Prevent overriding of theme's default toolbar settings (#4120)

* theme toolbar's handlers overwritten fix

* Fix handling for true values and add CHANGELOG

---------

Co-authored-by: david ruty <david.ruty@arche-mc2.fr>
Co-authored-by: Zihua Li <i@zihua.li>

CHANGELOG.md

@@ -1,5 +1,7 @@
 # [Unreleased]
 
+- Prevent overriding of theme's default toolbar settings mistakenly [#4120](https://github.com/quilljs/quill/pull/4120)
+
 # 2.0.0
 
 We are thrilled to announce the release of Quill 2.0! Please check out the [announcement post](https://slab.com/blog/announcing-quill-2-0/).

packages/quill/src/core/quill.ts

@@ -766,7 +766,7 @@ function expandModuleConfig(config: Record<string, unknown> | undefined) {
       ...expanded,
       [key]: value === true ? {} : value,
     }),
-    {},
+    {} as Record<string, unknown>,
   );
 }
 
@@ -797,22 +797,25 @@ function expandConfig(
   const { modules: quillModuleDefaults, ...quillDefaults } = Quill.DEFAULTS;
   const { modules: themeModuleDefaults, ...themeDefaults } = theme.DEFAULTS;
 
+  let userModuleOptions = expandModuleConfig(options.modules);
+  // Special case toolbar shorthand
+  if (
+    userModuleOptions != null &&
+    userModuleOptions.toolbar &&
+    userModuleOptions.toolbar.constructor !== Object
+  ) {
+    userModuleOptions = {
+      ...userModuleOptions,
+      toolbar: { container: userModuleOptions.toolbar },
+    };
+  }
+
   const modules: ExpandedQuillOptions['modules'] = merge(
     {},
     expandModuleConfig(quillModuleDefaults),
     expandModuleConfig(themeModuleDefaults),
-    expandModuleConfig(options.modules),
+    userModuleOptions,
   );
-  // Special case toolbar shorthand
-  if (
-    modules != null &&
-    modules.toolbar &&
-    modules.toolbar.constructor !== Object
-  ) {
-    modules.toolbar = {
-      container: modules.toolbar,
-    };
-  }
 
   const config = {
     ...quillDefaults,

packages/quill/test/unit/core/quill.spec.ts

@@ -764,6 +764,21 @@ describe('Quill', () => {
       });
     });
 
+    test('toolbar container shorthand with theme options', () => {
+      const config = expandConfig(`#${testContainerId}`, {
+        modules: {
+          toolbar: document.querySelector(`#${testContainerId}`),
+        },
+        theme: 'snow',
+      });
+      for (const [format, handler] of Object.entries(
+        Snow.DEFAULTS.modules.toolbar!.handlers ?? {},
+      )) {
+        // @ts-expect-error
+        expect(config.modules.toolbar.handlers[format]).toBe(handler);
+      }
+    });
+
     test('toolbar format array', () => {
       const config = expandConfig(`#${testContainerId}`, {
         modules: {