stream - Gulp:在另一个任务中使用一个任务的输出

Question

我有三个gulp任务，其中最后一个任务（allScripts）首先运行两个从属任务，然后从中加入结果文件。

在上一个任务中，我可以从前两个任务中删除两个结果文件，并从此以后幸福地生活在一起。

但是我在想，是否可以通过以某种方式“直接”将它们放入allScripts任务来避免这两个临时文件？

gulp.task('firstGroup', function() {
  return gulp.src('some/files/*.js')
    .pipe(doSomething())
    .pipe(concat('some-scripts.js'))
    .pipe(gulp.dest('dest'));
});

gulp.task('secondGroup', function() {
  return gulp.src('some/other/files/*.js')
    .pipe(doSomethingElse())
    .pipe(concat('some-other-scripts.js'))
    .pipe(gulp.dest('dest'));
});

gulp.task('allScripts', ['firstGroup','secondGroup'], function() {
  return gulp.src(['dest/some-scripts.js','dest/some-other-scripts.js'])
    .pipe(concat('all-scripts.js'))
    .pipe(gulp.dest('dest'))
    // delete the two src-files
});

Answer 1

如果一切都可以是一个任务，则可以使用gulp-merge插件将多个流合并为一个。如果任务需要分开，下面还有一个解决方案，但是请注意，该方法是一种hack，因为它依赖于Gulp中的暴露属性。

如果没有黑客解决方案，则将一项任务的输出用于另一项任务的输出，将需要中间存储，就像您对文件所做的一样。

单任务解决方案：

这是使用gulp-merge的准系统演示：

var gulp = require('gulp');
var gulpMerge = require('gulp-merge');
var concat = require('gulp-concat');
var replace = require('gulp-replace');

gulp.task('all-txt', function() {
    return gulpMerge(
            gulp.src('file1.txt')
                .pipe(replace(/foo/g, 'bar')),
            gulp.src('file2.txt')
                .pipe(replace(/baz/g, 'qux'))
        )
        .pipe(concat('all-text.txt'))
        .pipe(gulp.dest('dest'));
});

就您而言，并使用问题中的代码，它看起来像：

var gulp = require('gulp');
var gulpMerge = require('gulp-merge');
var concat = require('gulp-concat');
// ... your plugins

gulp.task('allScripts', function() {
    return gulpMerge(
            gulp.src('some/files/*.js')
                .pipe(doSomething())
                .pipe(concat('some-scripts.js')),
            gulp.src('some/other/files/*.js')
                .pipe(doSomethingElse())
                .pipe(concat('some-other-scripts.js'))
        )
        .pipe(concat('all-scripts.js'))
        .pipe(gulp.dest('dest'));
});

多任务解决方案：

如果您的任务结构无法使用上述方法将它们合并为一个任务，那么这是最好的选择。从某种意义上说，它依赖于 Gulp.tasks，这是一个非标准的公开属性，这有点怪异。没有任何保证可以在将来的Gulp版本中使用（当前已在Gulp v3.8.10中进行了测试）。

此代码段依赖于 event-stream包，因为它更健壮，并且我在 runTasksAndGetStreams函数中使用了它们的某些实用程序。

var gulp = require('gulp');

var concat = require('gulp-concat');
var replace = require('gulp-replace');
var es = require('event-stream');


gulp.task('all-txt', function() {
    return es.merge.apply(null, runTasksAndGetStreams(['file1-txt', 'file2-txt']))
        .pipe(concat('all-text.txt'))
        .pipe(gulp.dest('dest'));
});


gulp.task('file1-txt', ['random-task-dep'], function() {
    return gulp.src('file1.txt')
        .pipe(replace(/foo/g, 'bar'));
});

gulp.task('file2-txt', function() {
    return gulp.src('file2.txt')
        .pipe(replace(/baz/g, 'qux'));
});

gulp.task('random-task-dep', function() {
    return gulp.src('random-file.txt')
        .pipe(gulp.dest('dest'));
});



