Gulp: Use output from one task in another task
I have have three gulp tasks, where the last task (allScripts) runs the two dependent tasks first and then joins the resultant files from them.
I could, in the last task, delete the two result-files from the two first tasks and live happily ever after with the joined file.
But I was thinking, is it possible to avoid the two temporary files by somehow piping them into the allScripts task "directly"?
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
});
Solution 1:
If everything can be a single task, you can use the gulp-merge plugin to combine multiple streams into one. There is also a solution below if the tasks need to stay separate, but please note that that method is a hack because it relies on a exposed property in Gulp.
Without a hack solution, using the output from one task in another, would require intermediary storage, like what you are doing with a file.
Single task solution:
Here is a barebones demo using gulp-merge:
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'));
});
In your case and using the code in your question it would look like:
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'));
});
Multiple task solution:
If your task structure is such that you can not merge them into a single task using the method above, this is your best bet. It is a bit hacky in the sense that it relies on Gulp.tasks which is a non-standard exposed property. There is no gurantee that this will work with future versions of Gulp (currently tested with Gulp v3.8.10).
This snippet relies on the event-stream package because it is more robust and I use some of their utilities in the runTasksAndGetStreams function.
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;
});
}
Solution 2:
@MLM had the right idea with about combining streams.
But don't forget that Gulp's just Javascript.
Try this:
const merge = require('merge-stream');
// or pick an alternative stream-merge library:
//const merge = require('event-stream').merge; //1317 stars on GitHub
//const merge = require('merge-stream'); //102 stars on GitHub
//const merge = require('merge2'); //75 stars on GitHub
//const merge = require('stream-series'); //23 stars on GitHub, keeps events in order
//const merge = require('gulp-merge'); //renamed to merge2
/*const merge = require('streamqueue') //54 stars on GitHub
.bind(null, {objectMode: true}); //required for streamqueue vinyl streams
*/
function firstGroup() {
return gulp.src('some/files/*.js')
.pipe(doSomething())
.pipe(concat('some-scripts.js'));
}
gulp.task('firstGroup', funtion() {
return firstGroup()
.pipe(gulp.dest('dest'));
});
function secondGroup() {
return gulp.src('some/other/files/*.js')
.pipe(doSomethingElse())
.pipe(concat('some-other-scripts.js'));
}
gulp.task('secondGroup', function() {
return secondGroup()
.pipe(gulp.dest('dest'));
});
gulp.task('allScripts', function() {
return merge(firstGroup(), secondGroup())
.pipe(concat('all-scripts.js'))
.pipe(gulp.dest('dest'))
});
And probably name your tasks and their related functions a bit better than above.
That being said, it's probably still easier and more clear to delete the files in the last task.
var del = require('del');
gulp.task('allScripts', ['firstGroup','secondGroup'], function(done) {
var intermediariesGlob = ['dest/some-scripts.js','dest/some-other-scripts.js'];
gulp.src(intermediariesGlob)
.pipe(concat('all-scripts.js'))
.pipe(gulp.dest('dest'))
.on('end', function() {
del(intermediariesGlob)
.then(function() {done();}); //don't just then(done), the array returned by the promise will become the error parameter of done
});
});