Custom Templates

tsoa uses Handlebars templates to generate route files. You can customize these templates to fit your specific needs, add custom logic, or integrate with your framework in unique ways.

Understanding Templates

tsoa generates route files using Handlebars templates that are framework-specific:

Express: express.hbs
Koa: koa.hbs
Hapi: hapi.hbs

These templates receive metadata about your controllers, routes, and models to generate the registration code.

Template Context

The template context includes:

interface TemplateContext {
  controllers: Controller[];      // All controllers
  models: Models;                 // Type definitions
  useSecurity: boolean;           // Whether any route uses auth
  useFileUploads: boolean;        // Whether any route uploads files
  authenticationModule?: string;  // Path to auth module
  iocModule?: string;            // Path to IoC module
  esm: boolean;                  // Using ES modules
  minimalSwaggerConfig: object;  // OpenAPI config subset
  multerOpts?: object;           // Multer configuration
}

interface Controller {
  name: string;                   // Controller class name
  modulePath: string;             // Import path
  actions: Action[];              // Controller methods
}

interface Action {
  name: string;                   // Method name
  method: string;                 // HTTP method (get, post, etc.)
  fullPath: string;               // Complete route path
  parameters: Record<string, ParameterSchema>;
  security: Security[];           // Auth requirements
  successStatus: number;          // Success status code
  uploadFile: boolean;           // Has file upload
  uploadFileName: UploadField[]; // File field details
}

Creating Custom Templates

Create Template Directory

Create a directory for your custom templates:

mkdir -p templates

Copy Base Template

Copy the default template as a starting point:

# For Express
cp node_modules/tsoa/dist/routeGeneration/templates/express.hbs templates/

# For Koa
cp node_modules/tsoa/dist/routeGeneration/templates/koa.hbs templates/

# For Hapi
cp node_modules/tsoa/dist/routeGeneration/templates/hapi.hbs templates/

Configure tsoa

Point tsoa to your custom template:

tsoa.json

{
  "routes": {
    "routesDir": "src",
    "middleware": "express",
    "routesFileName": "routes.ts",
    "template": "templates/express.hbs"
  }
}

Customize Template

Modify the template to add your custom logic.

Common Customizations

Add Custom Imports

Add your own imports at the top:

/* tslint:disable */
/* eslint-disable */
// WARNING: This file was auto-generated with tsoa.
import type { TsoaRoute } from '@tsoa/runtime';
import { fetchMiddlewares, ExpressTemplateService } from '@tsoa/runtime';

// Custom imports
import { logger } from './utils/logger';
import { metrics } from './utils/metrics';
import { CustomError } from './errors';

{{#each controllers}}
import { {{name}} } from '{{modulePath}}';
{{/each}}

Add Request Logging

Log every request:

{{#each controllers}}
{{#each actions}}
    app.{{method}}('{{fullPath}}',
        {{#if security.length}}
        authenticateMiddleware({{json security}}),
        {{/if}}
        ...(fetchMiddlewares<RequestHandler>({{../name}})),
        ...(fetchMiddlewares<RequestHandler>({{../name}}.prototype.{{name}})),

        async function {{../name}}_{{name}}(request: ExRequest, response: ExResponse, next: any) {
            // Custom logging
            logger.info('Request', {
                controller: '{{../name}}',
                action: '{{name}}',
                method: '{{method}}',
                path: '{{fullPath}}',
                ip: request.ip
            });

            const startTime = Date.now();
            
            try {
                // ... existing validation and controller logic ...
                
                // Log success
                const duration = Date.now() - startTime;
                metrics.recordRequest('{{../name}}_{{name}}', duration, 'success');
            } catch (err) {
                const duration = Date.now() - startTime;
                metrics.recordRequest('{{../name}}_{{name}}', duration, 'error');
                return next(err);
            }
        });
{{/each}}
{{/each}}

Add Rate Limiting

Apply rate limiting to specific routes:

import rateLimit from 'express-rate-limit';

const rateLimiter = rateLimit({
    windowMs: 15 * 60 * 1000, // 15 minutes
    max: 100
});

{{#each controllers}}
{{#each actions}}
    app.{{method}}('{{fullPath}}',
        // Add rate limiting to POST/PUT/DELETE
        {{#if (or (eq method 'post') (eq method 'put') (eq method 'delete'))}}
        rateLimiter,
        {{/if}}
        // ... rest of middleware ...
    );
{{/each}}
{{/each}}

