Release/v0.1.0

CHANGELOG.md

@@ -5,6 +5,37 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Planned
+
+* Shared dependency graph compilation and analysis.
+* Unified dependency candidate selection for static validation.
+* Additional validation performance optimizations.
+
+## [[v0.4.0](https://github.com/The-FireHub-Project/Container/compare/v0.3.0...v0.4.0)] – 2026-10-23
+
+### Added
+* Comprehensive static container validation through `Container::validate()` by @dieselxxx
+* Structured validation results with issue types, severity levels, and dependency paths by @dieselxxx
+* Constructor dependency graph validation, including missing dependencies and circular references by @dieselxxx
+* Static validation of union, intersection, and disjunctive normal form (DNF) dependencies by @dieselxxx
+* Tagged service and collection injection validation by @dieselxxx
+* Explicit constructor parameter binding validation by @dieselxxx
+* Contextual binding validation, including implementation compatibility and unused bindings by @dieselxxx
+* Singleton-to-scoped lifetime mismatch detection for direct and transitive dependencies by @dieselxxx
+* Lifetime validation supports for contextual, composite, tagged, collection, and aliased dependencies by @dieselxxx
+* Runtime lifetime protection regression tests by @dieselxxx
+* Shared constructor metadata, dependency plan, and type-matching caches across validation stages by @dieselxxx
+* Canonical service identifier caching for alias resolution by @dieselxxx
+* Expanded PHPUnit coverage for dependency validation and service lifetime behavior by @dieselxxx
+
+### Changed
+* Consolidated constructor metadata analysis across validation components by @dieselxxx
+* Reduced redundant reflection and dependency plan compilation during validation by @dieselxxx
+* Improved consistency between static dependency analysis and runtime dependency resolution by @dieselxxx
+* Optimized alias resolution through shared caching within individual validation operations by @dieselxxx
+
 ## [[v0.3.0](https://github.com/The-FireHub-Project/Container/compare/v0.2.0...v0.3.0)] – 2026-10-22
 
