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espree's Issues

Switching location tracking

Espree is currently using the old mark() and markEnd() methods to track location (from Esprima 1.2.2). Esprima Harmony has two new methods markerCreate() and markerApply(). Before we can merge over more complex features, we need to switch location tracking to what's in Harmony.

Website design

We need a website to post Espree documentation and a demo. It would be nice if it had the same visual language as the eslint.org, but I don't think that's 100% necessary.

Want to back this issue? Post a bounty on it! We accept bounties via Bountysource.

Parser fails on generator methods

Espree parser fails on the following with Unexpected token *:

class Foo {
  *bar() {
  }
}

Test case:

var espree = require("espree");

espree.parse('class Foo {*bar() {}}', {
  "ecmaFeatures": {
    "classes": true,
    "generators": true,
    "objectLiteralShorthandMethods": true,
  },
});

Stack:

node_modules/espree/espree.js:5373
        throw e;
              ^
Error: Line 1: Unexpected token *
    at throwError (node_modules/espree/espree.js:2078:17)
    at throwUnexpected (node_modules/espree/espree.js:2141:5)
    at parseObjectPropertyKey (node_modules/espree/espree.js:2364:5)
    at parseClassBody (node_modules/espree/espree.js:4934:15)
    at parseClassDeclaration (node_modules/espree/espree.js:5023:17)
    at parseSourceElement (node_modules/espree/espree.js:5053:28)
    at parseSourceElements (node_modules/espree/espree.js:5101:25)
    at parseProgram (node_modules/espree/espree.js:5120:12)
    at Object.parse (node_modules/espree/espree.js:5361:19)
    at Object.<anonymous> (esp.js:3:8)

See eslint/eslint#1990.

Phase 1

Phase 1 is all about setting up the repository in such a way that it's easier to make changes later on.

  • Split up espree.js into as many small files as possible and place those small files in lib/
  • Change over build system to use ShellJS
  • Convert standalone build scripts into ShellJS
  • Create Mocha tests for small files
  • Upgrade ESLint and change code to match ESLint project styles
  • Create browserify build step for a browser-compatible version of espree.js

create-test / default-params issue

  1. the placeholder for empty defaults array members should possibly be undefined instead of null
  2. create-test-.js improperly changes undefined array members to null.

Recently when working on defaultParams and destructuring I noticed that I was having some mismatches with Esprima on the expected output, especially involving the placeholder when there are not defaults specified for each parameter.

When I use create-test to generate the expected output it seems to show [null, 1] for function(a, b=1){}, but when i actually console.log the output from Esprima, it looks like [undefined, 1].

Here is I think the source of the issue:
screen shot 2015-02-09 at 7 00 23 am

The only thing that makes me unsure is that the single test in esprima also shows null as the placeholder, but I can only assume they're using JSON.stringify in their tests, because Esprima will not generate that output:
https://github.com/jquery/esprima/blob/harmony/test/harmonytest.js#L2612

Let me know if you have any ideas otherwise I'll like manually change the tests to use undefined as part of #51, which changed some of the code around this area and caused me to bump into this issue.

Object literal shorthand generator methods have incorrect range

Perhaps this is intentional, but the range given to object literal shorthand generator methods includes only the method body {}. Since they key is part of the parent property and overlapping, non-ancestral ranges might get confusing, I'm not sure that the FunctionExpression's range should include all of *foo(arg1) {}, but it seems like the range should expand to at least (arg1) {}.

Related: eslint/eslint#1677

//test.js
var inspect = require('util').inspect,
    espree = require('espree');

var source = [
    "({",
    "    *foo(arg1) {}",
    "})"
].join("\n");

var ast = espree.parse(source, {
    range: true,
    tokens: true,
    ecmaFeatures: {
        generators: true,
        objectLiteralShorthandMethods: true
    }
});

console.log(inspect(ast.body[0].expression.properties[0]));
console.log(inspect(ast.body[0].expression.properties[0].value.params[0]));
console.log(inspect(ast.tokens));
$  node test.js
{ type: 'Property',
  key: { type: 'Identifier', name: 'foo', range: [ 8, 11 ] },
  value:
   { type: 'FunctionExpression',
     id: null,
     params: [ [Object] ],
     defaults: [],
     body: { type: 'BlockStatement', body: [], range: [Object] },
     rest: null,
     generator: true,
     expression: false,
     range: [ 18, 20 ] },
  kind: 'init',
  method: true,
  shorthand: false,
  computed: false,
  range: [ 7, 20 ] }
{ type: 'Identifier', name: 'arg1', range: [ 12, 16 ] }
[ { type: 'Punctuator', value: '(', range: [ 0, 1 ] },
  { type: 'Punctuator', value: '{', range: [ 1, 2 ] },
  { type: 'Punctuator', value: '*', range: [ 7, 8 ] },
  { type: 'Identifier', value: 'foo', range: [ 8, 11 ] },
  { type: 'Punctuator', value: '(', range: [ 11, 12 ] },
  { type: 'Identifier', value: 'arg1', range: [ 12, 16 ] },
  { type: 'Punctuator', value: ')', range: [ 16, 17 ] },
  { type: 'Punctuator', value: '{', range: [ 18, 19 ] },
  { type: 'Punctuator', value: '}', range: [ 19, 20 ] },
  { type: 'Punctuator', value: '}', range: [ 21, 22 ] },
  { type: 'Punctuator', value: ')', range: [ 22, 23 ] } ]

Edit: Add arg1 to output.

