5.2.1 (2017-10-30)
Bug fixes
Fix a token context corruption bug.
5.2.0 (2017-10-30)
Bug fixes
Fix token context tracking for class and function in property-name position.
Make sure %* isn't parsed as a valid operator.
The full and fullAncestor walkers no longer visit nodes multiple times.
Allow shorthand properties get and set to be followed by default values.
Disallow super when not in callee or object position.
New features
Support directive property on directive expression statements.
5.1.2 (2017-09-04)
Bug fixes
Disable parsing of legacy HTML-style comments in modules.
Fix parsing of async methods whose names are keywords.
5.1.1 (2017-07-06)
Bug fixes
Fix problem with disambiguating regexp and division after a class.
5.1.0 (2017-07-05)
Bug fixes
Fix tokenizing of regexps in an object-desctructuring for/of loop and after yield.
Parse zero-prefixed numbers with non-octal digits as decimal.
Allow object/array patterns in rest parameters.
Don't error when yield is used as a property name.
Allow async as a shorthand object property.
Make the ES module version of the loose parser actually work.
New features
Implement the template literal revision proposal for ES9.
New walker functions full and fullAncestor.
5.0.3 (2017-04-01)
Bug fixes
Fix spurious duplicate variable definition errors for named functions.
5.0.2 (2017-03-30)
Bug fixes
A binary operator after a parenthesized arrow expression is no longer incorrectly treated as an error.
5.0.0 (2017-03-28)
Bug fixes
Raise an error for duplicated lexical bindings.
Fix spurious error when an assignement expression occurred after a spread expression.
Accept regular expressions after of (in for/of), yield (in a generator), and braced arrow functions.
Allow labels in front or var declarations, even in strict mode.
Breaking changes
Parse declarations following export default as declaration nodes, not expressions. This means that class and function declarations nodes can now have null as their id.
4.0.11 (2017-02-07)
Bug fixes
Allow all forms of member expressions to be parenthesized as lvalue.
4.0.10 (2017-02-07)
Bug fixes
Don't expect semicolons after default-exported functions or classes, even when they are expressions.
Check for use of 'use strict' directives in non-simple parameter
functions, even when already in strict mode.
4.0.9 (2017-02-06)
Bug fixes
Fix incorrect error raised for parenthesized simple assignment
targets, so that (x) = 1 parses again.
4.0.8 (2017-02-03)
Bug fixes
Solve spurious parenthesized pattern errors by temporarily erring on the side of accepting programs that our delayed errors don't handle correctly yet.
4.0.7 (2017-02-02)
Bug fixes
Accept invalidly rejected code like (x).y = 2 again.
Don't raise an error when a function inside strict code has a non-simple parameter list.
4.0.6 (2017-02-02)
Bug fixes
Fix exponential behavior (manifesting itself as a complete hang for even relatively small source files) introduced by the new 'use strict' check.
4.0.5 (2017-02-02)
Bug fixes
Disallow parenthesized pattern expressions.
Allow keywords as export names.
Don't allow the async keyword to be parenthesized.
Properly raise an error when a keyword contains a character escape.
Allow "use strict" to appear after other string literal expressions.
Disallow labeled declarations.
4.0.4 (2016-12-19)
Bug fixes
Fix issue with loading acorn_loose.js with an AMD loader.
Fix crash when export was followed by a keyword that can't be
exported.
4.0.3 (2016-08-16)
Bug fixes
Allow regular function declarations inside single-statement if
branches in loose mode. Forbid them entirely in strict mode.
Properly parse properties named async in ES2017 mode.
Fix bug where reserved words were broken in ES2017 mode.
4.0.2 (2016-08-11)
Bug fixes
Don't ignore period or 'e' characters after octal numbers.
Fix broken parsing for call expressions in default parameter values of arrow functions.
4.0.1 (2016-08-08)
Bug fixes
Fix false positives in duplicated export name errors.
4.0.0 (2016-08-07)
Breaking changes
The default ecmaVersion option value is now 7.
A number of internal method signatures changed, so plugins might need to be updated.
Bug fixes
The parser now raises errors on duplicated export names.
arguments and eval can now be used in shorthand properties.
Duplicate parameter names in non-simple argument lists now always produce an error.
New features
The ecmaVersion option now also accepts year-style version numbers
(2015, etc).
Support for async/await syntax when ecmaVersion is >= 8.
Support for trailing commas in call expressions when ecmaVersion
is >= 8.
3.3.0 (2016-07-25)
Bug fixes
Fix bug in tokenizing of regexp operator after a function declaration.
Fix parser crash when parsing an array pattern with a hole.
New features
Implement check against complex argument lists in functions that enable strict mode in ES7.
3.2.0 (2016-06-07)
Bug fixes
Improve handling of lack of unicode regexp support in host environment.
Properly reject shorthand properties whose name is a keyword.
Don't crash when the loose parser is called without options object.
New features
Visitors created with visit.make now have their base as prototype,
rather than copying properties into a fresh object.
Make it possible to use visit.ancestor with a walk state.
3.1.0 (2016-04-18)
Bug fixes
Fix issue where the loose parser created invalid TemplateElement nodes for unclosed template literals.
Properly tokenize the division operator directly after a function expression.
Allow trailing comma in destructuring arrays.
New features
The walker now allows defining handlers for CatchClause nodes.
3.0.4 (2016-02-25)
Fixes
Allow update expressions as left-hand-side of the ES7 exponential operator.
3.0.2 (2016-02-10)
Fixes
Fix bug that accidentally made undefined a reserved word when
parsing ES7.
3.0.0 (2016-02-10)
Breaking changes
The default value of the ecmaVersion option is now 6 (used to be 5).
Support for comprehension syntax (which was dropped from the draft spec) has been removed.
Fixes
let and yield are now “contextual keywords”, meaning you can
mostly use them as identifiers in ES5 non-strict code.
A parenthesized class or function expression after export default is
now parsed correctly.
New features
When ecmaVersion is set to 7, Acorn will parse the exponentiation
operator (**).
The identifier character ranges are now based on Unicode 8.0.0.
Plugins can now override the raiseRecoverable method to override the
way non-critical errors are handled.
2.7.0 (2016-01-04)
Fixes
Stop allowing rest parameters in setters.
Make sure the loose parser always attaches a local property to
ImportNamespaceSpecifier nodes.
Disallow y rexexp flag in ES5.
Disallow \00 and \000 escapes in strict mode.
Raise an error when an import name is a reserved word.
2.6.4 (2015-11-12)
Fixes
Fix crash in loose parser when parsing invalid object pattern.
New features
Support plugins in the loose parser.
2.6.2 (2015-11-10)
Fixes
Don't crash when no options object is passed.
2.6.0 (2015-11-09)
Fixes
Add await as a reserved word in module sources.
Disallow yield in a parameter default value for a generator.
Forbid using a comma after a rest pattern in an array destructuring.
New features
Support parsing stdin in command-line tool.
2.5.2 (2015-10-27)
Fixes
Fix bug where the walker walked an exported let statement as an
expression.
2.5.0 (2015-10-27)
Fixes
Fix tokenizer support in the command-line tool.
In the loose parser, don't allow non-string-literals as import sources.
Stop allowing new.target outside of functions.
Remove legacy guard and guardedHandler properties from try nodes.
Stop allowing multiple __proto__ properties on an object literal in
strict mode.
Don't allow rest parameters to be non-identifier patterns.
Check for duplicate paramter names in arrow functions.