react-native/ReactCommon/cxxreact/JSCHelpers.cpp

// Copyright 2004-present Facebook. All Rights Reserved.

#include "JSCHelpers.h"

#include <JavaScriptCore/JSStringRef.h>
#include <folly/String.h>
#include <glog/logging.h>

#include "Value.h"

namespace facebook {
namespace react {

void installGlobalFunction(
    JSGlobalContextRef ctx,
    const char* name,
    JSObjectCallAsFunctionCallback callback) {
  JSStringRef jsName = JSStringCreateWithUTF8CString(name);
  JSObjectRef functionObj = JSObjectMakeFunctionWithCallback(
      ctx, jsName, callback);
  JSObjectRef globalObject = JSContextGetGlobalObject(ctx);
  JSObjectSetProperty(ctx, globalObject, jsName, functionObj, 0, NULL);
  JSStringRelease(jsName);
}

JSValueRef makeJSCException(
    JSContextRef ctx,
    const char* exception_text) {
  JSStringRef message = JSStringCreateWithUTF8CString(exception_text);
  JSValueRef exceptionString = JSValueMakeString(ctx, message);
  JSStringRelease(message);
  return JSValueToObject(ctx, exceptionString, NULL);
}

String jsStringFromBigString(const JSBigString& bigstr) {
  if (bigstr.isAscii()) {
    return String::createExpectingAscii(bigstr.c_str(), bigstr.size());
  } else {
    return String(bigstr.c_str());
  }
}

JSValueRef evaluateScript(JSContextRef context, JSStringRef script, JSStringRef source) {
  JSValueRef exn, result;
  result = JSEvaluateScript(context, script, NULL, source, 0, &exn);
  if (result == nullptr) {
    Value exception = Value(context, exn);

    std::string exceptionText = exception.toString().str();

    // The null/empty-ness of source tells us if the JS came from a
    // file/resource, or was a constructed statement.  The location
    // info will include that source, if any.
    std::string locationInfo = source != nullptr ? String::ref(source).str() : "";
    Object exObject = exception.asObject();
    auto line = exObject.getProperty("line");
    if (line != nullptr && line.isNumber()) {
      if (locationInfo.empty() && line.asInteger() != 1) {
        // If there is a non-trivial line number, but there was no
        // location info, we include a placeholder, and the line
        // number.
        locationInfo = folly::to<std::string>("<unknown file>:", line.asInteger());
      } else if (!locationInfo.empty()) {
        // If there is location info, we always include the line
        // number, regardless of its value.
        locationInfo += folly::to<std::string>(":", line.asInteger());
      }
    }

    if (!locationInfo.empty()) {
      exceptionText += " (" + locationInfo + ")";
    }

    LOG(ERROR) << "Got JS Exception: " << exceptionText;

    Value jsStack = exObject.getProperty("stack");
    if (jsStack.isNull() || !jsStack.isString()) {
      throwJSExecutionException("%s", exceptionText.c_str());
    } else {
      LOG(ERROR) << "Got JS Stack: " << jsStack.toString().str();
      throwJSExecutionExceptionWithStack(
        exceptionText.c_str(), jsStack.toString().str().c_str());
    }
  }
  return result;
}

JSValueRef makeJSError(JSContextRef ctx, const char *error) {
  JSValueRef nestedException = nullptr;
  JSValueRef args[] = { Value(ctx, String(error)) };
  JSObjectRef errorObj = JSObjectMakeError(ctx, 1, args, &nestedException);
  if (nestedException != nullptr) {
    return std::move(args[0]);
  }
  return errorObj;
}

JSValueRef translatePendingCppExceptionToJSError(JSContextRef ctx, const char *exceptionLocation) {
  std::ostringstream msg;
  try {
    throw;
  } catch (const std::bad_alloc& ex) {
    throw; // We probably shouldn't try to handle this in JS
  } catch (const std::exception& ex) {
    msg << "C++ Exception in '" << exceptionLocation << "': " << ex.what();
    return makeJSError(ctx, msg.str().c_str());
  } catch (const char* ex) {
    msg << "C++ Exception (thrown as a char*) in '" << exceptionLocation << "': " << ex;
    return makeJSError(ctx, msg.str().c_str());
  } catch (...) {
    msg << "Unknown C++ Exception in '" << exceptionLocation << "'";
    return makeJSError(ctx, msg.str().c_str());
  }
}

} }