WebAssembly · dschuff · Apr 9, 2025 · Apr 8, 2025 · Apr 9, 2025
@@ -2406,9 +2406,15 @@ class Module {
   // Optional user section IR representation.
   std::unique_ptr<DylinkSection> dylinkSection;
 
-  // Source maps debug info.
+  // Source maps debug info. All of these fields are read directly in from the
+  // source map and are encoded as in the original JSON (UTF-8 encoded with
+  // with escaped quotes and slashes). The string values are uninterpreted in
+  // Binaryen, and they are written directly back out without re-encoding.
   std::vector<std::string> debugInfoFileNames;
   std::vector<std::string> debugInfoSymbolNames;
+  std::string debugInfoSourceRoot;
+  std::string debugInfoFile;
+  std::vector<std::string> debugInfoSourcesContent;
 
   // `features` are the features allowed to be used in this module and should be
   // respected regardless of the value of`hasFeaturesSection`.

@@ -59,6 +59,16 @@ void SourceMapReader::parse(Module& wasm) {
     wasm.debugInfoFileNames.push_back(v->getCString());
   }
 
+  if (json.has("sourcesContent")) {
+    json::Ref sc = json["sourcesContent"];
+    if (!sc->isArray()) {
+      throw MapParseException("Source map sourcesContent is not an array");
+    }
+    for (size_t i = 0; i < sc->size(); i++) {
+      wasm.debugInfoSourcesContent.push_back(sc[i]->getCString());
+    }
+  }
+
   if (json.has("names")) {
     json::Ref n = json["names"];
     if (!n->isArray()) {
@@ -73,6 +83,22 @@ void SourceMapReader::parse(Module& wasm) {
     }
   }
 
+  if (json.has("sourceRoot")) {
+    json::Ref sr = json["sourceRoot"];
+    if (!sr->isString()) {
+      throw MapParseException("Source map sourceRoot is not a string");
+    }
+    wasm.debugInfoSourceRoot = sr->getCString();
+  }
+
+  if (json.has("file")) {
+    json::Ref f = json["file"];
+    if (!f->isString()) {
+      throw MapParseException("Source map file is not a string");
+    }
+    wasm.debugInfoFile = f->getCString();
+  }
+
   if (!json.has("mappings")) {
     throw MapParseException("Source map mappings missing");
   }

@@ -1226,25 +1226,40 @@ void WasmBinaryWriter::writeSourceMapProlog() {
     }
   }
 
-  *sourceMap << "\"sources\":[";
-  for (size_t i = 0; i < wasm->debugInfoFileNames.size(); i++) {
-    if (i > 0) {
-      *sourceMap << ",";
+  auto writeOptionalString = [&](const char* name, const std::string& str) {
+    if (!str.empty()) {
+      *sourceMap << "\"" << name << "\":\"" << str << "\",";
     }
-    // TODO respect JSON string encoding, e.g. quotes and control chars.
-    *sourceMap << "\"" << wasm->debugInfoFileNames[i] << "\"";
-  }
-  *sourceMap << "],\"names\":[";
+  };
 
-  for (size_t i = 0; i < wasm->debugInfoSymbolNames.size(); i++) {
-    if (i > 0) {
-      *sourceMap << ",";
+  writeOptionalString("file", wasm->debugInfoFile);
+  writeOptionalString("sourceRoot", wasm->debugInfoSourceRoot);
+
+  auto writeStringVector = [&](const char* name,
+                               const std::vector<std::string>& vec) {
+    *sourceMap << "\"" << name << "\":[";
+    for (size_t i = 0; i < vec.size(); i++) {
+      if (i > 0) {
+        *sourceMap << ",";
+      }
+      *sourceMap << "\"" << vec[i] << "\"";
     }
-    // TODO respect JSON string encoding, e.g. quotes and control chars.
-    *sourceMap << "\"" << wasm->debugInfoSymbolNames[i] << "\"";
+    *sourceMap << "],";
+  };
+
+  writeStringVector("sources", wasm->debugInfoFileNames);
+
+  if (!wasm->debugInfoSourcesContent.empty()) {
+    writeStringVector("sourcesContent", wasm->debugInfoSourcesContent);
   }
 
-  *sourceMap << "],\"mappings\":\"";
+  // TODO: This field is optional; maybe we should omit if it's empty.
+  // TODO: Binaryen actually does not correctly preserve symbol names when it
+  // rewrites the mappings. We should maybe just drop them, or else handle
+  // them correctly.
+  writeStringVector("names", wasm->debugInfoSymbolNames);
+
+  *sourceMap << "\"mappings\":\"";
 }
 
 static void writeBase64VLQ(std::ostream& out, int32_t n) {

@@ -153,3 +153,38 @@ TEST_F(SourceMapTest, Fibonacci) {
   // program?
   ExpectDbgLocEq(9999, 0, 8, 0, std::nullopt);
 }
+
+TEST_F(SourceMapTest, SourceMapSourceRootFile) {
+  std::string sourceMap = R"(
+    {
+      "version":3,
+      "file": "foo.wasm",
+      "sources":[],
+      "names":[],
+      "mappings": "",
+      "sourceRoot": "/foo/bar"
+    }
+  )";
+  parseMap(sourceMap);
+  EXPECT_EQ(wasm.debugInfoSourceRoot, "/foo/bar");
+  EXPECT_EQ(wasm.debugInfoFile, "foo.wasm");
+}
+
+TEST_F(SourceMapTest, SourcesContent) {
+  // The backslash escapes appear in the JSON encoding, and are preserved in
+  // the internal representation. The string values are uninterpreted in
+  // Binaryen, and they are written directly back out without re-encoding.
+  std::string sourceMap = R"(
+   {
+     "version": 3,
+     "sources": ["foo.c"],
+     "sourcesContent": ["#include <stdio.h> int main()\n{ printf(\"Gr\u00fc\u00df Gott, Welt!\"); return 0;}"],
+     "mappings" : ""
+   }
+  )";
+  parseMap(sourceMap);
+  ASSERT_EQ(wasm.debugInfoSourcesContent.size(), 1);
+  EXPECT_EQ(wasm.debugInfoSourcesContent[0],
+            "#include <stdio.h> int main()\\n{ printf(\\\"Gr\\u00fc\\u00df "
+            "Gott, Welt!\\\"); return 0;}");
+}
@@ -0,0 +1,14 @@
+;; RUN: wasm-opt %s.wasm -ism %s.map -osm %t -o %t2
+;; Running multiple times is needed here because the output is all on one line.
+;; RUN: cat %t | filecheck %s --check-prefix=FILE
+;; RUN: cat %t | filecheck %s --check-prefix=SOURCEROOT
+;; RUN: cat %t | filecheck %s --check-prefix=CONTENT
+
+
+;; This wat file is not actually part of the test (the binary file is used),
+;; but no comments are allowed in JSON so the RUN and CHECK lines are here.
+
+;; FILE: "file":"foo.wasm",
+;; SOURCEROOT: "sourceRoot":"/foo/bar",
+;; CONTENT: "sourcesContent":["#include <stdio.h> int main()\n{ printf(\"Gr\u00fc\u00df Gott, Welt!\"); return 0;}"]
+(module)
@@ -0,0 +1,9 @@
+{
+  "version":3,
+  "file": "foo.wasm",
+  "sources":[],
+  "names":[],
+  "mappings": "",
+  "sourceRoot": "/foo/bar",
+  "sourcesContent": ["#include <stdio.h> int main()\n{ printf(\"Gr\u00fc\u00df Gott, Welt!\"); return 0;}"]
+}