[moodle.git] / Gruntfile.js

// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
/* jshint node: true, browser: false */
/* eslint-env node */

/**
 * @copyright  2014 Andrew Nicols
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

/* eslint-env node */

/**
 * Calculate the cwd, taking into consideration the `root` option (for Windows).
 *
 * @param {Object} grunt
 * @returns {String} The current directory as best we can determine
 */
const getCwd = grunt => {
    const fs = require('fs');
    const path = require('path');

    let cwd = fs.realpathSync(process.env.PWD || process.cwd());

    // Windows users can't run grunt in a subdirectory, so allow them to set
    // the root by passing --root=path/to/dir.
    if (grunt.option('root')) {
        const root = grunt.option('root');
        if (grunt.file.exists(__dirname, root)) {
            cwd = fs.realpathSync(path.join(__dirname, root));
            grunt.log.ok('Setting root to ' + cwd);
        } else {
            grunt.fail.fatal('Setting root to ' + root + ' failed - path does not exist');
        }
    }

    return cwd;
};

/**
 * Register any stylelint tasks.
 *
 * @param {Object} grunt
 * @param {Array} files
 * @param {String} fullRunDir
 */
const registerStyleLintTasks = (grunt, files, fullRunDir) => {
    const getCssConfigForFiles = files => {
        return {
            stylelint: {
                css: {
                    // Use a fully-qualified path.
                    src: files,
                    options: {
                        configOverrides: {
                            rules: {
                                // These rules have to be disabled in .stylelintrc for scss compat.
                                "at-rule-no-unknown": true,
                            }
                        }
                    }
                },
            },
        };
    };

    const getScssConfigForFiles = files => {
        return {
            stylelint: {
                scss: {
                    options: {syntax: 'scss'},
                    src: files,
                },
            },
        };
    };

    let hasCss = true;
    let hasScss = true;

    if (files) {
        // Specific files were passed. Just set them up.
        grunt.config.merge(getCssConfigForFiles(files));
        grunt.config.merge(getScssConfigForFiles(files));
    } else {
        // The stylelint system does not handle the case where there was no file to lint.
        // Check whether there are any files to lint in the current directory.
        const glob = require('glob');

        const scssSrc = [];
        glob.sync(`${fullRunDir}/**/*.scss`).forEach(path => scssSrc.push(path));

        if (scssSrc.length) {
            grunt.config.merge(getScssConfigForFiles(scssSrc));
        } else {
            hasScss = false;
        }

        const cssSrc = [];
        glob.sync(`${fullRunDir}/**/*.css`).forEach(path => cssSrc.push(path));

        if (cssSrc.length) {
            grunt.config.merge(getCssConfigForFiles(cssSrc));
        } else {
            hasCss = false;
        }
    }

    const scssTasks = ['sass'];
    if (hasScss) {
        scssTasks.unshift('stylelint:scss');
    }
    grunt.registerTask('scss', scssTasks);

    const cssTasks = [];
    if (hasCss) {
        cssTasks.push('stylelint:css');
    }
    grunt.registerTask('rawcss', cssTasks);

    grunt.registerTask('css', ['scss', 'rawcss']);
};

/**
 * Grunt configuration.
 *
 * @param {Object} grunt
 */
module.exports = function(grunt) {
    const path = require('path');
    const tasks = {};
    const async = require('async');
    const DOMParser = require('xmldom').DOMParser;
    const xpath = require('xpath');
    const semver = require('semver');
    const watchman = require('fb-watchman');
    const watchmanClient = new watchman.Client();
    const fs = require('fs');
    const ComponentList = require(path.resolve('GruntfileComponents.js'));
    const sass = require('node-sass');

    // Verify the node version is new enough.
    var expected = semver.validRange(grunt.file.readJSON('package.json').engines.node);
    var actual = semver.valid(process.version);
    if (!semver.satisfies(actual, expected)) {
        grunt.fail.fatal('Node version not satisfied. Require ' + expected + ', version installed: ' + actual);
    }

