feat 🥁: add no-empty-style-blocks rule

Add comprehensive rule to detect and prevent empty CSS style blocks:

- Identify style objects with no properties
- Flag empty style blocks as potential code quality issues
- Provide auto-fix capability to remove empty blocks
- Handle edge cases like comments-only blocks

This rule helps maintain cleaner codebases by eliminating empty style definitions that often result from incomplete refactoring or forgotten implementations, reducing confusion and unnecessary code.

src/css-rules/no-empty-blocks/empty-nested-style-processor.ts

@@ -0,0 +1,75 @@
+import type { Rule } from 'eslint';
+import { TSESTree } from '@typescript-eslint/utils';
+import { isEmptyObject } from '../shared-utils/empty-object-processor.js';
+import { removeNodeWithComma } from './node-remover.js';
+import { areAllChildrenEmpty, getStyleKeyName } from './property-utils.js';
+
+/**
+ * Processes nested style objects like selectors and media queries.
+ */
+export function processEmptyNestedStyles(
+  ruleContext: Rule.RuleContext,
+  node: TSESTree.ObjectExpression,
+  reportedNodes: Set<TSESTree.Node>,
+): void {
+  node.properties.forEach((property) => {
+    if (property.type !== 'Property') {
+      return;
+    }
+
+    const propertyName = getStyleKeyName(property.key);
+    if (!propertyName) {
+      return;
+    }
+
+    // Handle selectors, media queries, and supports
+    if ((propertyName === 'selectors' || propertyName.startsWith('@')) && property.value.type === 'ObjectExpression') {
+      // If the container is empty or all its children are empty, remove the entire property
+      if (isEmptyObject(property.value) || areAllChildrenEmpty(property.value)) {
+        if (!reportedNodes.has(property)) {
+          reportedNodes.add(property);
+          const messageId =
+            propertyName === 'selectors'
+              ? 'emptySelectors'
+              : propertyName === '@media'
+                ? 'emptyMedia'
+                : propertyName === '@supports'
+                  ? 'emptySupports'
+                  : 'emptyConditionalStyle';
+
+          ruleContext.report({
+            node: property as Rule.Node,
+            messageId,
+            fix(fixer) {
+              return removeNodeWithComma(ruleContext, property, fixer);
+            },
+          });
+        }
+        return;
+      }
+
+      // Process individual selectors or media queries if we're not removing the entire container
+      property.value.properties.forEach((nestedProperty) => {
+        if (nestedProperty.type === 'Property') {
+          if (nestedProperty.value.type === 'ObjectExpression') {
+            if (isEmptyObject(nestedProperty.value)) {
+              if (!reportedNodes.has(nestedProperty)) {
+                reportedNodes.add(nestedProperty);
+                ruleContext.report({
+                  node: nestedProperty as Rule.Node,
+                  messageId: 'emptyNestedStyle',
+                  fix(fixer) {
+                    return removeNodeWithComma(ruleContext, nestedProperty, fixer);
+                  },
+                });
+              }
+            } else {
+              // Recursively process nested styles (for deeply nested selectors/media)
+              processEmptyNestedStyles(ruleContext, nestedProperty.value, reportedNodes);
+            }
+          }
+        }
+      });
+    }
+  });
+}