fix: prevent deleting the last variable variant on the ui (#2964)

frontend/src/component/feature/FeatureView/FeatureVariants/FeatureEnvironmentVariants/EnvironmentVariantModal/EnvironmentVariantModal.tsx

@@ -27,6 +27,7 @@ import cloneDeep from 'lodash.clonedeep';
 import { CloudCircle } from '@mui/icons-material';
 import PermissionSwitch from 'component/common/PermissionSwitch/PermissionSwitch';
 import { UPDATE_FEATURE_VARIANTS } from 'component/providers/AccessProvider/permissions';
+import { WeightType } from 'constants/variantTypes';
 
 const StyledFormSubtitle = styled('div')(({ theme }) => ({
     display: 'flex',
@@ -121,11 +122,6 @@ const payloadOptions = [
     { key: 'csv', label: 'csv' },
 ];
 
-enum WeightType {
-    FIX = 'fix',
-    VARIABLE = 'variable',
-}
-
 const EMPTY_PAYLOAD = { type: 'string', value: '' };
 
 enum ErrorField {

frontend/src/component/feature/FeatureView/FeatureVariants/FeatureEnvironmentVariants/EnvironmentVariantsCard/EnvironmentVariantsTable/EnvironmentVariantsTable.tsx

@@ -20,6 +20,7 @@ import { PayloadCell } from './PayloadCell/PayloadCell';
 import { OverridesCell } from './OverridesCell/OverridesCell';
 import { VariantsActionCell } from './VariantsActionsCell/VariantsActionsCell';
 import { useConditionallyHiddenColumns } from 'hooks/useConditionallyHiddenColumns';
+import { WeightType } from 'constants/variantTypes';
 
 const StyledTableContainer = styled('div')(({ theme }) => ({
     margin: theme.spacing(3, 0),
@@ -112,6 +113,7 @@ export const EnvironmentVariantsTable = ({
                     <VariantsActionCell
                         variant={original}
                         projectId={projectId}
+                        isLastVariableVariant={isProtectedVariant(original)}
                         environmentId={environment.name}
                         editVariant={onEditVariant}
                         deleteVariant={onDeleteVariant}
@@ -130,6 +132,23 @@ export const EnvironmentVariantsTable = ({
         []
     );
 
+    const isProtectedVariant = (variant: IFeatureVariant): boolean => {
+        const isVariable = variant.weightType === WeightType.VARIABLE;
+
+        const atLeastOneFixedVariant = variants.some(variant => {
+            return variant.weightType === WeightType.FIX;
+        });
+
+        const hasOnlyOneVariableVariant =
+            variants.filter(variant => {
+                return variant.weightType === WeightType.VARIABLE;
+            }).length == 1;
+
+        return (
+            atLeastOneFixedVariant && hasOnlyOneVariableVariant && isVariable
+        );
+    };
+
     const { data, getSearchText } = useSearch(columns, searchValue, variants);
 
     const { headerGroups, rows, prepareRow, setHiddenColumns } = useTable(

frontend/src/component/feature/FeatureView/FeatureVariants/FeatureEnvironmentVariants/EnvironmentVariantsCard/EnvironmentVariantsTable/VariantsActionsCell/VariantsActionsCell.tsx

@@ -4,10 +4,11 @@ import { ActionCell } from 'component/common/Table/cells/ActionCell/ActionCell';
 import { UPDATE_FEATURE_ENVIRONMENT_VARIANTS } from 'component/providers/AccessProvider/permissions';
 import { IFeatureVariant } from 'interfaces/featureToggle';
 
-interface IVarintsActionCellProps {
+interface IVariantsActionCellProps {
     projectId: string;
     environmentId: string;
     variant: IFeatureVariant;
+    isLastVariableVariant: boolean;
     editVariant: (variant: IFeatureVariant) => void;
     deleteVariant: (variant: IFeatureVariant) => void;
 }
@@ -16,9 +17,10 @@ export const VariantsActionCell = ({
     projectId,
     environmentId,
     variant,
+    isLastVariableVariant,
     editVariant,
     deleteVariant,
-}: IVarintsActionCellProps) => {
+}: IVariantsActionCellProps) => {
     return (
         <ActionCell>
             <PermissionIconButton
@@ -39,10 +41,13 @@ export const VariantsActionCell = ({
                 permission={UPDATE_FEATURE_ENVIRONMENT_VARIANTS}
                 data-testid={`VARIANT_DELETE_BUTTON_${variant.name}`}
                 projectId={projectId}
+                disabled={isLastVariableVariant}
                 environmentId={environmentId}
                 onClick={() => deleteVariant(variant)}
                 tooltipProps={{
-                    title: 'Delete variant',
+                    title: isLastVariableVariant
+                        ? 'You need to have at least one variable variant'
+                        : 'Delete variant',
                 }}
             >
                 <Delete />

frontend/src/component/feature/FeatureView/FeatureVariants/FeatureEnvironmentVariants/FeatureEnvironmentVariants.tsx

@@ -66,12 +66,8 @@ export const FeatureEnvironmentVariants = () => {
         patch: jsonpatch.Operation[];
         error?: string;
     } => {
-        try {
-            const updatedNewVariants = updateWeight(newVariants, 1000);
-            return { patch: createPatch(variants, updatedNewVariants) };
-        } catch (error: unknown) {
-            return { patch: [], error: formatUnknownError(error) };
-        }
+        const updatedNewVariants = updateWeight(newVariants, 1000);
+        return { patch: createPatch(variants, updatedNewVariants) };
     };
 
     const updateVariants = async (

frontend/src/constants/variantTypes.ts

@@ -0,0 +1,4 @@
+export enum WeightType {
+    FIX = 'fix',
+    VARIABLE = 'variable',
+}