fix(html/minifier): Fix script/style merging (#6443)

Author: alexander-akait

crates/swc_html_minifier/src/lib.rs

@@ -1827,32 +1827,29 @@ impl Minifier<'_> {
 
             let result = child_will_be_retained(&mut child, &mut new_children, children);
 
-            if result {
-                if self.options.remove_empty_metadata_elements
-                    && self.is_empty_metadata_element(&child)
-                {
-                    let need_continue = {
-                        let next_element = if let Some(Child::Element(element)) = children.get(0) {
-                            Some(element)
-                        } else if let Some(Child::Element(element)) = children.get(1) {
-                            Some(element)
-                        } else {
-                            None
-                        };
+            if self.options.remove_empty_metadata_elements {
+                if let Some(last_child @ Child::Element(_)) = new_children.last() {
+                    if self.is_empty_metadata_element(last_child) {
+                        new_children.pop();
 
-                        if let Some(element) = next_element {
-                            self.options.merge_metadata_elements
-                                && !self.allow_elements_to_merge(Some(&child), element)
-                        } else {
-                            true
-                        }
-                    };
+                        if let Child::Text(text) = &mut child {
+                            if let Some(Child::Text(prev_text)) = new_children.last_mut() {
+                                let mut new_data =
+                                    String::with_capacity(prev_text.data.len() + text.data.len());
 
-                    if need_continue {
-                        continue;
+                                new_data.push_str(&prev_text.data);
+                                new_data.push_str(&text.data);
+
+                                text.data = new_data.into();
+
+                                new_children.pop();
+                            }
+                        }
                     }
                 }
+            }
 
+            if result {
                 new_children.push(child);
             }
         }

crates/swc_html_minifier/tests/fixture/element/script-group/input.html

@@ -215,5 +215,13 @@
     var a = "test";console.log(a);console.log(a);console.log(a);
 </script>
 
+<div>breaker</div>
+<script></script>
+<script></script>
+
+<div>breaker</div>
+<script type="module"></script>
+<script type="module"></script>
+
 </body>
 </html>

crates/swc_html_minifier/tests/fixture/element/script-group/output.min.html

@@ -90,4 +90,12 @@
 <script type=module>var a="test";console.log(a),console.log(a),console.log(a)</script><script>var o="test";console.log(o);console.log(o);console.log(o)</script><script type=module>var a="test";console.log(a),console.log(a),console.log(a)</script>
 
 <div>breaker</div>
-<script>var o="test";console.log(o);console.log(o);console.log(o)</script><script type=module>var a="test";console.log(a),console.log(a),console.log(a)</script><script>var o="test";console.log(o);console.log(o);console.log(o)</script>
+<script>var o="test";console.log(o);console.log(o);console.log(o)</script><script type=module>var a="test";console.log(a),console.log(a),console.log(a)</script><script>var o="test";console.log(o);console.log(o);console.log(o)</script>
+
+<div>breaker</div>
+
+
+
+<div>breaker</div>
+<script type=module></script>
+<script type=module></script>

crates/swc_html_minifier/tests/fixture/element/style-group/input.html

@@ -90,5 +90,41 @@ <h1>Text</h1>
 <style type="unknown">a { color: red }</style><style type="unknown"></style>
 <div>test</div>
 <style type="text/css">a { color: red; }</style><style type="   text/css  ">div { color: blue; }</style>
+<div>EMPTY breaker</div>
+<style></style>
+<style></style>
+<div>breaker</div>
+<style></style>
+<style></style>
+<style></style>
+
+<div>breaker style tags</div>
+
+<style></style>
+
+<style></style>
+
+<style></style>
+
+<style></style>
+
+<style></style>
+
+<div>breaker style tags</div>
+
+<style></style><style></style><style></style><style></style><style></style>
+
+<div>breaker</div>
+<style></style>
+<script></script>
+<div>breaker</div>
+<script></script>
+<style></style>
+<div>breaker</div>
+<style></style>
+<span>test</span>
+<div>breaker</div>
+<span>test</span>
+<style></style>
 </body>
 </html>

crates/swc_html_minifier/tests/fixture/element/style-group/output.min.html

@@ -3,8 +3,7 @@
 <style>a{color:red}b{color:blue}</style>
 <div>test</div>
 <style>a{color:red}</style>
-<div>test</div>
-<style>a{color:red}</style>
+<div>test</div><style>a{color:red}</style>
 <div>test</div>
 <style>a,html,body{color:red}</style>
 <div>test</div>
@@ -20,4 +19,20 @@
 <div>test</div>
 <style type=unknown>a { color: red }</style><style type=unknown></style>
 <div>test</div>
-<style>a{color:red}div{color:blue}</style>
+<style>a{color:red}div{color:blue}</style>
+<div>EMPTY breaker</div>
+<div>breaker</div>
+
+<div>breaker style tags</div>
+
+<div>breaker style tags</div>
+
+
+
+<div>breaker</div>
+<div>breaker</div>
+<div>breaker</div>
+
+<span>test</span>
+<div>breaker</div>
+<span>test</span>