Debugger: move implementation to a separate folder.

src/liveedit-debugger.js

-// Copyright 2012 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// LiveEdit feature implementation. The script should be executed after
-// debug-debugger.js.
-
-// A LiveEdit namespace. It contains functions that modifies JavaScript code
-// according to changes of script source (if possible).
-//
-// When new script source is put in, the difference is calculated textually,
-// in form of list of delete/add/change chunks. The functions that include
-// change chunk(s) get recompiled, or their enclosing functions are
-// recompiled instead.
-// If the function may not be recompiled (e.g. it was completely erased in new
-// version of the script) it remains unchanged, but the code that could
-// create a new instance of this function goes away. An old version of script
-// is created to back up this obsolete function.
-// All unchanged functions have their positions updated accordingly.
-//
-// LiveEdit namespace is declared inside a single function constructor.
-
-"use strict";
-
-Debug.LiveEdit = new function() {
-
-  // Forward declaration for minifier.
-  var FunctionStatus;
-
-  // Applies the change to the script.
-  // The change is in form of list of chunks encoded in a single array as
-  // a series of triplets (pos1_start, pos1_end, pos2_end)
-  function ApplyPatchMultiChunk(script, diff_array, new_source, preview_only,
-      change_log) {
-
-    var old_source = script.source;
-
-    // Gather compile information about old version of script.
-    var old_compile_info = GatherCompileInfo(old_source, script);
-
-    // Build tree structures for old and new versions of the script.
-    var root_old_node = BuildCodeInfoTree(old_compile_info);
-
-    var pos_translator = new PosTranslator(diff_array);
-
-    // Analyze changes.
-    MarkChangedFunctions(root_old_node, pos_translator.GetChunks());
-
-    // Find all SharedFunctionInfo's that were compiled from this script.
-    FindLiveSharedInfos(root_old_node, script);
-
-    // Gather compile information about new version of script.
-    var new_compile_info;
-    try {
-      new_compile_info = GatherCompileInfo(new_source, script);
-    } catch (e) {
-      var failure =
-          new Failure("Failed to compile new version of script: " + e);
-      if (e instanceof SyntaxError) {
-        var details = {
-          type: "liveedit_compile_error",
-          syntaxErrorMessage: e.message
-        };
-        CopyErrorPositionToDetails(e, details);
-        failure.details = details;
-      }
-      throw failure;
-    }
-    var root_new_node = BuildCodeInfoTree(new_compile_info);
-
-    // Link recompiled script data with other data.
-    FindCorrespondingFunctions(root_old_node, root_new_node);
-
-    // Prepare to-do lists.
-    var replace_code_list = new Array();
-    var link_to_old_script_list = new Array();
-    var link_to_original_script_list = new Array();
-    var update_positions_list = new Array();
-
-    function HarvestTodo(old_node) {
-      function CollectDamaged(node) {
-        link_to_old_script_list.push(node);
-        for (var i = 0; i < node.children.length; i++) {
-          CollectDamaged(node.children[i]);
-        }
-      }
-
-      // Recursively collects all newly compiled functions that are going into
-      // business and should have link to the actual script updated.
-      function CollectNew(node_list) {
-        for (var i = 0; i < node_list.length; i++) {
-          link_to_original_script_list.push(node_list[i]);
-          CollectNew(node_list[i].children);
-        }
-      }
-
-      if (old_node.status == FunctionStatus.DAMAGED) {
-        CollectDamaged(old_node);
-        return;
-      }
-      if (old_node.status == FunctionStatus.UNCHANGED) {
-        update_positions_list.push(old_node);
-      } else if (old_node.status == FunctionStatus.SOURCE_CHANGED) {
-        update_positions_list.push(old_node);
-      } else if (old_node.status == FunctionStatus.CHANGED) {
-        replace_code_list.push(old_node);
-        CollectNew(old_node.unmatched_new_nodes);
-      }
-      for (var i = 0; i < old_node.children.length; i++) {
-        HarvestTodo(old_node.children[i]);
-      }
-    }
-
-    var preview_description = {
-        change_tree: DescribeChangeTree(root_old_node),
-        textual_diff: {
-          old_len: old_source.length,
-          new_len: new_source.length,
-          chunks: diff_array
-        },
-        updated: false
-    };
-
-    if (preview_only) {
-      return preview_description;
-    }
-
-    HarvestTodo(root_old_node);
-
-    // Collect shared infos for functions whose code need to be patched.
-    var replaced_function_infos = new Array();
-    for (var i = 0; i < replace_code_list.length; i++) {
-      var live_shared_function_infos =
-          replace_code_list[i].live_shared_function_infos;
-
-      if (live_shared_function_infos) {
-        for (var j = 0; j < live_shared_function_infos.length; j++) {
-          replaced_function_infos.push(live_shared_function_infos[j]);
-        }
-      }
-    }
-
-    // We haven't changed anything before this line yet.
-    // Committing all changes.
