As the fall season kicked into full gear, the LoopBack team was busy! We wrapped up items planned for our General Availability (GA) release and published the release on Wednesday, October 10th. On top of that, the team completed a number of stretch goals for the month and focused on helping our users with questions, bugs and feature requests. Moreover, the team also took part in two different conferences to spread the word on LoopBack 4. Read more to find out how it all unfolded.

LoopBack 4 October 2018 Milestone Update


LoopBack 4 GA

To wrap up our LoopBack 4 GA release, we had to finish all the remainder of the priority 1 items planned. This included:

  • Implementation of “belongsTo” relation consisting of:
    • Breaking cyclic dependency in two-way relations.
    • Introduction of type resolvers for property decorators.
    • Refactoring of relation based source files.
  • REST layer improvements such as:
    • using pre-compiled AJV validators to boost performance on resource creation requests.
    • making sure patch and put requests return JSON responses like other verbs.
  • Adding CLI template to render a default home page when scaffolding new applications.

The team went on to finish the checklist for LoopBack 4 GA release. This consisted of updating the status of the framework in all the README files in loopback-next monorepo and docs, updating LTS statuses, and releasing all packages at the new semver-major version of 1.0.0 once those items were completed. You can read more about the GA release in our announcement blog, which details our journey to this major milestone.


Adding the “belongsTo” relation introduced some complexities in our relations design, so we addressed those complexities first to finish its implementation. Before we could actually add “belongsTo” relation, we had to do some preparatory work.

Most importantly, we discovered a problem of cyclic references between models. When a Customer has many Order instances, and an Order belongs to a Customer, then a cyclic reference is created in the source code. For example, to create a Customer repository instance, we need an Order repository instance to allow us to access related orders. At the same time, to create the required Order repository instance, we need a Customer repository instance first, to access the customer each order belongs to.

To solve this problem, we reworked the way relations are configured and replaced direct model reference (e.g. @hasMany(Order)) with a type resolver (e.g. @hasMany(() => Order)). Similarly, repositories are accepting a Getter for obtaining instances of related repositories.

You can find more details about these changes in the following pull requests:

With the foundation changes in place, adding “belongsTo” implementation became relatively straightforward. See the pull request #1794 for details.

With two relations in place, our codebase became a bit convoluted. Most of the relations-related code lived in two files ( relation.decorator.ts and relation.factory.ts) that were huge in size and difficult to navigate around. Adding a new relation had a high risk of merge conflicts because it required updates of these two files.

To address this issue, we have refactored this part of our codebase as follows:

  • Two top-level files relation.types.ts and relation.decorator.ts define interfaces, types and functions shared by all relations.
  • There is one directory for each relation type, this directory contains all implementation bits.
  • Inside each per-relation directory, there are three relevant files (besides the index): a decorator, a repository and a repository/accessor factory.

The test files were not reorganized yet to avoid merge conflicts with the ongoing work on the hasOne relation, but it’s a task we would like to work on in the near future.


In order to provide consistent and smooth user experience when sending requests to your endpoints in LoopBack, we converted the boolean response we send back for PATCH and PUT requests to JSON response with the value. On top of that, we updated paths like PATCH /my-models and GET /my-model/count to give back JSON wrapped responses instead of number of updated instances and count of instances, respectively. Check out Pull Request#1170 for more details.

Moreover, we added the much needed API for serving static assets to the framework. The initial implementation had two major limitations:

  • Static assets could not be served from ‘/’.
  • The static assets api overrode LoopBack’s own underlying router.

Both the issues were resolved in subsequent updates. For more details, see PR#1848.

We also made a major performance improvement (close to 15x improvement in POST requests) by caching schema validators in incoming requests as well in PR#1829.

IBM Cloud Deployment

We have written a deployment guide to show how to create a Cloudant-based LoopBack app locally and deploy it to IBM Cloud using Cloud Foundry. It also shows how to use the Cloudant service provisioned on IBM Cloud in the application. We’ll be posting a blog about this next week with a bit more detail - stay tuned!

The team plans to look into deploying LoopBack 4 application to vendor-neutral deployment targets, such as Kubernetes.

Build Infrastructure

We are actively investigating how to leverage Project References introduced by TypeScript 3.0 in LoopBack monorepository to speed up the build and enable watching mode for the TypeScript compiler.

