proper escaping for errors

Author: obenjiro

Diff for: .eslintrc.json

@@ -180,7 +180,7 @@
         "no-shadow": "error",
         "no-shadow-restricted-names": "error",
         "no-spaced-func": "error",
-        "no-sync": "error",
+        "no-sync": "warn",
         "no-tabs": "off",
         "no-template-curly-in-string": "error",
         "no-ternary": "off",

Diff for: src/rd_parser.js

@@ -320,6 +320,9 @@ function call_rule_by_name(name) {
         var rule = state.rules.filter(function(r){
             return r.name === name;
         })[0];
+        if (!rule) {
+            throw new Error('failed to find rule by name - ' + name);
+        }
         var ast = rule.parser(state);
         return ast;
     }

Diff for: src/speg_parser.js

@@ -183,6 +183,7 @@ function parsing_string() {
     return rd.action('parsing_string', rd.sequence([
         rd.string('"'),
         rd.one_or_more(rd.ordered_choice([
+            rd.string('\\\\'),
             rd.string('\\"'),
             rd.regex_char('[^"]')
         ])),

Diff for: src/speg_visitor.js

@@ -138,7 +138,10 @@ SPEG_actions.prototype.parsing_optional = function(node) {
 };
 
 SPEG_actions.prototype.parsing_string = function(node) {
-    return rd.string(node.children[1].match);
+    return rd.string(node.children[1].match
+        .replace(/\\\\/g, '\\')
+        .replace(/\\"/g, '"')
+    );
 };
 
 SPEG_actions.prototype.parsing_regex_char = function(node) {

Diff for: test/speg_fixtures/escape.peg

@@ -0,0 +1,3 @@
+GRAMMAR test
+
+a -> "\\";

Diff for: test/speg_fixtures/escape.peg.json

@@ -0,0 +1,7 @@
+{
+    "type": "string", 
+    "start_position": 0, 
+    "match": "\\",
+    "rule": "a",
+    "end_position": 1
+}

Diff for: test/speg_fixtures/escape.peg.txt

@@ -0,0 +1 @@
+\

Diff for: test/speg_fixtures/stringstring.peg

@@ -0,0 +1,3 @@
+GRAMMAR test
+
+a -> "\"" "A";

Diff for: test/speg_fixtures/stringstring.peg.json

@@ -0,0 +1,21 @@
+{
+  "type": "sequence",
+  "rule": "a",
+  "start_position": 0, 
+  "children": [
+    {
+      "type": "string", 
+      "start_position": 0, 
+      "match": "\"", 
+      "end_position": 1
+    }, 
+    {
+      "type": "string", 
+      "start_position": 1, 
+      "match": "A", 
+      "end_position": 2
+    }
+  ], 
+  "match": "\"A", 
+  "end_position": 2
+}

Diff for: test/speg_fixtures/stringstring.peg.txt

@@ -0,0 +1 @@
+"A