-
-    // Check that function being patched is not currently on stack or drop them.
-    var dropped_functions_number =
-        CheckStackActivations(replaced_function_infos, change_log);
-
-    // Our current implementation requires client to manually issue "step in"
-    // command for correct stack state if the stack was modified.
-    preview_description.stack_modified = dropped_functions_number != 0;
-
-    // Start with breakpoints. Convert their line/column positions and
-    // temporary remove.
-    var break_points_restorer = TemporaryRemoveBreakPoints(script, change_log);
-
-    var old_script;
-
-    // Create an old script only if there are function that should be linked
-    // to old version.
-    if (link_to_old_script_list.length == 0) {
-      %LiveEditReplaceScript(script, new_source, null);
-      old_script = UNDEFINED;
-    } else {
-      var old_script_name = CreateNameForOldScript(script);
-
-      // Update the script text and create a new script representing an old
-      // version of the script.
-      old_script = %LiveEditReplaceScript(script, new_source,
-          old_script_name);
-
-      var link_to_old_script_report = new Array();
-      change_log.push( { linked_to_old_script: link_to_old_script_report } );
-
-      // We need to link to old script all former nested functions.
-      for (var i = 0; i < link_to_old_script_list.length; i++) {
-        LinkToOldScript(link_to_old_script_list[i], old_script,
-            link_to_old_script_report);
-      }
-
-      preview_description.created_script_name = old_script_name;
-    }
-
-    // Link to an actual script all the functions that we are going to use.
-    for (var i = 0; i < link_to_original_script_list.length; i++) {
-      %LiveEditFunctionSetScript(
-          link_to_original_script_list[i].info.shared_function_info, script);
-    }
-
-    for (var i = 0; i < replace_code_list.length; i++) {
-      PatchFunctionCode(replace_code_list[i], change_log);
-    }
-
-    var position_patch_report = new Array();
-    change_log.push( {position_patched: position_patch_report} );
-
-    for (var i = 0; i < update_positions_list.length; i++) {
-      // TODO(LiveEdit): take into account whether it's source_changed or
-      // unchanged and whether positions changed at all.
-      PatchPositions(update_positions_list[i], diff_array,
-          position_patch_report);
-
-      if (update_positions_list[i].live_shared_function_infos) {
-        update_positions_list[i].live_shared_function_infos.
-            forEach(function (info) {
-                %LiveEditFunctionSourceUpdated(info.raw_array);
-              });
-      }
-    }
-
-    break_points_restorer(pos_translator, old_script);
-
-    preview_description.updated = true;
-    return preview_description;
-  }
-  // Function is public.
-  this.ApplyPatchMultiChunk = ApplyPatchMultiChunk;
-
-
-  // Fully compiles source string as a script. Returns Array of
-  // FunctionCompileInfo -- a descriptions of all functions of the script.
-  // Elements of array are ordered by start positions of functions (from top
-  // to bottom) in the source. Fields outer_index and next_sibling_index help
-  // to navigate the nesting structure of functions.
-  //
-  // All functions get compiled linked to script provided as parameter script.
-  // TODO(LiveEdit): consider not using actual scripts as script, because
-  // we have to manually erase all links right after compile.
-  function GatherCompileInfo(source, script) {
-    // Get function info, elements are partially sorted (it is a tree of
-    // nested functions serialized as parent followed by serialized children.
-    var raw_compile_info = %LiveEditGatherCompileInfo(script, source);
-
-    // Sort function infos by start position field.
-    var compile_info = new Array();
-    var old_index_map = new Array();
-    for (var i = 0; i < raw_compile_info.length; i++) {
-      var info = new FunctionCompileInfo(raw_compile_info[i]);
-      // Remove all links to the actual script. Breakpoints system and
-      // LiveEdit itself believe that any function in heap that points to a
-      // particular script is a regular function.
-      // For some functions we will restore this link later.
-      %LiveEditFunctionSetScript(info.shared_function_info, UNDEFINED);
-      compile_info.push(info);
-      old_index_map.push(i);
-    }
-
-    for (var i = 0; i < compile_info.length; i++) {
-      var k = i;
-      for (var j = i + 1; j < compile_info.length; j++) {
-        if (compile_info[k].start_position > compile_info[j].start_position) {
-          k = j;
-        }
-      }
-      if (k != i) {
-        var temp_info = compile_info[k];
-        var temp_index = old_index_map[k];
-        compile_info[k] = compile_info[i];
-        old_index_map[k] = old_index_map[i];
-        compile_info[i] = temp_info;
-        old_index_map[i] = temp_index;
-      }
-    }
-
-    // After sorting update outer_index field using old_index_map. Also
-    // set next_sibling_index field.
-    var current_index = 0;
-
-    // The recursive function, that goes over all children of a particular
-    // node (i.e. function info).
