fix(codegen): sourcemap token name should be original name (#2843)

close https://github.com/oxc-project/oxc/issues/2753.

crates/oxc_codegen/src/gen.rs

@@ -1015,7 +1015,7 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for IdentifierReference<'a> {
         // }
         // }
         // }
-        p.add_source_mapping_for_name(self.span.start, &self.name);
+        p.add_source_mapping_for_name(self.span, &self.name);
         p.print_str(self.name.as_bytes());
     }
 }
@@ -1029,13 +1029,13 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for IdentifierName<'a> {
 
 impl<'a, const MINIFY: bool> Gen<MINIFY> for BindingIdentifier<'a> {
     fn gen(&self, p: &mut Codegen<{ MINIFY }>, _ctx: Context) {
-        p.print_symbol(self.span.start, self.symbol_id.get(), &self.name);
+        p.print_symbol(self.span, self.symbol_id.get(), &self.name);
     }
 }
 
 impl<'a, const MINIFY: bool> Gen<MINIFY> for LabelIdentifier<'a> {
     fn gen(&self, p: &mut Codegen<{ MINIFY }>, _ctx: Context) {
-        p.add_source_mapping_for_name(self.span.start, &self.name);
+        p.add_source_mapping_for_name(self.span, &self.name);
         p.print_str(self.name.as_bytes());
     }
 }
@@ -2057,7 +2057,7 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for ClassElement<'a> {
 
 impl<'a, const MINIFY: bool> Gen<MINIFY> for JSXIdentifier<'a> {
     fn gen(&self, p: &mut Codegen<{ MINIFY }>, _ctx: Context) {
-        p.add_source_mapping_for_name(self.span.start, &self.name);
+        p.add_source_mapping_for_name(self.span, &self.name);
         p.print_str(self.name.as_bytes());
     }
 }
@@ -2398,7 +2398,7 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for AccessorProperty<'a> {
 
 impl<'a, const MINIFY: bool> Gen<MINIFY> for PrivateIdentifier<'a> {
     fn gen(&self, p: &mut Codegen<{ MINIFY }>, _ctx: Context) {
-        p.add_source_mapping_for_name(self.span.start, &self.name);
+        p.add_source_mapping_for_name(self.span, &self.name);
         p.print(b'#');
         p.print_str(self.name.as_bytes());
     }

crates/oxc_codegen/src/lib.rs

@@ -303,7 +303,7 @@ impl<const MINIFY: bool> Codegen<MINIFY> {
         }
     }
 
-    fn print_symbol(&mut self, start: u32, _symbol_id: Option<SymbolId>, fallback: &Atom) {
+    fn print_symbol(&mut self, span: Span, _symbol_id: Option<SymbolId>, fallback: &Atom) {
         // if let Some(mangler) = &self.mangler {
         // if let Some(symbol_id) = symbol_id {
         // let name = mangler.get_symbol_name(symbol_id);
@@ -311,7 +311,7 @@ impl<const MINIFY: bool> Codegen<MINIFY> {
         // return;
         // }
         // }
-        self.add_source_mapping_for_name(start, fallback);
+        self.add_source_mapping_for_name(span, fallback);
         self.print_str(fallback.as_bytes());
     }
 
@@ -412,8 +412,8 @@ impl<const MINIFY: bool> Codegen<MINIFY> {
         self.sourcemap_builder.add_source_mapping(&self.code, position, None);
     }
 
-    fn add_source_mapping_for_name(&mut self, position: u32, name: &str) {
-        self.sourcemap_builder.add_source_mapping(&self.code, position, Some(name));
+    fn add_source_mapping_for_name(&mut self, span: Span, name: &str) {
+        self.sourcemap_builder.add_source_mapping_for_name(&self.code, span, name);
     }
 }
 

crates/oxc_codegen/src/sourcemap_builder.rs

@@ -1,3 +1,6 @@
+use std::sync::Arc;
+
+use oxc_span::Span;
 use oxc_syntax::identifier::{LS, PS};
 
 // Irregular line breaks - '\u{2028}' (LS) and '\u{2029}' (PS)
@@ -18,11 +21,11 @@ pub struct LineOffsetTable {
     byte_offset_to_start_of_line: usize,
 }
 
