Add disableFullscreenOnNarrow prop to SelectPanel for opt-out of fullscreen behavior

.changeset/good-ligers-pull.md

@@ -0,0 +1,5 @@
+---
+"@primer/react": minor
+---
+
+Add disableFullscreenOnNarrow prop to SelectPanel for opt-out of fullscreen behavior

packages/react/src/SelectPanel/SelectPanel.docs.json

@@ -183,6 +183,12 @@
       "type": "boolean",
       "description": "Whether to display the selected items at the top of the list",
       "default": "true"
+    },
+    {
+      "name": "disableFullscreenOnNarrow",
+      "type": "boolean",
+      "description": "Whether to disable fullscreen behavior on narrow viewports. When `true`, the panel will maintain its anchored position regardless of viewport size. When `false`, the panel will go fullscreen on narrow viewports (if feature flag is enabled).",
+      "defaultValue": "undefined (uses feature flag default)"
     }
   ],
   "subcomponents": []

packages/react/src/SelectPanel/SelectPanel.test.tsx

@@ -1066,6 +1066,100 @@ for (const useModernActionList of [false, true]) {
           expect(options[2]).toHaveTextContent('item three')
         })
       })
+
+      describe('disableFullscreenOnNarrow prop', () => {
+        const renderSelectPanelWithFlags = (flags: Record<string, boolean>, props: Record<string, unknown> = {}) => {
+          return render(
+            <FeatureFlags flags={flags}>
+              <ThemeProvider>
+                <SingleSelectPanel {...props} />
+              </ThemeProvider>
+            </FeatureFlags>,
+          )
+        }
+
+        // Create a single-select version to test ResponsiveCloseButton behavior
+        function SingleSelectPanel(passthroughProps: Record<string, unknown>) {
+          const [filter, setFilter] = React.useState('')
+          const [open, setOpen] = React.useState(false)
+
+          return (
+            <ThemeProvider>
+              <SelectPanel
+                title="test title"
+                subtitle="test subtitle"
+                items={items}
+                placeholder="Select an item"
+                placeholderText="Filter items"
+                selected={undefined}
+                onSelectedChange={() => {}}
+                filterValue={filter}
+                onFilterChange={value => {
+                  setFilter(value)
+                }}
+                open={open}
+                onOpenChange={open => setOpen(open)}
+                {...passthroughProps}
+              />
+            </ThemeProvider>
+          )
+        }
+
+        it('should opt out of fullscreen when disableFullscreenOnNarrow=true even when feature flag is enabled', async () => {
+          const user = userEvent.setup()
+
+          renderSelectPanelWithFlags(
+            {
+              primer_react_select_panel_with_modern_action_list: useModernActionList,
+              primer_react_select_panel_fullscreen_on_narrow: true,
+            },
+            {disableFullscreenOnNarrow: true},
+          )
+
+          await user.click(screen.getByText('Select an item'))
+
+          // When disableFullscreenOnNarrow=true, the ResponsiveCloseButton should not be present
+          // even when the feature flag is enabled, indicating no fullscreen behavior
+          const responsiveCloseButton = screen.queryByRole('button', {name: 'Cancel and close'})
+          expect(responsiveCloseButton).not.toBeInTheDocument()
+        })
+
+        it('should use fullscreen behavior when disableFullscreenOnNarrow=false and feature flag is enabled', async () => {
+          const user = userEvent.setup()
+
+          renderSelectPanelWithFlags(
+            {
+              primer_react_select_panel_with_modern_action_list: useModernActionList,
+              primer_react_select_panel_fullscreen_on_narrow: true,
+            },
+            {disableFullscreenOnNarrow: false},
+          )
+
+          await user.click(screen.getByText('Select an item'))
+
+          // When feature flag is true and disableFullscreenOnNarrow is false, the ResponsiveCloseButton should be present
+          // indicating fullscreen behavior is active
+          const responsiveCloseButton = screen.getByRole('button', {name: 'Cancel and close'})
+          expect(responsiveCloseButton).toBeInTheDocument()
+        })
+
+        it('should default to feature flag value when disableFullscreenOnNarrow is undefined', async () => {
+          const user = userEvent.setup()
+
+          // Test with feature flag disabled
+          renderSelectPanelWithFlags({
+            primer_react_select_panel_with_modern_action_list: useModernActionList,
+            primer_react_select_panel_fullscreen_on_narrow: false,
+          })
+
+          await user.click(screen.getByText('Select an item'))
+
+          // When feature flag is false and disableFullscreenOnNarrow is undefined,
+          // the ResponsiveCloseButton should not be present
+          const responsiveCloseButton = screen.queryByRole('button', {name: 'Cancel and close'})
+          expect(responsiveCloseButton).not.toBeInTheDocument()
+        })
+      })
     })
   })
 }

packages/react/src/SelectPanel/SelectPanel.tsx

@@ -101,6 +101,13 @@ interface SelectPanelBaseProps {
    */
   footer?: string | React.ReactElement
   showSelectedOptionsFirst?: boolean
+  /**
+   * Whether to disable fullscreen behavior on narrow viewports.
+   * When `true`, the panel will maintain its anchored position regardless of viewport size.
+   * When `false`, the panel will go fullscreen on narrow viewports (if feature flag is enabled).
+   * @default undefined (uses feature flag default)
+   */
+  disableFullscreenOnNarrow?: boolean
 }
 
 // onCancel is optional with variant=anchored, but required with variant=modal
@@ -172,6 +179,7 @@ function Panel({
   variant = 'anchored',
   secondaryAction,
   showSelectedOptionsFirst = true,
+  disableFullscreenOnNarrow,
   ...listProps
 }: SelectPanelProps): JSX.Element {
   const titleId = useId()
@@ -192,7 +200,8 @@ function Panel({
   const [prevOpen, setPrevOpen] = useState(open)
 
   const usingModernActionList = useFeatureFlag('primer_react_select_panel_with_modern_action_list')
-  const usingFullScreenOnNarrow = useFeatureFlag('primer_react_select_panel_fullscreen_on_narrow')
+  const featureFlagFullScreenOnNarrow = useFeatureFlag('primer_react_select_panel_fullscreen_on_narrow')
+  const usingFullScreenOnNarrow = disableFullscreenOnNarrow ? false : featureFlagFullScreenOnNarrow
   const shouldOrderSelectedFirst =
     useFeatureFlag('primer_react_select_panel_order_selected_at_top') && showSelectedOptionsFirst