add defaultTheme prop to specify default theme if no previous value stored

.changeset/orange-cars-glow.md

@@ -0,0 +1,6 @@
+---
+'@graphiql/react': minor
+'graphiql': minor
+---
+
+add new prop `defaultTheme` to set the default color preference theme

packages/graphiql-react/src/theme.ts

@@ -7,7 +7,7 @@ import { useStorageContext } from './storage';
  */
 export type Theme = 'light' | 'dark' | null;
 
-export function useTheme() {
+export function useTheme(defaultTheme: Theme = null) {
   const storageContext = useStorageContext();
 
   const [theme, setThemeInternal] = useState<Theme>(() => {
@@ -26,7 +26,7 @@ export function useTheme() {
           // Remove the invalid stored value
           storageContext.set(STORAGE_KEY, '');
         }
-        return null;
+        return defaultTheme;
     }
   });
 

packages/graphiql/cypress/e2e/theme.cy.ts

@@ -1,17 +1,32 @@
 describe('Theme', () => {
-  it('Switches to light theme when `forcedTheme` is light', () => {
-    cy.visit('/?query={test}&forcedTheme=light');
-    cy.get('body').should('have.class', 'graphiql-light');
-  });
+  describe('`forcedTheme`', () => {
+    it('Switches to light theme when `forcedTheme` is light', () => {
+      cy.visit('/?forcedTheme=light');
+      cy.get('body').should('have.class', 'graphiql-light');
+    });
+
+    it('Switches to dark theme when `forcedTheme` is dark', () => {
+      cy.visit('/?forcedTheme=dark');
+      cy.get('body').should('have.class', 'graphiql-dark');
+    });
 
-  it('Switches to dark theme when `forcedTheme` is dark', () => {
-    cy.visit('/?query={test}&forcedTheme=dark');
-    cy.get('body').should('have.class', 'graphiql-dark');
+    it('Defaults to light theme when `forcedTheme` value is invalid', () => {
+      cy.visit('/?forcedTheme=invalid');
+      cy.get('[data-value=settings]').click();
+      cy.get('.graphiql-dialog-section-title')
+        .eq(1)
+        .should('have.text', 'Theme'); // Check for the presence of the theme dialog
+    });
   });
 
-  it('Defaults to light theme when `forcedTheme` value is invalid', () => {
-    cy.visit('/?query={test}&forcedTheme=invalid');
-    cy.get('[data-value=settings]').click();
-    cy.get('.graphiql-dialog-section-title').eq(1).should('have.text', 'Theme'); // Check for the presence of the theme dialog
+  describe('`defaultTheme`', () => {
+    it('should have light theme', () => {
+      cy.visit('/?defaultTheme=light');
+      cy.get('body').should('have.class', 'graphiql-light');
+    });
+    it('should have dark theme', () => {
+      cy.visit('/?defaultTheme=dark');
+      cy.get('body').should('have.class', 'graphiql-dark');
+    });
   });
 });

packages/graphiql/resources/renderExample.js

@@ -95,5 +95,6 @@ root.render(
     onTabChange,
     forcedTheme: parameters.forcedTheme,
     defaultQuery: parameters.defaultQuery,
+    defaultTheme: parameters.defaultTheme,
   }),
 );

packages/graphiql/src/components/GraphiQL.tsx

@@ -40,6 +40,7 @@ import {
   Spinner,
   Tab,
   Tabs,
+  Theme,
   ToolbarButton,
   Tooltip,
   UnStyledButton,
@@ -219,6 +220,7 @@ export type GraphiQLInterfaceProps = WriteableEditorProps &
      * settings modal.
      */
     showPersistHeadersSettings?: boolean;
+    defaultTheme?: Theme;
     disableTabs?: boolean;
     /**
      * `forcedTheme` allows enforcement of a specific theme for GraphiQL.
@@ -263,7 +265,7 @@ export function GraphiQLInterface(props: GraphiQLInterfaceProps) {
   const merge = useMergeQuery();
   const prettify = usePrettifyEditors();
 
-  const { theme, setTheme } = useTheme();
+  const { theme, setTheme } = useTheme(props.defaultTheme);
 
   useEffect(() => {
     if (forcedTheme === 'system') {