fix: Correctly rewrite SourceMapHermes

src/builder.rs

@@ -26,6 +26,7 @@ pub struct SourceMapBuilder {
     source_root: Option<String>,
     sources: Vec<String>,
     source_contents: Vec<Option<String>>,
+    sources_mapping: Vec<u32>,
 }
 
 #[cfg(any(unix, windows, target_os = "redox"))]
@@ -57,6 +58,7 @@ impl SourceMapBuilder {
             source_root: None,
             sources: vec![],
             source_contents: vec![],
+            sources_mapping: vec![],
         }
     }
 
@@ -82,10 +84,15 @@ impl SourceMapBuilder {
 
     /// Registers a new source with the builder and returns the source ID.
     pub fn add_source(&mut self, src: &str) -> u32 {
+        self.add_source_with_id(src, !0)
+    }
+
+    fn add_source_with_id(&mut self, src: &str, old_id: u32) -> u32 {
         let count = self.sources.len() as u32;
         let id = *self.source_map.entry(src.into()).or_insert(count);
         if id == count {
             self.sources.push(src.into());
+            self.sources_mapping.push(old_id);
         }
         id
     }
@@ -144,7 +151,7 @@ impl SourceMapBuilder {
 
         let rv = to_read.len();
         for (src_id, path) in to_read {
-            if let Ok(mut f) = fs::File::open(&path) {
+            if let Ok(mut f) = fs::File::open(path) {
                 let mut contents = String::new();
                 if f.read_to_string(&mut contents).is_ok() {
                     self.set_source_contents(src_id, Some(&contents));
@@ -174,9 +181,23 @@ impl SourceMapBuilder {
         src_col: u32,
         source: Option<&str>,
         name: Option<&str>,
+    ) -> RawToken {
+        self.add_with_id(dst_line, dst_col, src_line, src_col, source, !0, name)
+    }
+
+    #[allow(clippy::too_many_arguments)]
+    fn add_with_id(
+        &mut self,
+        dst_line: u32,
+        dst_col: u32,
+        src_line: u32,
+        src_col: u32,
+        source: Option<&str>,
+        source_id: u32,
+        name: Option<&str>,
     ) -> RawToken {
         let src_id = match source {
-            Some(source) => self.add_source(source),
+            Some(source) => self.add_source_with_id(source, source_id),
             None => !0,
         };
         let name_id = match name {
@@ -223,12 +244,13 @@ impl SourceMapBuilder {
     /// optionally removing the name.
     pub fn add_token(&mut self, token: &Token<'_>, with_name: bool) -> RawToken {
         let name = if with_name { token.get_name() } else { None };
-        self.add(
+        self.add_with_id(
             token.get_dst_line(),
             token.get_dst_col(),
             token.get_src_line(),
             token.get_src_col(),
             token.get_source(),
+            token.get_src_id(),
             name,
         )
     }
@@ -249,6 +271,10 @@ impl SourceMapBuilder {
         }
     }
 
+    pub(crate) fn take_mapping(&mut self) -> Vec<u32> {
+        std::mem::take(&mut self.sources_mapping)
+    }
+
     /// Converts the builder into a sourcemap.
     pub fn into_sourcemap(self) -> SourceMap {
         let contents = if !self.source_contents.is_empty() {

src/decoder.rs

@@ -172,7 +172,7 @@ pub fn decode_regular(rsm: RawSourceMap) -> Result<SourceMap> {
                     if name_id >= names.len() as u32 {
                         fail!(Error::BadNameReference(name_id));
                     }
-                    name = name_id as u32;
+                    name = name_id;
                 }
             }
 

src/hermes.rs

@@ -100,7 +100,10 @@ impl SourceMapHermes {
 
     /// Resolves the name of the enclosing function for the given [`Token`].
     pub fn get_scope_for_token(&self, token: Token) -> Option<&str> {
-        let function_map = (self.function_maps.get(token.get_src_id() as usize))?.as_ref()?;
+        let function_map = self
+            .function_maps
+            .get(token.get_src_id() as usize)?
+            .as_ref()?;
 
         // Find the closest mapping, just like here:
         // https://github.com/facebook/metro/blob/63b523eb20e7bdf62018aeaf195bb5a3a1a67f36/packages/metro-symbolicate/src/SourceMetadataMapConsumer.js#L204-L231
@@ -120,10 +123,25 @@ impl SourceMapHermes {
     pub fn rewrite(self, options: &RewriteOptions<'_>) -> Result<Self> {
         let Self {
             sm,
-            function_maps,
-            raw_facebook_sources,
+            mut function_maps,
+            mut raw_facebook_sources,
         } = self;
-        let sm = sm.rewrite(options)?;
+
+        let (sm, mapping) = sm.rewrite_with_mapping(options)?;
+
+        if function_maps.len() >= mapping.len() {
+            function_maps = mapping
+                .iter()
+                .map(|idx| function_maps[*idx as usize].take())
+                .collect();
+            raw_facebook_sources = raw_facebook_sources.map(|mut sources| {
+                mapping
+                    .into_iter()
+                    .map(|idx| sources[idx as usize].take())
+                    .collect()
+            });
+        }
+
         Ok(Self {
             sm,
             function_maps,

src/types.rs

@@ -757,6 +757,14 @@ impl SourceMap {
     /// });
     /// ```
     pub fn rewrite(self, options: &RewriteOptions<'_>) -> Result<SourceMap> {
+        Ok(self.rewrite_with_mapping(options)?.0)
+    }
+
+    /// Same as `rewrite`, except also returns a remapping index for deduplicated `sources`.
+    pub(crate) fn rewrite_with_mapping(
+        self,
+        options: &RewriteOptions<'_>,
+    ) -> Result<(SourceMap, Vec<u32>)> {
         let mut builder = SourceMapBuilder::new(self.get_file());
 
         for token in self.tokens() {
@@ -795,7 +803,11 @@ impl SourceMap {
             builder.strip_prefixes(&prefixes);
         }
 
-        Ok(builder.into_sourcemap())
+        let mapping = builder.take_mapping();
+
+        let sm = builder.into_sourcemap();
+
+        Ok((sm, mapping))
     }
 }
 

tests/test_hermes.rs

@@ -4,6 +4,7 @@ use sourcemap::SourceMapHermes;
 fn test_react_native_hermes() {
     let input = include_bytes!("./fixtures/react-native-hermes/output.map");
     let sm = SourceMapHermes::from_reader(&input[..]).unwrap();
+    let sm = sm.rewrite(&Default::default()).unwrap();
 
     //    at foo (address at unknown:1:11939)
     assert_eq!(
@@ -24,6 +25,10 @@ fn test_react_native_hermes() {
 fn test_react_native_metro() {
     let input = include_bytes!("./fixtures/react-native-metro/output.js.map");
     let sm = SourceMapHermes::from_reader(&input[..]).unwrap();
+    // The given map has a bogus `__prelude__` first source, which is being
+    // dropped (as its not referenced) by rewriting the sourcemap, and thus
+    // the internal hermes mappings also need to be rewritten accordingly
+    let sm = sm.rewrite(&Default::default()).unwrap();
 
     //    at foo (output.js:1289:11)
     let token = sm.lookup_token(1288, 10).unwrap();