Remove info about found string from syntax errors

The |found| property wasn't very useful as it mostly contained just one
character or |null| (the exception being syntax errors triggered by
|error| or |expected|). Similarly, the "but XXX found" part of the error
message (based on the |found| property) wasn't much useful and was
redundant in presence of location info.

For these reasons, this commit removes the |found| property and
corresponding part of the error message from syntax errors. It also
modifies error location info slightly to cover a range of 0 characters,
not 1 character (except when the error is triggered by |error| or
|expected|). This corresponds more precisely to the actual situation.

Fixes #372.

README.md

@@ -127,8 +127,8 @@ Using the Parser
 Using the generated parser is simple — just call its `parse` method and pass an
 input string as a parameter. The method will return a parse result (the exact
 value depends on the grammar used to build the parser) or throw an exception if
-the input is invalid. The exception will contain `location`, `expected`, `found`
+the input is invalid. The exception will contain `location`, `expected` and
-and `message` properties with more details about the error.
+`message` properties with more details about the error.
 
     parser.parse("abba"); // returns ["a", "b", "b", "a"]
 

lib/compiler/passes/generate-js.js

@@ -777,10 +777,9 @@ function generateJS(ast, options) {
     '    child.prototype = new ctor();',
     '  }',
     '',
-    '  function peg$SyntaxError(message, expected, found, location) {',
+    '  function peg$SyntaxError(message, expected, location) {',
     '    this.message  = message;',
     '    this.expected = expected;',
-    '    this.found    = found;',
     '    this.location = location;',
     '    this.name     = "SyntaxError";',
     '',
@@ -972,7 +971,6 @@ function generateJS(ast, options) {
     '      throw peg$buildException(',
     '        null,',
     '        [{ type: "other", description: description }],',
-    '        input.substring(peg$savedPos, peg$currPos),',
     '        peg$computeLocation(peg$savedPos, peg$currPos)',
     '      );',
     '    }',
@@ -981,7 +979,6 @@ function generateJS(ast, options) {
     '      throw peg$buildException(',
     '        message,',
     '        null,',
-    '        input.substring(peg$savedPos, peg$currPos),',
     '        peg$computeLocation(peg$savedPos, peg$currPos)',
     '      );',
     '    }',
@@ -1057,7 +1054,7 @@ function generateJS(ast, options) {
     '      peg$maxFailExpected.push(expected);',
     '    }',
     '',
-    '    function peg$buildException(message, expected, found, location) {',
+    '    function peg$buildException(message, expected, location) {',
     '      function cleanupExpected(expected) {',
     '        var i = 1;',
     '',
@@ -1085,36 +1082,9 @@ function generateJS(ast, options) {
     '        }',
     '      }',
     '',
-    '      function buildMessage(expected, found) {',
+    '      function buildMessage(expected) {',
-    '        function stringEscape(s) {',
-    '          function hex(ch) { return ch.charCodeAt(0).toString(16).toUpperCase(); }',
