Extend InputDecoration borders for disabled/error/focused states (#19694)

Added five InputBorder properties to InputDecoration etc so that apps can control the appearance of an InputDecorator's border:  errorBorder, focusedBorder, focusedErrorBorder, disabledBorder, enabledBorder.

packages/flutter/lib/src/material/input_decorator.dart

@@ -1591,21 +1591,26 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
     return themeData.textTheme.caption.copyWith(color: color).merge(decoration.errorStyle);
   }
 
-  double get _borderWeight {
+  InputBorder _getDefaultBorder(ThemeData themeData) {
-    if (decoration.isCollapsed || decoration.border == InputBorder.none || !decoration.enabled)
+    Color borderColor;
-      return 0.0;
+    if (decoration.enabled) {
-    return isFocused ? 2.0 : 1.0;
+      borderColor = decoration.errorText == null
-  }
+        ? _getActiveColor(themeData)
-
+        : themeData.errorColor;
-  Color _getBorderColor(ThemeData themeData) {
+    } else {
-    if (!decoration.enabled) {
+      borderColor = (decoration.filled == true && decoration.border?.isOutline != true)
-      if (decoration.filled == true && !decoration.border.isOutline)
+        ? Colors.transparent
-        return Colors.transparent;
+        : themeData.disabledColor;
-      return themeData.disabledColor;
     }
-    return decoration.errorText == null
+
-      ? _getActiveColor(themeData)
+    double borderWeight;
-      : themeData.errorColor;
+    if (decoration.isCollapsed || decoration?.border == InputBorder.none || !decoration.enabled)
+      borderWeight = 0.0;
+    else
+      borderWeight = isFocused ? 2.0 : 1.0;
+
+    final InputBorder border = decoration.border ?? const UnderlineInputBorder();
+    return border.copyWith(borderSide: new BorderSide(color: borderColor, width: borderWeight));
   }
 
   @override
@@ -1627,23 +1632,22 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
       ),
     );
 
-    final InputBorder border = decoration.border.copyWith(
+    final bool isError = decoration.errorText != null;
-      borderSide: new BorderSide(
+    InputBorder border;
-        color: _getBorderColor(themeData),
+    if (!decoration.enabled)
-        width: _borderWeight,
+      border = isError ? decoration.errorBorder : decoration.disabledBorder;
-      ),
+    else if (isFocused)
-    );
+      border = isError ? decoration.focusedErrorBorder : decoration.focusedBorder;
+    else
+      border = isError ? decoration.errorBorder : decoration.enabledBorder;
+    border ??= _getDefaultBorder(themeData);
 
-    final Widget container = border == null
+    final Widget container = new _BorderContainer(
-      ? new DecoratedBox(
+      border: border,
-          decoration: new BoxDecoration(color: _getFillColor(themeData))
+      gap: _borderGap,
-        )
+      gapAnimation: _floatingLabelController.view,
-      : new _BorderContainer(
+      fillColor: _getFillColor(themeData),
-          border: border,
+    );
-          gap: _borderGap,
-          gapAnimation: _floatingLabelController.view,
-          fillColor: _getFillColor(themeData),
-        );
 
