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Improved & simplified error handling code.

redux
David Majda 13 years ago
parent
commit
bddb65ab9b
  1. 49
      lib/runtime.js
  2. 13
      test/compiler-test.js

49
lib/runtime.js

@ -87,7 +87,7 @@ PEG.Parser.prototype = {
function buildExpectedFromMatchFailures(failures) {
switch (failures.length) {
case 0:
return "nothing";
return "end of input";
case 1:
return failures[0].toString();
default:
@ -100,19 +100,13 @@ PEG.Parser.prototype = {
}
}
if (that._pos === 0) {
var expected = buildExpectedFromMatchFailures(
that._rightmostMatchFailures
);
var actual = that._rightmostMatchFailuresPos < that._input.length
? PEG.StringUtils.quote(
that._input.charAt(that._rightmostMatchFailuresPos)
)
: "end of input";
} else {
var expected = "end of input";
var actual = PEG.StringUtils.quote(that._input.charAt(that._pos));
}
var expected = buildExpectedFromMatchFailures(
that._rightmostMatchFailures
);
var pos = Math.max(that._pos, that._rightmostMatchFailuresPos);
var actual = pos < that._input.length
? PEG.StringUtils.quote(that._input.charAt(pos))
: "end of input";
return "Expected " + expected + " but " + actual + " found.";
}
@ -157,6 +151,33 @@ PEG.Parser.prototype = {
};
var result = this["_parse_" + this._startRule](initialContext);
/*
* The parser is now in one of the following three states:
*
* 1. The parser successfully parsed the whole input.
*
* - |result !== null|
* - |that._pos === input.length|
* - |that._rightmostMatchFailures.length| may or may not contain
* something
*
* 2. The parser successfully parsed only a part of the input.
*
* - |result !== null|
* - |that._pos < input.length|
* - |that._rightmostMatchFailures.length| may or may not contain
* something
*
* 3. The parser did not successfully parse any part of the input.
*
* - |result === null|
* - |that._pos === 0|
* - |that._rightmostMatchFailures.length| contains at least one failure
*
* All code following this comment (including called functions) must
* handle these states.
*/
if (result === null || this._pos !== input.length) {
var errorPosition = computeErrorPosition();
throw new PEG.Parser.SyntaxError(

13
test/compiler-test.js

@ -365,18 +365,25 @@ test("error messages", function() {
'Expected digits but end of input found.'
);
var choiceParser = PEG.buildParser('start: "a" / "b" / "c"');
var choiceParser1 = PEG.buildParser('start: "a" / "b" / "c"');
doesNotParseWithMessage(
choiceParser,
choiceParser1,
"def",
'Expected "a", "b" or "c" but "d" found.'
);
var choiceParser2 = PEG.buildParser('start: "a" "b" "c" / "a"');
doesNotParseWithMessage(
choiceParser2,
"abd",
'Expected "c" but "d" found.'
);
var emptyParser = PEG.buildParser('start: ');
doesNotParseWithMessage(
emptyParser,
"something",
'Expected nothing but "s" found.'
'Expected end of input but "s" found.'
);
});

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