    // Detect directories:
    // * gruntFilePath          The real path on disk to this Gruntfile.js
    // * cwd                    The current working directory, which can be overridden by the `root` option
    // * relativeCwd            The cwd, relative to the Gruntfile.js
    // * componentDirectory     The root directory of the component if the cwd is in a valid component
    // * inComponent            Whether the cwd is in a valid component
    // * runDir                 The componentDirectory or cwd if not in a component, relative to Gruntfile.js
    // * fullRunDir             The full path to the runDir
    const gruntFilePath = fs.realpathSync(process.cwd());
    const cwd = getCwd(grunt);
    const relativeCwd = path.relative(gruntFilePath, cwd);
    const componentDirectory = ComponentList.getOwningComponentDirectory(relativeCwd);
    const inComponent = !!componentDirectory;
    const runDir = inComponent ? componentDirectory : relativeCwd;
    const fullRunDir = fs.realpathSync(gruntFilePath + path.sep + runDir);
    grunt.log.debug('============================================================================');
    grunt.log.debug(`= Node version:        ${process.versions.node}`);
    grunt.log.debug(`= grunt version:       ${grunt.package.version}`);
    grunt.log.debug(`= process.cwd:         '` + process.cwd() + `'`);
    grunt.log.debug(`= process.env.PWD:     '${process.env.PWD}'`);
    grunt.log.debug(`= path.sep             '${path.sep}'`);
    grunt.log.debug('============================================================================');
    grunt.log.debug(`= gruntFilePath:       '${gruntFilePath}'`);
    grunt.log.debug(`= relativeCwd:         '${relativeCwd}'`);
    grunt.log.debug(`= componentDirectory:  '${componentDirectory}'`);
    grunt.log.debug(`= inComponent:         '${inComponent}'`);
    grunt.log.debug(`= runDir:              '${runDir}'`);
    grunt.log.debug(`= fullRunDir:          '${fullRunDir}'`);
    grunt.log.debug('============================================================================');

    if (inComponent) {
        grunt.log.ok(`Running tasks for component directory ${componentDirectory}`);
    }

    let files = null;
    if (grunt.option('files')) {
        // Accept a comma separated list of files to process.
        files = grunt.option('files').split(',');
    }

    // If the cwd is the amd directory in the current component then it will be empty.
    // If the cwd is a child of the component's AMD directory, the relative directory will not start with ..
    const inAMD = !path.relative(`${componentDirectory}/amd`, cwd).startsWith('..');

    // Globbing pattern for matching all AMD JS source files.
    let amdSrc = [];
    if (inComponent) {
        amdSrc.push(componentDirectory + "/amd/src/*.js");
        amdSrc.push(componentDirectory + "/amd/src/**/*.js");
    } else {
        amdSrc = ComponentList.getAmdSrcGlobList();
    }

    let yuiSrc = [];
    if (inComponent) {
        yuiSrc.push(componentDirectory + "/yui/src/**/*.js");
    } else {
        yuiSrc = ComponentList.getYuiSrcGlobList(gruntFilePath + '/');
    }

    /**
     * Function to generate the destination for the uglify task
     * (e.g. build/file.min.js). This function will be passed to
     * the rename property of files array when building dynamically:
     * http://gruntjs.com/configuring-tasks#building-the-files-object-dynamically
     *
     * @param {String} destPath the current destination
     * @param {String} srcPath the  matched src path
     * @return {String} The rewritten destination path.
     */
    var babelRename = function(destPath, srcPath) {
        destPath = srcPath.replace('src', 'build');
        destPath = destPath.replace('.js', '.min.js');
        return destPath;
    };