 ### Added

README.md

@@ -12,7 +12,7 @@
   /></a>
   <a href="#">
     <img
-      src="https://img.shields.io/badge/Version-0.3.0-d50000?style=flat&labelColor=30363d&logo=data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAzMzMuNjUxIDM4Ny4wOSI+CiAgICA8dGl0bGU+RmlyZWh1YiBJY29uPC90aXRsZT4KICAgIDxzdHlsZT4KICAgICAgICAuY29sb3Ige2ZpbGw6ICNkNTAwMDA7fQogICAgPC9zdHlsZT4KICAgIDxnPgogICAgICAgIDxwYXRoIGNsYXNzPSJjb2xvciIgZD0iTTI2Ny4xMDYsMjYyLjU2MWMxMC41LTE3LjYzMSwxOS42My0zNi45MzEsMjAuMTItNTcuNDUxYzAuNDktMjAuNTItOS42LTQyLjQxOS0yOC40Ni01MC41MmM1LjcxLDkuNjcsMTAuMjUsMjAuNjIsOS4yOCwzMS44MWMtMC45NywxMS4xOS04Ljg2LDIyLjM3LTIwLDI0Yy0xMC40OSwxLjUyOS0yMC43Ny01Ljg1MS0yNS41MS0xNS4zNGMtNC43NC05LjQ5MS00LjYyLTIwLjU2MS00LTMxLjE1QzIyNC4zOTYsNTYuMTcsMTQyLjA0Niw1Ljk0LDEyNy4yODYsMGMwLDAsMTEuNDksMTIuMzksMTMuODgsMzAuNTNjMS45LDE0LjQ0LDAuMTcsMjkuMjItMy4zNCw0My4yNGMtMTAuODgsNDMuMzUtMzYuODYsNzcuODItNTguNTksMTE2Yy0xNC41OCwyNS41OC0yNCw1NC4wNS0yMy4zMiw4My42OWMwLjc2LDM0LDE2LDY3LjksNDIuNzMsODguODdjMTMuMDUsMTAuMjI5LDI4LjMyLDE3LjY1LDQzLjg0LDIzLjI5Yy0yLjE5LTIuNjItNC44NS01LjYyLTctOC42MDFjLTE4LjY4LTI1LjkzOS0zMi4yNi01MS41LTMzLjE3LTg0LjEwOWMtMC43Ny0yOC4yMyw3LjQtNTMuOTMsMTUuMTQtODAuNjFjLTAuOTEsMy4xNCwxLjgzLDEwLjcsMi4xLDE0LjIxYzAuNDEsNS40LDAuNDYsMTAuODIsMC41LDE2LjIyMWMwLjA4LDExLjQ3LTAuMTQsMjMsMS4zMiwzNC4zNzljMy40MiwyNi43NCwxOC4yOCw0OS43MTEsNDMuMjYsNjEuMjAxYy04LjQ3LTE5LjY5LTkuMzEtMzYuMzAxLTEuMjgtNTYuNzIxYzYuMDUtMTUuMzY5LDE0LjcxLTI5Ljc3OSwxOC45NC00NS43NWM4LjYzLTMyLjU2LTIuNDItNjcuNjQtMjAuNzUtOTUuODljMTcuMzIsMTUuMzEsMzIsMzQuNDUsMzguMyw1Ni43YzcuMzYsMjYsMi44Niw1My41NiwwLDgwLjM5Yy0yLjUxLDIzLjIxLTMuNzEsNDgsNS40Miw3MC4wNWM4LDE5LjIzLDIyLjQsMjkuNTIxLDM5LjUxLDQwYy0zLjY0NC0zLjAxMS02LjU2Ni02LjgtOC41NS0xMS4wOWMtOS4xNi0xOC4zNy02LjczLTQwLjY2LDAuNzktNTkuNzZTMjU2LjYxNiwyODAuMiwyNjcuMTA2LDI2Mi41NjF6Ii8+CiAgICAgICAgPHBhdGggY2xhc3M9ImNvbG9yIiBkPSJNMTczLjEzNiwyMi40M2M1LjA3OCw0Ljk5MSw5Ljg3MiwxMC4yNjIsMTQuMzYsMTUuNzljMS43NzMsMi4xODcsMy40ODMsNC40LDUuMTMsNi42NGM3OS42NzQsMTQuMjQ0LDEzMi43MTYsOTAuMzgsMTE4LjQ3MiwxNzAuMDU0Yy02Ljk0NywzOC44NTctMjkuMjc2LDczLjI3LTYxLjkzMiw5NS40NDZjLTEuNDMsMy0yLjc3LDYtNCw5Yy0yLjUyOCw2LjM3Ny00LjMzLDEzLjAxOS01LjM3LDE5LjhjODIuODQ5LTQwLjMyOSwxMTcuMzE4LTE0MC4xODUsNzYuOTg5LTIyMy4wMzNDMjg5Ljg0OSw2MC43OSwyMzQuNjM1LDI0Ljc3NywxNzMuMTM2LDIyLjQzeiIvPgogICAgICAgIDxwYXRoIGNsYXNzPSJjb2xvciIgZD0iTTQ3LjA0NiwyNzMuNjA5di0wLjA4QzAuNDM1LDIwNy4zNTQsMTYuMjk2LDExNS45MjMsODIuNDcxLDY5LjMxM2MxNS4yNTQtMTAuNzQ0LDMyLjQyLTE4LjQ3Nyw1MC41NzUtMjIuNzgzYzAuMjEyLTQuOTYyLDAuMDA1LTkuOTMzLTAuNjItMTQuODZjLTAuMjUzLTEuODc1LTAuNjI0LTMuNzMxLTEuMTEtNS41NkM0MS4yOTksNDUuNzM4LTE1Ljc2MywxMzQuNjIzLDMuODY1LDIyNC42NGM3LjI4LDMzLjM5LDI0LjY0LDYzLjczOCw0OS43MzEsODYuOTRDNDkuNTU5LDI5OS4zMTQsNDcuMzUyLDI4Ni41Miw0Ny4wNDYsMjczLjYwOXoiLz4KICAgIDwvZz4KPC9zdmc+"
+      src="https://img.shields.io/badge/Version-0.4.0-d50000?style=flat&labelColor=30363d&logo=data:image/svg+xml;base64,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"
       alt="version"  
   /></a>  
   <a href="./LICENSE">
@@ -22,10 +22,6 @@
   /></a>
 </h1>
 
