Core

What it is responsible for

Core manages route-oriented execution through RouterExplorer, RouterExecutionContext, and RouterProxy. Its routing vocabulary includes Routes, RouteTree, RouteDefinition, PathsExplorer, RoutePathFactory, RouteParamsFactory, and IRouteParamsFactory; its exception-filter vocabulary includes RouterExceptionFilters and ExceptionsFilter. The subsystem also has REQUEST, REQUEST_CONTEXT_ID, and requestProvider among its named members. For SSE, its documented behavior transforms “messages” to W3C event stream content. Work enters through moduleKey, moduleName, handler, and metatype.

What it refuses

Core refuses the following stated conditions:

• ForbiddenException when !canActivate.
• UnknownRequestMappingException when isUndefined(path).
• InternalServerErrorException when !next.
• “You must return an Observable stream to use Server-Sent Events (SSE).” when !isObservable(value).
• InvalidExceptionFilterException when !Array.isArray(filters).
• InvalidClassScopeException when wrapperRef.scope is Scope.REQUEST or Scope.TRANSIENT, or when !wrapperRef….
• UnknownElementException when !instance.

What it needs, and who needs it

Core depends on Common, Websockets, and Microservices. The named dependent side includes integration, integration/inspector/src/common, sample/01-cats-app/src/common, sample/10-fastify/src/common, sample/19-auth-jwt/src/auth, sample/36-hmr-esm/src/common, integration/graphql-code-first/src/recipes, integration/injector/src/scoped, integration/inspector/src/core, integration/inspector/src/durable, integration/inspector/src/request-chain, and integration/scopes/src/durable. These projects and areas depend on Core itself. Core, in turn, depends on all three: Common, Websockets, and Microservices. Without Core, the listed dependents have an unsatisfied dependency; without those three, Core has unsatisfied dependencies.

Notable members

RouterExplorer carries the route-exploration side indicated by its name and sits alongside PathsExplorer, Routes, and RouteTree. RouterExecutionContext carries the execution-context side, while RouterProxy marks proxy work around that execution. RouterExceptionFilters carries exception-filter work, paired with ExceptionsFilter. RouteParamsFactory and IRouteParamsFactory identify parameter-factory work, and RoutePathFactory identifies path-factory work. RouteDefinition, RoutePathMetadata, ExcludeRouteMetadata, LegacyRouteConverter, and RouterModule show the related route-definition, metadata, conversion, and module surface. RouterProxyCallback names the callback counterpart to the proxy. Resolver, ParamProperties, ROUTES, and targetModulesByContainer extend the explicitly named routing and module-related surface of Core in this subsystem.

284 entities in packages/core. 5 other subsystems depend on it, which makes it the 2nd most depended-upon part of this codebase.

What it is made of

Its 284 entities sit in 157 files under packages/core: 106 classes, 44 functions, 41 interfaces, 29 doc comments and 64 more. messages.ts holds 14 of them — more than any other file here. AbstractHttpAdapter declares 50 methods, the widest surface here.

Where work enters

It publishes 7 HTTP endpoints — 5 GET and 2 ALL. None of them declares a guard.

• moduleKey — packages/core/middleware/container.ts:27
• moduleName — packages/core/middleware/container.ts:68
• handler — packages/core/middleware/middleware-module.ts:94
• metatype — packages/core/middleware/middleware-module.ts:202
• handler — packages/core/middleware/middleware-module.ts:287
• handler — packages/core/middleware/resolver.ts:18

How it refuses and fails

56 of its components record a refusal or a failure handler. 51 of them refuse work outright, under a condition written into the component itself. Their catch blocks handle a failure that already happened in 16 places. Of those 16, 7 log it and continue, 6 let it reach the caller and 3 turn it into a return value.

Boundaries

5 other subsystems depend on this one — Microservices, Platform Express, Platform Fastify, Testing, Websockets. Changing what it exposes changes them.

Those 5 hold 130 edges between them, unevenly: Microservices reaches in across 61 edges, against 2 from Platform Fastify. 473 edges leave it against 130 arriving — it reads more of this repository than this repository reads of it. What they reach is narrower than the folder: 42 of its 284 members carry every inbound edge — RuntimeException (11), NestContainer (9) and ApplicationConfig (8), plus 39 more. Of the 473 it sends out, 471 go to Common — more than to any other.

It depends on Common, Websockets, Microservices, and on nothing else in this repository.

How this code is named

These conventions cover most of the codebase. Learning them is faster than reading an index — each one lets you find any member of its family without looking it up.