perf: reduce source map json stringify

Cargo.toml

@@ -53,7 +53,7 @@ rayon              = { version = "1.10.0" }
 regex              = { version = "1.10.4" }
 ropey              = "1.6.1"
 rspack_resolver    = { version = "0.3.5", features = ["package_json_raw_json_api"] }
-rspack_sources     = { version = "=0.3.3" }
+rspack_sources     = { version = "=0.3.4" }
 rustc-hash         = { version = "1.1.0" }
 serde              = { version = "1.0.197" }
 serde_json         = { version = "1.0.115" }

crates/rspack_loader_lightningcss/src/lib.rs

@@ -9,7 +9,10 @@ use lightningcss::{
   targets::{Features, Targets},
   traits::IntoOwned,
 };
-use rspack_core::{rspack_sources::SourceMap, Loader, LoaderContext, RunnerContext};
+use rspack_core::{
+  rspack_sources::{encode_mappings, Mapping, OriginalLocation, SourceMap},
+  Loader, LoaderContext, RunnerContext,
+};
 use rspack_error::Result;
 use rspack_loader_runner::{Identifiable, Identifier};
 use tokio::sync::Mutex;
@@ -180,14 +183,36 @@ impl LightningCssLoader {
       .map_err(|_| rspack_error::error!("failed to generate css"))?;
 
     if enable_sourcemap {
-      let source_map = source_map
-        .to_json(None)
-        .map_err(|e| rspack_error::error!(e.to_string()))?;
-
-      loader_context.finish_with((
-        content.code,
-        SourceMap::from_json(&source_map).expect("should be able to generate source-map"),
-      ));
+      let mappings = encode_mappings(source_map.get_mappings().iter().map(|mapping| Mapping {
+        generated_line: mapping.generated_line,
+        generated_column: mapping.generated_column,
+        original: mapping.original.map(|original| OriginalLocation {
+          source_index: original.source,
+          original_line: original.original_line,
+          original_column: original.original_column,
+          name_index: original.name,
+        }),
+      }));
+      let rspack_source_map = SourceMap::new(
+        None,
+        mappings,
+        source_map
+          .get_sources()
+          .iter()
+          .map(|source| source.to_string().into())
+          .collect::<Vec<_>>(),
+        source_map
+          .get_sources_content()
+          .iter()
+          .map(|source| source.to_string().into())
+          .collect::<Vec<_>>(),
+        source_map
+          .get_names()
+          .iter()
+          .map(|source| source.to_string().into())
+          .collect::<Vec<_>>(),
+      );
+      loader_context.finish_with((content.code, rspack_source_map));
     } else {
       loader_context.finish_with(content.code);
     }

crates/rspack_loader_swc/src/lib.rs

@@ -9,7 +9,7 @@ use std::default::Default;
 use compiler::{IntoJsAst, SwcCompiler};
 use options::SwcCompilerOptionsWithAdditional;
 pub use options::SwcLoaderJsOptions;
-use rspack_core::{rspack_sources::SourceMap, Mode, RunnerContext};
+use rspack_core::{Mode, RunnerContext};
 use rspack_error::{error, AnyhowError, Diagnostic, Result};
 use rspack_loader_runner::{Identifiable, Identifier, Loader, LoaderContext};
 use rspack_plugin_javascript::ast::{self, SourceMapConfig};
@@ -87,12 +87,8 @@ impl SwcLoader {
     };
 
     let source = content.into_string_lossy();
-    let c = SwcCompiler::new(
-      resource_path.into_std_path_buf(),
-      source.clone(),
-      swc_options,
-    )
-    .map_err(AnyhowError::from)?;
+    let c = SwcCompiler::new(resource_path.into_std_path_buf(), source, swc_options)
+      .map_err(AnyhowError::from)?;
 
     let built = c
       .parse(None, |_| {
@@ -132,11 +128,6 @@ impl SwcLoader {
     }
     let ast = c.into_js_ast(program);
     let TransformOutput { code, map } = ast::stringify(&ast, codegen_options)?;
-
-    let map = map
-      .map(|m| SourceMap::from_json(&m))
-      .transpose()
-      .map_err(|e| error!(e.to_string()))?;
     loader_context.finish_with((code, map));
 
