angular / angular/components

bug(MatTable): Nested MatTable's rows have no border if I expand last row of parent MatTable

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#28,773 3 comments 1 reaction 0 assignees View on GitHub
area: material/table needs: discussion P5
Dominant language
TypeScript
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Description

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

When I have a nested MatTable set with expand feature, when I expand the last row of the parent table, all the cells in the child MatTable will have no border.
![image](https://github.com/angular/components/assets/65027545/dbbc6ed3-0e3b-46e3-ada7-d45e95e29772)

But If I am expanding any other rows except the last row, the nested MatTable is displaying fine.
![image](https://github.com/angular/components/assets/65027545/7575e8d5-770d-4526-94ba-659906241e6e)

I have found the reason that the styles from last row .mat-cell of the parent MatTable is being applied to all the child MatTable's .mat-cell

![image](https://github.com/angular/components/assets/65027545/1831a5c1-ba1a-4783-b86d-34578ce260b6)

### Reproduction

StackBlitz link: https://stackblitz.com/edit/5djdhn?file=src%2Fexample%2Ftable-expandable-rows-example.ts
Steps to reproduce:
1. Expand the 1st row of the MatTable and check row borders
2. Expand the last row of the MatTable and checkl the absence of row borders of the rows

### Expected Behavior

Only the last row of the nested MatTable will be applied with the `border-bottom: none` styles. not all the rows

### Actual Behavior

Every row inside the last row of MatTable's child MatTable is applied with `border-bottom: none` styles.

### Environment

Angular CLI: 17.0.1
Node: 18.19.0
Package Manager: npm 10.2.3
OS: win32 x64

Angular: 17.0.3
... animations, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package Version
-----------------------------------------------------------
@angular-devkit/architect 0.1700.1
@angular-devkit/build-angular 17.0.1
@angular-devkit/core 17.0.1
@angular-devkit/schematics 17.0.1
@angular/cdk 17.0.1
@angular/cli 17.0.1
@angular/material 17.0.1
@angular/material-luxon-adapter 17.0.1
@schematics/angular 17.0.1
rxjs 7.8.1
typescript 5.2.2
zone.js 0.14.2

Contributor guide

Open the contributing guide

Research direction

Start with the StackBlitz entry point at src/example/table-expandable-rows-example.ts and reproduce the issue by expanding the first row, then the last row. Inspect how the nested MatTable rows receive the parent table's last-row border styling. Done means only the final row of the nested table has border-bottom: none, while the other child rows retain their borders.

Written by the indexing model from the issue text.

Assessment

Tech stack
angular, typescript
Domain
frontend
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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