'ng update' does not work with yarn workspaces

先从 packages/angular/cli/commands/update-impl.ts 中约第 123 行链接的 update 命令实现开始，然后使用一个仅在 workspace-a/package.json 中包含 Angular 依赖的 Yarn workspace 重现该失败。验证从 workspace 目录进行依赖解析时的行为；当 ng update 能够找到并更新 workspace 的 Angular 依赖，且不要求它们存在于 root package.json 中时，即表示完成。

🐞 Bug report

Command (mark with an x)

- [ ] new
- [ ] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [X] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Is this a regression?

No

Description

I am utilizing yarn workspaces -feature in my project. Problem is that I have to keep Angular & AngularCLI dependencies on root packages.json, otherwise 'ng update' command can't figure out the version I currently have. I'd rather keep root package.json clean and move Angular & CLI dependencies to project/package.json to keep things isolated.

Looking at the code, update command resolves dependencies from root package, even when command is executed on package folder. Would it be possible to change behavior in a way that update would first check package dependencies and the fall back to root if nothing is found?

🔬 Minimal Reproduction

• init yarn workspace project as follows: https://yarnpkg.com/lang/en/docs/workspaces/
• init angular app with cli and move dependencies from root package.json to workspace-a/package.json (example from previous step)
• wait until new angular version is available
• cd to 'workspace-a' and run 'ng update'. Command fails to find any dependencies to update.

🔥 Exception or Error

N/A

🌍 Your Environment

Angular CLI: 8.0.3
Node: 10.15.3
OS: win32 x64
Angular: 8.0.1
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router, service-worker

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.800.3
@angular-devkit/build-angular     0.800.3
@angular-devkit/build-optimizer   0.800.3
@angular-devkit/build-webpack     0.800.3
@angular-devkit/core              8.0.3
@angular-devkit/schematics        8.0.3
@angular/cli                      8.0.3
@angular/pwa                      0.800.3
@ngtools/webpack                  8.0.3
@schematics/angular               8.0.3
@schematics/update                0.800.3
rxjs                              6.4.0
typescript                        3.4.5
webpack                           4.30.0

Root package.json:

  "dependencies": {},
  "devDependencies": {
    "npm-run-all": "^4.1.5"
  },

'workspace-a/package.json':

"dependencies": {
    "@angular/animations": "~8.0.1",
    "@angular/common": "~8.0.1",
    "@angular/compiler": "~8.0.1",
    "@angular/core": "~8.0.1",
    "@angular/forms": "~8.0.1",
    "@angular/platform-browser": "~8.0.1",
    "@angular/platform-browser-dynamic": "~8.0.1",
    "@angular/pwa": "^0.800.3",
    "@angular/router": "~8.0.1",
    "@angular/service-worker": "~8.0.1",
    "@auth0/angular-jwt": "^2.1.0",
    "@ngx-translate/core": "^11.0.1",
    ...
    "rxjs": "~6.4.0",
    "tslib": "^1.9.0",
    "zone.js": "~0.9.1"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "~0.800.0",
    "@angular/cli": "~8.0.3",
    "@angular/compiler-cli": "~8.0.1",
    "@angular/language-service": "~8.0.1",
    ...
  }

Anything else relevant?