Custom Error Handling

Add custom error handling logic:

async function {{../name}}_{{name}}(request: ExRequest, response: ExResponse, next: any) {
    let validatedArgs: any[] = [];
    try {
        validatedArgs = templateService.getValidatedArgs({
            args: args{{../name}}_{{name}},
            request,
            response
        });

        const controller = new {{../name}}();
        const result = await templateService.apiHandler({
            methodName: '{{name}}',
            controller,
            response,
            next,
            validatedArgs,
            successStatus: {{successStatus}},
        });
        
        return result;
    } catch (err) {
        // Custom error transformation
        if (err instanceof CustomError) {
            const status = err.statusCode || 500;
            return response.status(status).json({
                error: err.message,
                code: err.code,
                timestamp: new Date().toISOString()
            });
        }
        return next(err);
    }
}

Add Request Tracing

Add distributed tracing:

import { trace } from './utils/tracing';

async function {{../name}}_{{name}}(request: ExRequest, response: ExResponse, next: any) {
    const span = trace.startSpan('{{../name}}.{{name}}', {
        attributes: {
            'http.method': '{{method}}',
            'http.route': '{{fullPath}}',
            'http.user_agent': request.headers['user-agent']
        }
    });

    try {
        // ... existing logic ...
        span.setStatus({ code: 0 }); // Success
    } catch (err) {
        span.setStatus({ code: 2, message: err.message }); // Error
        throw err;
    } finally {
        span.end();
    }
}

Handlebars Helpers

Add custom Handlebars helpers for complex logic:

helpers.js

const Handlebars = require('handlebars');

// Check if method is POST, PUT, or DELETE
Handlebars.registerHelper('isMutation', function(method) {
    return ['post', 'put', 'delete', 'patch'].includes(method.toLowerCase());
});

// Check if route needs authentication
Handlebars.registerHelper('needsAuth', function(security) {
    return security && security.length > 0;
});

// Convert path to regex pattern
Handlebars.registerHelper('toRegex', function(path) {
    return path.replace(/{([^}]+)}/g, ':$1');
});

// Uppercase first letter
Handlebars.registerHelper('capitalize', function(str) {
    return str.charAt(0).toUpperCase() + str.slice(1);
});

Use in template:

{{#if (isMutation method)}}
    // This is a mutation operation
    validateCSRF(request);
{{/if}}

{{#if (needsAuth security)}}
    // This route needs authentication
{{/if}}

Framework-Specific Customizations

Express: Add CORS Headers

app.{{method}}('{{fullPath}}',
    (req, res, next) => {
        res.header('Access-Control-Allow-Origin', '*');
        res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE');
        next();
    },
    // ... rest of middleware ...
);

Koa: Add Response Time

router.{{method}}('{{fullPath}}',
    async (context: Context, next: Next) => {
        const start = Date.now();
        await next();
        const ms = Date.now() - start;
        context.set('X-Response-Time', `${ms}ms`);
    },
    // ... rest of middleware ...
);

Hapi: Add Custom Validation

server.route({
    method: '{{method}}',
    path: '{{fullPath}}',
    options: {
        pre: [
            // Custom pre-handler
            {
                method: async (request, h) => {
                    // Custom validation logic
                    return h.continue;
                }
            },
            // ... existing pre-handlers ...
        ],
        handler: {{#if ../../iocModule}}async {{/if}}function {{../name}}_{{name}}(request: Request, h: ResponseToolkit) {
            // ... handler logic ...
        }
    }
});

Advanced Patterns

Conditional Middleware

Apply middleware based on route metadata:

{{#each controllers}}
{{#each actions}}
    const middlewares_{{../name}}_{{name}} = [
        {{#if security.length}}
        authenticateMiddleware({{json security}}),
        {{/if}}
        {{#if (contains ../name "Admin")}}
        adminOnlyMiddleware,
        {{/if}}
        {{#if uploadFile}}
        upload.fields([{{#each uploadFileName}}{name: '{{name}}'}{{#unless @last}},{{/unless}}{{/each}}]),
        {{/if}}
        ...fetchMiddlewares<RequestHandler>({{../name}}),
        ...fetchMiddlewares<RequestHandler>({{../name}}.prototype.{{name}})
    ];
    
    app.{{method}}('{{fullPath}}', ...middlewares_{{../name}}_{{name}}, handler_{{../name}}_{{name}});
{{/each}}
{{/each}}

Route Versioning

const API_VERSION = process.env.API_VERSION || 'v1';

{{#each controllers}}
{{#each actions}}
    app.{{method}}(`/api/${API_VERSION}{{fullPath}}`,
        // ... middleware and handler ...
    );
{{/each}}
{{/each}}

Generate Route Documentation

// Auto-generated route documentation
export const routes = [
    {{#each controllers}}
    {{#each actions}}
    {
        controller: '{{../name}}',
        method: '{{name}}',
        httpMethod: '{{method}}',
        path: '{{fullPath}}',
        authenticated: {{#if security.length}}true{{else}}false{{/if}},
        fileUpload: {{uploadFile}},
        description: '{{description}}'
    },
    {{/each}}
    {{/each}}
];

