ng update --migrateOnly with pnpm doesn't recognize installed packages

[aquark]

🐞 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 (AFAIK)

Description

ng update --migrateOnly checks that the package is installed prior to performing migrations. However it ignores packages installed as symlinks. Since pnpm installs all packages as symlinks, it always (incorrectly) claims the package is not installed.

I am able to work around this issue by modifying findNodeDependencies in node_modules/@angular/cli/utilities/package-tree.js to remove the !child.isLink check.

🔬 Minimal Reproduction

First, create an Angular app with angular.json including "cli": {"packageManager": "pnpm"}, and ensure all packages are installed.

Then run (for example): ./node_modules/.bin/ng update --from 7.1.4 --migrateOnly @angular/common

🔥 Exception or Error

> ./node_modules/.bin/ng update --from 7.1.4 --migrateOnly @angular/common
Using package manager: 'pnpm'
Collecting installed dependencies...
Found 57 dependencies.
Package found in package.json but is not installed.
Exit status: 1

🌍 Your Environment

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/


Angular CLI: 8.2.0
Node: 10.16.0
OS: darwin x64
Angular: 8.2.0
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.802.0
@angular-devkit/build-angular     0.802.0
@angular-devkit/build-optimizer   0.802.0
@angular-devkit/build-webpack     0.802.0
@angular-devkit/core              8.2.0
@angular-devkit/schematics        8.2.0
@angular/cdk                      7.3.7
@angular/material                 7.3.7
@ngtools/webpack                  8.2.0
@schematics/angular               8.2.0
@schematics/update                0.802.0
rxjs                              6.5.2
typescript                        3.5.3
webpack                           4.38.0

Anything else relevant?
Nope.

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