    /**
     * Find thirdpartylibs.xml and generate an array of paths contained within
     * them (used to generate ignore files and so on).
     *
     * @return {array} The list of thirdparty paths.
     */
    var getThirdPartyPathsFromXML = function() {
        const thirdpartyfiles = ComponentList.getThirdPartyLibsList(gruntFilePath + '/');
        const libs = ['node_modules/', 'vendor/'];

        thirdpartyfiles.forEach(function(file) {
            const dirname = path.dirname(file);

            const doc = new DOMParser().parseFromString(grunt.file.read(file));
            const nodes = xpath.select("/libraries/library/location/text()", doc);

            nodes.forEach(function(node) {
                let lib = path.posix.join(dirname, node.toString());
                if (grunt.file.isDir(lib)) {
                    // Ensure trailing slash on dirs.
                    lib = lib.replace(/\/?$/, '/');
                }

                // Look for duplicate paths before adding to array.
                if (libs.indexOf(lib) === -1) {
                    libs.push(lib);
                }
            });
        });

        return libs;
    };

    /**
     * Get the list of feature files to pass to the gherkin linter.
     *
     * @returns {Array}
     */
    const getGherkinLintTargets = () => {
        if (files) {
            // Specific files were requested. Only check these.
            return files;
        }

        if (inComponent) {
            return [`${runDir}/tests/behat/*.feature`];
        }

        return ['**/tests/behat/*.feature'];
    };

    // Project configuration.
    grunt.initConfig({
        eslint: {
            // Even though warnings dont stop the build we don't display warnings by default because
            // at this moment we've got too many core warnings.
            // To display warnings call: grunt eslint --show-lint-warnings
            // To fail on warnings call: grunt eslint --max-lint-warnings=0
            // Also --max-lint-warnings=-1 can be used to display warnings but not fail.
            options: {
                quiet: (!grunt.option('show-lint-warnings')) && (typeof grunt.option('max-lint-warnings') === 'undefined'),
                maxWarnings: ((typeof grunt.option('max-lint-warnings') !== 'undefined') ? grunt.option('max-lint-warnings') : -1)
            },
            amd: {src: files ? files : amdSrc},
            // Check YUI module source files.
            yui: {src: files ? files : yuiSrc},
        },
        babel: {
            options: {
                sourceMaps: true,
                comments: false,
                plugins: [
                    'transform-es2015-modules-amd-lazy',
                    'system-import-transformer',
                    // This plugin modifies the Babel transpiling for "export default"
                    // so that if it's used then only the exported value is returned
                    // by the generated AMD module.
                    //
                    // It also adds the Moodle plugin name to the AMD module definition
                    // so that it can be imported as expected in other modules.
                    path.resolve('babel-plugin-add-module-to-define.js'),
                    '@babel/plugin-syntax-dynamic-import',
                    '@babel/plugin-syntax-import-meta',
                    ['@babel/plugin-proposal-class-properties', {'loose': false}],
                    '@babel/plugin-proposal-json-strings'
                ],
                presets: [
                    ['minify', {
                        // This minification plugin needs to be disabled because it breaks the
                        // source map generation and causes invalid source maps to be output.
                        simplify: false,
                        builtIns: false
                    }],
                    ['@babel/preset-env', {
                        targets: {
                            browsers: [
                                ">0.25%",
                                "last 2 versions",
                                "not ie <= 10",
                                "not op_mini all",
                                "not Opera > 0",
                                "not dead"
                            ]
                        },
                        modules: false,
                        useBuiltIns: false
                    }]
                ]
            },
            dist: {
                files: [{
                    expand: true,
                    src: files ? files : amdSrc,
                    rename: babelRename
                }]
            }
        },
        sass: {
            dist: {
                files: {
                    "theme/boost/style/moodle.css": "theme/boost/scss/preset/default.scss",
                    "theme/classic/style/moodle.css": "theme/classic/scss/classicgrunt.scss"
                }
            },
            options: {
                implementation: sass,
                includePaths: ["theme/boost/scss/", "theme/classic/scss/"]
            }
        },
        watch: {
            options: {
                nospawn: true // We need not to spawn so config can be changed dynamically.
            },
            amd: {
                files: inComponent
                    ? ['amd/src/*.js', 'amd/src/**/*.js']
                    : ['**/amd/src/**/*.js'],
                tasks: ['amd']
            },
            boost: {
                files: [inComponent ? 'scss/**/*.scss' : 'theme/boost/scss/**/*.scss'],
                tasks: ['scss']
            },
            rawcss: {
                files: [
                    '**/*.css',
                ],
                excludes: [
                    '**/moodle.css',
                    '**/editor.css',
                ],
                tasks: ['rawcss']
            },
            yui: {
                files: inComponent
                    ? ['yui/src/*.json', 'yui/src/**/*.js']
                    : ['**/yui/src/**/*.js'],
                tasks: ['yui']
            },
            gherkinlint: {
                files: [inComponent ? 'tests/behat/*.feature' : '**/tests/behat/*.feature'],
                tasks: ['gherkinlint']
            }
        },
        shifter: {
            options: {
                recursive: true,
                // Shifter takes a relative path.
                paths: files ? files : [runDir]
            }
        },
        gherkinlint: {
            options: {
                files: getGherkinLintTargets(),
            }
        },
    });