// Run the given tasks and returns their streams
// This will also take care of any task dependencies
//
// This is basically a custom gulp task orchestartor.
//
// Written for this SO question: http://stackoverflow.com/q/28334314/796832
// Gist: https://gist.github.com/MadLittleMods/d4083d2ba35e2f850161
//
// Params:
//      taskNames: string or array of strings of task names
//      debugLog: *optional* boolean to print some debug information to the console
function gulpRunTasksAndGetStreams(taskNames, /*optional*/debugLog) {
    // You can pass in a single task or an array of tasks to complete
    taskNames = [].concat(taskNames);

    // We polyfill the pieces of `gulp-util` that we use in case some one wants to use it without installing `gulp-util`
    var gutil;
    try {
        gutil = require('gulp-util');
    }
    catch(err) {
        gutil = {
            log: console.log,
            colors: {
                cyan: function(str) {
                    return str;
                },
                magenta: function(str) {
                    return str;
                }
            }
        };
    }

    var resultantTaskInfo = [];
    var taskMap = gulp.tasks;

    // Satisfy all of the task dependencies, create a placeholder stream, and collect the func 
    // to make the real stream to feed in later when the dependencies are done `mergedDepStream.on('end')`
    var mergedDepStream = null;
    taskNames.forEach(function(taskName) {
        var task = taskMap[taskName];

        if(debugLog) {
            gutil.log('root task:', gutil.colors.cyan(taskName), 'started working');
        }

        // Run any dependencies first
        var depStreamResult = runDependenciesRecursivelyForTask(taskName, taskMap);

        if(depStreamResult) {
            mergedDepStream = mergedDepStream ? es.merge(mergedDepStream, depStreamResult) : depStreamResult;
        }

        if(debugLog) {
            if(depStreamResult) {
                depStreamResult.on('end', function() {
                    gutil.log('root task:', gutil.colors.cyan(taskName), 'deps done');
                });
            }
            else {
                gutil.log('root task:', gutil.colors.cyan(taskName), 'no deps present');
            }
        }

        // Then push the task itself onto the list
        resultantTaskInfo.push({
            stream: es.through(),
            fn: task.fn
        });
    });

    // Once all of the dependencies have completed
    mergedDepStream.on('end', function() {

        if(debugLog) {
            gutil.log('All dependencies done, piping in real root tasks');
        }

        // Pipe the actual task into our placeholder
        resultantTaskInfo.forEach(function(taskInfo) {
            var actualTaskStream = taskInfo.fn();
            actualTaskStream.pipe(taskInfo.stream);
        });
    });


    // Recursively gets all of dependencies for a task in order
    function runDependenciesRecursivelyForTask(taskName, taskMap, mergedDependencyStream) {
        var task = taskMap[taskName];

        task.dep.forEach(function(depTaskName) {
            var depTask = taskMap[depTaskName];
            if(debugLog) {
                gutil.log('dep task:', gutil.colors.cyan(depTaskName), 'started working');
            }

            // Dependencies can have dependencies
            var recursiveStreamResult = null;
            if(depTask.dep.length) {
                recursiveStreamResult = runDependenciesRecursivelyForTask(depTaskName, taskMap, mergedDependencyStream);
                mergedDependencyStream = mergedDependencyStream ? es.merge(mergedDependencyStream, recursiveStreamResult) : recursiveStreamResult;
            }

            if(depTask.fn) {
                var whenStreamHandledCallback = function(/* we only use `noDeps` for logging */noDeps) {
                    if(debugLog) {
                        if(!noDeps) {
                            gutil.log('dep task:', gutil.colors.cyan(depTask.name), 'deps done');
                        }
                        else {
                            gutil.log('dep task:', gutil.colors.cyan(depTask.name), 'no deps present');
                        }
                    }

                    var depTaskStream = depTask.fn();
                    // Merge it in overall dependency progress stream
                    mergedDependencyStream = mergedDependencyStream ? es.merge(mergedDependencyStream, depTaskStream) : depTaskStream;
                };

                if(recursiveStreamResult === null) {
                    whenStreamHandledCallback(true);
                }
                else {
                    recursiveStreamResult.on('end', whenStreamHandledCallback);
                }
            }
        });

        return mergedDependencyStream;
    }


    // Return the (placeholder) streams which will get piped the real stream once the dependencies are done
    return resultantTaskInfo.map(function(taskInfo) {
        return taskInfo.stream;
    });
}