The spike in pull request #1636 has shown that it’s not possible to have multiple compilation targets (dist8 for Node.js 8.x, dist10 for Node.js 10.x) while using Project References. Considering how few language features are added by Node.js 10.x, we decided to switch back to single compilation target (distribution directory) and always build for ES2017 (Node.js 8.x).

  • In PR#1803, we reworked our build and runtime loaders to always use a single compilation target es2017 and a single output directory dist. With this change in place, we also simplified the build scripts defined in package.json and reworked package-level index.js files to always load code from dist. The project templates used by lb4 were updated accordingly too.

  • In PR#1809, we reworked few more places in our project templates to stop using @loopback/dist-util package.

  • In PR#1810, we have deprecated @loopback/dist-util package and removed any remaining references to it in our code base.

  • Finally, PR#1823 removed @loopback/dist-util from our monorepo.

If your project was created with a pre-1.0 version of our CLI tooling, then please upgrade it to follow the new project layout as scaffolded by the recent versions of our lb4 CLI command.

Stretch Goals

Home Page for LB4 Apps

When users first run a LoopBack 4 application and go to its root / page, they expect to see some sort of home page for it instead of a 404 not found page. Therefore, we decided it is neccessary to have a default home page which shows basic information about the application, and links to resources that developers find handy such as LoopBack’s API Explorer and the OpenAPI specification of the app. This also arised as we developed the E-Commerce example application and have some sort of front end as the home page for it.

We created a controller which renders a self-contained HTML at the base path of LoopBack 4 applications and added a template into our CLI package to include it for newly scaffold applications. Take a look at PR#1763 to see how it was done. In order to enable this feature, we made two enhancements. First, we improved our REST layer to allow controllers to have full control of the response sent back to the client in PR#1760. Second, we created a new booter which exported package.json contents to an application’s metadata, so it can be retrieved later from the application context. For more details, see PR#1764. We also modified our existing examples todo, todo-list, and soap-calculator to include it in PR#1814.

Community Support

During the month of October, we saw lots of user engagement with LoopBack 4 in terms of incoming issues and pull requests. We’d like to thank our users and maintainers for their continued interest and contributions! Our team has also worked on performance improvements, refactoring, and neat features that had pressing needs for our users. Here is a non-exhaustive list of some PRs in this regard:

  • Improving path validation and routing engine with trie in PR#1765.
  • Avoiding multiple array allocation in FilterBuilder in PR#1865.
  • Adding type saftey for query filter and where objects for intelliSense support in PR#1816.
  • Simplifying the code dealing with validation of relation definitions with InvalidRelationError class in PR#1840.
  • Generating schemas for x-ts-type extension in PR#1907.
  • Cleaning up our Todo tutorial in PR#1846.
  • Fixing glob options in CLI module to support Windows paths in PR#1958.
  • Not relying on transitive dependencies from Express in PR#1918.
  • Failing fast in our CLI prompts for invalid values in PR#1856.

LoopBack 3

We had continued focus on MongoDB connector in October for LoopBack 3. We added support for decimal128 type in PR#475 which needed it to support mongodb@3.4 or above. Meanwhile, we had two community PRs, one adding support for insensitive indexes in PR#417, and another changing the url parser used by the connector in PR#462, that introduced breaking changes and also required the connector to drop support for mongodb@3.2 which reached End of Life in September 2018. We made the neccessary changes in our CI infrastructure to accomodate those changes and were able to land all 3 PRs and release a minor and patch update versions for the connector. We continue to work on the connector and will be releasing a major release that includes those breaking changes shortly. Check out Issue#476 for more details.

We’ve also gone through certain LoopBack 3 packages to mark them as being in Active LTS such as loopback-boot, strong-remoting, loopback-workspace, and loopback-swagger.


While all of the above was in progress, our team had a chance to participate in two conferences - Node+JS Interactive held in Vancouver, BC, and CASCON held in Markham, Ontario. In Node+JS Interactive, we held a talk about building NodeJS projects at scale, and a hands-on workshop for getting started with LoopBack 4. Check out our blog on our involvement with Node+JS Interactive for more details and another one answering some FAQs.

The Toronto team also held a talk and poster session at CASCON (Annual International Conference on Computer Science and Software Engineering) 2018 for LoopBack 4 and received People’s Choice Exhibit award for our poster. Check out details here.

Call to Action

LoopBack’s future success depends on you. We appreciate your continuous support and engagement to make LoopBack even better and meaningful for your API creation experience. Please join us and help the project by: