🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update (schematics)
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Only tested with ^0.900.0

Description

For given snippet:

export function migrate(): Rule {
  return chain([
    externalSchematic('@schematics/update', 'update', {
      packages: ['@nguniversal/express-engine'],
      from: '8.0.0',
      to: '9.0.0',
    }),
    removeImportsInMainServerFile(),
  ]);
}

Both functions are invoked almost immediately, as provided in the screenshot below. If I understand correctly, chain() method containing externalSchematics with @schematics/update should respect the order and finish migration and then invoke another function in order. Tried approach with translating tree to observable in the second function, however, the outcome is the same. Looks like @schematics/update performs this asynchronously, causing the next functions to be invoked immediately. I haven't noticed this behavior for other migrations or schematics from Angular collections (like creating an app, component, service etc.).

🔬 Minimal Reproduction

Create simple migration containing externalSchematic('@schematics/update', 'update') for any given library.

🔥 Exception or Error

The red highlighted area is separate function that should be invoked after @schematics/update for the library has been completed.

🌍 Your Environment

Angular CLI: 9.0.7
Node: 10.16.0
OS: win32 x64

Angular: 9.0.7
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, localize, platform-browser
... platform-browser-dynamic, platform-server, router
... service-worker
Ivy Workspace: Yes

Package                            Version
------------------------------------------------------------
@angular-devkit/architect          0.900.7
@angular-devkit/build-angular      0.900.7
@angular-devkit/build-ng-packagr   0.900.7
@angular-devkit/build-optimizer    0.900.7
@angular-devkit/build-webpack      0.900.7
@angular-devkit/core               9.0.7
@angular-devkit/schematics         9.0.7
@ngtools/webpack                   9.0.7
@nguniversal/builders              9.0.2
@nguniversal/common                9.0.2
@nguniversal/express-engine        9.0.2
@schematics/angular                9.0.7
@schematics/update                 0.900.7
ng-packagr                         9.0.3
rxjs                               6.5.4
typescript                         3.7.5
webpack                            4.41.2

Anything else relevant?