{
    "category": "Plugin / Extensibility / IoC",
    "check": {
        "population": "every extension point, plugin, registration and dependency construction site",
        "freshness": "a verdict stands until a plugin, a registration or the composition root changes",
        "refusal": "the dependency rule, plugin contract test or banned-API rule fails a change that hardcodes an extension or hides a dependency",
        "observation": "imports from the core to plugins, construction sites and registry contents, read from source and at startup",
        "evidence": "none: the catalog states this check as a class, so a watched run belongs to each system that adopts it",
        "authority": "the extension contract, which every plugin conforms to while the core names no plugin"
    },
    "records": [
        {
            "id": "plugin-architecture",
            "name": "Plugin Architecture",
            "definition": "A convention of building a small core that discovers and loads plugins through declared extension points.",
            "type": "style",
            "scope": [
                "component",
                "runtime",
                "system"
            ],
            "requires": [
                "Extension Points",
                "Stable Interfaces",
                "Discovery"
            ],
            "reinforces": [
                "OCP",
                "Modularity"
            ],
            "enables": ["Runtime Extensibility"],
            "conflicts_with": ["Hardcoded Extensions"],
            "tensions_with": [
                "Static Analysis",
                "Security"
            ],
            "violated_by": ["lexicon:hardcoded-extensions"],
            "detected_by": [
                "direct plugin imports",
                "central switch for plugins"
            ],
            "measured_by": ["plugin isolation score"],
            "refactored_by": [
                "architecture:extension-points",
                "architecture:registry-pattern"
            ],
            "enforced_by": [
                "plugin contract tests",
                "dependency rules"
            ],
            "severity": "contextual",
            "exemplar": {
                "before": "class FooApp {\n  run() { new FooExport().run(); new BarExport().run(); }\n}",
                "after": "interface FooPlugin { name: string; setup(app: FooApp): void; }\nclass FooApp {\n  constructor(private readonly plugins: readonly FooPlugin[]) {}\n  run() { this.plugins.forEach(plugin => plugin.setup(this)); }\n}",
                "lang": "ts"
            }
        },
        {
            "id": "extension-points",
            "name": "Extension Points",
            "definition": "A mechanism that exposes named hooks or interfaces where new behavior can be added without editing the core.",
            "type": "mechanism",
            "scope": [
                "framework",
                "plugin",
                "module"
            ],
            "requires": [
                "Stable Interfaces",
                "Contracts"
            ],
            "reinforces": [
                "OCP",
                "Plugin Architecture"
            ],
            "enables": ["Third-Party Extension"],
            "conflicts_with": ["Closed Core"],
            "tensions_with": ["API Surface Growth"],
            "violated_by": ["lexicon:closed-core"],
            "detected_by": ["repeated core edits for variants"],
            "measured_by": ["extension coverage"],
            "refactored_by": ["lexicon:extract-interface"],
            "enforced_by": [
                "extension tests",
                "API review"
            ],
            "severity": "recommended",
            "exemplar": {
                "before": "function saveFoo(foo: Foo) {\n  validateFoo(foo);\n  fooStore.save(foo);\n  sendFooEmail(foo);\n}",
                "after": "type FooHooks = { beforeSave: Array<(foo: Foo) => void>; afterSave: Array<(foo: Foo) => void> };\nfunction saveFoo(foo: Foo, hooks: FooHooks) {\n  hooks.beforeSave.forEach(hook => hook(foo));\n  fooStore.save(foo);\n  hooks.afterSave.forEach(hook => hook(foo));\n}",
                "lang": "ts"
            }
        },
        {
            "id": "inversion-of-control",
            "name": "Inversion of Control (IoC)",
            "definition": "A design rule that a framework or composition root owns object creation and control flow, and application code supplies the parts it calls.",
            "type": "principle",
            "scope": [
                "framework",
                "runtime",
                "component"
            ],
            "requires": [
                "Abstraction",
                "Composition Root"
            ],
            "reinforces": [
                "DIP",
                "Dependency Injection"
            ],
            "enables": [
                "Framework Control Flow",
                "Plugins"
            ],
            "conflicts_with": ["Direct Control Ownership"],
            "tensions_with": ["Traceability"],
            "violated_by": ["lexicon:direct-control-ownership"],
            "detected_by": ["scattered object lifecycle construction"],
            "measured_by": ["composition centralization"],
            "refactored_by": [
                "architecture:dependency-injection",
                "lexicon:composition-root"
            ],
            "enforced_by": ["lifecycle rules"],
            "severity": "recommended",
            "exemplar": {
                "before": "class FooJob {\n  run() {\n    const store = new SqlFooStore();\n    return store.save(makeFoo());\n  }\n}",
                "after": "class FooJob {\n  constructor(private readonly make: () => Foo, private readonly store: FooStore) {}\n  run() { return this.store.save(this.make()); }\n}\ncontainer.run(FooJob);",
                "lang": "ts"
            }
        },
        {
            "id": "dependency-injection",
            "distinctFrom": [
                {
                    "id": "architecture:adapter-pattern",
                    "reason": "Dependency injection supplies a dependency from outside, while an adapter makes an incompatible interface fit the one expected."
