c): void {
    shell_exec($c);
};
$run((string) $_GET['cmd']); // TaintedShell, through the closure

$mongo = new MongoDB\Driver\Manager('mongodb://localhost');
$mongo->executeQuery('db.users', new MongoDB\Driver\Query(['name' => $_GET['name']])); // TaintedNosql

/** @return mixed */
function body() {
    return json_decode((string) file_get_contents('php://input'), true);
}
eval((string) body()); // TaintedEval: php://input is a source

• New taint kinds: TaintedNosql (MongoDB sinks), TaintedLlmPrompt (prompt injection), and TaintedUrlComponent / TaintedUrlPath (query and path injection). curl options and CURLFile are reported by what they do: SSRF, header injection, file access, sleep or callables. Every taint type is now documented (Add nosql taint type and mark MongoDB sinks #11944, [7.x] Add TaintedLlmPrompt issue type for prompt injection detection #11746, Add new taint kinds for query and path injection #12097, Report curl options and CURLFile by what they do: SSRF, header injection, files, sleep and callables #12099, Document every taint type #12468).
• New sources: php://input, STDIN, the client-sent entries of $_SERVER and $_FILES, getopt(), $argv, DNS answers, exception messages, and the files, paths and URLs builtins read (Taint php://input & STDIN sources, and propagate taint through closures #11945, Taint the entries of $_SERVER and $_FILES the client sends #12086, Treat the command-line options getopt() returns as a taint source of user input #12246, Treat $argv, bound with global or read through $GLOBALS too, as a taint source of user input #12245, Taint DNS answers, and the paths and URLs more builtins read, write and connect to #12135, Taint the messages of exceptions, and the exceptions a catch block gets #12139).
• Taint now flows through closures and callable parameters, generators and iterators, by-reference parameters, foreach by reference, global and static variables, trait method bodies, promoted constructor properties, __toString(), inherited methods and their overrides, exceptions, and builtin functions and objects (Taint what closures are called with and return through variables and callable parameters #12147, Taint what generators yield and what iterating over objects gives #12096, Taint what functions and builtins leave in by-reference parameters #12095, Taint the array a foreach by reference writes into #12121, Track taints through global variables, with a node per global shared by $GLOBALS and global #12243, Track taints through the static variables of function-likes across their calls #12255, Track taint through the bodies of trait methods, keyed by the class using the trait #12272, Make the taints of promoted constructor parameters flow into their properties #12091, Convert an object to a string with the taints of what its __toString returns #12127, Taint the result of a call on an interface or base class with the returns of its overrides #12262, Make taints flow through the builtins that return data from their arguments #12084, Taint what builtin objects are given and give back, described by a dictionary #12102).
• Fewer false positives: taints a type can't carry are removed (an int has no html taint). Array keys are tracked much more precisely. Inferred-pure functions are specialized per call, and @psalm-cli-only marks code whose output isn't an HTML response (Remove the taints a value's type cannot hold, at returns, sources and assignments #12079, Drop the taints a narrowed type can't carry, also where it can carry others #12348, Assign under each literal the key of an array assignment can be #12150, Taint analysis: know more array keys (literal unions, array_map(), convergences, key starts of lists) and stop at keys overwritten in specialized calls #12375, Specialize taints of calls to inferred-pure functions #12048, Add @psalm-cli-only: what command-line code prints isn't an HTML sink #12459).
• Library stubs: Psalm ships taint and purity stubs for Guzzle, PSR-7, PSR-18, psr/log, Monolog, mongodb/mongodb, amphp (http-client, byte-stream, file, process), phpClickHouse, PhpSpreadsheet, Archive_Tar, php-vips, webklex/php-imap and webmozart/assert. A stub is loaded only when your code uses the library (loadLibraryStubs, on by default) (Load the stubs Psalm ships for libraries when the scanned code uses one of their classes #12460–Add a library stub for the emails webklex/php-imap receives as taint sources #12467, Load a library stub when the scanned code declares one of its functions #12481–Add a library stub for the NoSQL sinks of mongodb/mongodb's Collection and Database #12484).
• More expressive annotations (docs):
  • conditional sinks: @psalm-taint-sink ($mode is 0 ? null : 'html') $content (Support conditional taint sinks: @psalm-taint-sink ($mode is 0 ? null : 'html') $content #12458);
  • sinks on array values only: @psalm-taint-sink sql $params[*] (Taint analysis: sinks on the values of an array parameter only ($param[*]) #12171);
  • sources under one key of the return value: @psalm-taint-source input return['key'] (Support @psalm-taint-source input return['key']: a source under a key of the return only #12455);
  • taint complements: ~(html|has_quotes) (Accept taint complements ~(kind|kind): every taint, custom ones included, but the kinds listed #12300);
  • @psalm-flow through callables (($compute()) -> return), the receiver (($this) -> return), $this properties, and keyed stores (($value) -> Store::$data[$key]) (Support @psalm-flow ($compute()) -> return: what a callable parameter returns flows to the return #12299, Let @psalm-flow ($this) -> return carry the taints of the object a method is called on #12302, Let @psalm-flow set and return properties of $this by name #12456, Follow values through keyed stores: @psalm-flow ($value) -> Store::$data[$key] and back to return #12312, Store what callables return in keyed stores: @psalm-flow ($compute()) -> Store::$data[$key] #12327);
  • @psalm-taint-property-bag (Read and write the properties of a class through the array property @psalm-taint-property-bag names #12486);
  • custom taints declared in psalm.xml (Declare custom taints in psalm.xml, optionally added to the input aliases #12330).
• Plugin API for taints: Codebase::getTaintNode(), getTaintPropertyNode(), addTaintPath(), getReceiverTaintPath(), and the taint nodes of a call's return value, arguments and receiver (Let plugins add taint paths: Codebase::getTaintNode(), getTaintPropertyNode(), addTaintPath() #12454, Add Codebase::getReceiverTaintPath(), the path along which a method of a builtin class returns what its object holds #12414, Let plugins get the taint nodes of the return, arguments and object of a call, and assign properties #12489, Let plugins give an expression the taint nodes of a list, without their internal ids #12535).

