Angular 库 Monorepo：是否可以为每个库使用不同的版本？

Question

just a simple question I can't seem to find an answer for.

I'm trying to build a monorepo which should be able to use angular-cli v8, but still being able to compile and build libraries (mainly components and services) made for v2, v3, v4, etc..

Many things have changed between versions, so let's take an example:

Angular prior to V5 uses @angular/http .

Our current version(8) uses @angular/common/http

I already tried to apply a specific version in the library's package.json, but it doesn't seem to work anyway and, during build time (And even in the IDE), it tells me it can't find @angular/http , as it is deprecated since Angular V5.

Is there any possible way to provide us the functionality we need?

It was not my choice to go for such a monorepo, so please avoid comments about "what a bad pattern.".. I'd just like to know if there's a chance to make it work the way I expect it to.

Answer 1

Sadly, the answer is No.

When working with Angular source code you are tightly coupled to a specific version of Angular. So most projects on GitHub maintain separate working branches in Git for each Angular version.

You have to then install Angular's compiling chain via NPM in the local node_modules and perform builds via npm build so that the correct versions of Angular are used to compile that code, because your global install of Angular CLI will likely be tracking the latest stable release. That means that Angular CLI for 8 can not be used to build a project for Angular 6.

The above applies mainly to Angular Libraries. So if you build a component library for Angular 7, and want to also support Angular 8. You need two branches of that library that build for those versions.

I'm trying to build a monorepo which should be able to use angular-cli v8, but still being able to compile and build libraries (mainly components and services) made for v2, v3, v4, etc..

It doesn't really matter. You can not consume an Angular v2 Library in Angular v8 application. Angular is the peer dependency here. So component libraries do not bundle their own dependency of the framework library. Instead, they are compiled to join the peer dependency used by the owning application. That means, that all your libraries must be compiled with the same Angular version compiled by the application that will use.

NPM will install dependency packages that differ by minor versions. So Angular 8.0.0 libraries will be installed with Angular 8.9.9 applications, but technically it's just good fortune if the library works with that version. You don't know until you've tested it, but NPM will not install the library for a peer of 8.0.0 with a project that is using 9.0.0. The only way to make that happen is to change the peer dependency defined by the component library, but the luck is in compiling it with the application and seeing if it works. Angular has a long history of not being purely API compatible with previous versions (ie the router recently changed in how lazy modules are loaded as an example).

I hope this answers your question. I might have gone a little off topic here.

Answer 2

@Reactgular is right in regards to this not being possible. However the rest is not completely correct. I suggest you build your library with Angular 7. This way it would usually be compatible with Angular 6-8. If you are not using rxjs — then it could even work with Angular 4-5 (Angular 6 moved to rxjs 6 and there were breaking changes). Not a lot of the API has changed so that really depends on what you use from the framework.