Update module functionality

  • add test to validate that sourceType="module" effectible enables strict mode (e.g.: WithStatement is invalid in modules)
  • ImportDeclaration and ExportDeclaration cannot be used inside functions (missing tests and implementation)
  • Enable classes for export and export default declarations (all TODOs are in the code, very straight forward)

Lost contributions?

This repository README states: "Espree starts as a fork of Esprima v1.2.2". However, all of history of Esprima up to this point have been conflated into one initial commit. It seems it would be more fair to Esprima contributors to preserve the history.

Allow return in global scope

For Node.js compatibility, it would be good to add the option to use return in the global scope.

Working on this now.

What's up with the `extra` object?

Trying to wrap my head around the extra object, which seems to be used everywhere for everything. Is it just a combination of parsing options & parsing state?

Remove TryStatement.handlers

Ref estree/estree#1:

interface TryStatement <: Statement {
    // ....
    handler: CatchClause | null;
    handlers: [ CatchClause ]; // Removed
    // ....
}

The handlers array on TryStatement nodes was replaced with a single handler, which may be either a CatchClause or null.
#70 added support for the singular handler property. The next step is to remove handlers. This will be a breaking change.

For loops allow let even with blockBindings is false

Currently, for loops (for, for-in, for-of) all allow let to be used even when blockBindings is set to false. So this works fine:

for (let x of y) {
}

With this config:

{
    blockBindings: false,
    forOf: true
}

This should throw an error instead.

Template string tokens are strange

The way that template string tokens are generated is pretty strange. This code:

var foo = `hi${bar}`;

Is tokenized as:

[
    {
        "type": "Keyword",
        "value": "var"
    },
    {
        "type": "Identifier",
        "value": "foo"
    },
    {
        "type": "Punctuator",
        "value": "="
    },
    {
        "value": "`hi${"
    },
    {
        "type": "Identifier",
        "value": "bar"
    },
    {
        "type": "Punctuator",
        "value": "}"
    },
    {
        "type": "Punctuator",
        "value": ";"
    }
]

So the first part of the template string is represented by a token without a type, and then the rest are just regular tokens, completely losing the end of the template string.

Features as modules

In the README you say you're going to break the code base down into smaller files in a CommonJS pattern. Would it be possible to make it so that features are not dependent on one another. So say you don't care about parsing comments the comment module doesn't need to get loaded or included.

Thinking about this because I have a library where I want to use Esprima (or any proper code parser) instead of hacky regular expressions but the size of the libraries are just too large. Being able to shrink it down to just what I need could solve my issue.

Implement JSX syntax

Add support for JSX syntax. This should be done in the same form as esprima-fb.

Support test fixtures for when feature = false does not result in an error

For Unicode code point escapes, the string values are still valid JavaScript regardless of the feature state. But the test runner is hard-coded to check for a thrown error if the features is set to off. Thus, I'm unable to write passing tests for this feature.

A few ideas:

  1. Add an option to *.config.js to skip this second test
  2. Remove the test entirely, since I'm not sure how valuable it is to us (checking that new features aren't backwards compatible).

@nzakas thoughts?

Trailing comments lost with return and debugger statements

I noticed that ReturnStatement nodes doesn’t have leadingComments and trailingComments attached in some cases.

The following code example fails and doen’t have leadingComments or trailingComments:

function a() {
    /* before */
    return;
    /* after */
}

The following code examples work:

Without ReturnStatement:

function a() {
    /* before */
    b();
    /* after */
}

Only one leading comment:

function a() {
    /* before */
    return;
}

Only one trailing comment:

function a() {
    return;
    /* after */
}

Same problem with the debugger statement.

Esprima bug: https://code.google.com/p/esprima/issues/detail?id=609

Lines are calculated wrong when relying on ASI

Given the following example:

a()

gives the following loc for the Programm AST node:

"loc": {
    "start": {
        "line": 1,
        "column": 0
    },
    "end": {
        "line": 1,
        "column": 3
    }
}

if you have an extra line break

a()

you get the following loc:

"loc": {
    "start": {
        "line": 1,
        "column": 0
    },
    "end": {
        "line": 2,
        "column": 0
    }
}

Each extra line will increase loc.end.line

a()






"loc": {
    "start": {
        "line": 1,
        "column": 0
    },
    "end": {
        "line": 8,
        "column": 0
    }
}

But if you use a semicolon after the CallExpression you will get a different loc for Program even if you have multiple empty lines:

a();






"loc": {
    "start": {
        "line": 1,
        "column": 0
    },
    "end": {
        "line": 1,
        "column": 4
    }
}

