Add shouldClearSelectionOnInput input on material auto suggest input.

This used be a hidden configuration based on whether a selection model is set.
For places where a selection model was explicitly passed, this makes no difference.
For places where a selection model wasn't explicitly passed, this will cause the selection item to be deselected in the popup UI when input is changed after selection. But no output will be changed.

PiperOrigin-RevId: 214308663

angular_components/lib/material_input/material_auto_suggest_input.dart

@@ -124,8 +124,6 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
     RelativePosition.AdjacentTopRight
   ];
 
-  final SelectionModel _defaultSelection = SelectionModel.single();
-
   final String popupId;
   final String inputId;
 
@@ -135,24 +133,42 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
 
   bool _isInitialized = false;
 
-  /// Whether to clear the text once the item is selected from the menu.
+  /// Whether to clear the input text once the item is selected from the menu.
+  ///
+  /// Defaults to false.
+  // TODO(google): rename this to shouldClearInputOnSelection.
   @Input()
   bool shouldClearOnSelection = false;
 
+  /// Whether to clear the selected value from the selection model when the
+  /// input text changes.
+  ///
+  /// Defaults to true.
+  @Input()
+  bool shouldClearSelectionOnInput = true;
+
   /// Whether to cause dropdown to be closed on activation.
+  ///
+  /// Defaults to true.
   @Input()
   bool closeOnActivate = true;
 
   /// Whether to hide the checkbox before the selection item for multi-select.
+  ///
+  /// Defaults to false.
   @Input()
   bool hideCheckbox = false;
 
   /// Whether the popup should automatically reposition itself based on space
   /// available relative to the viewport.
+  ///
+  /// Defaults to true.
   @Input()
   bool enforceSpaceConstraints = true;
 
   /// Whether to clamp the popup position so that it never goes offscreen.
+  ///
+  /// Defaults to false.
   @Input()
   bool constrainToViewport = false;
 
@@ -187,6 +203,8 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
   /// [selection] are changed:
   /// 1) first selected value in [selection] is active in [options]
   /// 2) if [selection] has no selected values, nothing is active in [options]
+  ///
+  /// Defaults to false.
   @Input()
   bool initialActivateSelection = false;
 
@@ -195,10 +213,13 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
   /// Allow filtering of suggestions as the user is typing.
   ///
   /// When `false` always show the full list of suggestions.
+  /// Defaults to true.
   @Input()
   bool filterSuggestions = true;
 
   /// Whether to close on enter even for string non matching options.
+  ///
+  /// Defaults to false.
   @Input()
   bool closeOnEnter = false;
 
@@ -208,6 +229,8 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
 
   /// Whether or not the suggestion popup width is at least as wide as the input
   /// width.
+  ///
+  /// Defaults to false.
   @Input()
   bool popupMatchInputWidth = false;
 
@@ -231,6 +254,7 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
   /// Show or hide the trailing close icon.
   ///
   /// Clicking on the icon clears the input text and hides the popup.
+  /// Defaults to false.
   @Input()
   bool showClearIcon = false;
 
@@ -312,7 +336,7 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
     if (_cd != null) {
       _cd.valueAccessor = this;
     }
-    selection = _defaultSelection;
+    selection = SelectionModel.single();
   }
 
   /// Publishes events when input text changes (on keypress.)
@@ -575,7 +599,7 @@ class MaterialAutoSuggestInputComponent extends MaterialSelectBase
       return false;
     }
 
-    if (selection != _defaultSelection &&
+    if (shouldClearSelectionOnInput &&
         !shouldClearOnSelection &&
         _lastSelectedItem != null) {
       // deselect previously selected item as the component was not asked to

examples/material_input_example/lib/material_auto_suggest_input_full_demo.dart

@@ -112,6 +112,7 @@ class MaterialAutoSuggestInputFullDemoComponent {
   bool showClearIconTooltip = false;
   bool hideCheckbox = false;
   bool shouldClearOnSelection = false;
+  bool shouldClearSelectionOnInput = true;
   bool useLabelFactory = false;
   bool useFactoryRenderer = false;
   bool disabled = false;

examples/material_input_example/lib/material_auto_suggest_input_full_demo.html

@@ -42,6 +42,7 @@ <h2>Multi selection</h2>
         [clearIconTooltip]="clearIconTooltip"
         [hideCheckbox]="hideCheckbox"
         [shouldClearOnSelection]="shouldClearOnSelection"
+        [shouldClearSelectionOnInput]="shouldClearSelectionOnInput"
         [label]="label"
         [labelFactory]="labelFactory"
         [leadingGlyph]="leadingGlyph"
@@ -80,7 +81,10 @@ <h3>Options</h3>
     </material-checkbox>
     <br>
     <material-checkbox [(checked)]="shouldClearOnSelection">
-      Clear on selection
+      Clear input on selection
+    </material-checkbox>
+    <material-checkbox [(checked)]="shouldClearSelectionOnInput">
+      Clear selection on input
     </material-checkbox>
     <br>
     <material-checkbox [(checked)]="popupMatchInputWidth">