Unable to use MatStepper with transclusion

[rpd10]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Since there is not currently a responsive stepper, I am attempting to write a component that will switch between a horizontal and vertical stepper depending on the size of the viewport. My idea was that the responsive-stepper would not define any steps inside it. It would use *ngIf to determine which stepper to render, and then use <ng-content> transclusion to allow other components to include the actual steps.

What is the current behavior?

When I attempt to use <mat-step> outside of a stepper, I get an error No provider for MatStepper. I have set up a stackblitz reproduction of the bug, the error is visible in the console.

What are the steps to reproduce?

https://stackblitz.com/edit/angular-dfvcxd

What is the use-case or motivation for changing an existing behavior?

I'm working in an enterprise and I'd like to be able to define a responsive stepper component once, and let others reuse it in a generic fashion. I'm open to other strategies to achieve this.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Material beta 12

Is there anything else we should know?

[julianobrasil]

I have never test it, but you could try, instead of <mat-step>, use a div as a container with the attribute ngProjectAs="mat-step". It will work if mat-stepper expects mat-step to be a select attribute value of an ng-content. I doubt, but take a look at the source code and give it a shot if you think It makes sense.

[EDIT]: It won't work for the reason described above: https://github.com/angular/material2/blob/master/src/lib/stepper/stepper-horizontal.html

[rpd10]

Thanks for the suggestion, I did give it a shot but that didn't work either (as I saw you just commented).

I started down the path of just having 2 steppers inside my component, using ngIf to hide them, and then to avoid duplicating logic, pulling out the content of the mat-steps into separate components - something like this:

<mat-card>
  <mat-card-content>
    <mat-horizontal-stepper linear="true" *ngIf="facade.largeScreen">
      <mat-step label="Verify Account" [stepControl]="verify.group">
        <dash-password-verify #verify></dash-password-verify>
      </mat-step>
      <mat-step label="New Password">
        <dash-password-choose></dash-password-choose>
      </mat-step>
      <mat-step label="Secondary Email">
        <dash-password-email></dash-password-email>
      </mat-step>
    </mat-horizontal-stepper>
        
    <mat-vertical-stepper linear="true" *ngIf="!facade.largeScreen">
      <mat-step label="Verify Account" [stepControl]="verify.group">
        <dash-password-verify></dash-password-verify>
      </mat-step>
      <mat-step label="New Password">
        <dash-password-choose></dash-password-choose>
      </mat-step>
      <mat-step label="Secondary Email">
        <dash-password-email></dash-password-email>
      </mat-step>
    </mat-vertical-stepper>
  </mat-card-content>
</mat-card>

However, I think that will have its own set of issues. When one component is destroyed, I think I'm going to end up losing the user's form state, unless I put in code to manage it separately. The same problems would apply if I were to use fxShow/fxHide from @angular/flex-layout, since there would be two instances of the controls.

It sounds like the only way forward at this time is to have the form/forms contained within a single component, and duplicate the markup for both steppers, which is less than ideal.

[willshowell]

@rpd10 I think this may be possible if MatStepper would use descendants: true on it's ContentChildren query, (there's a lot more discussion on #6625 about a related, but slightly different problem)

https://github.com/angular/material2/blob/0ea43700efb105aa02ad3b1d3f800bf4a9925883/src/lib/stepper/stepper.ts#L69-L75

You may also be able to create your own implementation of MatStepper that adds the correct classes and animations,

https://github.com/angular/material2/blob/0ea43700efb105aa02ad3b1d3f800bf4a9925883/src/lib/stepper/stepper.ts#L103-L127

[tbnovaes]

any updates on this one?

[cmsImagine]

I got around this for now by having an <ng-container>, the <mat-step> then another <ng-container> with an *ngTemplateOutlet pointed at the template which in turn has <ng-content> in it. I feel like there has to be a better way but I haven't found it yet.

[geyuqiu]

@cmsImagine could you please tell us more about your solution (in code)?

[FTello31]

any updates on this one? x2

[chriszrc]

I didn't find a way to transclude the full template, but if you're looking to just transclude everything but the title and the previous/next buttons, then this worked:

<ng-template #matStep1 let-fileInput="fileInput">
  <p>
  My form
  </p>
  <mat-form-field>
    <input matInput placeholder="Upload" [formControl]="fileInput" required autocomplete="off">
    <mat-error *ngIf="fileInput.hasError('required')">
      File is <strong>required</strong>
    </mat-error>
  </mat-form-field>
</ng-template>

<mat-horizontal-stepper #horizontalStepper fxFlex>
     <mat-step [stepControl]="fileInput">
        <ng-template matStepLabel>{{STEP_NAMES.step1}}</ng-template>
        <ng-container *ngTemplateOutlet="matStep1;context:{fileInput: fileInput}">
        </ng-container>
        <button mat-button class="button-back" type="button">Back</button>
        <button mat-flat-button color="accent" matStepperNext type="button" (click)="markAsTouched(fileInput)">Next</button>
     </mat-step>
</mat-horizontal-stepper>

[mmalerba]

This is a limitation of Angular's content projection. angular/angular#37319 has been filed to hopefully improve some of the short-comings

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