-    function ResetIndexes(new_parent_index, old_parent_index) {
-      var previous_sibling = -1;
-      while (current_index < compile_info.length &&
-          compile_info[current_index].outer_index == old_parent_index) {
-        var saved_index = current_index;
-        compile_info[saved_index].outer_index = new_parent_index;
-        if (previous_sibling != -1) {
-          compile_info[previous_sibling].next_sibling_index = saved_index;
-        }
-        previous_sibling = saved_index;
-        current_index++;
-        ResetIndexes(saved_index, old_index_map[saved_index]);
-      }
-      if (previous_sibling != -1) {
-        compile_info[previous_sibling].next_sibling_index = -1;
-      }
-    }
-
-    ResetIndexes(-1, -1);
-    Assert(current_index == compile_info.length);
-
-    return compile_info;
-  }
-
-
-  // Replaces function's Code.
-  function PatchFunctionCode(old_node, change_log) {
-    var new_info = old_node.corresponding_node.info;
-    if (old_node.live_shared_function_infos) {
-      old_node.live_shared_function_infos.forEach(function (old_info) {
-        %LiveEditReplaceFunctionCode(new_info.raw_array,
-                                     old_info.raw_array);
-
-        // The function got a new code. However, this new code brings all new
-        // instances of SharedFunctionInfo for nested functions. However,
-        // we want the original instances to be used wherever possible.
-        // (This is because old instances and new instances will be both
-        // linked to a script and breakpoints subsystem does not really
-        // expects this; neither does LiveEdit subsystem on next call).
-        for (var i = 0; i < old_node.children.length; i++) {
-          if (old_node.children[i].corresponding_node) {
-            var corresponding_child_info =
-                old_node.children[i].corresponding_node.info.
-                    shared_function_info;
-
-            if (old_node.children[i].live_shared_function_infos) {
-              old_node.children[i].live_shared_function_infos.
-                  forEach(function (old_child_info) {
-                    %LiveEditReplaceRefToNestedFunction(
-                        old_info.info,
-                        corresponding_child_info,
-                        old_child_info.info);
-                  });
-            }
-          }
-        }
-      });
-
-      change_log.push( {function_patched: new_info.function_name} );
-    } else {
-      change_log.push( {function_patched: new_info.function_name,
-          function_info_not_found: true} );
-    }
-  }
-
-
-  // Makes a function associated with another instance of a script (the
-  // one representing its old version). This way the function still
-  // may access its own text.
-  function LinkToOldScript(old_info_node, old_script, report_array) {
-    if (old_info_node.live_shared_function_infos) {
-      old_info_node.live_shared_function_infos.
-          forEach(function (info) {
-            %LiveEditFunctionSetScript(info.info, old_script);
-          });
-
-      report_array.push( { name: old_info_node.info.function_name } );
-    } else {
-      report_array.push(
-          { name: old_info_node.info.function_name, not_found: true } );
-    }
-  }
-
-
-  // Returns function that restores breakpoints.
-  function TemporaryRemoveBreakPoints(original_script, change_log) {
-    var script_break_points = GetScriptBreakPoints(original_script);
-
-    var break_points_update_report = [];
-    change_log.push( { break_points_update: break_points_update_report } );
-
-    var break_point_old_positions = [];
-    for (var i = 0; i < script_break_points.length; i++) {
-      var break_point = script_break_points[i];
-
-      break_point.clear();
-
-      // TODO(LiveEdit): be careful with resource offset here.
-      var break_point_position = Debug.findScriptSourcePosition(original_script,
-          break_point.line(), break_point.column());
-
-      var old_position_description = {
-          position: break_point_position,
-          line: break_point.line(),
-          column: break_point.column()
-      };
-      break_point_old_positions.push(old_position_description);
-    }
-
-
-    // Restores breakpoints and creates their copies in the "old" copy of
-    // the script.
-    return function (pos_translator, old_script_copy_opt) {
-      // Update breakpoints (change positions and restore them in old version
-      // of script.
