Restored before/after handlers.

peglib.h

@@ -1182,13 +1182,15 @@ public:
         holder_->accept(v);
     }
 
-    std::string                   name;
-    size_t                        id;
-    Action                        action;
-    std::function<std::string ()> error_message;
-    bool                          ignoreSemanticValue;
-    bool                          enablePackratParsing;
-    bool                          is_token;
+    std::string                    name;
+    size_t                         id;
+    Action                         action;
+    std::function<void (any& dt)>  before;
+    std::function<void (any& dt)>  after;
+    std::function<std::string ()>  error_message;
+    bool                           ignoreSemanticValue;
+    bool                           enablePackratParsing;
+    bool                           is_token;
 
 private:
     friend class DefinitionReference;
@@ -1225,6 +1227,10 @@ inline size_t Holder::parse(const char* s, size_t n, SemanticValues& sv, Context
     c.packrat(s, outer_->id, len, val, [&](any& val) {
         auto& chldsv = c.push();
 
+        if (outer_->before) {
+            outer_->before(dt);
+        }
+
         const auto& rule = *ope_;
         len = rule.parse(s, n, chldsv, c, dt);
 
@@ -1251,6 +1257,10 @@ inline size_t Holder::parse(const char* s, size_t n, SemanticValues& sv, Context
             }
         }
 
+        if (outer_->after) {
+            outer_->after(dt);
+        }
+
         c.pop();
     });
 
@@ -1793,8 +1803,13 @@ private:
 
         if (!r.ret) {
             if (log) {
-                auto line = line_info(s, r.error_pos);
-                log(line.first, line.second, r.message.empty() ? "syntax error" : r.message);
+                if (r.message_pos) {
+                    auto line = line_info(s, r.message_pos);
+                    log(line.first, line.second, r.message);
+                } else {
+                    auto line = line_info(s, r.error_pos);
+                    log(line.first, line.second, "syntax error");
+                }
             }
             return nullptr;
         }
@@ -2279,8 +2294,13 @@ private:
     void output_log(const char* s, size_t n, Log log, const Definition::Result& r) const {
         if (log) {
             if (!r.ret) { 
-                auto line = line_info(s, r.error_pos);
-                log(line.first, line.second, r.message.empty() ? "syntax error" : r.message);
+                if (r.message_pos) {
+                    auto line = line_info(s, r.message_pos);
+                    log(line.first, line.second, r.message);
+                } else {
+                    auto line = line_info(s, r.error_pos);
+                    log(line.first, line.second, "syntax error");
+                }
             } else if (r.len != n) {
                 auto line = line_info(s, s + r.len);
                 log(line.first, line.second, "syntax error");

test/test.cc

@@ -213,6 +213,48 @@ TEST_CASE("Lambda action test", "[general]")
     REQUIRE(ss == "hello");
 }
 
+TEST_CASE("before/after handlers test", "[general]")
+{
+    parser parser(R"(
+        START  <- LTOKEN '=' RTOKEN
+        LTOKEN <- TOKEN
+        RTOKEN <- TOKEN
+        TOKEN  <- [A-Za-z]+
+    )");
+
+    parser["LTOKEN"].before = [&](any& dt) {
+        auto& require_upper_case = *dt.get<bool*>();
+        require_upper_case = false;
+    };
+    parser["LTOKEN"].after = [&](any& dt) {
+        auto& require_upper_case = *dt.get<bool*>();
+        require_upper_case = true;
+    };
+
+    parser["TOKEN"] = [&](const SemanticValues& sv, any& dt) {
+        auto& require_upper_case = *dt.get<bool*>();
+        if (require_upper_case) {
+            const auto& s = sv.str();
+            if (!std::all_of(s.begin(), s.end(), ::isupper)) {
+                throw parse_error("should be upper case string...");
+            }
+        }
+    };
+
+    bool require_upper_case = false;
+    any dt = &require_upper_case;
+    REQUIRE(parser.parse("hello=world", dt) == false);
+    REQUIRE(parser.parse("HELLO=world", dt) == false);
+    REQUIRE(parser.parse("hello=WORLD", dt) == true);
+    REQUIRE(parser.parse("HELLO=WORLD", dt) == true);
+
+    parser.log = [&](size_t ln, size_t col, const string& msg) {
+        REQUIRE(ln == 1);
+        REQUIRE(col == 7);
+    };
+    parser.parse("hello=world", dt);
+}
+
 TEST_CASE("Skip token test", "[general]")
 {
     peg::parser parser(