Clarify null termination requirements of SourceMapParser

Summary:
Clarify that the SourceMapParser must always receive a null-terminated
buffer. Remove the `StringRef` overload since accessing past the end of
a `StringRef` is unusual.

Reviewed By: avp

Differential Revision: D68963920

fbshipit-source-id: 69ac05f5b8831e39753124493d939648a28e1299

include/hermes/SourceMap/SourceMapParser.h

@@ -19,24 +19,14 @@ namespace hermes {
 /// parses.
 class SourceMapParser {
  public:
-  /// Parse input \p sourceMap and return parsed SourceMap.
+  /// Parse input \p sourceMap and return parsed SourceMap. \p sourceMap must
+  /// have a past-the-end null terminator.
   /// On failure if malformed, prints an error message and returns nullptr.
   static std::unique_ptr<SourceMap> parse(
       llvh::MemoryBufferRef sourceMap,
       llvh::StringRef baseDir,
       SourceErrorManager &sm);
 
-  /// Parse input \p sourceMapContent and return parsed SourceMap.
-  /// Set the filename of the map file to "<source map>".
-  /// On failure if malformed, prints an error message and returns nullptr.
-  static std::unique_ptr<SourceMap> parse(
-      llvh::StringRef sourceMapContent,
-      llvh::StringRef baseDir,
-      SourceErrorManager &sm) {
-    return parse(
-        llvh::MemoryBufferRef(sourceMapContent, "<source map>"), baseDir, sm);
-  }
-
  private:
   SourceMapParser() = delete;
   SourceMapParser(SourceMapParser &) = delete;

lib/SourceMap/c-api.cpp

@@ -44,8 +44,8 @@ extern "C" HermesSourceMap *hermes_source_map_parse(
   SourceErrorManager sm;
   SimpleDiagHandlerRAII handler(sm);
 
-  auto sourceMap =
-      SourceMapParser::parse(llvh::StringRef(source, len - 1), {}, sm);
+  llvh::MemoryBufferRef mbref(llvh::StringRef{source, len - 1}, "<source map>");
+  auto sourceMap = SourceMapParser::parse(mbref, {}, sm);
   // Defensive programming.
   if (!sourceMap && !handler.haveErrors())
     sm.error(SMLoc{}, "internal error");

unittests/VMRuntime/StackTracesTreeTest.cpp

@@ -122,7 +122,8 @@ struct StackTracesTreeTest : public RuntimeTestFixtureBase {
     llvh::raw_string_ostream resStream(res);
     SourceErrorManager sm;
     sourceMapGen.outputAsJSON(resStream);
-    auto sourceMap = SourceMapParser::parse(res, /* baseDir */ "", sm);
+    llvh::MemoryBufferRef smBuf(res, "");
+    auto sourceMap = SourceMapParser::parse(smBuf, /* baseDir */ "", sm);
     assert(
         sm.getErrorCount() == 0 && "source map generation or parsing failed");
     return sourceMap;