                },
                {
                    "id": "lexicon:composition-root",
                    "reason": "Dependency injection is passing dependencies in, while the composition root is the one place where they are wired."
                },
                {
                    "id": "architecture:ports-and-adapters-architecture",
                    "reason": "Dependency injection is how one object receives its dependencies, while ports and adapters is how a whole core is isolated from its technologies."
                },
                {
                    "id": "architecture:singleton-pattern",
                    "reason": "Dependency injection passes a dependency in, while a singleton is reached through a global access point."
                }
            ],
            "name": "Dependency Injection",
            "aliases": ["DI"],
            "definition": "A design pattern that passes an object its dependencies from outside, usually through its constructor.",
            "type": "pattern",
            "scope": [
                "class",
                "module",
                "component"
            ],
            "requires": [
                "Abstraction",
                "Composition Root"
            ],
            "reinforces": [
                "DIP",
                "Testability"
            ],
            "enables": [
                "Mocking",
                "Replaceability"
            ],
            "conflicts_with": [
                "Hardcoded Instantiation",
                "Ambient Context"
            ],
            "tensions_with": ["Constructor Complexity"],
            "violated_by": ["lexicon:hardcoded-instantiation"],
            "detected_by": ["direct construction of external dependencies"],
            "measured_by": ["injected dependency ratio"],
            "refactored_by": ["architecture:factory-pattern"],
            "enforced_by": [
                "lint rules",
                "dependency review"
            ],
            "severity": "recommended",
            "exemplar": {
                "before": "class FooService {\n  private readonly clock = new SystemClock();\n  private readonly store = new SqlFooStore();\n}",
                "after": "class FooService {\n  constructor(private readonly clock: Clock, private readonly store: FooStore) {}\n}",
                "lang": "ts"
            }
        },
        {
            "id": "service-registry",
            "distinctFrom": [
                {
                    "id": "architecture:health-checks",
                    "reason": "A service registry resolves a key to a registered service, while health checks report whether an instance is ready to serve."
                }
            ],
            "name": "Service Registry",
            "definition": "A mechanism where services or plugins register under a key and are resolved by that key at runtime.",
            "type": "mechanism",
            "scope": [
                "runtime",
                "service",
                "plugin"
            ],
            "requires": ["Registration Protocol"],
            "reinforces": [
                "Discovery",
                "Runtime Binding"
            ],
            "enables": ["Dynamic Resolution"],
            "conflicts_with": ["Hardcoded Lookup"],
            "tensions_with": ["Registry Availability"],
            "violated_by": ["lexicon:hardcoded-lookup"],
            "detected_by": ["static lookup tables"],
            "measured_by": ["registry coverage"],
            "refactored_by": ["architecture:service-discovery"],
            "enforced_by": [
                "startup checks",
                "health checks"
            ],
            "severity": "contextual",
            "exemplar": {
                "before": "const fooService = new FooService(new SqlFooStore());\nconst barService = new BarService(new SqlBarStore());",
                "after": "const services = new ServiceRegistry();\nservices.register(\"FooStore\", () => new SqlFooStore());\nservices.register(\"FooService\", r => new FooService(r.resolve(\"FooStore\")));",
                "lang": "ts"
            }
        },
        {
            "id": "registry-pattern",
            "distinctFrom": [
                {
                    "id": "architecture:factory-pattern",
                    "reason": "A registry replaces a conditional over kinds with a keyed table, while a factory owns how one object and its defaults are built."
