ava: Forking for every test file is slow

We’re not and tbh it’s annoying that we’ll probably have too. Why can’t the system just pool the load for us instead of we doing it manually? I hate computers so much… Let’s experiement with what kind of number is optimal. I’m thinking (require('os').cpus().length || 1) * 2;.

I have a very big project that I wanted to try ava on. After having the Activity Monitor (Mac OS X 10.11) open and seeing 50+ node process, it brought my system to its knees. It’d be cool if there was some kind of limit.

I think the biggest improvement will come from moving Babel to the main thread.

So have we actually profiled AVA to determine that babel is indeed the culprit? Or is it speculation?

Definitely not speculation. Moving Babel to the main thread for tests created significant speed improvements. It stands to reason the same improvements could be realized by moving source transpilation out of the forks.

Something else to consider - forking for every test at once is going to cause problems.

Already considered. See #791.

@spudly - I actually have a start on this already. I will post some code soon.

Basically, it needs to help identify test.only, test.serial.only, etc.

@sindresorhus: Or, a slightly more sane idea: Make a map of every file in our dependency tree mapped to it’s contents, then hook require to use those instead of the file system. Example:

var files = new Map([
    ["./lib/test.js", "'use strict';\nvar isGeneratorFn = require('is-generator-fn');\nvar maxTimeout = require('max-timeout');\nvar Promise = require('bluebird');\nvar fnName = require('fn-name');\nvar co = require('co-with-promise');\nvar observableToPromise = require('observable-to-promise');\nvar isPromise = require('is-promise');\nvar isObservable = require('is-observable');\nvar assert = require('./assert');\nvar enhanceAssert = require('./enhance-assert');\nvar globals = require('./globals');\n\nfunction Test(title, fn) {\nif (!(this instanceof Test)) {\n\t\treturn new Test(title, fn);\n\t}\n\n\tif (typeof title === 'function') {\n\t\tfn = title;\n\t\ttitle = null;\n\t}\n\n\tassert.is(typeof fn, 'function', 'you must provide a callback');\n\n\tthis.title = title || fnName(fn) || '[anonymous]';\n\tthis.fn = isGeneratorFn(fn) ? co.wrap(fn) : fn;\n\tthis.assertions = [];\n\tthis.planCount = null;\n\tthis.duration = null;\n\tthis.assertError = undefined;\n\n\tObject.defineProperty(this, 'assertCount', {\n\t\tenumerable: true,\n\t\tget: function () {\n\t\t\treturn this.assertions.length;\n\t\t}\n\t});\n\n\t// TODO(jamestalmage): make this an optional constructor arg instead of having Runner set it after the fact.\n\t// metadata should just always exist, otherwise it requires a bunch of ugly checks all over the place.\n\tthis.metadata = {};\n\n\t// store the time point before test execution\n\t// to calculate the total time spent in test\n\tthis._timeStart = null;\n\n\t// workaround for Babel giving anonymous functions a name\n\tif (this.title === 'callee$0$0') {\n\t\tthis.title = '[anonymous]';\n\t}\n}\n\nmodule.exports = Test;\n\nTest.prototype._assert = function (promise) {\n\tthis.assertions.push(promise);\n};\n\nTest.prototype._setAssertError = function (err) {\n\tif (this.assertError !== undefined) {\n\t\treturn;\n\t}\n\n\tif (err === undefined) {\n\t\terr = 'undefined';\n\t}\n\n\tthis.assertError = err;\n};\n\nTest.prototype.plan = function (count) {\n\tif (typeof count !== 'number') {\n\t\tthrow new TypeError('Expected a number');\n\t}\n\n\tthis.planCount = count;\n\n\t// in case the `planCount` doesn't match `assertCount,\n\t// we need the stack of this function to throw with a useful stack\n\tthis.planStack = new Error().stack;\n};\n\nTest.prototype.run = function () {\n\tvar self = this;\n\n\tthis.promise = Promise.pending();\n\n\t// TODO(vdemedes): refactor this to avoid storing the promise\n\tif (!this.fn) {\n\t\tthis.exit();\n\t\treturn undefined;\n\t}\n\n\tthis._timeStart = globals.now();\n\n\t// wait until all assertions are complete\n\tthis._timeout = globals.setTimeout(function () {}, maxTimeout);\n\n\tvar ret;\n\n\ttry {\n\t\tret = this.fn(this._publicApi());\n\t} catch (err) {\n\t\tthis._setAssertError(err);\n\t\tthis.exit();\n\t}\n\n\tvar asyncType = 'promises';\n\n\tif (isObservable(ret)) {\n\t\tasyncType = 'observables';\n\t\tret = observableToPromise(ret);\n\t}\n\n\tif (isPromise(ret)) {\n\t\tif (this.metadata.callback) {\n\t\t\tself._setAssertError(new Error('Do not return ' + asyncType + ' from tests declared via `test.cb(...)