Nestjs Doctor

/nestjs-doctor — NestJS Health Scanner & Fixer

v0.4.32

Scan the NestJS codebase, present a prioritized health report, and offer to fix every issue found.

Step 1: Scan

Run nestjs-doctor and capture the full JSON output:

npx nestjs-doctor $ARGUMENTS --json 2>/dev/null

Step 2: Summarize

Parse the JSON output above. Present a summary:

• Score: value / 100 (label)
• Severity counts: errors, warnings, info
• Project info: name, NestJS version, ORM, file count, module count

Step 3: Report

Group diagnostics by severity (errors first, then warnings, then info). Within each severity, group by category (security > correctness > architecture > performance).

For each group show:

• Rule name and severity
• Message and help text
• Number of occurrences
• Affected file paths (with line numbers)

If there are more than 30 diagnostics, show the top 30 (prioritizing errors and warnings) and ask if the user wants to see the rest.

Step 4: Offer to Fix

Ask the developer what they want to fix:

1. Fix all — apply fixes for every diagnostic
2. Fix by category — fix all issues in a specific category (security, correctness, architecture, performance)
3. Fix specific rules — fix only specific rule violations
4. Review only — no changes, just the report

Step 5: Fix

For each diagnostic to fix:

1. Read the affected file
2. Apply the appropriate fix based on the rule (see Fix Guide below)
3. Explain what was changed and why

Fix Guide by Rule

Security

• no-hardcoded-secrets: Extract the secret value to an environment variable. Import ConfigService, inject it, and use this.configService.get('ENV_VAR_NAME'). Add the env var name to .env.example if it exists.
• no-wildcard-cors: Replace origin: '*' or origin: true with an explicit allowlist array or configService.get('CORS_ORIGINS').split(',').
• no-unsafe-raw-query: Replace template literal interpolation in raw SQL with parameterized queries. Use $1, $2 placeholders (Postgres) or ? (MySQL) and pass values as the second argument.
• no-eval: Remove eval() or new Function(). Replace with safe alternatives: JSON.parse() for JSON, a proper expression parser for dynamic evaluation, or refactor to avoid dynamic code execution entirely.
• no-csrf-disabled: Remove the code that explicitly disables CSRF protection, or add a comment explaining why it's intentionally disabled with a // nestjs-doctor-ignore comment.
• no-dangerous-redirects: Validate redirect URLs against an allowlist of trusted domains. Never pass user input directly to res.redirect().
• no-weak-crypto: Replace createHash('md5') or createHash('sha1') with createHash('sha256') or stronger.
• no-exposed-env-vars: Replace direct process.env.X access with ConfigService. Inject ConfigService and use this.configService.get('X') or this.configService.getOrThrow('X').
• require-validation-pipe: Add a validation pipe. Either add @UsePipes(new ValidationPipe()) to the handler/controller, or use a global validation pipe in main.ts, or add a DTO class with class-validator decorators.
• no-exposed-stack-trace: Remove error.stack from response objects. Log the stack trace server-side with this.logger.error(error.stack) and return a generic error message to the client.
• require-auth-guard: Add @UseGuards(AuthGuard) to the controller class or individual routes. If intentionally public, add a comment explaining why.

