fix(material-experimental/mdc-form-field): fix prefix/suffix padding

src/material-experimental/mdc-form-field/_form-field-sizing.scss

@@ -36,3 +36,11 @@ $mat-form-field-with-label-input-padding-bottom: 8px;
 // same reasoning applies to the padding for text fields without label.
 $mat-form-field-no-label-padding-bottom: 16px;
 $mat-form-field-no-label-padding-top: 16px;
+
+// The amount of padding between the icon prefix/suffix and the infix.
+// This assumes that the icon will be a 24px square with 12px padding.
+$mat-form-field-icon-prefix-infix-padding: 4px;
+
+// The amount of padding between the end of the form-field and the infix for a form-field with no
+// icons.
+$mat-form-field-end-padding: 16px;

src/material-experimental/mdc-form-field/_mdc-text-field-structure-overrides.scss

@@ -40,6 +40,31 @@
     flex: auto;
   }
 
+  // The icon prefix/suffix is closer to the edge of the form-field than the infix is in a
+  // form-field with no prefix/suffix. Therefore the standard padding has to be removed when showing
+  // an icon prefix or suffix. We can't rely on MDC's styles for this because we use a different
+  // structure for our form-field in order to support arbitrary height input elements.
+  .mat-mdc-form-field-has-icon-prefix .mat-mdc-text-field-wrapper {
+    padding-left: 0;
+  }
+  .mat-mdc-form-field-has-icon-suffix .mat-mdc-text-field-wrapper {
+    padding-right: 0;
+  }
+  [dir='rtl'] {
+    // Undo the above padding removals which only apply in LTR languages.
+    .mat-mdc-text-field-wrapper {
+      padding-left: form-field-sizing.$mat-form-field-end-padding;
+      padding-right: form-field-sizing.$mat-form-field-end-padding;
+    }
+    // ...and apply the correct padding resets for RTL languages.
+    .mat-mdc-form-field-has-icon-suffix .mat-mdc-text-field-wrapper {
+      padding-left: 0;
+    }
+    .mat-mdc-form-field-has-icon-prefix .mat-mdc-text-field-wrapper {
+      padding-right: 0;
+    }
+  }
+
   // The default MDC text-field implementation does not support labels which always float.
   // MDC only renders the placeholder if the input is focused. We extend this to show the
   // placeholder if the form-field label is set to always float.

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

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Directive, InjectionToken} from '@angular/core';
+import {Directive, ElementRef, InjectionToken} from '@angular/core';
 
 /**
  * Injection token that can be used to reference instances of `MatPrefix`. It serves as
@@ -20,4 +20,10 @@ export const MAT_PREFIX = new InjectionToken<MatPrefix>('MatPrefix');
   selector: '[matPrefix], [matIconPrefix], [matTextPrefix]',
   providers: [{provide: MAT_PREFIX, useExisting: MatPrefix}],
 })
-export class MatPrefix {}
+export class MatPrefix {
+  _isText = false;
+
+  constructor(elementRef: ElementRef) {
+    this._isText = elementRef.nativeElement.hasAttribute('matTextPrefix');
+  }
+}

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

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Directive, InjectionToken} from '@angular/core';
+import {Directive, ElementRef, InjectionToken} from '@angular/core';
 
 /**
  * Injection token that can be used to reference instances of `MatSuffix`. It serves as
@@ -20,4 +20,10 @@ export const MAT_SUFFIX = new InjectionToken<MatSuffix>('MatSuffix');
   selector: '[matSuffix], [matIconSuffix], [matTextSuffix]',
   providers: [{provide: MAT_SUFFIX, useExisting: MatSuffix}],
 })
-export class MatSuffix {}
+export class MatSuffix {
+  _isText = false;
+
+  constructor(elementRef: ElementRef) {
+    this._isText = elementRef.nativeElement.hasAttribute('matTextSuffix');
+  }
+}

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

@@ -44,10 +44,10 @@
       </ng-template>
     </div>
 
-    <div class="mat-mdc-form-field-icon-prefix" *ngIf="_prefixChildren.length" #iconPrefixContainer>
+    <div class="mat-mdc-form-field-icon-prefix" *ngIf="_hasIconPrefix" #iconPrefixContainer>
       <ng-content select="[matPrefix], [matIconPrefix]"></ng-content>
     </div>
-    <div class="mat-mdc-form-field-text-prefix" *ngIf="_prefixChildren.length" #textPrefixContainer>
+    <div class="mat-mdc-form-field-text-prefix" *ngIf="_hasTextPrefix" #textPrefixContainer>
       <ng-content select="[matTextPrefix]"></ng-content>
     </div>
 
@@ -59,10 +59,10 @@
       <ng-content></ng-content>
     </div>
 
-    <div class="mat-mdc-form-field-text-suffix" *ngIf="_suffixChildren.length">
+    <div class="mat-mdc-form-field-text-suffix" *ngIf="_hasTextSuffix">
       <ng-content select="[matTextSuffix]"></ng-content>
     </div>
-    <div class="mat-mdc-form-field-icon-suffix" *ngIf="_suffixChildren.length">
+    <div class="mat-mdc-form-field-icon-suffix" *ngIf="_hasIconSuffix">
       <ng-content select="[matSuffix], [matIconSuffix]"></ng-content>
     </div>
   </div>