Error for "missing argument in class setters" fails to format

Using espree master, this code :

espree.parse('class A { set foo(){} }', { ecmaFeatures: { classes: true }});

Throws :

Error: ASSERT: Message reference must be in range
    at assert (/home/ubuntu/workspace/espree.js:78:15)
    at /home/ubuntu/workspace/espree.js:2083:17
    at String.replace (native)
    at throwError (/home/ubuntu/workspace/espree.js:2080:29)
    at throwErrorTolerant (/home/ubuntu/workspace/espree.js:2106:20)
    at tryParseMethodDefinition (/home/ubuntu/workspace/espree.js:2438:17)
    at parseClassBody (/home/ubuntu/workspace/espree.js:4984:22)
    at parseClassDeclaration (/home/ubuntu/workspace/espree.js:5065:17)
    at parseSourceElement (/home/ubuntu/workspace/espree.js:5095:28)
    at parseSourceElements (/home/ubuntu/workspace/espree.js:5143:25)

I think tryParseMethodDefinition L2438 should be throwErrorTolerant(lookahead, Messages.UnexpectedToken, lookahead.value);

Add ECMAScript version filter

This feature allows an extra ecmascript option to be passed to the parse() method. This determines the syntax will be accepted by the parser. The default is all syntax (similar to Esprima) and the valid values are currently 5 and 6.

To test, it's easiest to use let and const. Espree already parses them but technically these are not allowed in ECMAScript 5. So when ecmascript is 5, using let and const should throw an error.

super should be allowed in classes by default

Right now, I need to enable classes and superInFunctions in order to use super() in a class. Classes should always be allowed to use super regardless of the superInFunctions flag.

Shorthand property named "get" fails to parse 

var espree = require('espree');

espree.parse('var a = {get};', {
    ecmaFeatures: {
        objectLiteralShorthandProperties: true
    }
});

Raises Error: Line 1: Unexpected token }

Rename get to anything else, and it works.

Support TryStatement.handler

Ref estree/estree#1:

interface TryStatement <: Statement {
    // ....
    handler: CatchClause | null;
    handlers: [ CatchClause ]; // Removed
    // ....
}

The handlers array on TryStatement nodes was replaced with a single handler, which may be either a CatchClause or null.

Presumably the best way to do this is to port jquery/esprima#1034, a backward-compatible change which adds handler and preserves handlers, then remove handlers as a breaking change later?

Add ECMAScript 6 features

This is a rollup that will let us keep track of ES6 progress.

  • let declarations
  • const declarations
  • Regular expression u flag
  • Regular expression y flag
  • Binary literals
  • New octal literals
  • Arrow functions
  • Default parameters
  • Rest parameters
  • Spread operator
  • super references
  • Classes
  • for-of loops
  • Generators
  • Object literal property shorthand
  • Object literal method shorthand
  • Object literal computed properties
  • Template strings
  • Destructuring
  • Unicode code point escapes
  • Allow duplicate object literal properties (except __proto__)
  • Modules

Update ClassDeclaration/ClassExpression name -> ID

Esprima incorrectly implemented ClassDeclaration and ClassExpression, and since I copied that, we have the same problem. The issue is that ESTree specified the name of a class as id while we are using name. So, we need to switch to use id instead.

Destructured catch clause doesn't work

Given the following snippet, with ESLint I get an error on the catch line with Unexpected token {

function x({a}) {
  try {
    const {b} = a;
  }
  catch({stack}) {
  }
}

Empty paren in expression throws TypeError

The following example crashes eslint (caused by the last line in the file):

var left, aSize, bSize;

aSize = {
  width: 800,
  height: 600
};

bSize = {
  width: 200,
  height: 100
};

left = (aSize.width/2) - ()

with error

eslint test.js

/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/token-store.js:181
            starts[right.range[0]] + padding
                              ^
TypeError: Cannot read property '0' of undefined
    at EventEmitter.api.getTokensBetween (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/token-store.js:181:31)
    at RuleContext.(anonymous function) [as getTokensBetween] (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/rule-context.js:82:33)
    at isSpaced (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/rules/space-infix-ops.js:21:34)
    at EventEmitter.checkBinary (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/rules/space-infix-ops.js:40:14)
    at EventEmitter.emit (events.js:117:20)
    at Controller.controller.traverse.enter (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/eslint.js:673:25)
    at Controller.__execute (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/node_modules/estraverse/estraverse.js:397:31)
    at Controller.traverse (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/node_modules/estraverse/estraverse.js:495:28)
    at EventEmitter.module.exports.api.verify (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/eslint.js:666:24)
    at processFile (/home/julien/.nvm/v0.10.30/lib/node_modules/eslint/lib/cli-engine.js:172:27)

Looks like parentheses in the end of the line left = (aSize.width / 2) - () treated as ArrowParameterPlaceHolder

https://www.dropbox.com/s/0oltkd0vbdo0iew/Screenshot%202015-02-10%2018.51.52.png?dl=0

eslint/eslint#1816
AtomLinter/linter-eslint#28

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