A new purity model: capabilities

@psalm-pure, @psalm-mutation-free and @psalm-external-mutation-free are replaced by capabilities, modelled on Hack's contexts and capabilities. A function-like declares exactly which side effects it may have: read-props, write-this-props, write-props, read-globals, write-globals, write-refs, io and time, with pure and impure at the two ends (#11984):

<?php
/** @psalm-capabilities time */
function today(): string {
    return date('Y-m-d'); // no issue
}

/** @psalm-pure */
function todayWrong(): string {
    return date('Y-m-d'); // ImpureFunctionCall: ... requires time
}

• Psalm infers purity across the call graph. Where an annotation could be added, it can suggest one: set <psalm suggestPurityAnnotations="true"> to get MissingPureAnnotation and MissingImmutableAnnotation (and their abstract and interface variants), and run --alter --issues=MissingPureAnnotation,MissingImmutableAnnotation to add the annotations. The --alter command works without the attribute. The suggestions are opt-in.
• Pure and read-only functions are taint-specialized automatically, so annotating your code also removes false positives from security analysis.
• Builtins, SPL, the Random, phpredis and MongoDB extensions and more declare what they do.
• clone, __toString(), __invoke(), ArrayAccess, destructors, new $class and parameter defaults are now checked too.
• @psalm-pure can be used on classes, and plugins can declare the capabilities of the methods they handle.

The new Purity Model article explains the model in full.

Purity templates

Many functions are only as pure as what they are given: array_map() is pure when its callback is. Purity templates are template parameters whose values are capability sets instead of types, like Hack's [ctx $f] contexts. A function can now be both pure and higher-order, and each call costs only what its arguments do (#11984).

With Closure[_], a function takes its purity from the closure it is given:

<?php
/**
 * @psalm-pure
 * @param Closure[_](int): int $f
 */
function apply(Closure $f, int $x): int {
    return $f($x);
}

/** @psalm-pure */
function double(int $x): int {
    return apply(fn(int $y): int => $y * 2, $x); // no issue: the closure is pure
}

/** @psalm-pure */
function noisy(int $x): int {
    return apply(function (int $y): int { echo $y; return $y; }, $x); // ImpureFunctionCall: The context is pure but function call on apply requires io
}

/** @psalm-pure */
function lengths(array $words): array {
    return array_map(fn(string $w): int => strlen($w), $words); // no issue: builtins taking callbacks work the same way
}

On a class, a purity template lets each subclass decide what its methods may do:

<?php
/** @psalm-purity-template P */
abstract class Handler {
    /**
     * @psalm-pure
     * @psalm-purity-from-template P
     */
    abstract public function handle(string $input): string;
}

/** @extends Handler[pure] */
final class Upper extends Handler {
    /** @psalm-pure */
    #[Override]
    public function handle(string $input): string {
        return strtoupper($input);
    }
}

/** @extends Handler[io] */
final class Printer extends Handler {
    /** @psalm-capabilities io */
    #[Override]
    public function handle(string $input): string {
        echo $input;
        return $input;
    }
}

/** @psalm-pure */
function viaUpper(Upper $handler): string {
    return $handler->handle('a'); // no issue: Upper binds P to pure
}

/** @psalm-pure */
function viaPrinter(Printer $handler): string {
    return $handler->handle('a'); // ImpureMethodCall: The context is pure but method Printer::handle requires io
}

Traversable, Iterator, IteratorAggregate and Generator have a purity template, for what iterating over them does. iterable has one too. A generator with a purity annotation binds it to what its body does:

<?php
/**
 * @psalm-pure
 * @param Traversable[pure]<int, int> $xs
 */
function sum(Traversable $xs): int {
    $total = 0;
    foreach ($xs as $x) { // no issue
        $total += $x;
    }
    return $total;
}

/**
 * @psalm-pure
 * @param Traversable<int, int> $xs
 */
function sumAny(Traversable $xs): int {
    $total = 0;
    foreach ($xs as $x) { // ImpureMethodCall: The context is pure but iterating over Traversable<int, int> requires impure
        $total += $x;
    }
    return $total;
}

/**
 * @psalm-pure
 * @return Generator<int, int>
 */
function numbers(): Generator {
    yield 1;
    yield 2;
}

/** @psalm-pure */
function total(): int {
    return sum(numbers()); // no issue: numbers() returns a Generator[pure]
}

• Syntax: purity arguments go in square brackets before the type arguments, as in Hack: Closure[io](int): void, Handler[pure], Iterator[pure]<int, string>, Box[io]<int>. Named templates are declared with @psalm-purity-template P and used with @psalm-purity-from-template P.
• Bounds and defaults are written as a chain: @psalm-purity-template write-this-props <= C(write-this-props) <= write-this-props|write-props|io. A method may use the lower bound unconditionally. Subclasses must stay within the bounds, and get the default when they don't bind the template.
• Constructors can bind a class template from their arguments, with a Closure[P] parameter or a conditional @return on __construct. For example, new ArrayObject([...]) is an ArrayObject[pure], so a pure function may fill an ArrayObject it created (Charge the class purity templates constructors depend on at new #12116, Let a constructor's @return give the type of the object it constructs #12179, Charge ArrayObject and ArrayIterator mutators write-props only when their storage is an object #12190).
• Purity templates are checked across overrides, traits and closures nested in a templated scope (Compare the purity templates of overriding methods by their bounds #12015, Check trait methods against the purity template bindings of the class using the trait #12126, Let closures carry the purity templates of the scopes they are nested in #12027).
• Inferred too: Psalm infers the purity of calls to templated functions, and --alter adds Closure[_] to the closure parameters a function calls (Purity templates: omitted purity arguments, instanceof narrowing, inference of templated calls #12077, Add the _ purity to the closure parameters a function-like calls with --alter #12019).
• Builtins and SPL taking callbacks or iterators are declared with purity templates: array_map, usort, preg_replace_callback, iterator_to_array, CallbackFilterIterator, Fiber and more (Declare what the methods of the SPL classes do #12122).

See Purity templates in the Purity Model article.

Graph-based dead code detection

Unused code is now found on a graph of references (#11939). Code is used only if it can be reached from an entry point, so classes and methods referenced only by other unused code, cycles included, are reported. Exceptions that are created but never thrown are reported too (#12487):

<?php
final class Service {
    public function run(int $id): void {
        if ($id < 0) {
            new InvalidArgumentException('negative id'); // UnusedMethodCall: ... never thrown or used
        }
        echo $id;
    }
}

final class Ping {                                     // UnusedClass
    public static function ping(): void { Pong::pong(); }
}

final class Pong {                                     // UnusedClass
    public static function pong(): void { Ping::ping(); }
}

(new Service())->run(1);

--find-unused-psalm-suppress now also checks suppressions on classes and on Tainted* issues.

Type system

• Template defaults: a template can declare a default type, @template T = Default or @template T of Bound = Default, on classes, interfaces, traits, functions and methods. Psalm uses it when the type argument is left out: in @extends/@implements/@use, in a generic type with only its first arguments (Result<int>), in new, and in calls that don't infer the template. Libraries can add a template without breaking every Foo<A> their users wrote, and those users no longer get MissingTemplateParam. See Template defaults.

  <?php
  /**
   * @template TValue
   * @template TError of Throwable = RuntimeException
   */
  final class Result {
      /** @var TError|null */
      public ?Throwable $error = null;
  }
  
  /** @param Result<int> $result */
  function handle(Result $result): void {
      $error = $result->error; // RuntimeException|null (Psalm 6: MissingTemplateParam, Throwable|null)
  }
  
  /** @template T */
  interface Option {
      /**
       * @template TResult = T
       * @param (callable(T): TResult)|null $map
       * @return Option<TResult>
       */
      public function map(?callable $map = null): Option;
  }
  
  /** @param Option<int> $option */
  function check(Option $option): void {
      $same = $option->map(); // Option<int> (Psalm 6: Option<never>)
  }

• New types and syntax: decimal-int-string and non-decimal-int-string, global constant wildcards, conditional types on types that depend on a template, is not in conditional types, and exact intersections of scalar and conditional types.