    /**
     * Generate ignore files (utilising thirdpartylibs.xml data)
     */
    tasks.ignorefiles = function() {
        // An array of paths to third party directories.
        const thirdPartyPaths = getThirdPartyPathsFromXML();
        // Generate .eslintignore.
        const eslintIgnores = [
            '# Generated by "grunt ignorefiles"',
            '*/**/yui/src/*/meta/',
            '*/**/build/',
        ].concat(thirdPartyPaths);
        grunt.file.write('.eslintignore', eslintIgnores.join('\n'));

        // Generate .stylelintignore.
        const stylelintIgnores = [
            '# Generated by "grunt ignorefiles"',
            '**/yui/build/*',
            'theme/boost/style/moodle.css',
            'theme/classic/style/moodle.css',
        ].concat(thirdPartyPaths);
        grunt.file.write('.stylelintignore', stylelintIgnores.join('\n'));
    };

    /**
     * Shifter task. Is configured with a path to a specific file or a directory,
     * in the case of a specific file it will work out the right module to be built.
     *
     * Note that this task runs the invidiaul shifter jobs async (becase it spawns
     * so be careful to to call done().
     */
    tasks.shifter = function() {
        var done = this.async(),
            options = grunt.config('shifter.options');

        // Run the shifter processes one at a time to avoid confusing output.
        async.eachSeries(options.paths, function(src, filedone) {
            var args = [];
            args.push(path.normalize(__dirname + '/node_modules/shifter/bin/shifter'));

            // Always ignore the node_modules directory.
            args.push('--excludes', 'node_modules');

            // Determine the most appropriate options to run with based upon the current location.
            if (grunt.file.isMatch('**/yui/**/*.js', src)) {
                // When passed a JS file, build our containing module (this happen with
                // watch).
                grunt.log.debug('Shifter passed a specific JS file');
                src = path.dirname(path.dirname(src));
                options.recursive = false;
            } else if (grunt.file.isMatch('**/yui/src', src)) {
                // When in a src directory --walk all modules.
                grunt.log.debug('In a src directory');
                args.push('--walk');
                options.recursive = false;
            } else if (grunt.file.isMatch('**/yui/src/*', src)) {
                // When in module, only build our module.
                grunt.log.debug('In a module directory');
                options.recursive = false;
            } else if (grunt.file.isMatch('**/yui/src/*/js', src)) {
                // When in module src, only build our module.
                grunt.log.debug('In a source directory');
                src = path.dirname(src);
                options.recursive = false;
            }

            if (grunt.option('watch')) {
                grunt.fail.fatal('The --watch option has been removed, please use `grunt watch` instead');
            }

