+ .pipe(identityMap()) // .js and .css files will get a generated sourcemap
+ .pipe(sourcemaps.write())
+ .pipe(gulp.dest(...))
+```
+
+## API
+
+### `identityMap()`
+
+Returns an `objectMode` Transform stream that processes each file with a `.sourceMap` property and buffered contents. A sourcemap is generated and attached for each `.js` and `.css` file.
+[**Compiling to JavaScript, and Debugging with Source Maps**](https://hacks.mozilla.org/2013/05/compiling-to-javascript-and-debugging-with-source-maps/)
+Takes a map function as the only argument. Returns an `objectMode` Transform stream.
+
+#### `mapFn(sourcePath, file)`
+
+The map function is called once per value of the `sources` array of a `sourceMap` attached to each [`Vinyl`][vinyl-url] object passed through the stream. The map function is called with the `sourcePath` string from the `sources` array and the `file` object it originated from. The return value replaces the original value in the array.
+
+If a `Vinyl` object doesn't have a `sourceMap` or `sourceMap.sources` property, the file is passed through the stream without having the `mapFn` called.
+
+All `sources` are normalized to use `/` instead of `\\` as path separators.
+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.
+
+## 5.5.2 (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 regression in walker causing property values in object patterns to be walked as expressions.
+
+Fix misleading error message for octal escapes in template strings.
+
+## 5.5.0 (2018-02-27)
+
+### Bug fixes
+
+Support object spread in the AST walker.
+
+### 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.
+
+## 5.4.1 (2018-02-02)
+
+### Bug fixes
+
+5.4.0 somehow accidentally included an old version of walk.js.
+
+## 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.
+
+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](https://github.com/estree/estree/compare/b3de58c9997504d6fba04b72f76e6dd1619ee4eb...1da8e603237144f44710360f8feb7a9977e905e0) 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](https://github.com/tc39/proposal-template-literal-revision) 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.
+ - [`acorn-objj`](https://github.com/cappuccino/acorn-objj): [Objective-J](http://www.cappuccino-project.org/learn/objective-j.html) language parser built as Acorn plugin
+
+ Plugins for ECMAScript proposals:
+
+ - [`acorn-stage3`](https://github.com/acornjs/acorn-stage3): Parse most stage 3 proposals, bundling:
+ - [`acorn-static-class-property-initializer`](https://github.com/victor-homyakov/acorn-static-class-property-initializer): Partial support for static class properties from [ES Class Fields & Static Properties Proposal](https://github.com/tc39/proposal-class-public-fields) to support static property initializers in [React components written as ES6+ classes](https://babeljs.io/blog/2015/06/07/react-on-es6-plus)
+ } else if (/invalid (unicode|regexp|number)|expecting unicode|octal literal|is reserved|directly after number|expected number in radix/i.test(msg)) {
+ while (pos < this.input.length && !isSpace(this.input.charCodeAt(pos))) { ++pos; }
+ } else if (/character escape|expected hexadecimal/i.test(msg)) {
+ } else if (/invalid (unicode|regexp|number)|expecting unicode|octal literal|is reserved|directly after number|expected number in radix/i.test(msg)) {
+ while (pos < this.input.length && !isSpace(this.input.charCodeAt(pos))) { ++pos; }
+ } else if (/character escape|expected hexadecimal/i.test(msg)) {
+Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](https://github.com/jonschlinkert/ansi-gray/issues/new)