Angular and Micro-Frontends

Instead of outright suggesting AGAINST this idea mainly due to separate stack requirements I will lay out the trade offs and provide some restrictions which will make this possible.

the page consists of several components which would be running autonomously

We all know this is offered out of box in Angular components with clear demarcation of inputs and output.

Small CAVEAT: When/If you pass objects for @Input and emit event objects with @Output() interacting components must agree on a defined interface upfront.

Workaround: Create another TypeScript project which just defines these artifacts. All other "component projects" would depend on a specific version of this.

each component is managed by one dev-team

Dev Teams can distribute the components just like other Angular projects in the opensource are doing. They can publish their artifacts to some npm repository. To develop attributable components I recommend you refer to Angular Material2 which may be overwhelming or you may use something like ngx-library-builder (based on Angular Team Member filipesilva/angular-quickstart-lib ) that each component team uses.

CAVEAT: Till this date angular team does not have a quick component library sharing project setup as evident in Angular CLI. But numerous developers have created some sort of library builders to fill the gap in Angular CLI.

each team can change, update and deploy their components without breaking components of other teams

Have your main project pull all the components and perform a periodic/change triggered build/deploy on some CI server. This is essentially producing AOT production builds with all the latest component releases. As an added bonus you can have some abstract e2e tests built to do some automated integration testing ensuring side effects of one component does not break other components.

CAVEAT: It will be difficult to govern how each team develops the components i.e. they are doing optimal usage and disposition of memory, CPU, and other resources. e.g. what if one team starts creating subscriptions and does not remove them. Using some static code analysis can be useful but you will not have this source code available at this time - unless they also publish their source code.

each team chooses its own toolstack

This is a complete deal breaker unless if you mean "toolstack" as in developer tools such as IDEs and some of the "devDependencies". Although certain parts of "devDependencies" of each team must have the same exact versions of angular dev kits such as compilers etc.

At the least each team must use same Angular, RxJS etc.

Most importantly care should be taken that each of the team does not bootstrap any components - only the main projects will have a bootstrap module and that will bootstrap the root component. This will help answer your zone.js issue

Does this work with Angular?

If you recognize the limitations and provide governance I suggest go for it.

We asked ourselves the same question. Unfortunately, it seems that the answer to the question

Is there any solution other than "iframes" to get multiple Angular (5) Apps running on the same Page (edit: where each Angular app can use a different Angular version)?

currently is

No, unfortunately not, as long as you want to use Angular‘s change detection (which uses zone.js).

Due to zone.js Angular pollutes the global scope. Even worse zone.js patches an awful lot of browser APIs (https://github.com/angular/zone.js/blob/master/STANDARD-APIS.md) to detect when a zone is completed.

It’s only possible to use different versions of a framework in one page without side effects if the framework does not touch global scope (this seems to be true for React und Vue). Then you can bundle different framework versions with each application via Webpack (with separated scope and the downside that the size of each application bundle increases).

So, if you want to build a web page with Angular where different applications/modules should be integrated on one page, the only feasible solution currently is to create a deployment monolith (e.g. bundle different modules from different teams in one Angular application by a CI/CD system as bhantol explained in his answer).

It seems that the Angular team is also aware of the problem and that they might tackle it with following major versions. See robwormwald’s answer on the following Github issue regarding the Angular Elements roadmap: https://github.com/angular/angular/issues/20891

Hopefully there will be more information by the Angular team on that topic when the next major version Angular 6 is release at the end of march.

It seems that there has been a solution for your needs for a while now. Take a look at Single-SPA project HERE.

It's a wrapper SPA project for your micro SPA projects.

Take a look at Angular Elements (Custom Elements). https://moduscreate.com/blog/angular-elements-ngcomponents-everywhere/

The new Ionic version (4) is totally based on it to be able to be used on every version of Angular and on every JS frameworks.

For that, they created https://stenciljs.com/ that will help you to create Custom Elements.

But if all teams are using Angular, each of them can create a library using ngm for example.

Yes you can.

However you don't really want to get stuck in a framework when you are writing web components, because the whole point of a web component is to be reused possibly anywhere.

I share your vision, it's definitely better for the quality of the software as well as the productivity of developers to work on focused features rather than large apps when it comes to implementation.

Finally, what you are looking for right now is not Angular, but StencilJS. Stencil is a compiler for web components who also generate a virtual DOM inside your component to improve it's UI performances. Check it out ;-)