-[![PHPStan](https://github.com/The-FireHub-Project/Container/actions/workflows/PHPStan.yml/badge.svg?branch=develop)](https://github.com/The-FireHub-Project/Container/actions/workflows/PHPStan.yml)
-[![PHPUnit](https://github.com/The-FireHub-Project/Container/actions/workflows/PHPUnit.yml/badge.svg?branch=develop)](https://github.com/The-FireHub-Project/Container/actions/workflows/PHPUnit.yml)
-[![Codecov](https://codecov.io/gh/The-FireHub-Project/Container/branch/develop/graph/badge.svg?token=XW2YEONF51)](https://app.codecov.io/gh/The-FireHub-Project/Container/tree/develop)
-
 <p>
   <a href="https://github.com/The-FireHub-Project/Container">
     <img
@@ -77,47 +73,69 @@ This repository serves as a foundational runtime component for FireHub applicati
 
 ---
 
-## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Development Branch
+## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Repository Purpose
+
+FireHub Container is the dependency injection and service resolution component of the FireHub ecosystem.
+
+Built on the contracts provided by FireHub Core, it supplies the mechanisms required to register, construct, resolve, and manage application services.
+
+The purpose of this repository is to centralize dependency management while preserving separation of concerns between service definitions, runtime implementation, and application execution.
 
-⚠️ **This is the `develop` branch**
+The Container architecture is designed to support:
 
-- Unstable
-- APIs may change without notice
-- Not intended for production use
+- Service registration and dependency resolution
+- Interface-to-implementation bindings
+- Instance, factory, and class-based service definitions
+- Singleton and transient service lifetimes
+- Dependency graph resolution and circular dependency detection
+- Immutable service registrations after container construction
+- Future support for autowiring and execution-scoped services
 
-## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Branch Purpose
+FireHub Container follows the architectural principles of The FireHub Project by separating responsibilities between contracts, dependency management, and application lifecycle orchestration.
 
-The `develop` branch is the **primary integration branch** for all ongoing development.
+The Container does not control application execution or kernel lifecycle transitions. Instead, it provides dependency management services that can be integrated into applications through the appropriate bootstrap and composition mechanisms.
 
-It serves as the staging area where:
-- Feature branches are merged
-- Bug fixes are integrated
-- Experimental work is stabilized
-- Code is prepared for upcoming releases
+## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Security
 
-All **release branches** are created **from `develop`**.
+For security reporting and guidelines, please refer to our [SECURITY.md](https://github.com/The-FireHub-Project/.github/blob/master/.github/SECURITY.md) file.
 
-## Stability Guarantee
+## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Community
 
-❌ No backward compatibility guarantee  
-❌ APIs may change without notice  
-❌ Behavior may be incomplete or inconsistent  
-❌ Breaking changes are expected
+![GitHub watchers](https://img.shields.io/github/watchers/The-FireHub-Project/Container?style=social)
+![GitHub Repo stars](https://img.shields.io/github/stars/The-FireHub-Project/Container?style=social)
+![GitHub forks](https://img.shields.io/github/forks/The-FireHub-Project/Container?style=social)
 
-This branch is intended **only for contributors and advanced testers**.
+- Be sure to review the [Code of Conduct](https://github.com/The-FireHub-Project/.github/blob/master/.github/CODE_OF_CONDUCT.md).
+- Read a [Contributing](https://github.com/The-FireHub-Project/.github/blob/master/.github/CONTRIBUTING.md) file to see how you can contribute to this project.
+- Read our [Security policy](https://github.com/The-FireHub-Project/.github/blob/master/.github/SECURITY.md) file to see how you can report a vulnerability.
+- Review the project [Governance model](https://github.com/The-FireHub-Project/.github/blob/master/.github/GOVERNANCE.md), including roles, decision-making, RFC process, and releases.
 
-## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Composer Usage (Not Recommended)
+## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Support
+
+<p>
+  <a href="https://github.com/The-FireHub-Project/Container/issues?q=is%3Aissue%20state%3Aopen">
+    <img
+      src="https://img.shields.io/github/issues/The-FireHub-Project/Container?style=flat&logo=github&logoColor=959da5&label=in%20progress%20issues&labelColor=31373e"
+      alt="GitHub in-progress issues"
+  /></a>
+  <a href="https://github.com/The-FireHub-Project/Container/issues?q=is%3Aissue">
+    <img
+      src="https://img.shields.io/github/issues-search?query=repo%3AThe-FireHub-Project%Foundaton&style=flat&logo=github&logoColor=959da5&label=total%20issues&labelColor=31373e"
+      alt="GitHub total issues"
+  /></a>
+  <a href="https://github.com/The-FireHub-Project/Container/issues?q=is%3Apr%20is%3Aopen">
+    <img
+      src="https://img.shields.io/github/issues-pr/The-FireHub-Project/Container?style=flat&logo=github&logoColor=959da5&labelColor=31373e"
+      alt="GitHub opened pull requests"
+  /></a>
+</p>
 
-For internal testing only:
+For help with FireHub products, please refer to the following resources:
 
-```json
-{
-  "require": {
-    "the-firehub-project/container": "dev-develop"
-  }
-}
-```
-⚠️ Never use dev-develop in production.
+- **General questions & discussions**: [GitHub Discussions](https://github.com/orgs/The-FireHub-Project/discussions)
+- **Bug reports & issues**: [Support](https://github.com/The-FireHub-Project/Container/issues)
+- **Documentation & guides**: [FireHub Docs](https://the-firehub-project.github.io)
+- **Commercial support** (Pro/Enterprise): contact your account manager
 
 ## <img src="https://raw.githubusercontent.com/The-FireHub-Project/the-firehub-project.github.io/master/resources/graphics/icons/firehub.svg" width="15" alt="FireHub Icon"> Authors and Contributors
 
@@ -134,4 +152,4 @@ Architecture guidelines, design principles, and ecosystem documentation are avai
 
 This software is licensed under the Apache-2.0 License.
 
-For more details, read the full license [here](./LICENSE).
+For more details, read the full license [here](./LICENSE).

src/Container.php

@@ -24,6 +24,7 @@
     ContainerState, ContextualBindingRegistry, DisposalTracker, InstanceStore, ParameterBindingRegistry,
     ResolutionContext, ScopeRegistry, TagRegistry
 };
+use FireHub\Container\Validation\Result;
 use FireHub\Container\Exception\ {
     ContainerActiveScopesException, InvalidTagNameException, ServiceNotFoundException
 };
@@ -1213,4 +1214,33 @@ public function isFrozen ():bool {
 
