gulp-sourcemaps

What is gulp-sourcemaps?

The gulp-sourcemaps package is a plugin for Gulp that allows you to generate source maps for your files. Source maps are files that map from the transformed source to the original source, enabling you to debug your code more easily by seeing the original source in your browser's developer tools.

What are gulp-sourcemaps's main functionalities?

Initialize Source Maps

This feature initializes the source map generation process. The `sourcemaps.init()` method is called before any transformations are applied to the files, and `sourcemaps.write('.')` writes the source maps to the same directory as the transformed files.

const gulp = require('gulp');
const sourcemaps = require('gulp-sourcemaps');

gulp.task('default', function () {
  return gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
    .pipe(sourcemaps.write('.'))
    .pipe(gulp.dest('dist'));
});

Write Inline Source Maps

This feature writes the source maps inline within the transformed files. The `sourcemaps.write()` method without any arguments will embed the source map directly into the output file.

const gulp = require('gulp');
const sourcemaps = require('gulp-sourcemaps');

gulp.task('default', function () {
  return gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('dist'));
});

Custom Source Map Path

This feature allows you to specify a custom path for the source maps. The `sourcemaps.write('../maps')` method writes the source maps to a directory named 'maps' that is one level up from the output directory.

const gulp = require('gulp');
const sourcemaps = require('gulp-sourcemaps');

gulp.task('default', function () {
  return gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
    .pipe(sourcemaps.write('../maps'))
    .pipe(gulp.dest('dist'));
});

Other packages similar to gulp-sourcemaps

gulp-sourcemap

The gulp-sourcemap package is another plugin for generating source maps in Gulp. It is similar to gulp-sourcemaps but is less popular and has fewer features. It is a simpler alternative for basic source map generation needs.

gulp-babel

The gulp-babel package is primarily used for transpiling JavaScript using Babel, but it also has built-in support for generating source maps. It is a good choice if you are already using Babel for transpilation and want to generate source maps as part of the same process.

gulp-uglify

The gulp-uglify package is used for minifying JavaScript files. It can also generate source maps for the minified files. It is useful if you want to combine minification and source map generation in a single step.

README

gulp-sourcemaps

Sourcemap support for gulpjs.

Usage

All the examples here works with Gulp 4. To see examples related to Gulp 3, you can read them here.

Write inline source maps

Inline source maps are embedded in the source file.

Example:

var gulp = require('gulp');
var plugin1 = require('gulp-plugin1');
var plugin2 = require('gulp-plugin2');
var sourcemaps = require('gulp-sourcemaps');

function javascript() {
  gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
      .pipe(plugin1())
      .pipe(plugin2())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('dist'));
};


exports.javascript = javascript;

All plugins between sourcemaps.init() and sourcemaps.write() need to have support for gulp-sourcemaps. You can find a list of such plugins in the wiki.

Write external source map files

To write external source map files, pass a path relative to the destination to sourcemaps.write().

Example:

var gulp = require('gulp');
var plugin1 = require('gulp-plugin1');
var plugin2 = require('gulp-plugin2');
var sourcemaps = require('gulp-sourcemaps');

function javascript() {
  gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
      .pipe(plugin1())
      .pipe(plugin2())
    .pipe(sourcemaps.write('../maps'))
    .pipe(gulp.dest('dist'));
};

exports.javascript = javascript;

Load existing source maps

To load existing source maps, pass the option loadMaps: true to sourcemaps.init().

Example:

var gulp = require('gulp');
var plugin1 = require('gulp-plugin1');
var plugin2 = require('gulp-plugin2');
var sourcemaps = require('gulp-sourcemaps');

function javascript() {
  gulp.src('src/**/*.js')
    .pipe(sourcemaps.init({loadMaps: true}))
      .pipe(plugin1())
      .pipe(plugin2())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('dist'));
};

exports.javascript = javascript;

Handle large files

To handle large files, pass the option largeFile: true to sourcemaps.init().

