From 79c55b1618342781c0029f5fe44ca90c3f37907a Mon Sep 17 00:00:00 2001
From: Michael Uleysky <uleysky@poi.dvo.ru>
Date: Fri, 5 Aug 2016 15:36:32 +1000
Subject: [PATCH] Add support for extended error reporting by functions
 (functions can return ObjectError object with description of error).

---
 include/common.h | 38 ++++++++++++++++++++++++++++++++------
 src/object.cpp   | 12 ++++++++++--
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/include/common.h b/include/common.h
index 02dea26..79a257b 100644
--- a/include/common.h
+++ b/include/common.h
@@ -36,15 +36,17 @@ inline std::string ToString<std::string>(std::string s) {return s;}
 // Base class for all objects
 class EXPORT ObjectBase
 {
-protected:
-// No save by default
-virtual const int8_t* Blob(size_t* size) const { *size=0; return 0; }
-virtual void DeallocBlob(const int8_t* ptr) const {};
-public:
+ protected:
+ bool err;
+ // No save by default
+ virtual const int8_t* Blob(size_t* size) const { *size=0; return 0; }
+ virtual void DeallocBlob(const int8_t* ptr) const {};
+ ObjectBase():err(false) {}
+ public:
 
- ObjectBase() = default;
  ObjectBase(const ObjectBase&) = delete;
  bool Save(const char* fname) const;
+ bool isError() const {return err;}
  // Pure virtual api
  virtual ~ObjectBase(){}
  virtual ObjectBase* Copy() const=0;
@@ -149,6 +151,30 @@ class OBTypeM<Func>
 };
 
 
+// Error class
+class EXPORT ObjectError: public ObjectBase
+{
+ std::string function, reason;
+ ObjectError() = delete;
+ ObjectError(const ObjectError&) = delete;
+ ObjectError(ObjectError&&) = delete;
+ public:
+ template<class F, class R>
+ ObjectError(F f, R r):function(f),reason(r) {ObjectBase::err=true;}
+ const std::string& Function() const {return function;}
+ const std::string& Reason() const {return reason;}
+ // Pure virtual overrides
+ ObjectBase* Copy() const override {return new ObjectError(function,reason);}
+ bool Print() const override
+ {
+  COUT(NORMAL)<<std::endl<<"Object type: "<<Type()<<std::endl;
+  COUT(NORMAL)<<"Value: "<<Function()<<": "<<Reason()<<std::endl;
+  return true;
+ }
+ std::string Type() const override {return "ERROR";}
+};
+
+
 // Template for objects without specific constructor/destructor
 template<class T>
 class EXPORT ObjectSimple: public ObjectBase
diff --git a/src/object.cpp b/src/object.cpp
index e6ffc1b..5060402 100644
--- a/src/object.cpp
+++ b/src/object.cpp
@@ -158,21 +158,29 @@ ObjectBase* Evaluate(ExecExpr& exp, bool* err)
     // Functions check already done, we know that our function exists.
     // Sequentally call all functions with given name
     auto bounds=G_funcs.equal_range(cse->Name());
+    std::list<const ObjectError*> errl;
     for(auto f=bounds.first; f!=bounds.second; ++f)
     {
      res=(*(f->second))(arg);
-     if(res!=nullptr) break;
+     if( !(res==nullptr || res->isError()) ) break;
+     if(res==nullptr) errl.push_back(new ObjectError("Some function", "unknown reason"));
+     else errl.push_back(dynamic_cast<const ObjectError*>(res));
     }
     // Remove previous element
     exp.erase(pr);
 
     // Error handling
-    if(nullptr==res)
+    if(!errl.empty())
     {
      const struct grammatic_location& loc=cse->Location();
      *err=true; // Raise error flag
      COUT(ERROR)<<"Can't evaluate function "<<cse->Name()<<" at line "<<loc.first_line<<", position "<<loc.first_column<<std::endl;
      for(const auto& inc: loc.incstack) COUT(ERROR)<<"   included from "<<inc.filename<<" at line "<<inc.line<<", position "<<inc.column<<std::endl;
+     for(auto& e: errl)
+     {
+      COUT(ERROR)<<e->Function()<<": "<<e->Reason()<<std::endl;
+      delete e;
+     }
      return nullptr;
     }
     // Replace function on returned value