     final TextStyle inlineLabelStyle = inlineStyle.merge(decoration.labelStyle);
     final Widget label = decoration.labelText == null ? null : new _Shaker(
@@ -1759,7 +1763,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
     if (decoration.isCollapsed) {
       floatingLabelHeight = 0.0;
       contentPadding = decorationContentPadding ?? EdgeInsets.zero;
-    } else if (!decoration.border.isOutline) {
+    } else if (!border.isOutline) {
       // 4.0: the vertical gap between the inline elements and the floating label.
       floatingLabelHeight = 4.0 + 0.75 * inlineLabelStyle.fontSize;
       if (decoration.filled == true) { // filled == null same as filled == false
@@ -1786,7 +1790,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
         isCollapsed: decoration.isCollapsed,
         floatingLabelHeight: floatingLabelHeight,
         floatingLabelProgress: _floatingLabelController.value,
-        border: decoration.border,
+        border: border,
         borderGap: _borderGap,
         icon: icon,
         input: widget.child,
@@ -1856,6 +1860,11 @@ class InputDecoration {
     this.counterStyle,
     this.filled,
     this.fillColor,
+    this.errorBorder,
+    this.focusedBorder,
+    this.focusedErrorBorder,
+    this.disabledBorder,
+    this.enabledBorder,
     this.border,
     this.enabled = true,
   }) : assert(enabled != null), isCollapsed = false;
@@ -1891,7 +1900,12 @@ class InputDecoration {
        suffixText = null,
        suffixStyle = null,
        counterText = null,
-       counterStyle = null;
+       counterStyle = null,
+       errorBorder = null,
+       focusedBorder = null,
+       focusedErrorBorder = null,
+       disabledBorder = null,
+       enabledBorder = null;
 
   /// An icon to show before the input field and outside of the decoration's
   /// container.
@@ -2119,16 +2133,147 @@ class InputDecoration {
   /// [errorText], and [counterText].
   final Color fillColor;
 