-    '',
-    /*
-     * ECMA-262, 5th ed., 7.8.4: All characters may appear literally in a string
-     * literal except for the closing quote character, backslash, carriage
-     * return, line separator, paragraph separator, and line feed. Any character
-     * may appear in the form of an escape sequence.
-     *
-     * For portability, we also escape all control and non-ASCII characters.
-     * Note that "\0" and "\v" escape sequences are not used because JSHint does
-     * not like the first and IE the second.
-     */
-    '          return s',
-    '            .replace(/\\\\/g,   \'\\\\\\\\\')',   // backslash
-    '            .replace(/"/g,    \'\\\\"\')',        // closing double quote
-    '            .replace(/\\x08/g, \'\\\\b\')',       // backspace
-    '            .replace(/\\t/g,   \'\\\\t\')',       // horizontal tab
-    '            .replace(/\\n/g,   \'\\\\n\')',       // line feed
-    '            .replace(/\\f/g,   \'\\\\f\')',       // form feed
-    '            .replace(/\\r/g,   \'\\\\r\')',       // carriage return
-    '            .replace(/[\\x00-\\x07\\x0B\\x0E\\x0F]/g, function(ch) { return \'\\\\x0\' + hex(ch); })',
-    '            .replace(/[\\x10-\\x1F\\x80-\\xFF]/g,    function(ch) { return \'\\\\x\'  + hex(ch); })',
-    '            .replace(/[\\u0100-\\u0FFF]/g,         function(ch) { return \'\\\\u0\' + hex(ch); })',
-    '            .replace(/[\\u1000-\\uFFFF]/g,         function(ch) { return \'\\\\u\'  + hex(ch); });',
-    '        }',
-    '',
     '        var expectedDescs = new Array(expected.length),',
-    '            expectedDesc, foundDesc, i;',
+    '            expectedDesc, i;',
     '',
     '        for (i = 0; i < expected.length; i++) {',
     '          expectedDescs[i] = expected[i].description;',
@@ -1126,9 +1096,7 @@ function generateJS(ast, options) {
     '              + expectedDescs[expected.length - 1]',
     '          : expectedDescs[0];',
     '',
-    '        foundDesc = found ? "\\"" + stringEscape(found) + "\\"" : "end of input";',
+    '        return "Expected " + expectedDesc + ".";',
-    '',
-    '        return "Expected " + expectedDesc + " but " + foundDesc + " found.";',
     '      }',
     '',
     '      if (expected !== null) {',
@@ -1136,9 +1104,8 @@ function generateJS(ast, options) {
     '      }',
     '',
     '      return new peg$SyntaxError(',
-    '        message !== null ? message : buildMessage(expected, found),',
+    '        message !== null ? message : buildMessage(expected),',
     '        expected,',
-    '        found,',
     '        location',
     '      );',
     '    }',
@@ -1178,10 +1145,7 @@ function generateJS(ast, options) {
     '      throw peg$buildException(',
     '        null,',
     '        peg$maxFailExpected,',
-    '        peg$maxFailPos < input.length ? input.charAt(peg$maxFailPos) : null,',
+    '        peg$computeLocation(peg$maxFailPos, peg$maxFailPos)',
-    '        peg$maxFailPos < input.length',
-    '          ? peg$computeLocation(peg$maxFailPos, peg$maxFailPos + 1)',
-    '          : peg$computeLocation(peg$maxFailPos, peg$maxFailPos)',
     '      );',
     '    }',
     '  }',

