feat(material-experimental/mdc-form-field): Add option for dynamic su…

…ffix height based on number of hints and errors.

src/dev-app/mdc-input/mdc-input-demo.html

@@ -415,6 +415,71 @@ <h4>Textarea</h4>
   </mat-card-content>
 </mat-card>
 
+<mat-card class="demo-card demo-basic">
+  <mat-toolbar color="primary">Dynamic Suffix Sizing</mat-toolbar>
+  <mat-card-content>
+    <p>
+      One validation
+      <mat-form-field appearance="fill" [color]="color" suffixSizing="dynamic">
+        <mat-label>Fill appearance</mat-label>
+        <input matInput [(ngModel)]="fillAppearance" required>
+        <mat-error>This field is required</mat-error>
+      </mat-form-field>
+    </p>
+
+    <p>
+      One hint and one validation
+      <mat-form-field appearance="fill" [color]="color" suffixSizing="dynamic">
+        <mat-label>Fill appearance</mat-label>
+        <input matInput [(ngModel)]="fillAppearance" required>
+        <mat-error>This field is required</mat-error>
+        <mat-hint>Please type something here</mat-hint>
+      </mat-form-field>
+    </p>
+
+    <p>
+      Multiple errors
+      <mat-form-field appearance="fill" [color]="color" suffixSizing="dynamic">
+        <mat-label>Fill appearance</mat-label>
+        <input matInput [(ngModel)]="fillAppearance" required>
+        <mat-error>AAA</mat-error>
+        <mat-error>BBB</mat-error>
+        <mat-error>CCC</mat-error>
+      </mat-form-field>
+    </p>
+
+    <p>
+      Multiple hints
+      <mat-form-field appearance="fill" [color]="color" suffixSizing="dynamic">
+        <mat-label>Fill appearance</mat-label>
+        <input matInput>
+        <mat-hint>aaa</mat-hint>
+        <mat-hint>bbb</mat-hint>
+        <mat-hint>ccc</mat-hint>
+      </mat-form-field>
+    </p>
+
+    <p>
+      Multiple hints with differing alignment
+      <mat-form-field appearance="fill" [color]="color" suffixSizing="dynamic">
+        <mat-label>Fill appearance</mat-label>
+        <input matInput>
+        <mat-hint>aaa</mat-hint>
+        <mat-hint align="end">bbb</mat-hint>
+        <mat-hint align="end">ccc</mat-hint>
+      </mat-form-field>
+    </p>
+
+    <p>
+      No hints or errors
+      <mat-form-field appearance="fill" [color]="color" suffixSizing="dynamic">
+        <mat-label>Fill appearance</mat-label>
+        <input matInput>
+      </mat-form-field>
+    </p>
+  </mat-card-content>
+</mat-card>
+
 <mat-card class="demo-card demo-basic">
   <mat-toolbar color="primary">Number Inputs</mat-toolbar>
   <mat-card-content>

src/material-experimental/mdc-form-field/form-field.html

@@ -71,7 +71,8 @@
 </div>
 
 <div class="mat-mdc-form-field-subscript-wrapper mat-mdc-form-field-bottom-align"
-     [ngSwitch]="_getDisplayedMessages()">
+     [ngSwitch]="_getDisplayedMessages()"
+     [style.height.px]="_getDynamicSuffixHeight()">
   <div class="mat-mdc-form-field-error-wrapper" *ngSwitchCase="'error'"
        [@transitionMessages]="_subscriptAnimationState">
     <ng-content select="mat-error"></ng-content>

src/material-experimental/mdc-form-field/form-field.ts

@@ -61,6 +61,9 @@ export type FloatLabelType = 'always' | 'auto';
 /** Possible appearance styles for the form field. */
 export type MatFormFieldAppearance = 'fill' | 'outline';
 
+/** Behaviors for how the suffix height is set. */
+export type SuffixSizingBehavior = 'fixed' | 'dynamic';
+
 /**
  * Represents the default options for the form field that can be configured
  * using the `MAT_FORM_FIELD_DEFAULT_OPTIONS` injection token.
@@ -69,6 +72,7 @@ export interface MatFormFieldDefaultOptions {
   appearance?: MatFormFieldAppearance;
   hideRequiredMarker?: boolean;
   floatLabel?: FloatLabelType;
+  suffixSizing?: SuffixSizingBehavior;
 }
 
 /**
@@ -87,6 +91,9 @@ const DEFAULT_APPEARANCE: MatFormFieldAppearance = 'fill';
 /** Default appearance used by the form-field. */
 const DEFAULT_FLOAT_LABEL: FloatLabelType = 'auto';
 
+/** Default way that the suffix element height is set. */
+const DEFAULT_SUFFIX_SIZING: SuffixSizingBehavior = 'fixed';
+
 /**
  * Default transform for docked floating labels in a MDC text-field. This value has been
  * extracted from the MDC text-field styles because we programmatically modify the docked
@@ -100,6 +107,11 @@ const FLOATING_LABEL_DEFAULT_DOCKED_TRANSFORM = `translateY(-50%)`;
  */
 const WRAPPER_HORIZONTAL_PADDING = 16;
 
+/** Height provided for each row of text when using dynamic suffix sizing. */
+const SUFFIX_ROW_HEIGHT = 16;
+/** Space added to dynamic suffix height if rows of text are present. */
+const SUFFIX_ROW_SPACER = 4;
+
 /** Container for form controls that applies Material Design styling and behavior. */
 @Component({
   selector: 'mat-form-field',
@@ -206,6 +218,15 @@ export class MatFormField
   }
   private _appearance: MatFormFieldAppearance = DEFAULT_APPEARANCE;
 
+  @Input()
+  get suffixSizing(): SuffixSizingBehavior {
+    return this._suffixSizing || this._defaults?.suffixSizing || DEFAULT_SUFFIX_SIZING;
+  }
+  set suffixSizing(value: SuffixSizingBehavior) {
+    this._suffixSizing = value || this._defaults?.suffixSizing || DEFAULT_SUFFIX_SIZING;
+  }
+  private _suffixSizing: SuffixSizingBehavior = DEFAULT_SUFFIX_SIZING;
+
   /** Text for the form field hint. */
   @Input()
   get hintLabel(): string {
@@ -604,6 +625,18 @@ export class MatFormField
       : 'hint';
   }
 
+  /** Determines height of suffix when in dynamic suffix sizing mode. */
+  _getDynamicSuffixHeight(): number | null {
+    if (this.suffixSizing !== 'dynamic') return null;
+
+    const numSuffixRows =
+      this._getDisplayedMessages() === 'error'
+        ? this._errorChildren.length
+        : Math.min(this._hintChildren.length, 1);
+
+    return numSuffixRows && numSuffixRows * SUFFIX_ROW_HEIGHT + SUFFIX_ROW_SPACER;
+  }
+
   /** Refreshes the width of the outline-notch, if present. */
   _refreshOutlineNotchWidth() {
     if (!this._hasOutline() || !this._floatingLabel) {