adjust source maps to account for node script wrapping

front_end/ndb/NdbMain.js

@@ -356,11 +356,6 @@ Ndb.RestartActionDelegate = class {
   }
 };
 
-SDK.DebuggerModel.prototype.scheduleStepIntoAsync = function() {
-  this._agent.scheduleStepIntoAsync();
-  this._agent.invoke_stepInto({breakOnAsyncCall: true});
-};
-
 // Temporary hack until frontend with fix is rolled.
 // fix: TBA.
 SDK.Target.prototype.decorateLabel = function(label) {
@@ -375,6 +370,23 @@ DOMTokenList.prototype.toggle = function(token, force) {
   return originalToggle.call(this, token, !!force);
 };
 
+/**
+ * @param {string} sourceURL
+ * @param {string} modulePrefix
+ * @param {SDK.DebuggerModel} debuggerModel
+ * @return {!Promise<boolean>}
+ */
+async function isNodeWrappedModule(sourceURL, modulePrefix, debuggerModel) {
+  for (const script of debuggerModel.scripts()) {
+    if (script.sourceURL === sourceURL) {
+      const content = await script.originalContentProvider().requestContent();
+      return content.startsWith(modulePrefix);
+    }
+  }
+
+  return false;
+}
+
 /**
  * @param {string} sourceMapURL
  * @param {string} compiledURL
@@ -385,11 +397,28 @@ SDK.TextSourceMap.load = async function(sourceMapURL, compiledURL) {
   const {payload, error} = await Ndb.backend.loadSourceMap(sourceMapURL, compiledURL);
   if (error || !payload)
     return null;
+
+  let textSourceMap;
   try {
-    return new SDK.TextSourceMap(compiledURL, sourceMapURL, payload);
+    textSourceMap = new SDK.TextSourceMap(compiledURL, sourceMapURL, payload);
   } catch (e) {
     console.error(e);
     Common.console.warn('DevTools failed to parse SourceMap: ' + sourceMapURL);
     return null;
   }
+
+  if (textSourceMap._baseURL.startsWith('file://')) {
+    try {
+      const modulePrefix = await Ndb.backend.getNodeScriptPrefix();
+      const debuggerModel = Array.from(Bindings.debuggerWorkspaceBinding._debuggerModelToData.keys())[1];
+      if (await isNodeWrappedModule(compiledURL, modulePrefix, debuggerModel))
+        for (const mapping of textSourceMap.mappings()) mapping.columnNumber += modulePrefix.length;
+    } catch (e) {
+      console.error(e);
+      Common.console.warn('DevTools failed to fix SourceMap for node script: ' + sourceMapURL);
+      // return the source map anyways.
+    }
+  }
+
+  return textSourceMap;
 };

lib/backend.js

@@ -17,6 +17,11 @@ const which = require('which');
 
 const fsReadFile = util.promisify(fs.readFile);
 
+const MODULE_WRAP_PREFIX = (() => {
+  const wrapped = require('module').wrap('☃');
+  return wrapped.substring(0, wrapped.indexOf('☃'));
+})();
+
 class Backend {
   constructor(window) {
     this._window = window;
@@ -72,6 +77,10 @@ class Backend {
     }
   }
 
+  getNodeScriptPrefix() {
+    return MODULE_WRAP_PREFIX;
+  }
+
   which(command) {
     return new Promise(resolve => which(command, (error, resolvedPath) => resolve({
       resolvedPath: resolvedPath,