lib/parser.js

@@ -13,10 +13,9 @@ module.exports = (function() {
     child.prototype = new ctor();
   }
 
-  function peg$SyntaxError(message, expected, found, location) {
+  function peg$SyntaxError(message, expected, location) {
     this.message  = message;
     this.expected = expected;
-    this.found    = found;
     this.location = location;
     this.name     = "SyntaxError";
 
@@ -407,7 +406,6 @@ module.exports = (function() {
       throw peg$buildException(
         null,
         [{ type: "other", description: description }],
-        input.substring(peg$savedPos, peg$currPos),
         peg$computeLocation(peg$savedPos, peg$currPos)
       );
     }
@@ -416,7 +414,6 @@ module.exports = (function() {
       throw peg$buildException(
         message,
         null,
-        input.substring(peg$savedPos, peg$currPos),
         peg$computeLocation(peg$savedPos, peg$currPos)
       );
     }
@@ -492,7 +489,7 @@ module.exports = (function() {
       peg$maxFailExpected.push(expected);
     }
 
-    function peg$buildException(message, expected, found, location) {
+    function peg$buildException(message, expected, location) {
       function cleanupExpected(expected) {
         var i = 1;
 
@@ -515,26 +512,9 @@ module.exports = (function() {
         }
       }
 
-      function buildMessage(expected, found) {
+      function buildMessage(expected) {
-        function stringEscape(s) {
-          function hex(ch) { return ch.charCodeAt(0).toString(16).toUpperCase(); }
-
-          return s
-            .replace(/\\/g,   '\\\\')
-            .replace(/"/g,    '\\"')
-            .replace(/\x08/g, '\\b')
-            .replace(/\t/g,   '\\t')
-            .replace(/\n/g,   '\\n')
-            .replace(/\f/g,   '\\f')
-            .replace(/\r/g,   '\\r')
-            .replace(/[\x00-\x07\x0B\x0E\x0F]/g, function(ch) { return '\\x0' + hex(ch); })
-            .replace(/[\x10-\x1F\x80-\xFF]/g,    function(ch) { return '\\x'  + hex(ch); })
-            .replace(/[\u0100-\u0FFF]/g,         function(ch) { return '\\u0' + hex(ch); })
-            .replace(/[\u1000-\uFFFF]/g,         function(ch) { return '\\u'  + hex(ch); });
-        }
-
         var expectedDescs = new Array(expected.length),
-            expectedDesc, foundDesc, i;
+            expectedDesc, i;
 
         for (i = 0; i < expected.length; i++) {
           expectedDescs[i] = expected[i].description;
@@ -546,9 +526,7 @@ module.exports = (function() {
               + expectedDescs[expected.length - 1]
           : expectedDescs[0];
 
-        foundDesc = found ? "\"" + stringEscape(found) + "\"" : "end of input";
+        return "Expected " + expectedDesc + ".";
-
-        return "Expected " + expectedDesc + " but " + foundDesc + " found.";
       }
 
       if (expected !== null) {
@@ -556,9 +534,8 @@ module.exports = (function() {
       }
 
       return new peg$SyntaxError(
-        message !== null ? message : buildMessage(expected, found),
+        message !== null ? message : buildMessage(expected),
         expected,
-        found,
         location
       );
     }
@@ -4959,10 +4936,7 @@ module.exports = (function() {
       throw peg$buildException(
         null,
         peg$maxFailExpected,
-        peg$maxFailPos < input.length ? input.charAt(peg$maxFailPos) : null,
+        peg$computeLocation(peg$maxFailPos, peg$maxFailPos)
-        peg$maxFailPos < input.length
-          ? peg$computeLocation(peg$maxFailPos, peg$maxFailPos + 1)
-          : peg$computeLocation(peg$maxFailPos, peg$maxFailPos)
       );
     }
   }

spec/behavior/generated-parser-behavior.spec.js

@@ -1268,9 +1268,8 @@ describe("generated parser behavior", function() {
                 );
 
             expect(parser).toFailToParse("a", {
-              message:  'Expected a but "a" found.',
+              message:  'Expected a.',
               expected: [{ type: "other", description: "a" }],
-              found:    "a",
               location: {
                 start: { offset: 0, line: 1, column: 1 },
                 end:   { offset: 1, line: 1, column: 2 }
@@ -1287,7 +1286,6 @@ describe("generated parser behavior", function() {
             expect(parser).toFailToParse("a", {
               message:  "a",
               expected: null,
-              found:    "a",
               location: {
                 start: { offset: 0, line: 1, column: 1 },
                 end:   { offset: 1, line: 1, column: 2 }
@@ -1403,26 +1401,12 @@ describe("generated parser behavior", function() {
         });
       });
 
-      describe("found string reporting", function() {
-        it("reports found string correctly at the end of input", function() {
-          var parser = PEG.buildParser('start = "a"', options);
-
-          expect(parser).toFailToParse("", { found: null });
-        });
-
-        it("reports found string correctly in the middle of input", function() {
-          var parser = PEG.buildParser('start = "a"', options);
-
-          expect(parser).toFailToParse("b", { found: "b" });
-        });
-      });
-
       describe("message building", function() {
         it("builds message correctly with no alternative", function() {
           var parser = PEG.buildParser('start = "a"', options);
 
           expect(parser).toFailToParse("ab", {
-            message: 'Expected end of input but "b" found.'
+            message: 'Expected end of input.'
           });
         });
 
@@ -1430,7 +1414,7 @@ describe("generated parser behavior", function() {
           var parser = PEG.buildParser('start = "a"', options);
 
           expect(parser).toFailToParse("b", {
-            message: 'Expected "a" but "b" found.'
+            message: 'Expected "a".'
           });
         });
 