-  /// The border to draw around the decoration's container.
+  /// The border to display when the [InputDecorator] does not have the focus and
+  /// is showing an error.
+  ///
+  /// See also:
+  ///  * [InputDecorator.isFocused], which is true if the [InputDecorator]'s child
+  ///    has the focus.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder errorBorder;
+
+  /// The border to display when the [InputDecorator] has the focus and is not
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecorator.isFocused], which is true if the [InputDecorator]'s child
+  ///    has the focus.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder focusedBorder;
+
+  /// The border to display when the [InputDecorator] has the focus and is
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecorator.isFocused], which is true if the [InputDecorator]'s child
+  ///    has the focus.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder focusedErrorBorder;
+
+  /// The border to display when the [InputDecorator] is disabled and is not
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecoration.enabled], which is false if the [InputDecorator] is disabled.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder disabledBorder;
+
+  /// The border to display when the [InputDecorator] is enabled and is not
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecoration.enabled], which is false if the [InputDecorator] is disabled.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder enabledBorder;
+
+  /// The shape of the border to draw around the decoration's container.
   ///
   /// The decoration's container is the area which is filled if [isFilled] is
   /// true and bordered per the [border]. It's the area adjacent to
-  /// [decoration.icon] and above the widgets that contain [helperText],
+  /// [InputDecoration.icon] and above the widgets that contain
-  /// [errorText], and [counterText].
+  /// [InputDecoration.helperText], [InputDecoration.errorText], and
+  /// [InputDecoration.counterText].
   ///
-  /// The default value of this property is `const UnderlineInputBorder()`.
+  /// The border's bounds, i.e. the value of `border.getOuterPath()`, define
+  /// the area to be filled.
+  ///
+  /// This property is only used when the appropriate one of [errorBorder],
+  /// [focusedBorder], [focusedErrorBorder], [disabledBorder], or [enabledBorder]
+  /// is not specified. This border's [InputBorder.borderSide] property is
+  /// configured by the InputDecorator, depending on the values of
+  /// [InputDecoration.errorText], [InputDecoration.enabled],
+  /// [InputDecorator.isFocused and the current [Theme].
+  ///
+  /// Typically one of [UnderlineInputBorder] or [OutlineInputBorder].
+  /// If null, InputDecorator's default is `const UnderlineInputBorder()`.
   ///
   /// See also:
+  ///
+  ///  * [InputBorder.none], which doesn't draw a border.
   ///  * [UnderlineInputBorder], which draws a horizontal line at the
   ///    bottom of the input decorator's container.
   ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
@@ -2168,6 +2313,11 @@ class InputDecoration {
     TextStyle counterStyle,
     bool filled,
     Color fillColor,
+    InputBorder errorBorder,
+    InputBorder focusedBorder,
+    InputBorder focusedErrorBorder,
+    InputBorder disabledBorder,
+    InputBorder enabledBorder,
     InputBorder border,
     bool enabled,
   }) {
@@ -2194,6 +2344,11 @@ class InputDecoration {
       counterStyle: counterStyle ?? this.counterStyle,
       filled: filled ?? this.filled,
       fillColor: fillColor ?? this.fillColor,
+      errorBorder: errorBorder ?? this.errorBorder,
+      focusedBorder: focusedBorder ?? this.focusedBorder,
+      focusedErrorBorder: focusedErrorBorder ?? this.focusedErrorBorder,
+      disabledBorder: disabledBorder ?? this.disabledBorder,
+      enabledBorder: enabledBorder ?? this.enabledBorder,
       border: border ?? this.border,
       enabled: enabled ?? this.enabled,
     );
@@ -2218,6 +2373,11 @@ class InputDecoration {
       counterStyle: counterStyle ?? theme.counterStyle,
       filled: filled ?? theme.filled,
       fillColor: fillColor ?? theme.fillColor,
+      errorBorder: errorBorder ?? theme.errorBorder,
+      focusedBorder: focusedBorder ?? theme.focusedBorder,
+      focusedErrorBorder: focusedErrorBorder ?? theme.focusedErrorBorder,
+      disabledBorder: disabledBorder ?? theme.disabledBorder,
+      enabledBorder: enabledBorder ?? theme.enabledBorder,
       border: border ?? theme.border,
     );
   }
@@ -2252,6 +2412,11 @@ class InputDecoration {
         && typedOther.counterStyle == counterStyle
         && typedOther.filled == filled
         && typedOther.fillColor == fillColor
+        && typedOther.errorBorder == errorBorder
+        && typedOther.focusedBorder == focusedBorder
+        && typedOther.focusedErrorBorder == focusedErrorBorder
+        && typedOther.disabledBorder == disabledBorder
+        && typedOther.enabledBorder == enabledBorder
         && typedOther.border == border
         && typedOther.enabled == enabled;
   }
@@ -2265,12 +2430,12 @@ class InputDecoration {
       helperText,
       helperStyle,
       hintText,
+      hintStyle,
+      errorText,
+      errorStyle,
+      errorMaxLines,
+      isDense,
       hashValues( // Over 20 fields...
-        hintStyle,
-        errorText,
-        errorStyle,
-        errorMaxLines,
-        isDense,
         contentPadding,
         isCollapsed,
         prefixIcon,
@@ -2283,6 +2448,11 @@ class InputDecoration {
         counterStyle,
         filled,
         fillColor,
+        errorBorder,
+        focusedBorder,
+        focusedErrorBorder,
+        disabledBorder,
+        enabledBorder,
         border,
         enabled,
       ),
@@ -2332,6 +2502,16 @@ class InputDecoration {
       description.add('filled: true');
     if (fillColor != null)
       description.add('fillColor: $fillColor');
+    if (errorBorder != null)
+      description.add('errorBorder: $errorBorder');
+    if (focusedBorder != null)
+      description.add('focusedBorder: $focusedBorder');
+    if (focusedErrorBorder != null)
+      description.add('focusedErrorBorder: $focusedErrorBorder');
+    if (disabledBorder != null)
+      description.add('disabledBorder: $disabledBorder');
+    if (enabledBorder != null)
+      description.add('enabledBorder: $enabledBorder');
     if (border != null)
       description.add('border: $border');
     if (!enabled)
@@ -2370,11 +2550,15 @@ class InputDecorationTheme extends Diagnosticable {
     this.counterStyle,
     this.filled = false,
     this.fillColor,
-    this.border = const UnderlineInputBorder(),
+    this.errorBorder,
+    this.focusedBorder,
+    this.focusedErrorBorder,
+    this.disabledBorder,
+    this.enabledBorder,
+    this.border,
   }) : assert(isDense != null),
        assert(isCollapsed != null),
-       assert(filled != null),
+      assert(filled != null);
-       assert(border != null);
 