Example:

var gulp = require('gulp');
var plugin1 = require('gulp-plugin1');
var plugin2 = require('gulp-plugin2');
var sourcemaps = require('gulp-sourcemaps');

function javascript() {
  gulp.src('src/**/*.js')
    .pipe(sourcemaps.init({largeFile: true}))
      .pipe(plugin1())
      .pipe(plugin2())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('dist'));
};

exports.javascript = javascript;

Handle source files from different directories

Use the base option on gulp.src to make sure all files are relative to a common base directory.

Example:

var gulp = require('gulp');
var plugin1 = require('gulp-plugin1');
var plugin2 = require('gulp-plugin2');
var sourcemaps = require('gulp-sourcemaps');

function javascript() {
gulp.src(['src/test.js', 'src/testdir/test2.js'], { base: 'src' })
    .pipe(sourcemaps.init())
      .pipe(plugin1())
      .pipe(plugin2())
    .pipe(sourcemaps.write('../maps'))
    .pipe(gulp.dest('dist'));
};

exports.javascript = javascript;

Alter sources property on sourcemaps

The exported mapSources method gives full control over the source paths. It takes a function that is called for every source and receives the default source path as a parameter and the original vinyl file.

Example:

function javascript() {
  var stream = gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
      .pipe(plugin1())
      .pipe(plugin2())
      // be careful with the sources returned otherwise contents might not be loaded properly
      .pipe(sourcemaps.mapSources(function(sourcePath, file) {
        // source paths are prefixed with '../src/'
        return '../src/' + sourcePath;
      }))
    .pipe(sourcemaps.write('../maps')
    .pipe(gulp.dest('public/scripts'));
};

exports.javascript = javascript;

Generate Identity Sourcemap

The exported identityMap method allows you to generate a full valid source map encoding no changes (slower, only for Javascript and CSS) instead of the default empty source map (no mappings, fast). Use this option if you get missing or incorrect mappings, e.g. when debugging.

Example:

function javascript() {
  var stream = gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
      // An identity sourcemap will be generated at this step
      .pipe(sourcemaps.identityMap())
      .pipe(plugin1())
      .pipe(plugin2())
    .pipe(sourcemaps.write('../maps')
    .pipe(gulp.dest('public/scripts'));
};

exports.javascript = javascript;

Init Options

• loadMaps

  Set to true to load existing maps for source files. Supports the following:

  • inline source maps
  • source map files referenced by a sourceMappingURL= comment
  • source map files with the same name (plus .map) in the same directory

• identityMap

  This option is deprecated. Upgrade to use our sourcemap.identityMap API.

Write Options

• addComment

  By default a comment containing / referencing the source map is added. Set this to false to disable the comment (e.g. if you want to load the source maps by header).

  Example:

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write('../maps', {addComment: false}))
      .pipe(gulp.dest('dist'));
  };
  
  exports.javascript = javascript;
  

• includeContent

  By default the source maps include the source code. Pass false to use the original files.

  Including the content is the recommended way, because it "just works". When setting this to false you have to host the source files and set the correct sourceRoot.

• sourceRoot

  Set the location where the source files are hosted (use this when includeContent is set to false). This is usually a URL (or an absolute URL path), not a local file system path. By default the source root is '' or in case destPath is set, the relative path from the source map to the source base directory (this should work for many dev environments). If a relative path is used (empty string or one starting with a .), it is interpreted as a path relative to the destination. The plugin rewrites it to a path relative to each source map.

  Example:

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write({includeContent: false, sourceRoot: '/src'}))
      .pipe(gulp.dest('dist'));
  };
  
  exports.javascript = javascript;
  

  Example (using a function):

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write({
        includeContent: false,
        sourceRoot: function(file) {
          return '/src';
        }
       }))
      .pipe(gulp.dest('dist'));
  };
  
  exports.javascript = javascript;
  

  Example (relative path):

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write('.', {includeContent: false, sourceRoot: '../src'}))
      .pipe(gulp.dest('dist'));
  };
  
  exports.javascript = javascript;
  

  In this case for a file written to dist/subdir/example.js, the source map is written to dist/subdir/example.js.map and the sourceRoot will be ../../src (resulting in the full source path ../../src/subdir/example.js).