            // Add the stderr option if appropriate
            if (grunt.option('verbose')) {
                args.push('--lint-stderr');
            }

            if (grunt.option('no-color')) {
                args.push('--color=false');
            }

            var execShifter = function() {

                grunt.log.ok("Running shifter on " + src);
                grunt.util.spawn({
                    cmd: "node",
                    args: args,
                    opts: {cwd: src, stdio: 'inherit', env: process.env}
                }, function(error, result, code) {
                    if (code) {
                        grunt.fail.fatal('Shifter failed with code: ' + code);
                    } else {
                        grunt.log.ok('Shifter build complete.');
                        filedone();
                    }
                });
            };

            // Actually run shifter.
            if (!options.recursive) {
                execShifter();
            } else {
                // Check that there are yui modules otherwise shifter ends with exit code 1.
                if (grunt.file.expand({cwd: src}, '**/yui/src/**/*.js').length > 0) {
                    args.push('--recursive');
                    execShifter();
                } else {
                    grunt.log.ok('No YUI modules to build.');
                    filedone();
                }
            }
        }, done);
    };

    tasks.gherkinlint = function() {
        const done = this.async();
        const options = grunt.config('gherkinlint.options');

        // Grab the gherkin-lint linter and required scaffolding.
        const linter = require('gherkin-lint/dist/linter.js');
        const featureFinder = require('gherkin-lint/dist/feature-finder.js');
        const configParser = require('gherkin-lint/dist/config-parser.js');
        const formatter = require('gherkin-lint/dist/formatters/stylish.js');

        // Run the linter.
        return linter.lint(
            featureFinder.getFeatureFiles(grunt.file.expand(options.files)),
            configParser.getConfiguration(configParser.defaultConfigFileName)
        )
        .then(results => {
            // Print the results out uncondtionally.
            formatter.printResults(results);

            return results;
        })
        .then(results => {
            // Report on the results.
            // The done function takes a bool whereby a falsey statement causes the task to fail.
            return results.every(result => result.errors.length === 0);
        })
        .then(done); // eslint-disable-line promise/no-callback-in-promise
    };

    tasks.startup = function() {
        // Are we in a YUI directory?
        if (path.basename(path.resolve(cwd, '../../')) == 'yui') {
            grunt.task.run('yui');
        // Are we in an AMD directory?
        } else if (inAMD) {
            grunt.task.run('amd');
        } else {
            // Run them all!.
            grunt.task.run('css');
            grunt.task.run('js');
            grunt.task.run('gherkinlint');
        }
    };

    /**
     * This is a wrapper task to handle the grunt watch command. It attempts to use
     * Watchman to monitor for file changes, if it's installed, because it's much faster.
     *
     * If Watchman isn't installed then it falls back to the grunt-contrib-watch file
     * watcher for backwards compatibility.
     */
    tasks.watch = function() {
        var watchTaskDone = this.async();
        var watchInitialised = false;
        var watchTaskQueue = {};
        var processingQueue = false;

        // Grab the tasks and files that have been queued up and execute them.
        var processWatchTaskQueue = function() {
            if (!Object.keys(watchTaskQueue).length || processingQueue) {
                // If there is nothing in the queue or we're already processing then wait.
                return;
            }

            processingQueue = true;

            // Grab all tasks currently in the queue.
            var queueToProcess = watchTaskQueue;
            // Reset the queue.
            watchTaskQueue = {};

            async.forEachSeries(
                Object.keys(queueToProcess),
                function(task, next) {
                    var files = queueToProcess[task];
                    var filesOption = '--files=' + files.join(',');
                    grunt.log.ok('Running task ' + task + ' for files ' + filesOption);

                    // Spawn the task in a child process so that it doesn't kill this one
                    // if it failed.
                    grunt.util.spawn(
                        {
                            // Spawn with the grunt bin.
                            grunt: true,
                            // Run from current working dir and inherit stdio from process.
                            opts: {
                                cwd: fullRunDir,
                                stdio: 'inherit'
                            },
                            args: [task, filesOption]
                        },
                        function(err, res, code) {
                            if (code !== 0) {
                                // The grunt task failed.
                                grunt.log.error(err);
                            }