-      for (var i = 0; i < script_break_points.length; i++) {
-        var break_point = script_break_points[i];
-        if (old_script_copy_opt) {
-          var clone = break_point.cloneForOtherScript(old_script_copy_opt);
-          clone.set(old_script_copy_opt);
-
-          break_points_update_report.push( {
-            type: "copied_to_old",
-            id: break_point.number(),
-            new_id: clone.number(),
-            positions: break_point_old_positions[i]
-            } );
-        }
-
-        var updated_position = pos_translator.Translate(
-            break_point_old_positions[i].position,
-            PosTranslator.ShiftWithTopInsideChunkHandler);
-
-        var new_location =
-            original_script.locationFromPosition(updated_position, false);
-
-        break_point.update_positions(new_location.line, new_location.column);
-
-        var new_position_description = {
-            position: updated_position,
-            line: new_location.line,
-            column: new_location.column
-        };
-
-        break_point.set(original_script);
-
-        break_points_update_report.push( { type: "position_changed",
-          id: break_point.number(),
-          old_positions: break_point_old_positions[i],
-          new_positions: new_position_description
-          } );
-      }
-    };
-  }
-
-
-  function Assert(condition, message) {
-    if (!condition) {
-      if (message) {
-        throw "Assert " + message;
-      } else {
-        throw "Assert";
-      }
-    }
-  }
-
-  function DiffChunk(pos1, pos2, len1, len2) {
-    this.pos1 = pos1;
-    this.pos2 = pos2;
-    this.len1 = len1;
-    this.len2 = len2;
-  }
-
-  function PosTranslator(diff_array) {
-    var chunks = new Array();
-    var current_diff = 0;
-    for (var i = 0; i < diff_array.length; i += 3) {
-      var pos1_begin = diff_array[i];
-      var pos2_begin = pos1_begin + current_diff;
-      var pos1_end = diff_array[i + 1];
-      var pos2_end = diff_array[i + 2];
-      chunks.push(new DiffChunk(pos1_begin, pos2_begin, pos1_end - pos1_begin,
-          pos2_end - pos2_begin));
-      current_diff = pos2_end - pos1_end;
-    }
-    this.chunks = chunks;
-  }
-  PosTranslator.prototype.GetChunks = function() {
-    return this.chunks;
-  };
-
-  PosTranslator.prototype.Translate = function(pos, inside_chunk_handler) {
-    var array = this.chunks;
-    if (array.length == 0 || pos < array[0].pos1) {
-      return pos;
-    }
-    var chunk_index1 = 0;
-    var chunk_index2 = array.length - 1;
-
-    while (chunk_index1 < chunk_index2) {
-      var middle_index = Math.floor((chunk_index1 + chunk_index2) / 2);
-      if (pos < array[middle_index + 1].pos1) {
-        chunk_index2 = middle_index;
-      } else {
-        chunk_index1 = middle_index + 1;
-      }
-    }
-    var chunk = array[chunk_index1];
-    if (pos >= chunk.pos1 + chunk.len1) {
-      return pos + chunk.pos2 + chunk.len2 - chunk.pos1 - chunk.len1;
-    }
-
-    if (!inside_chunk_handler) {
-      inside_chunk_handler = PosTranslator.DefaultInsideChunkHandler;
-    }
-    return inside_chunk_handler(pos, chunk);
-  };
-
-  PosTranslator.DefaultInsideChunkHandler = function(pos, diff_chunk) {
-    Assert(false, "Cannot translate position in changed area");
-  };
-
-  PosTranslator.ShiftWithTopInsideChunkHandler =
-      function(pos, diff_chunk) {
-    // We carelessly do not check whether we stay inside the chunk after
-    // translation.
-    return pos - diff_chunk.pos1 + diff_chunk.pos2;
-  };
-
-  var FunctionStatus = {
-      // No change to function or its inner functions; however its positions
-      // in script may have been shifted.
-      UNCHANGED: "unchanged",
-      // The code of a function remains unchanged, but something happened inside
-      // some inner functions.
-      SOURCE_CHANGED: "source changed",
-      // The code of a function is changed or some nested function cannot be
-      // properly patched so this function must be recompiled.
-      CHANGED: "changed",
-      // Function is changed but cannot be patched.
-      DAMAGED: "damaged"
-  };
-
-  function CodeInfoTreeNode(code_info, children, array_index) {
-    this.info = code_info;
-    this.children = children;
-    // an index in array of compile_info
-    this.array_index = array_index;
-    this.parent = UNDEFINED;
-
-    this.status = FunctionStatus.UNCHANGED;
-    // Status explanation is used for debugging purposes and will be shown
-    // in user UI if some explanations are needed.
-    this.status_explanation = UNDEFINED;
-    this.new_start_pos = UNDEFINED;
-    this.new_end_pos = UNDEFINED;
-    this.corresponding_node = UNDEFINED;
-    this.unmatched_new_nodes = UNDEFINED;
-
-    // 'Textual' correspondence/matching is weaker than 'pure'
-    // correspondence/matching. We need 'textual' level for visual presentation
-    // in UI, we use 'pure' level for actual code manipulation.
-    // Sometimes only function body is changed (functions in old and new script
-    // textually correspond), but we cannot patch the code, so we see them
-    // as an old function deleted and new function created.
-    this.textual_corresponding_node = UNDEFINED;
-    this.textually_unmatched_new_nodes = UNDEFINED;
-
-    this.live_shared_function_infos = UNDEFINED;
-  }
-
-  // From array of function infos that is implicitly a tree creates
-  // an actual tree of functions in script.
-  function BuildCodeInfoTree(code_info_array) {
-    // Throughtout all function we iterate over input array.
-    var index = 0;
-
-    // Recursive function that builds a branch of tree.