   /// The style to use for [InputDecoration.labelText] when the label is
   /// above (i.e., vertically adjacent to) the input field.
@@ -2476,7 +2660,124 @@ class InputDecorationTheme extends Diagnosticable {
   /// true and bordered per the [border].
   final Color fillColor;
 
-  /// The border to draw around the decoration's container.
+  /// The border to display when the [InputDecorator] does not have the focus and
+  /// is showing an error.
+  ///
+  /// See also:
+  ///  * [InputDecorator.isFocused], which is true if the [InputDecorator]'s child
+  ///    has the focus.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder errorBorder;
+
+  /// The border to display when the [InputDecorator] has the focus and is not
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecorator.isFocused], which is true if the [InputDecorator]'s child
+  ///    has the focus.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder focusedBorder;
+
+  /// The border to display when the [InputDecorator] has the focus and is
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecorator.isFocused], which is true if the [InputDecorator]'s child
+  ///    has the focus.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+ ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder focusedErrorBorder;
+
+   /// The border to display when the [InputDecorator] is disabled and is not
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecoration.enabled], which is false if the [InputDecorator] is disabled.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [enabledBorder], displayed when [InputDecoration.enabled] is true
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder disabledBorder;
+
+  /// The border to display when the [InputDecorator] is enabled and is not
+  /// showing an error.
+  ///
+  /// See also:
+  ///
+  ///  * [InputDecoration.enabled], which is false if the [InputDecorator] is disabled.
+  ///  * [InputDecoration.errorText], the error shown by the [InputDecorator], if non-null.
+  ///  * [border], for a description of where the [InputDecorator] border appears.
+  ///  * [UnderlineInputBorder], an [InputDecorator] border which draws a horizontal
+  ///    line at the bottom of the input decorator's container.
+  ///  * [OutlineInputBorder], an [InputDecorator] border which draws a
+  ///    rounded rectangle around the input decorator's container.
+  ///  * [InputBorder.none], which doesn't draw a border.
+  ///  * [errorBorder], displayed when [InputDecorator.isFocused] is false
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [focusedBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is null.
+  ///  * [focusedErrorBorder], displayed when [InputDecorator.isFocused] is true
+  ///    and [InputDecoration.errorText] is non-null.
+  ///  * [disabledBorder], displayed when [InputDecoration.enabled] is false
+  ///    and [InputDecoration.errorText] is null.
+  final InputBorder enabledBorder;
+
+  /// The shape of the border to draw around the decoration's container.
   ///
   /// The decoration's container is the area which is filled if [isFilled] is
   /// true and bordered per the [border]. It's the area adjacent to
@@ -2484,12 +2785,21 @@ class InputDecorationTheme extends Diagnosticable {
   /// [InputDecoration.helperText], [InputDecoration.errorText], and
   /// [InputDecoration.counterText].
   ///
-  /// The default value of this property is `const UnderlineInputBorder()`.
+  /// The border's bounds, i.e. the value of `border.getOuterPath()`, define
-  ///
-  /// The border's bounds, i.e. the value of `border.getOuterPath()`, defines
   /// the area to be filled.
   ///
+  /// This property is only used when the appropriate one of [errorBorder],
+  /// [focusedBorder], [focusedErrorBorder], [disabledBorder], or [enabledBorder]
+  /// is not specified. This border's [InputBorder.borderSide] property is
+  /// configured by the InputDecorator, depending on the values of
+  /// [InputDecoration.errorText], [InputDecoration.enabled],
+  /// [InputDecorator.isFocused and the current [Theme].
+  ///
+  /// Typically one of [UnderlineInputBorder] or [OutlineInputBorder].
+  /// If null, InputDecorator's default is `const UnderlineInputBorder()`.
+  ///
   /// See also:
+  ///
   ///  * [InputBorder.none], which doesn't draw a border.
   ///  * [UnderlineInputBorder], which draws a horizontal line at the
   ///    bottom of the input decorator's container.
@@ -2514,6 +2824,11 @@ class InputDecorationTheme extends Diagnosticable {
     properties.add(new DiagnosticsProperty<TextStyle>('counterStyle', counterStyle, defaultValue: defaultTheme.counterStyle));
     properties.add(new DiagnosticsProperty<bool>('filled', filled, defaultValue: defaultTheme.filled));
     properties.add(new DiagnosticsProperty<Color>('fillColor', fillColor, defaultValue: defaultTheme.fillColor));
+    properties.add(new DiagnosticsProperty<InputBorder>('errorBorder', errorBorder, defaultValue: defaultTheme.errorBorder));
+    properties.add(new DiagnosticsProperty<InputBorder>('focusedBorder', focusedBorder, defaultValue: defaultTheme.focusedErrorBorder));
+    properties.add(new DiagnosticsProperty<InputBorder>('focusedErrorborder', focusedErrorBorder, defaultValue: defaultTheme.focusedErrorBorder));
+    properties.add(new DiagnosticsProperty<InputBorder>('disabledBorder', disabledBorder, defaultValue: defaultTheme.disabledBorder));
+    properties.add(new DiagnosticsProperty<InputBorder>('enabledBorder', enabledBorder, defaultValue: defaultTheme.enabledBorder));
     properties.add(new DiagnosticsProperty<InputBorder>('border', border, defaultValue: defaultTheme.border));
   }
 }

