Method ErrorHandler

app.go:1550–1585

ErrorHandler is the application's method in charge of finding the appropriate handler for the given request. It searches any mounted sub fibers by their prefixes and if it finds a match, it uses that error handler. Otherwise, it uses the configured error handler for the app, which if not set is the

(ctx Ctx, err error)

// error handler. Otherwise, it uses the configured error handler for
// the app, which if not set is the DefaultErrorHandler.
func (app *App) ErrorHandler(ctx Ctx, err error) error {
	// Fast path: no mounted sub-apps, so no prefix lookup is needed
	if len(app.mountFields.appListKeys) == 0 {
		return app.config.ErrorHandler(ctx, err)
	}

	var (
		mountedErrHandler  ErrorHandler
		mountedPrefixParts int
	)

	normalizedPath := utils.AddTrailingSlashString(ctx.Path())

	for _, prefix := range app.mountFields.appListKeys {
		subApp := app.mountFields.appList[prefix]
		normalizedPrefix := utils.AddTrailingSlashString(prefix)

		if prefix != "" && strings.HasPrefix(normalizedPath, normalizedPrefix) {
			// Count slashes instead of splitting - more efficient
			parts := strings.Count(prefix, "/") + 1
			if mountedPrefixParts <= parts {
				if subApp.configured.ErrorHandler != nil {
					mountedErrHandler = subApp.config.ErrorHandler
				}

				mountedPrefixParts = parts
			}
		}
	}

	if mountedErrHandler != nil {
		return mountedErrHandler(ctx, err)
	}

	return app.config.ErrorHandler(ctx, err)
}

// serverErrorHandler is a wrapper around the application's error handler method
// user for the fasthttp server configuration. It maps a set of fasthttp errors to fiber