7.4.0 (2020-08-03)
New features
Add support for logical assignment operators.
Add support for numeric separators.
7.3.1 (2020-06-11)
Bug fixes
Make the string in the version export match the actual library version.
7.3.0 (2020-06-11)
Bug fixes
Fix a bug that caused parsing of object patterns with a property named set that had a default value to fail.
New features
Add support for optional chaining (?.).
7.2.0 (2020-05-09)
Bug fixes
Fix precedence issue in parsing of async arrow functions.
New features
Add support for nullish coalescing.
Add support for import.meta.
Support export * as ... syntax.
Upgrade to Unicode 13.
6.4.1 (2020-03-09)
Bug fixes
More carefully check for valid UTF16 surrogate pairs in regexp validator.
7.1.1 (2020-03-01)
Bug fixes
Treat \8 and \9 as invalid escapes in template strings.
Allow unicode escapes in property names that are keywords.
Don't error on an exponential operator expression as argument to await.
More carefully check for valid UTF16 surrogate pairs in regexp validator.
7.1.0 (2019-09-24)
Bug fixes
Disallow trailing object literal commas when ecmaVersion is less than 5.
New features
Add a static acorn property to the Parser class that contains the entire module interface, to allow plugins to access the instance of the library that they are acting on.
7.0.0 (2019-08-13)
Breaking changes
Changes the node format for dynamic imports to use the ImportExpression node type, as defined in ESTree.
Makes 10 (ES2019) the default value for the ecmaVersion option.
6.3.0 (2019-08-12)
New features
sourceType: "module" can now be used even when ecmaVersion is less than 6, to parse module-style code that otherwise conforms to an older standard.
6.2.1 (2019-07-21)
Bug fixes
Fix bug causing Acorn to treat some characters as identifier characters that shouldn't be treated as such.
Fix issue where setting the allowReserved option to "never" allowed reserved words in some circumstances.
6.2.0 (2019-07-04)
Bug fixes
Improve valid assignment checking in for/in and for/of loops.
Disallow binding let in patterns.
New features
Support bigint syntax with ecmaVersion >= 11.
Support dynamic import syntax with ecmaVersion >= 11.
Upgrade to Unicode version 12.
6.1.1 (2019-02-27)
Bug fixes
Fix bug that caused parsing default exports of with names to fail.
6.1.0 (2019-02-08)
Bug fixes
Fix scope checking when redefining a var as a lexical binding.
New features
Split up parseSubscripts to use an internal parseSubscript method to make it easier to extend with plugins.
6.0.7 (2019-02-04)
Bug fixes
Check that exported bindings are defined.
Don't treat \u180e as a whitespace character.
Check for duplicate parameter names in methods.
Don't allow shorthand properties when they are generators or async methods.
Forbid binding await in async arrow function's parameter list.
6.0.6 (2019-01-30)
Bug fixes
The content of class declarations and expressions is now always parsed in strict mode.
Don't allow let or const to bind the variable name let.
Treat class declarations as lexical.
Don't allow a generator function declaration as the sole body of an if or else.
Ignore "use strict" when after an empty statement.
Allow string line continuations with special line terminator characters.
Treat for bodies as part of the for scope when checking for conflicting bindings.
Fix bug with parsing yield in a for loop initializer.
Implement special cases around scope checking for functions.
6.0.5 (2019-01-02)
Bug fixes
Fix TypeScript type for Parser.extend and add allowAwaitOutsideFunction to options type.
Don't treat let as a keyword when the next token is { on the next line.
Fix bug that broke checking for parentheses around an object pattern in a destructuring assignment when preserveParens was on.
6.0.4 (2018-11-05)
Bug fixes
Further improvements to tokenizing regular expressions in corner cases.
6.0.3 (2018-11-04)
Bug fixes
Fix bug in tokenizing an expression-less return followed by a function followed by a regular expression.
Remove stray symlink in the package tarball.
6.0.2 (2018-09-26)
Bug fixes
Fix bug where default expressions could fail to parse inside an object destructuring assignment expression.
6.0.1 (2018-09-14)
Bug fixes
Fix wrong value in version export.
6.0.0 (2018-09-14)
Bug fixes
Better handle variable-redefinition checks for catch bindings and functions directly under if statements.
Forbid new.target in top-level arrow functions.
Fix issue with parsing a regexp after yield in some contexts.
New features
The package now comes with TypeScript definitions.
Breaking changes
The default value of the ecmaVersion option is now 9 (2018).
Plugins work differently, and will have to be rewritten to work with this version.
The loose parser and walker have been moved into separate packages (acorn-loose and acorn-walk).
5.7.3 (2018-09-10)
Bug fixes
Fix failure to tokenize regexps after expressions like x.of.
Better error message for unterminated template literals.
5.7.2 (2018-08-24)
Bug fixes
Properly handle allowAwaitOutsideFunction in for statements.
Treat function declarations at the top level of modules like let bindings.
Don't allow async function declarations as the only statement under a label.
5.7.0 (2018-06-15)
New features
Upgraded to Unicode 11.
5.6.0 (2018-05-31)
New features
Allow U+2028 and U+2029 in string when ECMAVersion >= 10.
Allow binding-less catch statements when ECMAVersion >= 10.
Add allowAwaitOutsideFunction option for parsing top-level await.
5.5.3 (2018-03-08)
Bug fixes
A second republish of the code in 5.5.1, this time with yarn, to hopefully get valid timestamps.
5.5.2 (2018-03-08)
Bug fixes
A republish of the code in 5.5.1 in an attempt to solve an issue with the file timestamps in the npm package being 0.
5.5.1 (2018-03-06)
Bug fixes
Fix misleading error message for octal escapes in template strings.
5.5.0 (2018-02-27)
New features
The identifier character categorization is now based on Unicode version 10.
Acorn will now validate the content of regular expressions, including new ES9 features.
5.4.0 (2018-02-01)
Bug fixes
Disallow duplicate or escaped flags on regular expressions.
Disallow octal escapes in strings in strict mode.
New features
Add support for async iteration.
Add support for object spread and rest.
5.3.0 (2017-12-28)
Bug fixes
Fix parsing of floating point literals with leading zeroes in loose mode.
Allow duplicate property names in object patterns.
Don't allow static class methods named prototype.
Disallow async functions directly under if or else.
Parse right-hand-side of for/of as an assignment expression.
Stricter parsing of for/in.
Don't allow unicode escapes in contextual keywords.
New features
Parsing class members was factored into smaller methods to allow plugins to hook into it.
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.
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.
New features
Implement the template literal revision proposal for ES9.
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 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.
New features
Visitors created with visit.make now have their base as prototype, rather than copying properties into a fresh object.
3.1.0 (2016-04-18)
Bug fixes
Properly tokenize the division operator directly after a function expression.
Allow trailing comma in destructuring arrays.
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.
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.
2.6.2 (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.
2.5.0 (2015-10-27)
Fixes
Fix tokenizer support in the command-line tool.
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.