Prevents infinite loop in Table._computeColumnWidths (#36262)

packages/flutter/lib/src/rendering/table.dart

@@ -918,10 +918,7 @@ class RenderTable extends RenderBox {
       // columns shrinking them proportionally until we have no
       // available columns, then do the same to the non-flexible ones.
       int availableColumns = columns;
-      // Handle double precision errors which causes this loop to become
-      // stuck in certain configurations.
-      const double minimumDeficit = precisionErrorTolerance;
-      while (deficit > minimumDeficit && totalFlex > minimumDeficit) {
+      while (deficit > precisionErrorTolerance && totalFlex > precisionErrorTolerance) {
         double newTotalFlex = 0.0;
         for (int x = 0; x < columns; x += 1) {
           if (flexes[x] != null) {
@@ -943,14 +940,14 @@ class RenderTable extends RenderBox {
         }
         totalFlex = newTotalFlex;
       }
-      if (deficit > 0.0) {
+      while (deficit > precisionErrorTolerance && availableColumns > 0) {
         // Now we have to take out the remaining space from the
         // columns that aren't minimum sized.
         // To make this fair, we repeatedly remove equal amounts from
         // each column, clamped to the minimum width, until we run out
         // of columns that aren't at their minWidth.
-        do {
         final double delta = deficit / availableColumns;
+        assert(delta != 0);
         int newAvailableColumns = 0;
         for (int x = 0; x < columns; x += 1) {
           final double availableDelta = widths[x] - minWidths[x];
@@ -967,7 +964,6 @@ class RenderTable extends RenderBox {
           }
         }
         availableColumns = newAvailableColumns;
-        } while (deficit > 0.0 && availableColumns > 0);
       }
     }
     return widths;

packages/flutter/test/rendering/table_test.dart

@@ -217,4 +217,30 @@ void main() {
     pumpFrame();
     expect(table, paints..path()..path()..path()..path()..path()..path());
   });
+
+  test('Table flex sizing', () {
+    const BoxConstraints cellConstraints =
+        BoxConstraints.tightFor(width: 100, height: 100);
+    final RenderTable table = RenderTable(
+      textDirection: TextDirection.rtl,
+      children: <List<RenderBox>>[
+        List<RenderBox>.generate(
+          7,
+          (int _) => RenderConstrainedBox(additionalConstraints: cellConstraints),
+        ),
+      ],
+      columnWidths: const <int, TableColumnWidth>{
+        0: FlexColumnWidth(1.0),
+        1: FlexColumnWidth(0.123),
+        2: FlexColumnWidth(0.123),
+        3: FlexColumnWidth(0.123),
+        4: FlexColumnWidth(0.123),
+        5: FlexColumnWidth(0.123),
+        6: FlexColumnWidth(0.123),
+      },
+    );
+
+    layout(table, constraints: BoxConstraints.tight(const Size(800.0, 600.0)));
+    expect(table.hasSize, true);
+  });
 }

packages/flutter/test/widgets/table_test.dart

@@ -376,6 +376,36 @@ void main() {
     // If the above bug is present this test will never terminate.
   });
 
+  testWidgets('Calculating flex columns with small width deficit', (WidgetTester tester) async {
+    const SizedBox cell = SizedBox(width: 1, height: 1);
+    // If the error is present, pumpWidget() will fail due to an unsatisfied
+    // assertion during the layout phase.
+    await tester.pumpWidget(
+      ConstrainedBox(
+        constraints: BoxConstraints.tight(const Size(600, 800)),
+        child: Directionality(
+          textDirection: TextDirection.ltr,
+          child: Table(
+            columnWidths: const <int, TableColumnWidth>{
+              0: FlexColumnWidth(1.0),
+              1: FlexColumnWidth(0.123),
+              2: FlexColumnWidth(0.123),
+              3: FlexColumnWidth(0.123),
+              4: FlexColumnWidth(0.123),
+              5: FlexColumnWidth(0.123),
+              6: FlexColumnWidth(0.123),
+            },
+            children: <TableRow>[
+              TableRow(children: List<Widget>.filled(7, cell)),
+              TableRow(children: List<Widget>.filled(7, cell)),
+            ],
+          ),
+        ),
+      ),
+    );
+    expect(tester.takeException(), null);
+  });
+
   testWidgets('Table widget - repump test', (WidgetTester tester) async {
     await tester.pumpWidget(
       Directionality(