• Constructor @return types.

• New IntMaskComparison issue for int-masks compared by value.

PHP 8.5 and 8.6

• Psalm runs on PHP 8.6 and has a PHP 8.6 call map.

• The PHP 8.5 pipe operator and PHP 8.6 partial function application are fully typed: Psalm infers the type of every pipeline stage and the signature of every partially applied closure, so a stage that doesn't fit the previous one is reported :

  <?php
  function slug(string $title): string {
      return $title
          |> trim(...)
          |> strtolower(...)
          |> str_replace(' ', '-', ?); // no issue: each stage is typed
  }
  
  function lowercaseWords(string $title): string {
      return $title |> explode(' ', ?) |> strtolower(...); // InvalidArgument: Argument 1 of strtolower expects string, but non-empty-list<string> provided
  }
  
  function wrongLength(string $title): string {
      return $title |> trim(...) |> strlen(...); // InvalidReturnStatement: 'int<0, max>' does not match 'string'
  }

Plugins

• Versioned plugin API: Psalm's version number no longer tracks the plugin API. Breaking changes to the plugin API may ship in any Psalm release, including minor and patch releases. The psalm/psalm-plugin-api metapackage tracks them instead (Introduce psalm plugin API #11739). Its major version is bumped for every breaking change, and its readme lists the changes. Plugins should require it with a caret range (^0.4): Composer will then only install the plugin with a Psalm release whose plugin API it was written for.
• Bundled plugins: Psalm requires psalm/plugin-phpunit, plugin-mockery, plugin-symfony, plugin-laravel and plugin-sabre-event, and enables each one, plus the webmozart/assert plugin, when your composer.json uses the matching library (loadLibraryPlugins, on by default) (Require the psalm/* plugins and enable them, and the webmozart/assert plugin, for the libraries a project uses #12568, Require psalm/plugin-laravel 4.x, the line built for Psalm 7.x #12570, Enable the Laravel plugin when composer.json requires orchestra/testbench #12571).
• Plugin issues can have custom documentation URLs, and respect ERROR_LEVEL ([7.x] Allow plugin issues to specify custom documentation URLs #11735, [7.x] Respect ERROR_LEVEL for plugin-defined issues #11736).

CLI and configuration

• --init-ci generates a GitHub Actions workflow that runs the official Docker image, pinned to the Psalm version in your composer.lock. The docs now cover the Psalm GitHub Action and the Psalm Security Scan action, which sends security analysis results to GitHub code scanning.
• The official Docker image is now ghcr.io/psalm/psalm.
• The old compact output format is renamed table, and a new, truly compact compact format is added.
• <unsuppressibleIssues> makes the issues it lists impossible to suppress.
• Faster startup: less scanning, and single-file scans no longer build the full project file list. Composer's autoloader is no longer deep-scanned.
• More detailed progress output, including for taint graph resolution, and short, actionable CLI messages.

Upgrading

For most projects, upgrading is as simple as updating the Composer dependency:

composer require --dev vimeo/psalm:^7.0 -W

Everything else is in the upgrade guide.

Most projects will notice:

• Taint analysis runs by default. Set runTaintAnalysis="false" to opt out.
• If enabled via <psalm suggestPurityAnnotations="true">, new MissingPureAnnotation/MissingImmutableAnnotation issues appear for code that can be annotated. Fix them with --alter --issues=MissingPureAnnotation,MissingImmutableAnnotation. The annotations Psalm adds improve both security analysis and type inference:
  • Fewer security false positives: Psalm specializes the taints of calls to pure and read-only functions and methods per call site. Tainted input passed at one call then no longer taints the result of every other call. Without annotations, Psalm can only infer this for functions and methods that can't be overridden.
  • Better type inference: Psalm remembers the results of methods of immutable classes between calls, so $a->get() !== null ? $a->get() : '' is a string. Without @psalm-immutable, the second call is still ?string.
  • Checked contracts: pure code can call the annotated functions, and every override and implementation is checked not to do more than the annotation allows.

Thanks

Thanks to everyone who contributed to Psalm 7, and to everyone who tested the betas and release candidates and reported issues!

Full Changelog: 6.20.3...7.0.0

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This discussion was created from the release Psalm 7.