Testing Custom Templates

Validate Generated Code

# Generate routes
npm run tsoa routes

# Check for TypeScript errors
tsc --noEmit

# Run tests
npm test

Template Debugging

Add debug output to see template context:

{{!-- Debug: Output all controllers --}}
{{log controllers}}

{{!-- Debug: Check a specific value --}}
{{#if useSecurity}}
    {{log "Security is enabled"}}
{{/if}}

Best Practices

Keep Changes Minimal

Only customize what’s necessary. The default templates are well-tested and maintained.

Version Control Templates

Keep your custom templates in version control and document changes.

Test Thoroughly

Test all route scenarios after template changes: authentication, file uploads, validation, etc.

Stay Compatible

When upgrading tsoa, check if template structure has changed and update your customizations.

Use Comments

Document why you made specific customizations in template comments.

Troubleshooting

Template Syntax Errors

If routes generation fails:

Check Handlebars syntax
Verify all {{#if}} blocks are closed with {{/if}}
Ensure {{#each}} loops are closed with {{/each}}
Validate JSON output with {{json value}}

TypeScript Errors

If generated code has TypeScript errors:

Check imports are correct
Verify type annotations
Ensure proper indentation
Test with a simple route first

Runtime Errors

If routes fail at runtime:

Verify middleware order
Check async/await usage
Validate error handling
Test with curl or Postman

Examples

Complete Custom Express Template

A minimal custom template:

templates/express.hbs

/* tslint:disable */
/* eslint-disable */
import type { RequestHandler, Router } from 'express';
import { ExpressTemplateService } from '@tsoa/runtime';
{{#each controllers}}
import { {{name}} } from '{{modulePath}}';
{{/each}}

const models: any = {{{json models}}};
const templateService = new ExpressTemplateService(models, {{{json minimalSwaggerConfig}}});

export function RegisterRoutes(app: Router) {
    {{#each controllers}}
    {{#each actions}}
    app.{{method}}('{{fullPath}}', async (req, res, next) => {
        try {
            const args = templateService.getValidatedArgs({
                args: {{{json parameters}}},
                request: req,
                response: res
            });
            
            const controller = new {{../name}}();
            const result = await (controller as any).{{name}}(...Object.values(args));
            
            res.status({{successStatus}}).json(result);
        } catch (err) {
            next(err);
        }
    });
    {{/each}}
    {{/each}}
}

Custom Templates

Understanding Templates

Template Context

Creating Custom Templates

Common Customizations

Add Custom Imports

Add Request Logging

Add Rate Limiting

Custom Error Handling

Add Request Tracing

Handlebars Helpers

Framework-Specific Customizations

Express: Add CORS Headers

Koa: Add Response Time

Hapi: Add Custom Validation

Advanced Patterns

Conditional Middleware

Route Versioning

Generate Route Documentation

Testing Custom Templates

Validate Generated Code

Template Debugging

Best Practices

Troubleshooting

Template Syntax Errors

TypeScript Errors

Runtime Errors

Examples

Complete Custom Express Template

Next Steps

OpenAPI Versions

Advanced Configuration

Documentation Index

​Understanding Templates

​Template Context

​Creating Custom Templates

​Common Customizations

​Add Custom Imports

​Add Request Logging

​Add Rate Limiting

​Custom Error Handling

​Add Request Tracing

​Handlebars Helpers

​Framework-Specific Customizations

​Express: Add CORS Headers

​Koa: Add Response Time

​Hapi: Add Custom Validation

​Advanced Patterns

​Conditional Middleware

​Route Versioning

​Generate Route Documentation

​Testing Custom Templates

​Validate Generated Code

​Template Debugging

​Best Practices

​Troubleshooting

​Template Syntax Errors

​TypeScript Errors

​Runtime Errors

​Examples

​Complete Custom Express Template

​Next Steps

OpenAPI Versions

Advanced Configuration

Understanding Templates

Template Context

Creating Custom Templates

Common Customizations

Add Custom Imports

Add Request Logging

Add Rate Limiting

Custom Error Handling

Add Request Tracing

Handlebars Helpers

Framework-Specific Customizations

Express: Add CORS Headers

Koa: Add Response Time

Hapi: Add Custom Validation

Advanced Patterns

Conditional Middleware

Route Versioning

Generate Route Documentation

Testing Custom Templates

Validate Generated Code

Template Debugging

Best Practices

Troubleshooting

Template Syntax Errors

TypeScript Errors

Runtime Errors

Examples

Complete Custom Express Template

Next Steps