fix: project settings flag limit not properly set (#5317)

https://linear.app/unleash/issue/SR-169/ticket-1107-project-feature-flag-limit-is-not-correctly-updated

Fixes #5315, an issue where it would not be possible to set an empty
flag limit.
This also fixes the UI behavior: Before, when the flag limit field was
emptied, it would disappear from the UI.

I'm a bit unsure of the original intent of the `(data.defaultStickiness
!== undefined || data.featureLimit !== undefined)` condition. We're in
an update method, triggered by a PUT endpoint - I think it's safe to
assume that we'll always want to set these values to whatever they come
as, we just need to convert them to `null` in case they are not present
(i.e. `undefined`).

frontend/src/component/project/Project/ProjectForm/ProjectForm.tsx

@@ -184,8 +184,8 @@ const ProjectForm: React.FC<IProjectForm> = ({
                 }
             />
             <ConditionallyRender
-                condition={mode === 'Edit' && Boolean(setFeatureLimit)}
+                condition={mode === 'Edit'}
-                show={
+                show={() => (
                     <>
                         <Box
                             sx={{
@@ -202,17 +202,15 @@ const ProjectForm: React.FC<IProjectForm> = ({
                             Leave it empty if you don’t want to add a limit
                         </StyledSubtitle>
                         <StyledInputContainer>
-                            {featureLimit && setFeatureLimit && (
                             <StyledInput
                                 label={'Limit'}
                                 name='value'
                                 type={'number'}
-                                    value={featureLimit}
+                                value={featureLimit!}
                                 onChange={(e) =>
-                                        setFeatureLimit(e.target.value)
+                                    setFeatureLimit!(e.target.value)
                                 }
                             />
-                            )}
                             <ConditionallyRender
                                 condition={
                                     featureCount !== undefined &&
@@ -226,7 +224,7 @@ const ProjectForm: React.FC<IProjectForm> = ({
                             />
                         </StyledInputContainer>
                     </>
-                }
+                )}
             />
             <ConditionallyRender
                 condition={mode === 'Create' && isEnterprise()}

frontend/src/component/project/Project/hooks/useProjectForm.ts

@@ -82,7 +82,7 @@ const useProjectForm = (
 
     const getFeatureLimitAsNumber = () => {
         if (featureLimit === '') {
-            return undefined;
+            return null;
         }
         return Number(featureLimit);
     };

src/lib/db/project-store.ts

@@ -244,8 +244,9 @@ class ProjectStore implements IProjectStore {
         const settingsRow = await this.db(SETTINGS_TABLE)
             .insert({
                 project: project.id,
-                project_mode: project.mode,
                 default_stickiness: project.defaultStickiness,
+                feature_limit: project.featureLimit,
+                project_mode: project.mode,
             })
             .returning('*');
         return this.mapRow({ ...row[0], ...settingsRow[0] });
@@ -265,6 +266,7 @@ class ProjectStore implements IProjectStore {
             await this.db(TABLE)
                 .where({ id: data.id })
                 .update(this.fieldToRow(data));
+
             if (
                 data.defaultStickiness !== undefined ||
                 data.featureLimit !== undefined