perf(lsp): optimize formatting minified files (#20829)

cli/lsp/language_server.rs

@@ -1651,11 +1651,11 @@ impl Inner {
     }
 
     // spawn a blocking task to allow doing other work while this is occurring
-    let format_result = deno_core::unsync::spawn_blocking({
+    let text_edits = deno_core::unsync::spawn_blocking({
       let fmt_options = self.fmt_options.options.clone();
       let document = document.clone();
       move || {
-        match document.maybe_parsed_source() {
+        let format_result = match document.maybe_parsed_source() {
           Some(Ok(parsed_source)) => {
             format_parsed_source(&parsed_source, &fmt_options)
           }
@@ -1672,26 +1672,24 @@ impl Inner {
             // it's not a js/ts file, so attempt to format its contents
             format_file(&file_path, &document.content(), &fmt_options)
           }
+        };
+        match format_result {
+          Ok(Some(new_text)) => Some(text::get_edits(
+            &document.content(),
+            &new_text,
+            document.line_index().as_ref(),
+          )),
+          Ok(None) => Some(Vec::new()),
+          Err(err) => {
+            lsp_warn!("Format error: {:#}", err);
+            None
+          }
         }
       }
     })
     .await
     .unwrap();
 
-    let text_edits = match format_result {
-      Ok(Some(new_text)) => Some(text::get_edits(
-        &document.content(),
-        &new_text,
-        document.line_index().as_ref(),
-      )),
-      Ok(None) => Some(Vec::new()),
-      Err(err) => {
-        // TODO(lucacasonato): handle error properly
-        lsp_warn!("Format error: {:#}", err);
-        None
-      }
-    };
-
     self.performance.measure(mark);
     if let Some(text_edits) = text_edits {
       if text_edits.is_empty() {

cli/lsp/text.rs

@@ -210,6 +210,18 @@ pub fn get_edits(a: &str, b: &str, line_index: &LineIndex) -> Vec<TextEdit> {
   if a == b {
     return vec![];
   }
+  // Heuristic to detect things like minified files. `diff()` is expensive.
+  if b.chars().filter(|c| *c == '\n').count()
+    > line_index.utf8_offsets.len() * 3
+  {
+    return vec![TextEdit {
+      range: lsp::Range {
+        start: lsp::Position::new(0, 0),
+        end: line_index.position_utf16(TextSize::from(a.len() as u32)),
+      },
+      new_text: b.to_string(),
+    }];
+  }
   let chunks = diff(a, b);
   let mut text_edits = Vec::<TextEdit>::new();
   let mut iter = chunks.iter().peekable();