                            // Move on to the next task.
                            next();
                        }
                    );
                },
                function() {
                    // No longer processing.
                    processingQueue = false;
                    // Once all of the tasks are done then recurse just in case more tasks
                    // were queued while we were processing.
                    processWatchTaskQueue();
                }
            );
        };

        const originalWatchConfig = grunt.config.get(['watch']);
        const watchConfig = Object.keys(originalWatchConfig).reduce(function(carry, key) {
            if (key == 'options') {
                return carry;
            }

            const value = originalWatchConfig[key];

            const taskNames = value.tasks;
            const files = value.files;
            let excludes = [];
            if (value.excludes) {
                excludes = value.excludes;
            }

            taskNames.forEach(function(taskName) {
                carry[taskName] = {
                    files,
                    excludes,
                };
            });

            return carry;
        }, {});

        watchmanClient.on('error', function(error) {
            // We have to add an error handler here and parse the error string because the
            // example way from the docs to check if Watchman is installed doesn't actually work!!
            // See: https://github.com/facebook/watchman/issues/509
            if (error.message.match('Watchman was not found')) {
                // If watchman isn't installed then we should fallback to the other watch task.
                grunt.log.ok('It is recommended that you install Watchman for better performance using the "watch" command.');

                // Fallback to the old grunt-contrib-watch task.
                grunt.renameTask('watch-grunt', 'watch');
                grunt.task.run(['watch']);
                // This task is finished.
                watchTaskDone(0);
            } else {
                grunt.log.error(error);
                // Fatal error.
                watchTaskDone(1);
            }
        });

        watchmanClient.on('subscription', function(resp) {
            if (resp.subscription !== 'grunt-watch') {
                return;
            }

            resp.files.forEach(function(file) {
                grunt.log.ok('File changed: ' + file.name);

                var fullPath = fullRunDir + '/' + file.name;
                Object.keys(watchConfig).forEach(function(task) {

                    const fileGlobs = watchConfig[task].files;
                    var match = fileGlobs.some(function(fileGlob) {
                        return grunt.file.isMatch(`**/${fileGlob}`, fullPath);
                    });

                    if (match) {
                        // If we are watching a subdirectory then the file.name will be relative
                        // to that directory. However the grunt tasks  expect the file paths to be
                        // relative to the Gruntfile.js location so let's normalise them before
                        // adding them to the queue.
                        var relativePath = fullPath.replace(gruntFilePath + '/', '');
                        if (task in watchTaskQueue) {
                            if (!watchTaskQueue[task].includes(relativePath)) {
                                watchTaskQueue[task] = watchTaskQueue[task].concat(relativePath);
                            }
                        } else {
                            watchTaskQueue[task] = [relativePath];
                        }
                    }
                });
            });

            processWatchTaskQueue();
        });

        process.on('SIGINT', function() {
            // Let the user know that they may need to manually stop the Watchman daemon if they
            // no longer want it running.
            if (watchInitialised) {
                grunt.log.ok('The Watchman daemon may still be running and may need to be stopped manually.');
            }

            process.exit();
        });

        // Initiate the watch on the current directory.
        watchmanClient.command(['watch-project', fullRunDir], function(watchError, watchResponse) {
            if (watchError) {
                grunt.log.error('Error initiating watch:', watchError);
                watchTaskDone(1);
                return;
            }

            if ('warning' in watchResponse) {
                grunt.log.error('warning: ', watchResponse.warning);
            }

            var watch = watchResponse.watch;
            var relativePath = watchResponse.relative_path;
            watchInitialised = true;

            watchmanClient.command(['clock', watch], function(clockError, clockResponse) {
                if (clockError) {
                    grunt.log.error('Failed to query clock:', clockError);
                    watchTaskDone(1);
                    return;
                }

