Debugger: refactor ScopeIterator, FrameInspector and DebugEvaluate.

src/debug/debug-evaluate.h

+// Copyright 2015 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.
+
+#ifndef V8_DEBUG_DEBUG_EVALUATE_H_
+#define V8_DEBUG_DEBUG_EVALUATE_H_
+
+#include "src/frames.h"
+#include "src/objects.h"
+
+namespace v8 {
+namespace internal {
+
+class DebugEvaluate : public AllStatic {
+ public:
+  static MaybeHandle<Object> Global(Isolate* isolate, Handle<String> source,
+                                    bool disable_break,
+                                    Handle<Object> context_extension);
+
+  // Evaluate a piece of JavaScript in the context of a stack frame for
+  // debugging.  Things that need special attention are:
+  // - Parameters and stack-allocated locals need to be materialized.  Altered
+  //   values need to be written back to the stack afterwards.
+  // - The arguments object needs to materialized.
+  static MaybeHandle<Object> Local(Isolate* isolate, StackFrame::Id frame_id,
+                                   int inlined_jsframe_index,
+                                   Handle<String> source, bool disable_break,
+                                   Handle<Object> context_extension);
+
+ private:
+  // This class builds a context chain for evaluation of expressions
+  // in debugger.
+  // The scope chain leading up to a breakpoint where evaluation occurs
+  // looks like:
+  // - [a mix of with, catch and block scopes]
+  //    - [function stack + context]
+  //      - [outer context]
+  // The builder materializes all stack variables into properties of objects;
+  // the expression is then evaluated as if it is inside a series of 'with'
+  // statements using those objects. To this end, the builder builds a new
+  // context chain, based on a scope chain:
+  //   - every With and Catch scope begets a cloned context
+  //   - Block scope begets one or two contexts:
+  //       - if a block has context-allocated varaibles, its context is cloned
+  //       - stack locals are materizalized as a With context
+  //   - Local scope begets a With context for materizalized locals, chained to
+  //     original function context. Original function context is the end of
+  //     the chain.
+  class ContextBuilder {
+   public:
+    ContextBuilder(Isolate* isolate, JavaScriptFrame* frame,
+                   int inlined_jsframe_index);
+
+    void UpdateValues();
+
+    Handle<Context> innermost_context() const { return innermost_context_; }
+    Handle<SharedFunctionInfo> outer_info() const { return outer_info_; }
+
+   private:
+    struct ContextChainElement {
+      Handle<Context> original_context;
+      Handle<Context> cloned_context;
+      Handle<JSObject> materialized_object;
+      Handle<ScopeInfo> scope_info;
+    };
+
+    void RecordContextsInChain(Handle<Context>* inner_context,
+                               Handle<Context> first, Handle<Context> last);
+
+    Handle<JSObject> NewJSObjectWithNullProto();
+
+    // Helper function to find or create the arguments object for
+    // Runtime_DebugEvaluate.
+    void MaterializeArgumentsObject(Handle<JSObject> target,
+                                    Handle<JSFunction> function);
+
+    Handle<Context> MaterializeReceiver(Handle<Context> target,
+                                        Handle<JSFunction> function);
+
+    Handle<SharedFunctionInfo> outer_info_;
+    Handle<Context> innermost_context_;
+    List<ContextChainElement> context_chain_;
+    Isolate* isolate_;
+    JavaScriptFrame* frame_;
+    int inlined_jsframe_index_;
+  };
+
+  static MaybeHandle<Object> Evaluate(Isolate* isolate,
+                                      Handle<SharedFunctionInfo> outer_info,
+                                      Handle<Context> context,
+                                      Handle<Object> context_extension,
+                                      Handle<Object> receiver,
+                                      Handle<String> source);
+};
+
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_DEBUG_DEBUG_EVALUATE_H_