-    function BuildNode() {
-      var my_index = index;
-      index++;
-      var child_array = new Array();
-      while (index < code_info_array.length &&
-          code_info_array[index].outer_index == my_index) {
-        child_array.push(BuildNode());
-      }
-      var node = new CodeInfoTreeNode(code_info_array[my_index], child_array,
-          my_index);
-      for (var i = 0; i < child_array.length; i++) {
-        child_array[i].parent = node;
-      }
-      return node;
-    }
-
-    var root = BuildNode();
-    Assert(index == code_info_array.length);
-    return root;
-  }
-
-  // Applies a list of the textual diff chunks onto the tree of functions.
-  // Determines status of each function (from unchanged to damaged). However
-  // children of unchanged functions are ignored.
-  function MarkChangedFunctions(code_info_tree, chunks) {
-
-    // A convenient iterator over diff chunks that also translates
-    // positions from old to new in a current non-changed part of script.
-    var chunk_it = new function() {
-      var chunk_index = 0;
-      var pos_diff = 0;
-      this.current = function() { return chunks[chunk_index]; };
-      this.next = function() {
-        var chunk = chunks[chunk_index];
-        pos_diff = chunk.pos2 + chunk.len2 - (chunk.pos1 + chunk.len1);
-        chunk_index++;
-      };
-      this.done = function() { return chunk_index >= chunks.length; };
-      this.TranslatePos = function(pos) { return pos + pos_diff; };
-    };
-
-    // A recursive function that processes internals of a function and all its
-    // inner functions. Iterator chunk_it initially points to a chunk that is
-    // below function start.
-    function ProcessInternals(info_node) {
-      info_node.new_start_pos = chunk_it.TranslatePos(
-          info_node.info.start_position);
-      var child_index = 0;
-      var code_changed = false;
-      var source_changed = false;
-      // Simultaneously iterates over child functions and over chunks.
-      while (!chunk_it.done() &&
-          chunk_it.current().pos1 < info_node.info.end_position) {
-        if (child_index < info_node.children.length) {
-          var child = info_node.children[child_index];
-
-          if (child.info.end_position <= chunk_it.current().pos1) {
-            ProcessUnchangedChild(child);
-            child_index++;
-            continue;
-          } else if (child.info.start_position >=
-              chunk_it.current().pos1 + chunk_it.current().len1) {
-            code_changed = true;
-            chunk_it.next();
-            continue;
-          } else if (child.info.start_position <= chunk_it.current().pos1 &&
-              child.info.end_position >= chunk_it.current().pos1 +
-              chunk_it.current().len1) {
-            ProcessInternals(child);
-            source_changed = source_changed ||
-                ( child.status != FunctionStatus.UNCHANGED );
-            code_changed = code_changed ||
-                ( child.status == FunctionStatus.DAMAGED );
-            child_index++;
-            continue;
-          } else {
-            code_changed = true;
-            child.status = FunctionStatus.DAMAGED;
-            child.status_explanation =
-                "Text diff overlaps with function boundary";
-            child_index++;
-            continue;
-          }
-        } else {
-          if (chunk_it.current().pos1 + chunk_it.current().len1 <=
-              info_node.info.end_position) {
-            info_node.status = FunctionStatus.CHANGED;
-            chunk_it.next();
-            continue;
-          } else {
-            info_node.status = FunctionStatus.DAMAGED;
-            info_node.status_explanation =
-                "Text diff overlaps with function boundary";
-            return;
-          }
-        }
-        Assert("Unreachable", false);
-      }
-      while (child_index < info_node.children.length) {
-        var child = info_node.children[child_index];
-        ProcessUnchangedChild(child);
-        child_index++;
-      }
-      if (code_changed) {
-        info_node.status = FunctionStatus.CHANGED;
-      } else if (source_changed) {
-        info_node.status = FunctionStatus.SOURCE_CHANGED;
-      }
-      info_node.new_end_pos =
-          chunk_it.TranslatePos(info_node.info.end_position);
-    }
-
-    function ProcessUnchangedChild(node) {
-      node.new_start_pos = chunk_it.TranslatePos(node.info.start_position);
-      node.new_end_pos = chunk_it.TranslatePos(node.info.end_position);
-    }
-
-    ProcessInternals(code_info_tree);
-  }
-
-  // For each old function (if it is not damaged) tries to find a corresponding
-  // function in new script. Typically it should succeed (non-damaged functions
-  // by definition may only have changes inside their bodies). However there are
-  // reasons for correspondence not to be found; function with unmodified text
-  // in new script may become enclosed into other function; the innocent change
-  // inside function body may in fact be something like "} function B() {" that
-  // splits a function into 2 functions.
-  function FindCorrespondingFunctions(old_code_tree, new_code_tree) {
-
-    // A recursive function that tries to find a correspondence for all
-    // child functions and for their inner functions.
