BaseExceptionFilterContext

Kind: Class

Source: packages/core/exceptions/base-exception-filter-context.ts

Part of: Core

BaseExceptionFilterContext resolves exception filter metadata into executable ExceptionFilter instances. It supports both direct filter objects and dependency-injected filter classes, using module context and reflection metadata to locate registered providers.

Extends: ContextCreator

Methods

Properties

Where it refuses work

• BaseExceptionFilterContext stops the work with an early return when isEmpty(metadata).
• BaseExceptionFilterContext stops the work with an early return when isObject.
• BaseExceptionFilterContext stops the work with an early return when !instanceWrapper.
• BaseExceptionFilterContext stops the work with an early return when !this.moduleContext.
• BaseExceptionFilterContext stops the work with an early return when !moduleRef.

Diagram

mermaid
graph LR
  A[Exception filter metadata] --> B[BaseExceptionFilterContext]
  B --> C{Filter is an object?}
  C -->|Yes| D[Use filter instance]
  C -->|No| E[Find InstanceWrapper in module injectables]
  E --> F[Resolve instance for context ID]
  D --> G[Validate catch() method]
  F --> G
  G --> H[Concrete ExceptionFilter instances]

Usage

ts
import {
  ArgumentsHost,
  Catch,
  ExceptionFilter,
} from '@nestjs/common';
import { BaseExceptionFilterContext } from '@nestjs/core/exceptions';

// A filter object can be resolved without looking up a DI provider.
@Catch(Error)
class LogErrorFilter implements ExceptionFilter {
  catch(exception: Error, host: ArgumentsHost) {
    console.error('Request failed:', exception.message);
  }
}

// In framework integration code, `container` is Nest's NestContainer instance.
const filterContext = new BaseExceptionFilterContext(container);

const filters = filterContext.createConcreteContext<
  ExceptionFilter[],
  ExceptionFilter[]
>([new LogErrorFilter()]);

// `filters` contains only valid objects that implement catch().
filters.forEach(filter => filter.catch(new Error('Example'), host));

AI Coding Instructions

• Resolve filter classes through getFilterInstance() so request-scoped and dependency-injected providers use the correct context ID.
• Ensure every resolved filter implements a callable catch() method; invalid or unresolved filters are excluded from the concrete context.
• Set the active module context before resolving class-based filters, since getInstanceByMetatype() searches that module’s injectable providers.
• Use reflectCatchExceptions() to read @Catch() metadata rather than manually inspecting decorator metadata keys.

Relationships

• IMPORTS → FILTER_CATCH_EXCEPTIONS
• IMPORTS → Type
• IMPORTS → ExceptionFilter
• IMPORTS → isEmpty
• IMPORTS → isFunction

Used by

2 references from 2 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (2)

• ExceptionFiltersContext — packages/microservices/context/exception-filters-context.ts:16
• ExceptionFiltersContext — packages/websockets/context/exception-filters-context.ts:10