User ngTemplateOutletContext been modified unexpectedly

[JounQin]

🐞 bug report

Affected Package

The issue is caused by package @angular/core

Is this a regression?

No

Description

User ngTemplateOutletContext is been modified at https://github.com/angular/angular/blob/master/packages/common/src/directives/ng_template_outlet.ts#L104 because the _viewRef.context is pointed at https://github.com/angular/angular/blob/master/packages/core/src/render3/instructions/shared.ts#L137.

🔬 Minimal Reproduction

https://stackblitz.com/edit/angular-ivy-tstyd6?file=src%2Fcomponents%2Fselect.component.ts

🔥 Exception or Error

Click label: option2-5, the top value will change correctly, be then click label: option1 the top value will not change which is incorrect.

This is because the ngTemplateOutletContext is pointed to the first context and always been modified, but when clicking label: option1, the context has been changed to last context content https://github.com/angular/angular/blob/master/packages/common/src/directives/ng_template_outlet.ts#L68.

🌍 Your Environment

Angular Version:

Angular CLI: 11.0.3
Node: 12.20.0
OS: darwin x64

Angular: 11.0.3
... animations, cli, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router
Ivy Workspace: Yes

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.1002.0
@angular-devkit/core         10.2.0
@angular-devkit/schematics   11.0.3
@angular/cdk                 11.0.2
@angular/flex-layout         11.0.0-beta.33
@schematics/angular          11.0.3
@schematics/update           0.1100.3
rxjs                         6.6.3
typescript                   4.1.2

Anything else relevant?

[crisbeto]

Should be fixed by #40360. Also see the PR for more context around why it currently works this way.

[JounQin]

@crisbeto Thanks for your reply. Close in favor of #24515.

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