@@ -1438,46 +1422,19 @@ describe("generated parser behavior", function() {
           var parser = PEG.buildParser('start = "a" / "b" / "c"', options);
 
           expect(parser).toFailToParse("d", {
-            message: 'Expected "a", "b" or "c" but "d" found.'
+            message: 'Expected "a", "b" or "c".'
-          });
-        });
-
-        it("builds message correctly at the end of input", function() {
-          var parser = PEG.buildParser('start = "a"', options);
-
-          expect(parser).toFailToParse("", {
-            message: 'Expected "a" but end of input found.'
-          });
-        });
-
-        it("builds message correctly in the middle of input", function() {
-          var parser = PEG.buildParser('start = "a"', options);
-
-          expect(parser).toFailToParse("b", {
-            message: 'Expected "a" but "b" found.'
           });
         });
       });
 
       describe("position reporting", function() {
-        it("reports position correctly at the end of input", function() {
+        it("reports position correctly with no trailing input", function() {
-          var parser = PEG.buildParser('start = "a"', options);
-
-          expect(parser).toFailToParse("", {
-            location: {
-              start: { offset: 0, line: 1, column: 1 },
-              end:   { offset: 0, line: 1, column: 1 }
-            }
-          });
-        });
-
-        it("reports position correctly in the middle of input", function() {
           var parser = PEG.buildParser('start = "a"', options);
 
           expect(parser).toFailToParse("b", {
             location: {
               start: { offset: 0, line: 1, column: 1 },
-              end:   { offset: 1, line: 1, column: 2 }
+              end:   { offset: 0, line: 1, column: 1 }
             }
           });
         });
@@ -1488,7 +1445,7 @@ describe("generated parser behavior", function() {
           expect(parser).toFailToParse("aa", {
             location: {
               start: { offset: 1, line: 1, column: 2 },
-              end:   { offset: 2, line: 1, column: 3 }
+              end:   { offset: 1, line: 1, column: 2 }
             }
           });
         });
@@ -1504,7 +1461,7 @@ describe("generated parser behavior", function() {
           expect(parser).toFailToParse("1\n2\n\n3\n\n\n4 5 x", {
             location: {
               start: { offset: 13, line: 7, column: 5 },
-              end:   { offset: 14, line: 7, column: 6 }
+              end:   { offset: 13, line: 7, column: 5 }
             }
           });
 
@@ -1512,19 +1469,19 @@ describe("generated parser behavior", function() {
           expect(parser).toFailToParse("1\rx", {     // Old Mac
             location: {
               start: { offset: 2, line: 2, column: 1 },
-              end:   { offset: 3, line: 2, column: 2 }
+              end:   { offset: 2, line: 2, column: 1 }
             }
           });
           expect(parser).toFailToParse("1\r\nx", {   // Windows
             location: {
               start: { offset: 3, line: 2, column: 1 },
-              end:   { offset: 4, line: 2, column: 2 }
+              end:   { offset: 3, line: 2, column: 1 }
             }
           });
           expect(parser).toFailToParse("1\n\rx", {   // mismatched
             location: {
               start: { offset: 3, line: 3, column: 1 },
-              end:   { offset: 4, line: 3, column: 2 }
+              end:   { offset: 3, line: 3, column: 1 }
             }
           });
 
@@ -1532,13 +1489,13 @@ describe("generated parser behavior", function() {
           expect(parser).toFailToParse("1\u2028x", {   // line separator
             location: {
               start: { offset: 2, line: 2, column: 1 },
-              end:   { offset: 3, line: 2, column: 2 }
+              end:   { offset: 2, line: 2, column: 1 }
             }
           });
           expect(parser).toFailToParse("1\u2029x", {   // paragraph separator
             location: {
               start: { offset: 2, line: 2, column: 1 },
-              end:   { offset: 3, line: 2, column: 2 }
+              end:   { offset: 2, line: 2, column: 1 }
             }
           });
         });