-    function ProcessNode(old_node, new_node) {
-      var scope_change_description =
-          IsFunctionContextLocalsChanged(old_node.info, new_node.info);
-      if (scope_change_description) {
-          old_node.status = FunctionStatus.CHANGED;
-      }
-
-      var old_children = old_node.children;
-      var new_children = new_node.children;
-
-      var unmatched_new_nodes_list = [];
-      var textually_unmatched_new_nodes_list = [];
-
-      var old_index = 0;
-      var new_index = 0;
-      while (old_index < old_children.length) {
-        if (old_children[old_index].status == FunctionStatus.DAMAGED) {
-          old_index++;
-        } else if (new_index < new_children.length) {
-          if (new_children[new_index].info.start_position <
-              old_children[old_index].new_start_pos) {
-            unmatched_new_nodes_list.push(new_children[new_index]);
-            textually_unmatched_new_nodes_list.push(new_children[new_index]);
-            new_index++;
-          } else if (new_children[new_index].info.start_position ==
-              old_children[old_index].new_start_pos) {
-            if (new_children[new_index].info.end_position ==
-                old_children[old_index].new_end_pos) {
-              old_children[old_index].corresponding_node =
-                  new_children[new_index];
-              old_children[old_index].textual_corresponding_node =
-                  new_children[new_index];
-              if (scope_change_description) {
-                old_children[old_index].status = FunctionStatus.DAMAGED;
-                old_children[old_index].status_explanation =
-                    "Enclosing function is now incompatible. " +
-                    scope_change_description;
-                old_children[old_index].corresponding_node = UNDEFINED;
-              } else if (old_children[old_index].status !=
-                  FunctionStatus.UNCHANGED) {
-                ProcessNode(old_children[old_index],
-                    new_children[new_index]);
-                if (old_children[old_index].status == FunctionStatus.DAMAGED) {
-                  unmatched_new_nodes_list.push(
-                      old_children[old_index].corresponding_node);
-                  old_children[old_index].corresponding_node = UNDEFINED;
-                  old_node.status = FunctionStatus.CHANGED;
-                }
-              }
-            } else {
-              old_children[old_index].status = FunctionStatus.DAMAGED;
-              old_children[old_index].status_explanation =
-                  "No corresponding function in new script found";
-              old_node.status = FunctionStatus.CHANGED;
-              unmatched_new_nodes_list.push(new_children[new_index]);
-              textually_unmatched_new_nodes_list.push(new_children[new_index]);
-            }
-            new_index++;
-            old_index++;
-          } else {
-            old_children[old_index].status = FunctionStatus.DAMAGED;
-            old_children[old_index].status_explanation =
-                "No corresponding function in new script found";
-            old_node.status = FunctionStatus.CHANGED;
-            old_index++;
-          }
-        } else {
-          old_children[old_index].status = FunctionStatus.DAMAGED;
-          old_children[old_index].status_explanation =
-              "No corresponding function in new script found";
-          old_node.status = FunctionStatus.CHANGED;
-          old_index++;
-        }
-      }
-
-      while (new_index < new_children.length) {
-        unmatched_new_nodes_list.push(new_children[new_index]);
-        textually_unmatched_new_nodes_list.push(new_children[new_index]);
-        new_index++;
-      }
-
-      if (old_node.status == FunctionStatus.CHANGED) {
-        if (old_node.info.param_num != new_node.info.param_num) {
-          old_node.status = FunctionStatus.DAMAGED;
-          old_node.status_explanation = "Changed parameter number: " +
-              old_node.info.param_num + " and " + new_node.info.param_num;
-        }
-      }
-      old_node.unmatched_new_nodes = unmatched_new_nodes_list;
-      old_node.textually_unmatched_new_nodes =
-          textually_unmatched_new_nodes_list;
-    }
-
-    ProcessNode(old_code_tree, new_code_tree);
-
-    old_code_tree.corresponding_node = new_code_tree;
-    old_code_tree.textual_corresponding_node = new_code_tree;
-
-    Assert(old_code_tree.status != FunctionStatus.DAMAGED,
-        "Script became damaged");
-  }
-
-  function FindLiveSharedInfos(old_code_tree, script) {
-    var shared_raw_list = %LiveEditFindSharedFunctionInfosForScript(script);
-
-    var shared_infos = new Array();
-
-    for (var i = 0; i < shared_raw_list.length; i++) {
-      shared_infos.push(new SharedInfoWrapper(shared_raw_list[i]));
-    }
-
-    // Finds all SharedFunctionInfos that corresponds to compile info
-    // in old version of the script.
-    function FindFunctionInfos(compile_info) {
-      var wrappers = [];
-
-      for (var i = 0; i < shared_infos.length; i++) {
-        var wrapper = shared_infos[i];
-        if (wrapper.start_position == compile_info.start_position &&
-            wrapper.end_position == compile_info.end_position) {
-          wrappers.push(wrapper);
-        }
-      }
-
-      if (wrappers.length > 0) {
-        return wrappers;
-      }
-    }
-
-    function TraverseTree(node) {
-      node.live_shared_function_infos = FindFunctionInfos(node.info);
-
-      for (var i = 0; i < node.children.length; i++) {
-        TraverseTree(node.children[i]);
-      }
-    }
-
-    TraverseTree(old_code_tree);
-  }
-
-
-  // An object describing function compilation details. Its index fields
-  // apply to indexes inside array that stores these objects.