     }
 
+    /**
+     * ### Validates registered service definitions
+     *
+     * Performs static validation of the container configuration without instantiating services or executing factory
+     * callbacks.
+     *
+     * Validation does not freeze or modify the container.
+     * @since 1.0.0
+     *
+     * @uses \FireHub\Container\Validation::validate() To validate registered service definitions.
+     *
+     * @throws \FireHub\Container\Exception\ServiceInstantiationException If a constructor parameter contains invalid
+     * injection attributes or unsupported dependency metadata.
+     * @throws \FireHub\Container\Exception\AmbiguousDependencyException If multiple candidates are eligible.
+     * @throws \FireHub\Container\Exception\ServiceInstantiationException If the composite type is unsupported.
+     *
+     * @return \FireHub\Container\Validation\Result Container validation result.
+     */
+    public function validate ():Result {
+
+        return new Validator(
+            $this->registry,
+            $this->parameters,
+            $this->contextual,
+            $this->tags
+        )->validate();
+
+    }
+
 }

src/Internal/CanonicalIdCache.php

@@ -0,0 +1,132 @@
+<?php declare(strict_types = 1);
+
+/**
+ * This file is part of the FireHub Project ecosystem
+ *
+ * @author Danijel Galić <danijel.galic@outlook.com>
+ * @copyright 2026-present The FireHub Project - All rights reserved
+ * @license https://opensource.org/license/Apache-2-0 Apache License, Version 2.0
+ *
+ * @php-version >=8.2
+ * @package Container
+ */
+
+namespace FireHub\Container\Internal;
+
+use FireHub\Container\Registry;
+use FireHub\Container\Definition\Alias;
+use FireHub\Runtime;
+
+/**
+ * ### Caches canonical service identifiers
+ *
+ * Resolves registered alias chains to their final service identifiers.
+ *
+ * Successfully resolved identifiers and invalid alias chains are cached for reuse throughout a single container
+ * validation operation.
+ *
+ * Circular and unresolved aliases return null.
+ *
+ * The cache assumes that service registrations remain unchanged during its lifetime.
+ * @since 1.0.0
+ *
+ * @internal
+ */
+final class CanonicalIdCache {
+
+    /**
+     * ### Cached canonical identifiers
+     * @since 1.0.0
+     *
+     * @var array<class-string, null|class-string>
+     */
+    private array $cache = [];
+
+    /**
+     * ### Constructor
+     * @since 1.0.0
+     *
+     * @param \FireHub\Container\Registry $registry <p>
+     * Registered service definitions.
+     * </p>
+     */
+    public function __construct (
+        private readonly Registry $registry
+    ) {}
+
+    /**
+     * ### Gets the canonical service identifier
+     *
+     * Follows alias chains and caches their resolved targets.
+     *
+     * Invalid and circular alias chains are cached as null.
+     * @since 1.0.0
+     *
+     * @uses \FireHub\Container\Registry::find() To retrieve a service definition.
+     * @uses \FireHub\Container\Registry::has() To check if an alias target exists.
+     * @uses \FireHub\Runtime\Arr\Access::keyExists() To check if a key exists in an array.
+     *
+     * @param class-string $id <p>
+     * Service identifier.
+     * </p>
+     *
+     * @return null|class-string Canonical service identifier.
+     */
+    public function get (string $id):?string {
+
+        if (Runtime\Arr\Access::keyExists($this->cache, $id))
+            return $this->cache[$id]; // @phpstan-ignore offsetAccess.notFound
+
+        $visited = []; $path = []; $current = $id;
+        while (true) {
+
+            if (Runtime\Arr\Access::keyExists($this->cache, $id)) { // @phpstan-ignore if.alwaysFalse
+
+                $canonical = $this->cache[$current]; // @phpstan-ignore offsetAccess.notFound
+
+                break;
+
+            }
+
+            if (isset($visited[$current])) {
+
+                $canonical = null;
+
+                break;
+
+            }
+
+            $visited[$current] = true;
+
+            $path[] = $current;
+
+            $definition = $this->registry->find($current);
+
+            if (!$definition instanceof Alias) {
+
+                $canonical = $current;
+
+                break;
+
+            }
+
+            $current = $definition->target;
+
+            if (!$this->registry->has($current)) {
+
+                $canonical = null;
+
+                break;
+
+            }
+
+        }
+
+        foreach ($path as $visited_id)
+            $this->cache[$visited_id] = $canonical;
+
+        return $canonical;
+
+    }
+
+}