                }
            ],
            "name": "Registry Pattern",
            "definition": "A design pattern that replaces a conditional over kinds with a keyed table that each kind registers itself into.",
            "type": "pattern",
            "scope": [
                "runtime",
                "module",
                "plugin"
            ],
            "requires": ["Keyed Registration"],
            "reinforces": [
                "Discovery",
                "Factory Pattern"
            ],
            "enables": ["Dynamic Lookup"],
            "conflicts_with": ["Direct Reference"],
            "tensions_with": ["Global State"],
            "violated_by": ["lexicon:ungoverned-global-registry"],
            "detected_by": ["mutable global maps without lifecycle"],
            "measured_by": ["registry consistency"],
            "refactored_by": ["lexicon:narrow-type"],
            "enforced_by": ["registry validation"],
            "severity": "contextual",
            "exemplar": {
                "before": "function makeFoo(kind: string) {\n  if (kind === \"foo\") return new Foo1();\n  if (kind === \"bar\") return new Bar();\n  throw new Error(\"unknown kind\");\n}",
                "after": "type FooFactory = () => Foo;\nconst registry = new Map<string, FooFactory>();\nexport const registerFoo = (kind: string, factory: FooFactory) => registry.set(kind, factory);\nexport const makeFoo = (kind: string) => registry.get(kind)?.() ?? fail(`unknown ${kind}`);",
                "lang": "ts"
            }
        },
        {
            "id": "service-locator-pattern",
            "name": "Service Locator Pattern",
            "definition": "A design pattern in which code fetches its dependencies from a global registry at the point of use.",
            "type": "pattern",
            "scope": [
                "runtime",
                "dependency access"
            ],
            "requires": ["Registry"],
            "reinforces": ["Runtime Lookup"],
            "enables": ["Late Resolution"],
            "conflicts_with": [],
            "tensions_with": [
                "Testability",
                "DIP",
                "Explicit Dependencies"
            ],
            "violated_by": ["lexicon:hidden-dependency"],
            "detected_by": ["service locator calls inside domain logic"],
            "measured_by": ["hidden dependency count"],
            "refactored_by": ["architecture:dependency-injection"],
            "enforced_by": ["banned API rules"],
            "severity": "discouraged",
            "exemplar": {
                "before": "class FooController {\n  save(foo: Foo) {\n    const store = serviceLocator.resolve<FooStore>(\"FooStore\");\n    return store.save(foo);\n  }\n}",
                "after": "class FooController {\n  constructor(private readonly store: FooStore) {}\n  save(foo: Foo) { return this.store.save(foo); }\n}",
                "lang": "ts"
            }
        },
        {
            "id": "feature-toggle",
            "name": "Feature Toggle",
            "aliases": ["Feature Flag"],
            "definition": "A mechanism that switches a code path on or off at runtime from externally held flag state, so a release can happen without a deploy.",
            "type": "mechanism",
            "scope": [
                "application",
                "release",
                "runtime"
            ],
            "requires": ["Externalized Flag State"],
            "reinforces": [
                "Continuous Delivery",
                "Runtime Extensibility"
            ],
            "enables": [
                "Decoupled Deploy and Release",
                "Gradual Rollout"
            ],
            "conflicts_with": ["Hardcoded Branch Constant"],
            "tensions_with": ["Flag Debt"],
            "violated_by": ["lexicon:hardcoded-branch-constant"],
            "detected_by": ["compile-time flags requiring redeploy to flip"],
            "measured_by": ["redeploys per behavior change"],
            "refactored_by": [],
            "enforced_by": ["release review"],
            "severity": "contextual",
            "exemplar": {
                "before": "if (NEW_FOO_FLOW_ENABLED) runNewFooFlow();\nelse runOldFooFlow();",
                "after": "if (featureFlags.enabled(\"new-foo-flow\", { user, percentage: 10 })) runNewFooFlow();\nelse runOldFooFlow();",
                "lang": "ts"
            }
        }
    ]
}