-  function FunctionCompileInfo(raw_array) {
-    this.function_name = raw_array[0];
-    this.start_position = raw_array[1];
-    this.end_position = raw_array[2];
-    this.param_num = raw_array[3];
-    this.code = raw_array[4];
-    this.code_scope_info = raw_array[5];
-    this.scope_info = raw_array[6];
-    this.outer_index = raw_array[7];
-    this.shared_function_info = raw_array[8];
-    this.next_sibling_index = null;
-    this.raw_array = raw_array;
-  }
-
-  function SharedInfoWrapper(raw_array) {
-    this.function_name = raw_array[0];
-    this.start_position = raw_array[1];
-    this.end_position = raw_array[2];
-    this.info = raw_array[3];
-    this.raw_array = raw_array;
-  }
-
-  // Changes positions (including all statements) in function.
-  function PatchPositions(old_info_node, diff_array, report_array) {
-    if (old_info_node.live_shared_function_infos) {
-      old_info_node.live_shared_function_infos.forEach(function (info) {
-          %LiveEditPatchFunctionPositions(info.raw_array,
-                                          diff_array);
-      });
-
-      report_array.push( { name: old_info_node.info.function_name } );
-    } else {
-      // TODO(LiveEdit): function is not compiled yet or is already collected.
-      report_array.push(
-          { name: old_info_node.info.function_name, info_not_found: true } );
-    }
-  }
-
-  // Adds a suffix to script name to mark that it is old version.
-  function CreateNameForOldScript(script) {
-    // TODO(635): try better than this; support several changes.
-    return script.name + " (old)";
-  }
-
-  // Compares a function scope heap structure, old and new version, whether it
-  // changed or not. Returns explanation if they differ.
-  function IsFunctionContextLocalsChanged(function_info1, function_info2) {
-    var scope_info1 = function_info1.scope_info;
-    var scope_info2 = function_info2.scope_info;
-
-    var scope_info1_text;
-    var scope_info2_text;
-
-    if (scope_info1) {
-      scope_info1_text = scope_info1.toString();
-    } else {
-      scope_info1_text = "";
-    }
-    if (scope_info2) {
-      scope_info2_text = scope_info2.toString();
-    } else {
-      scope_info2_text = "";
-    }
-
-    if (scope_info1_text != scope_info2_text) {
-      return "Variable map changed: [" + scope_info1_text +
-          "] => [" + scope_info2_text + "]";
-    }
-    // No differences. Return undefined.
-    return;
-  }
-
-  // Minifier forward declaration.
-  var FunctionPatchabilityStatus;
-
-  // For array of wrapped shared function infos checks that none of them
-  // have activations on stack (of any thread). Throws a Failure exception
-  // if this proves to be false.
-  function CheckStackActivations(shared_wrapper_list, change_log) {
-    var shared_list = new Array();
-    for (var i = 0; i < shared_wrapper_list.length; i++) {
-      shared_list[i] = shared_wrapper_list[i].info;
-    }
-    var result = %LiveEditCheckAndDropActivations(shared_list, true);
-    if (result[shared_list.length]) {
-      // Extra array element may contain error message.
-      throw new Failure(result[shared_list.length]);
-    }
-
-    var problems = new Array();
-    var dropped = new Array();
-    for (var i = 0; i < shared_list.length; i++) {
-      var shared = shared_wrapper_list[i];
-      if (result[i] == FunctionPatchabilityStatus.REPLACED_ON_ACTIVE_STACK) {
-        dropped.push({ name: shared.function_name } );
-      } else if (result[i] != FunctionPatchabilityStatus.AVAILABLE_FOR_PATCH) {
-        var description = {
-            name: shared.function_name,
-            start_pos: shared.start_position,
-            end_pos: shared.end_position,
-            replace_problem:
-                FunctionPatchabilityStatus.SymbolName(result[i])
-        };
-        problems.push(description);
-      }
-    }
-    if (dropped.length > 0) {
-      change_log.push({ dropped_from_stack: dropped });
-    }
-    if (problems.length > 0) {
-      change_log.push( { functions_on_stack: problems } );
-      throw new Failure("Blocked by functions on stack");
-    }
-
-    return dropped.length;
-  }
-
-  // A copy of the FunctionPatchabilityStatus enum from liveedit.h
-  var FunctionPatchabilityStatus = {
-      AVAILABLE_FOR_PATCH: 1,
-      BLOCKED_ON_ACTIVE_STACK: 2,
-      BLOCKED_ON_OTHER_STACK: 3,
-      BLOCKED_UNDER_NATIVE_CODE: 4,
-      REPLACED_ON_ACTIVE_STACK: 5,
-      BLOCKED_UNDER_GENERATOR: 6,
-      BLOCKED_ACTIVE_GENERATOR: 7
-  };
-
-  FunctionPatchabilityStatus.SymbolName = function(code) {
-    var enumeration = FunctionPatchabilityStatus;
-    for (var name in enumeration) {
-      if (enumeration[name] == code) {
-        return name;
-      }
-    }
-  };
-
-
-  // A logical failure in liveedit process. This means that change_log
-  // is valid and consistent description of what happened.
