externalSchematic('@schematics/update', 'update') doesn't respect order in chain() for migration

🐞 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?

[psmul]

@iKrishnaSahu Appreciate mentioning me to this thread! Sadly we haven’t found another solution, so we decided to do things other way. At least we know we shouldn’t wait for any update in this case.

[klemenoslaj]

Potentially I have the same problem with a custom schematic (not a migration). Please let me know if this should be a separate issue.

---

In my example I have the following code:

return chain([
  externalSchematic('@schematics/angular', 'library', { ...options, lintFix: false }),
  !options.skipTsConfig ? overwriteLibraryTSConfigPaths(options) : noop(),
]);

With overwriteLibraryTSConfigPaths we modify the tsconfig.json paths, but it’s always empty, even tho the library schematic should it’s own paths there already.