• destPath

  Set the destination path (the same you pass to gulp.dest()). If the source map destination path is not a sub path of the destination path, this is needed to get the correct path in the file property of the source map. In addition, it allows to automatically set a relative sourceRoot if none is set explicitly.

• sourceMappingURLPrefix

  Specify a prefix to be prepended onto the source map URL when writing external source maps. Relative paths will have their leading dots stripped.

  Example:

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write('../maps', {
        sourceMappingURLPrefix: 'https://asset-host.example.com/assets'
      }))
      .pipe(gulp.dest('public/scripts'));
  };
  
  exports.javascript = javascript;
  

  This will result in a source mapping URL comment like sourceMappingURL=https://asset-host.example.com/assets/maps/helloworld.js.map.

• sourceMappingURL

  If you need full control over the source map URL you can pass a function to this option. The output of the function must be the full URL to the source map (in function of the output file).

  Example:

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write('../maps', {
        sourceMappingURL: function(file) {
          return 'https://asset-host.example.com/' + file.relative + '.map';
        }
      }))
      .pipe(gulp.dest('public/scripts'));
  };
  
  exports.javascript = javascript;
  

  This will result in a source mapping URL comment like sourceMappingURL=https://asset-host.example.com/helloworld.js.map.

• mapFile

  This option allows to rename the map file. It takes a function that is called for every map and receives the default map path as a parameter.

  Example:

  function javascript() {
    var stream = gulp.src('src/**/*.js')
      .pipe(sourcemaps.init())
        .pipe(plugin1())
        .pipe(plugin2())
      .pipe(sourcemaps.write('../maps', {
        mapFile: function(mapFilePath) {
          // source map files are named *.map instead of *.js.map
          return mapFilePath.replace('.js.map', '.map');
        }
      }))
      .pipe(gulp.dest('public/scripts'));
  };
  
  exports.javascript = javascript;
  

• mapSources

  This option is deprecated. Upgrade to use our sourcemap.mapSources API.

• charset

  Sets the charset for inline source maps. Default: utf8

• clone

  Clones the original file for creation of the map file. Could be important if file history is important. See file.clone() for possible options. Default: {deep:false, contents:false}

Plugin developers only:

• How to add source map support to plugins

  • Generate a source map for the transformation the plugin is applying
  • Important: Make sure the paths in the generated source map (file and sources) are relative to file.base (e.g. use file.relative).
  • Apply this source map to the vinyl file. E.g. by using vinyl-sourcemaps-apply. This combines the source map of this plugin with the source maps coming from plugins further up the chain.
  • Add your plugin to the wiki page

  Example:

  var through = require('through2');
  var applySourceMap = require('vinyl-sourcemaps-apply');
  var myTransform = require('myTransform');
  
  module.exports = function(options) {
  
    function transform(file, encoding, callback) {
      // generate source maps if plugin source-map present
      if (file.sourceMap) {
        options.makeSourceMaps = true;
      }
  
      // do normal plugin logic
      var result = myTransform(file.contents, options);
      file.contents = new Buffer(result.code);
  
      // apply source map to the chain
      if (file.sourceMap) {
        applySourceMap(file, result.map);
      }
  
      this.push(file);
      callback();
    }
  
    return through.obj(transform);
  };
  

  • Verify sourcemaps are working

    See example below or refer to test/write.js

  Example:

  var stream = plugin();
  var init = sourcemaps.init();
  var write = sourcemaps.write();
  
  init.pipe(stream).pipe(write);
  
  write.on('data', function (file) {
    assert(...);
    cb();
  });
  
  init.write(new gutil.File(...));
  init.end();
  

Debugging

All debugging output relies on visionmedia/debug. Follow the directions to set the environment variable $DEBUG.

For a few examples of debug you could use:

  DEBUG='gulp-sourcemaps:*' #everything
  DEBUG='gulp-sourcemaps:init' #init/index.js
  DEBUG='gulp-sourcemaps:init:*' #init/index.internals.js
  DEBUG='gulp-sourcemaps:write:' #write/index.js
  DEBUG='gulp-sourcemaps:write:*' #write/index.internals.js
  DEBUG='gulp-sourcemaps:write:,gulp-sourcemaps:init:**' #write/index.internals.js and init/index.internals.js