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

@@ -7,7 +7,6 @@
 @use '../mdc-helpers/mdc-helpers';
 @import '@material/textfield/mixins.import';
 
-
 // Base styles for MDC text-field, notched-outline, floating label and line-ripple.
 @include mdc-text-field-without-ripple(
   $query: mdc-helpers.$mat-base-styles-without-animation-query);
@@ -52,9 +51,32 @@
   width: 100%;
 }
 
+// Vertically center icons.
 .mat-mdc-form-field-icon-prefix,
 .mat-mdc-form-field-icon-suffix {
   align-self: center;
+  // The line-height can cause the prefix/suffix container to be taller than the actual icons,
+  // breaking the vertical centering. To prevent this we set the line-height to 0.
+  line-height: 0;
+}
+
+// The prefix/suffix needs a little extra padding between the icon and the infix. Because we need to
+// support arbitrary height input elements, we use a different DOM structure for prefix and suffix
+// icons, and therefore can't rely on MDC for these styles.
+.mat-mdc-form-field-icon-prefix,
+[dir='rtl'] .mat-mdc-form-field-icon-suffix {
+  padding: 0 form-field-sizing.$mat-form-field-icon-prefix-infix-padding 0 0;
+}
+.mat-mdc-form-field-icon-suffix,
+[dir='rtl'] .mat-mdc-form-field-icon-prefix {
+  padding: 0 0 0 form-field-sizing.$mat-form-field-icon-prefix-infix-padding;
+}
+
+.mat-mdc-form-field-icon-prefix,
+.mat-mdc-form-field-icon-suffix {
+  & > .mat-icon {
+    padding: 12px;
+  }
 }
 
 // Infix that contains the projected content (usually an input or a textarea). We ensure

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

@@ -102,6 +102,8 @@ const FLOATING_LABEL_DEFAULT_DOCKED_TRANSFORM = `translateY(-50%)`;
   host: {
     'class': 'mat-mdc-form-field',
     '[class.mat-mdc-form-field-label-always-float]': '_shouldAlwaysFloat()',
+    '[class.mat-mdc-form-field-has-icon-prefix]': '_hasIconPrefix',
+    '[class.mat-mdc-form-field-has-icon-suffix]': '_hasIconSuffix',
 
     // Note that these classes reuse the same names as the non-MDC version, because they can be
     // considered a public API since custom form controls may use them to style themselves.
@@ -197,6 +199,11 @@ export class MatFormField implements AfterViewInit, OnDestroy, AfterContentCheck
   }
   private _hintLabel = '';
 
+  _hasIconPrefix = false;
+  _hasTextPrefix = false;
+  _hasIconSuffix = false;
+  _hasTextSuffix = false;
+
   // Unique id for the internal form field label.
   readonly _labelId = `mat-mdc-form-field-label-${nextUniqueId++}`;
 
@@ -438,13 +445,24 @@ export class MatFormField implements AfterViewInit, OnDestroy, AfterContentCheck
     }
   }
 
+  private _checkPrefixAndSuffixTypes() {
+    this._hasIconPrefix = !!this._prefixChildren.find(p => !p._isText);
+    this._hasTextPrefix = !!this._prefixChildren.find(p => p._isText);
+    this._hasIconSuffix = !!this._suffixChildren.find(s => !s._isText);
+    this._hasTextSuffix = !!this._suffixChildren.find(s => s._isText);
+  }
+
   /** Initializes the prefix and suffix containers. */
   private _initializePrefixAndSuffix() {
+    this._checkPrefixAndSuffixTypes();
     // Mark the form-field as dirty whenever the prefix or suffix children change. This
     // is necessary because we conditionally display the prefix/suffix containers based
     // on whether there is projected content.
     merge(this._prefixChildren.changes, this._suffixChildren.changes)
-      .subscribe(() => this._changeDetectorRef.markForCheck());
+      .subscribe(() => {
+        this._checkPrefixAndSuffixTypes();
+        this._changeDetectorRef.markForCheck();
+      });
   }
 
   /**
@@ -667,15 +685,19 @@ export class MatFormField implements AfterViewInit, OnDestroy, AfterContentCheck
       this._needsOutlineLabelOffsetUpdateOnStable = true;
       return;
     }
-    const iconPrefixContainer = this._iconPrefixContainer.nativeElement as HTMLElement;
-    const textPrefixContainer = this._textPrefixContainer.nativeElement as HTMLElement;
+    const iconPrefixContainer = this._iconPrefixContainer?.nativeElement;
+    const textPrefixContainer = this._textPrefixContainer?.nativeElement;
     // If the directionality is RTL, the x-axis transform needs to be inverted. This
     // is because `transformX` does not change based on the page directionality.
     const labelHorizontalOffset =
       (this._dir.value === 'rtl' ? -1 : 1) * (
-          iconPrefixContainer.getBoundingClientRect().width +
-          textPrefixContainer.getBoundingClientRect().width
-        );
+          (iconPrefixContainer ?
+              // If there's an icon prefix, we disable the default 16px padding,
+              // so make sure to account for that.
+              (iconPrefixContainer?.getBoundingClientRect().width ?? 0) - 16 : 0
+          ) +
+          (textPrefixContainer?.getBoundingClientRect().width ?? 0)
+      );
 
     // Update the transform the floating label to account for the prefix container. Note
     // that we do not want to overwrite the default transform for docked floating labels.