Correctness

• no-missing-injectable: Add @Injectable() decorator to the class. Import it from @nestjs/common.
• no-duplicate-routes: Remove or rename the duplicate route. Change the HTTP method or path to make each route unique.
• no-missing-guard-method: Add the canActivate(context: ExecutionContext): boolean | Promise<boolean> | Observable<boolean> method to the guard class. Implement CanActivate interface.
• no-missing-pipe-method: Add the transform(value: any, metadata: ArgumentMetadata) method to the pipe class. Implement PipeTransform interface.
• no-missing-filter-catch: Add the catch(exception: T, host: ArgumentHost) method to the exception filter class. Implement ExceptionFilter interface.
• no-missing-interceptor-method: Add the intercept(context: ExecutionContext, next: CallHandler): Observable<any> method. Implement NestInterceptor interface.
• require-inject-decorator: Add @Inject('TOKEN_NAME') decorator to untyped constructor parameters, or add a proper type annotation.
• prefer-readonly-injection: Add the readonly modifier to constructor-injected parameters: constructor(private readonly myService: MyService).
• require-lifecycle-interface: Add the corresponding interface to the class implements clause. E.g., if using onModuleInit(), add implements OnModuleInit.
• no-empty-handlers: Add implementation to the empty HTTP handler. If it's a placeholder, add a throw new NotImplementedException().
• no-async-without-await: Either add an await expression, remove the async keyword, or if it intentionally returns a Promise, remove async and return the promise directly.
• no-duplicate-module-metadata: Remove duplicate entries from @Module() arrays (providers, controllers, imports, exports).
• no-missing-module-decorator: Add @Module({}) decorator to the class. Import it from @nestjs/common.

Architecture

• no-business-logic-in-controllers: Extract the business logic (loops, complex conditionals, data transforms) into a service method. The controller should only call the service and return the result.
• no-repository-in-controllers: Remove the repository injection from the controller. Create or use an existing service that wraps the repository, and inject that service instead.
• no-orm-in-controllers: Remove PrismaService/EntityManager/DataSource injection from the controller. Create or use an existing service that wraps the ORM operations.
• no-circular-module-deps: Break the circular dependency. Extract shared functionality into a separate module, use forwardRef(() => Module), or restructure the module boundaries.
• no-manual-instantiation: Replace new SomeService() with constructor injection. Add the service to the module's providers and inject it via the constructor.
• no-orm-in-services: Consider introducing a repository layer. Create a repository class that wraps ORM operations, and inject the repository into the service instead of the ORM directly.
• no-god-module: Split the module into smaller, focused feature modules. Group related providers together and create dedicated modules for each feature area.
• no-god-service: Split the service into smaller, focused services. Extract groups of related methods into separate service classes.
• require-feature-modules: Move providers out of AppModule into dedicated feature modules. Create feature modules and register providers there instead.
• prefer-constructor-injection: Replace @Inject() property injection with constructor injection. Move the dependency to a constructor parameter.
• require-module-boundaries: Replace deep imports (import { X } from '../other-module/services/x.service') with imports through the module's public API (barrel file / index.ts).
• prefer-interface-injection: Consider creating an interface/abstract class for the dependency and injecting that instead of the concrete implementation.
• no-barrel-export-internals: Remove repository re-exports from barrel files. Repositories should only be accessible within their own module.

Performance

• no-sync-io: Replace synchronous I/O (readFileSync, writeFileSync, etc.) with async equivalents (readFile, writeFile from fs/promises).
• no-query-in-loop: Replace the N+1 query pattern. Use batch queries, Promise.all(), or eager loading/joins to fetch all related data in a single query.
• no-blocking-constructor: Move async operations and loops out of the constructor into onModuleInit() lifecycle hook. Implement OnModuleInit interface.
• no-dynamic-require: Replace require(variable) with a static import or a switch/map pattern that uses static require() calls.
• no-unused-providers: Remove the unused provider from the module's providers array, or start using it. If it's intended for external consumers, add it to the module's exports.
• no-logging-in-loops: Move logging outside the loop, log a summary after the loop completes, or use conditional logging (e.g., log every Nth iteration).
• no-unnecessary-async: Remove the async keyword since the function contains no await expressions. If it returns a Promise, return it directly without async.
• prefer-pagination: Add pagination parameters (skip/take, limit/offset, or cursor-based) to findMany()/find() calls to avoid loading unbounded result sets.
• no-unused-module-exports: Remove the unused export from the module's exports array, or start importing the module where the exported provider is needed.
• no-orphan-modules: Import this module in another module that needs it, or remove it if it's truly unused. If it's the root module, this can be ignored.

Step 6: Verify

After applying fixes, suggest re-running the scan:

Fixes applied. Run /nestjs-doctor again to verify the score improved.

Source: RoloBits/nestjs-doctor — distributed by TomeVault.