packages/flutter/test/material/input_decorator_test.dart

@@ -62,7 +62,7 @@ double getBorderBottom(WidgetTester tester) {
   return box.size.height;
 }
 
-BorderSide getBorderSide(WidgetTester tester) {
+InputBorder getBorder(WidgetTester tester) {
   if (!tester.any(findBorderPainter()))
     return null;
   final CustomPaint customPaint = tester.widget(findBorderPainter());
@@ -70,7 +70,11 @@ BorderSide getBorderSide(WidgetTester tester) {
   final dynamic/*_InputBorderTween */ inputBorderTween = inputBorderPainter.border;
   final Animation<double> animation = inputBorderPainter.borderAnimation;
   final dynamic/*_InputBorder */ border = inputBorderTween.evaluate(animation);
-  return border.borderSide;
+  return border;
+}
+
+BorderSide getBorderSide(WidgetTester tester) {
+  return getBorder(tester)?.borderSide;
 }
 
 double getBorderWeight(WidgetTester tester) => getBorderSide(tester)?.width;
@@ -1650,4 +1654,140 @@ void main() {
       contains('contentPadding: EdgeInsetsDirectional(5.0, 0.0, 0.0, 0.0)'),
     );
   });
+
+  testWidgets('InputDecoration borders', (WidgetTester tester) async {
+    const InputBorder errorBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.red, width: 1.5),
+    );
+    const InputBorder focusedBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.green, width: 4.0),
+    );
+    const InputBorder focusedErrorBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.teal, width: 5.0),
+    );
+    const InputBorder disabledBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.grey, width: 0.0),
+    );
+    const InputBorder enabledBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.blue, width: 2.5),
+    );
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          // errorText: null (default)
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    expect(getBorder(tester), enabledBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        isFocused: true,
+        decoration: const InputDecoration(
+          // errorText: null (default)
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // border changes are animated
+    expect(getBorder(tester), focusedBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        isFocused: true,
+        decoration: const InputDecoration(
+          errorText: 'error',
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // border changes are animated
+    expect(getBorder(tester), focusedErrorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          errorText: 'error',
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // border changes are animated
+    expect(getBorder(tester), errorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          errorText: 'error',
+          enabled: false,
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // border changes are animated
+    expect(getBorder(tester), errorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          // errorText: false (default)
+          enabled: false,
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // border changes are animated
+    expect(getBorder(tester), disabledBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        isFocused: true,
+        decoration: const InputDecoration(
+          // errorText: null (default)
+          enabled: false,
+          errorBorder: errorBorder,
+          focusedBorder: focusedBorder,
+          focusedErrorBorder: focusedErrorBorder,
+          disabledBorder: disabledBorder,
+          enabledBorder: enabledBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // border changes are animated
+    expect(getBorder(tester), disabledBorder);
+  });
 }