-  function Failure(message) {
-    this.message = message;
-  }
-  // Function (constructor) is public.
-  this.Failure = Failure;
-
-  Failure.prototype.toString = function() {
-    return "LiveEdit Failure: " + this.message;
-  };
-
-  function CopyErrorPositionToDetails(e, details) {
-    function createPositionStruct(script, position) {
-      if (position == -1) return;
-      var location = script.locationFromPosition(position, true);
-      if (location == null) return;
-      return {
-        line: location.line + 1,
-        column: location.column + 1,
-        position: position
-      };
-    }
-
-    if (!("scriptObject" in e) || !("startPosition" in e)) {
-      return;
-    }
-
-    var script = e.scriptObject;
-
-    var position_struct = {
-      start: createPositionStruct(script, e.startPosition),
-      end: createPositionStruct(script, e.endPosition)
-    };
-    details.position = position_struct;
-  }
-
-  // A testing entry.
-  function GetPcFromSourcePos(func, source_pos) {
-    return %GetFunctionCodePositionFromSource(func, source_pos);
-  }
-  // Function is public.
-  this.GetPcFromSourcePos = GetPcFromSourcePos;
-
-  // LiveEdit main entry point: changes a script text to a new string.
-  function SetScriptSource(script, new_source, preview_only, change_log) {
-    var old_source = script.source;
-    var diff = CompareStrings(old_source, new_source);
-    return ApplyPatchMultiChunk(script, diff, new_source, preview_only,
-        change_log);
-  }
-  // Function is public.
-  this.SetScriptSource = SetScriptSource;
-
-  function CompareStrings(s1, s2) {
-    return %LiveEditCompareStrings(s1, s2);
-  }
-
-  // Applies the change to the script.
-  // The change is always a substring (change_pos, change_pos + change_len)
-  // being replaced with a completely different string new_str.
-  // This API is a legacy and is obsolete.
-  //
-  // @param {Script} script that is being changed
-  // @param {Array} change_log a list that collects engineer-readable
-  //     description of what happened.
-  function ApplySingleChunkPatch(script, change_pos, change_len, new_str,
-      change_log) {
-    var old_source = script.source;
-
-    // Prepare new source string.
-    var new_source = old_source.substring(0, change_pos) +
-        new_str + old_source.substring(change_pos + change_len);
-
-    return ApplyPatchMultiChunk(script,
-        [ change_pos, change_pos + change_len, change_pos + new_str.length],
-        new_source, false, change_log);
-  }
-
-  // Creates JSON description for a change tree.
-  function DescribeChangeTree(old_code_tree) {
-
-    function ProcessOldNode(node) {
-      var child_infos = [];
-      for (var i = 0; i < node.children.length; i++) {
-        var child = node.children[i];
-        if (child.status != FunctionStatus.UNCHANGED) {
-          child_infos.push(ProcessOldNode(child));
-        }
-      }
-      var new_child_infos = [];
-      if (node.textually_unmatched_new_nodes) {
-        for (var i = 0; i < node.textually_unmatched_new_nodes.length; i++) {
-          var child = node.textually_unmatched_new_nodes[i];
-          new_child_infos.push(ProcessNewNode(child));
-        }
-      }
-      var res = {
-        name: node.info.function_name,
-        positions: DescribePositions(node),
-        status: node.status,
-        children: child_infos,
-        new_children: new_child_infos
-      };
-      if (node.status_explanation) {
-        res.status_explanation = node.status_explanation;
-      }
-      if (node.textual_corresponding_node) {
-        res.new_positions = DescribePositions(node.textual_corresponding_node);
-      }
-      return res;
-    }
-
-    function ProcessNewNode(node) {
-      var child_infos = [];
-      // Do not list ancestors.
-      if (false) {
-        for (var i = 0; i < node.children.length; i++) {
-          child_infos.push(ProcessNewNode(node.children[i]));
-        }
-      }
-      var res = {
-        name: node.info.function_name,
-        positions: DescribePositions(node),
-        children: child_infos,
-      };
-      return res;
-    }
-
-    function DescribePositions(node) {
-      return {
-        start_position: node.info.start_position,
-        end_position: node.info.end_position
-      };
-    }
-
-    return ProcessOldNode(old_code_tree);
-  }
-
-  // Functions are public for tests.
-  this.TestApi = {
-    PosTranslator: PosTranslator,
-    CompareStrings: CompareStrings,
-    ApplySingleChunkPatch: ApplySingleChunkPatch
-  };
-};