                // Generate the expression query used by watchman.
                // Documentation is limited, but see https://facebook.github.io/watchman/docs/expr/allof.html for examples.
                // We generate an expression to match any value in the files list of all of our tasks, but excluding
                // all value in the  excludes list of that task.
                //
                // [anyof, [
                //      [allof, [
                //          [anyof, [
                //              ['match', validPath, 'wholename'],
                //              ['match', validPath, 'wholename'],
                //          ],
                //          [not,
                //              [anyof, [
                //                  ['match', invalidPath, 'wholename'],
                //                  ['match', invalidPath, 'wholename'],
                //              ],
                //          ],
                //      ],
                var matchWholeName = fileGlob => ['match', fileGlob, 'wholename'];
                var matches = Object.keys(watchConfig).map(function(task) {
                    const matchAll = [];
                    matchAll.push(['anyof'].concat(watchConfig[task].files.map(matchWholeName)));

                    if (watchConfig[task].excludes.length) {
                        matchAll.push(['not', ['anyof'].concat(watchConfig[task].excludes.map(matchWholeName))]);
                    }

                    return ['allof'].concat(matchAll);
                });

                matches = ['anyof'].concat(matches);

                var sub = {
                    expression: matches,
                    // Which fields we're interested in.
                    fields: ["name", "size", "type"],
                    // Add our time constraint.
                    since: clockResponse.clock
                };

                if (relativePath) {
                    /* eslint-disable camelcase */
                    sub.relative_root = relativePath;
                }

                watchmanClient.command(['subscribe', watch, 'grunt-watch', sub], function(subscribeError) {
                    if (subscribeError) {
                        // Probably an error in the subscription criteria.
                        grunt.log.error('failed to subscribe: ', subscribeError);
                        watchTaskDone(1);
                        return;
                    }

                    grunt.log.ok('Listening for changes to files in ' + fullRunDir);
                });
            });
        });
    };

    // On watch, we dynamically modify config to build only affected files. This
    // method is slightly complicated to deal with multiple changed files at once (copied
    // from the grunt-contrib-watch readme).
    var changedFiles = Object.create(null);
    var onChange = grunt.util._.debounce(function() {
        var files = Object.keys(changedFiles);
        grunt.config('eslint.amd.src', files);
        grunt.config('eslint.yui.src', files);
        grunt.config('shifter.options.paths', files);
        grunt.config('gherkinlint.options.files', files);
        grunt.config('babel.dist.files', [{expand: true, src: files, rename: babelRename}]);
        changedFiles = Object.create(null);
    }, 200);

    grunt.event.on('watch', function(action, filepath) {
        changedFiles[filepath] = action;
        onChange();
    });

    // Register NPM tasks.
    grunt.loadNpmTasks('grunt-contrib-uglify');
    grunt.loadNpmTasks('grunt-contrib-watch');
    grunt.loadNpmTasks('grunt-sass');
    grunt.loadNpmTasks('grunt-eslint');
    grunt.loadNpmTasks('grunt-stylelint');
    grunt.loadNpmTasks('grunt-babel');

    // Rename the grunt-contrib-watch "watch" task because we're going to wrap it.
    grunt.renameTask('watch', 'watch-grunt');

    // Register JS tasks.
    grunt.registerTask('shifter', 'Run Shifter against the current directory', tasks.shifter);
    grunt.registerTask('gherkinlint', 'Run gherkinlint against the current directory', tasks.gherkinlint);
    grunt.registerTask('ignorefiles', 'Generate ignore files for linters', tasks.ignorefiles);
    grunt.registerTask('watch', 'Run tasks on file changes', tasks.watch);
    grunt.registerTask('yui', ['eslint:yui', 'shifter']);
    grunt.registerTask('amd', ['eslint:amd', 'babel']);
    grunt.registerTask('js', ['amd', 'yui']);

    // Register CSS tasks.
    registerStyleLintTasks(grunt, files, fullRunDir);

    // Register the startup task.
    grunt.registerTask('startup', 'Run the correct tasks for the current directory', tasks.startup);

    // Register the default task.
    grunt.registerTask('default', ['startup']);
};