     Ok(())

crates/rspack_plugin_javascript/src/ast/stringify.rs

@@ -1,6 +1,7 @@
 use std::sync::Arc;
 
 use rspack_ast::javascript::Ast;
+use rspack_core::rspack_sources::{self, encode_mappings, Mapping, OriginalLocation};
 use rspack_error::{miette::IntoDiagnostic, Result};
 use swc_core::base::config::JsMinifyFormatOptions;
 use swc_core::base::sourcemap;
@@ -105,14 +106,44 @@ pub fn print(
   };
 
   let map = if source_map_config.enable {
-    let mut buf = vec![];
-
-    source_map
-      .build_source_map_with_config(&src_map_buf, input_source_map, source_map_config)
-      .to_writer(&mut buf)
-      .unwrap_or_else(|e| panic!("{}", e.to_string()));
-    // SAFETY: This buffer is already sanitized
-    Some(unsafe { String::from_utf8_unchecked(buf) })
+    let combined_source_map =
+      source_map.build_source_map_with_config(&src_map_buf, input_source_map, source_map_config);
+
+    let mappings = encode_mappings(combined_source_map.tokens().map(|token| Mapping {
+      generated_line: token.get_dst_line() + 1,
+      generated_column: token.get_dst_col(),
+      original: if token.has_source() {
+        Some(OriginalLocation {
+          source_index: token.get_src_id(),
+          original_line: token.get_src_line() + 1,
+          original_column: token.get_src_col(),
+          name_index: if token.has_name() {
+            Some(token.get_name_id())
+          } else {
+            None
+          },
+        })
+      } else {
+        None
+      },
+    }));
+
+    Some(rspack_sources::SourceMap::new(
+      combined_source_map.get_file().map(|file| file.to_string()),
+      mappings,
+      combined_source_map
+        .sources()
+        .map(|source| source.to_string().into())
+        .collect::<Vec<_>>(),
+      combined_source_map
+        .source_contents()
+        .map(|source| source.unwrap_or_default().to_string().into())
+        .collect::<Vec<_>>(),
+      combined_source_map
+        .names()
+        .map(|source| source.to_string().into())
+        .collect::<Vec<_>>(),
+    ))
   } else {
     None
   };

crates/rspack_plugin_javascript/src/lib.rs

@@ -15,14 +15,15 @@ pub mod utils;
 pub mod visitors;
 mod webpack_comment;
 pub use parser_plugin::*;
+use rspack_core::rspack_sources::SourceMap;
 
 pub use crate::plugin::infer_async_modules_plugin::InferAsyncModulesPlugin;
 pub use crate::plugin::*;
 
 #[derive(Debug)]
 pub struct TransformOutput {
   pub code: String,
-  pub map: Option<String>,
+  pub map: Option<SourceMap>,
 }
 
 #[derive(Debug)]

crates/rspack_plugin_javascript/src/utils/eval/eval_source.rs

@@ -20,7 +20,7 @@ pub fn eval_source<T: Display>(
   error_title: T,
 ) -> Option<BasicEvaluatedExpression> {
   let cm: Arc<swc_core::common::SourceMap> = Default::default();
-  let fm = cm.new_source_file(Arc::new(FileName::Anon), source.clone());
+  let fm = cm.new_source_file(Arc::new(FileName::Anon), source);
   let result = parse_file_as_expr(
     &fm,
     Syntax::Es(EsSyntax::default()),
@@ -38,7 +38,7 @@ pub fn eval_source<T: Display>(
           span.lo.0.saturating_sub(1) as usize,
           span.hi.0.saturating_sub(1) as usize,
           format!("{error_title} warning"),
-          format!("failed to parse {}", json!(source)),
+          format!("failed to parse {}", json!(fm.src.as_ref())),
         )
         .with_severity(Severity::Warning),
       ));

crates/rspack_plugin_swc_js_minimizer/src/lib.rs

@@ -11,7 +11,7 @@ use cow_utils::CowUtils;
 use once_cell::sync::OnceCell;
 use rayon::prelude::*;
 use regex::Regex;
-use rspack_core::rspack_sources::{ConcatSource, MapOptions, RawSource, SourceExt, SourceMap};
+use rspack_core::rspack_sources::{ConcatSource, MapOptions, RawSource, SourceExt};
 use rspack_core::rspack_sources::{Source, SourceMapSource, SourceMapSourceOptions};
 use rspack_core::{
   AssetInfo, ChunkUkey, Compilation, CompilationAsset, CompilationParams, CompilationProcessAssets,
@@ -241,11 +241,11 @@ async fn process_assets(&self, compilation: &mut Compilation) -> Result<()> {
             return Ok(())
           }
         };
-        let source = if let Some(map) = &output.map {
+        let source = if let Some(source_map) = output.map {
           SourceMapSource::new(SourceMapSourceOptions {
             value: output.code,
             name: filename,
-            source_map: SourceMap::from_json(map).expect("should be able to generate source-map"),
+            source_map,
             original_source: None,
             inner_source_map: input_source_map,
             remove_original_source: true,