angular/components

mat-hint not animated when showed for first time on condition

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#9,747 opened on Feb 2, 2018

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P4area: material/form-fieldhelp wanted

Description

Bug, feature request, or proposal:

Maybe a bug, definitely a feature

What is the expected behavior?

When I put a condition on the mat-hint element (for instance, show it only if a character has been typed), the element should be animated and slide in from the input.

What is the current behavior?

At first, the element isn't animated. Until a mat-error is shown, the element won't be animated.

What are the steps to reproduce?

Stackblitz

Contributor guide

Tech stack
angulartypescriptcss
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Angular MaterialCSS animation concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
The issue likely involves the mat hint animation within Angular Material's form field component. Check the components directory under src/material/form field for animation related code. The Stackblitz demo shows that the hint element doesn't animate on initial conditional display. Examine the animation trigger for the hint element and compare with how mat error animates. Look for differences in the Angular animation state transitions.