-#[derive(Default)]
 #[allow(clippy::struct_field_names)]
 pub struct SourcemapBuilder {
     enable_sourcemap: bool,
     source_id: u32,
+    original_source: Arc<str>,
     last_generated_update: usize,
     last_position: Option<u32>,
     last_search_line: usize,
@@ -32,25 +35,53 @@ pub struct SourcemapBuilder {
     generated_column: u32,
 }
 
+impl Default for SourcemapBuilder {
+    fn default() -> Self {
+        Self {
+            enable_sourcemap: false,
+            source_id: 0,
+            original_source: "".into(),
+            last_generated_update: 0,
+            last_position: None,
+            last_search_line: 0,
+            line_offset_tables: vec![],
+            sourcemap_builder: oxc_sourcemap::SourceMapBuilder::default(),
+            generated_line: 0,
+            generated_column: 0,
+        }
+    }
+}
+
 impl SourcemapBuilder {
     pub fn with_name_and_source(&mut self, name: &str, source: &str) {
         self.enable_sourcemap = true;
         self.line_offset_tables = Self::generate_line_offset_tables(source);
         self.source_id = self.sourcemap_builder.set_source_and_content(name, source);
+        self.original_source = source.into();
     }
 
     pub fn into_sourcemap(self) -> Option<oxc_sourcemap::SourceMap> {
         self.enable_sourcemap.then(|| self.sourcemap_builder.into_sourcemap())
     }
 
-    pub fn add_source_mapping(&mut self, output: &[u8], position: u32, name: Option<&str>) {
+    pub fn add_source_mapping_for_name(&mut self, output: &[u8], span: Span, name: &str) {
+        // SAFETY: search original string by span.
+        let original_name =
+            unsafe { self.original_source.get_unchecked(span.start as usize..span.end as usize) };
+        // The token name should be original name.
+        // If it hasn't change, name should be `None` to reduce `SourceMap` size.
+        let token_name = if original_name == name { None } else { Some(original_name.into()) };
+        self.add_source_mapping(output, span.start, token_name);
+    }
+
+    pub fn add_source_mapping(&mut self, output: &[u8], position: u32, name: Option<Arc<str>>) {
         if self.enable_sourcemap {
             if matches!(self.last_position, Some(last_position) if last_position >= position) {
                 return;
             }
             let (original_line, original_column) = self.search_original_line_and_column(position);
             self.update_generated_line_and_column(output);
-            let name_id = name.map(|s| self.sourcemap_builder.add_name(s));
+            let name_id = name.map(|s| self.sourcemap_builder.add_name(&s));
             self.sourcemap_builder.add_token(
                 self.generated_line,
                 self.generated_column,
@@ -349,4 +380,24 @@ mod test {
         create_mappings("abc\r\n", 1, 0);
         create_mappings("ÖÖ\nÖ\nÖÖÖ", 2, 3);
     }
+
+    #[test]
+    fn add_source_mapping_for_name() {
+        let output = "ac".as_bytes();
+        let mut builder = SourcemapBuilder::default();
+        builder.with_name_and_source("x.js", "ab");
+        builder.add_source_mapping_for_name(output, Span::new(0, 1), "a");
+        builder.add_source_mapping_for_name(output, Span::new(1, 2), "c");
+        let sm = builder.into_sourcemap().unwrap();
+        // The name `a` not change.
+        assert_eq!(
+            sm.get_source_view_token(0_u32).as_ref().and_then(|token| token.get_name()),
+            None
+        );
+        // The name `b` -> `c`, save `b` to token.
+        assert_eq!(
+            sm.get_source_view_token(1_u32).as_ref().and_then(|token| token.get_name()),
+            Some("b")
+        );
+    }
 }

crates/oxc_sourcemap/src/sourcemap.rs

@@ -72,6 +72,10 @@ impl SourceMap {
         self.tokens.get(index as usize)
     }
 
+    pub fn get_source_view_token(&self, index: u32) -> Option<SourceViewToken<'_>> {
+        self.tokens.get(index as usize).map(|token| SourceViewToken::new(token, self))
+    }
+
     /// Get raw tokens.
     pub fn get_tokens(&self) -> impl Iterator<Item = &Token> {
         self.tokens.iter()