`, if you want to return a promise simply declare the test via `test(...)`'));\n\t\t\tthis.exit();\n\t\t\treturn this.promise.promise;\n\t\t}\n\n\t\tret\n\t\t\t.then(function () {\n\t\t\t\tself.exit();\n\t\t\t})\n\t\t\t.catch(function (err) {\n\t\t\t\tself._setAssertError(err);\n\t\t\t\tself.exit();\n\t\t\t});\n\t} else if (!this.metadata.callback) {\n\t\tthis.exit();\n\t}\n\n\treturn this.promise.promise;\n};\n\nObject.defineProperty(Test.prototype, 'end', {\n\tget: function () {\n\t\tif (this.metadata.callback) {\n\t\t\treturn this._end.bind(this);\n\t\t}\n\t\tthrow new Error('t.end is not supported in this context. To use t.end as a callback, you must use \"callback mode\" via `test.cb(testName, fn)` ');\n\t}\n});\n\nTest.prototype._end = function (err) {\n\tif (err) {\n\t\tthis._setAssertError(new assert.AssertionError({\n\t\t\tactual: err,\n\t\t\tmessage: 'Callback called with an error → ' + err,\n\t\t\toperator: 'callback'\n\t\t}));\n\n\t\tthis.exit();\n\t\treturn;\n\t}\n\n\tif (this.endCalled) {\n\t\tthrow new Error('.end() called more than once');\n\t}\n\n\tthis.endCalled = true;\n\tthis.exit();\n};\n\nTest.prototype._checkPlanCount = function () {\n\tif (this.assertError === undefined && this.planCount !== null && this.planCount !== this.assertions.length) {\n\t\tthis._setAssertError(new assert.AssertionError({\n\t\t\tactual: this.assertions.length,\n\t\t\texpected: this.planCount,\n\t\t\tmessage: 'Assertion count does not match planned',\n\t\t\toperator: 'plan'\n\t\t}));\n\n\t\t//this.assertError.stack = this.planStack;\n\t}\n};\n\nTest.prototype.exit = function () {\n\tvar self = this;\n\n\tthis._checkPlanCount();\n\n\tPromise.all(this.assertions)\n\t\t.catch(function (err) {\n\t\t\tself._setAssertError(err);\n\t\t})\n\t\t.finally(function () {\n\t\t\t// calculate total time spent in test\n\t\t\tself.duration = globals.now() - self._timeStart;\n\n\t\t\t// stop infinite timer\n\t\t\tglobals.clearTimeout(self._timeout);\n\n\t\t\tself._checkPlanCount();\n\n\t\t\tif (!self.ended) {\n\t\t\t\tself.ended = true;\n\n\t\t\t\tglobals.setImmediate(function () {\n\t\t\t\t\tif (self.assertError !== undefined) {\n\t\t\t\t\t\tself.promise.reject(self.assertError);\n\t\t\t\t\t\treturn;\n\t\t\t\t\t}\n\n\t\t\t\t\tself.promise.resolve(self);\n\t\t\t\t});\n\t\t\t}\n\t\t});\n};\n\nTest.prototype._publicApi = function () {\n\tvar self = this;\n\tvar api = {skip: {}};\n\n\t// Getters\n\t[\n\t\t'assertCount',\n\t\t'title',\n\t\t'end'\n\t]\n\t\t.forEach(function (name) {\n\t\t\tObject.defineProperty(api, name, {\n\t\t\t\tenumerable: name === 'end' ? self.metadata.callback : true,\n\t\t\t\tget: function () {\n\t\t\t\t\treturn self[name];\n\t\t\t\t}\n\t\t\t});\n\t\t});\n\n\t// Get / Set\n\tObject.defineProperty(api, 'context', {\n\t\tenumerable: true,\n\t\tget: function () {\n\t\t\treturn self.context;\n\t\t},\n\t\tset: function (context) {\n\t\t\tself.context = context;\n\t\t}\n\t});\n\n\t// Bound Functions\n\tapi.plan = this.plan.bind(this);\n\n\tfunction skipFn() {\n\t\tself._assert(Promise.resolve());\n\t}\n\n\tfunction onAssertionEvent(event) {\n\t\tvar promise;\n\t\tif (event.assertionThrew) {\n\t\t\tevent.error.powerAssertContext = event.powerAssertContext;\n\t\t\tpromise = Promise.reject(event.error);\n\t\t} else {\n\t\t\tpromise = Promise.resolve(observableToPromise(event.returnValue));\n\t\t}\n\t\tpromise = promise\n\t\t\t.catch(function (err) {\n\t\t\t\terr.originalMessage = event.originalMessage;\n\t\t\t\treturn Promise.reject(err);\n\t\t\t});\n\t\tself._assert(promise);\n\t}\n\n\tvar enhanced = enhanceAssert({\n\t\tassert: assert,\n\t\tonSuccess: onAssertionEvent,\n\t\tonError: onAssertionEvent\n\t});\n\n\t// Patched assert methods: increase assert count and store errors.\n\tObject.keys(assert).forEach(function (el) {\n\t\tapi.skip[el] = skipFn;\n\t\tapi[el] = enhanced[el].bind(enhanced);\n\t});\n\n\tapi._capt = enhanced._capt.bind(enhanced);\n\tapi._expr = enhanced._expr.bind(enhanced);\n\n\treturn api;\n};\n"],
    // etc.
]);

var actualRequire = require._extensions['.js'];
require._extensions['.js'] = function (module, filename) {
    if (files.has(filename)) return module._compile(filename);
    return actualRequire.apply(this, arguments);
};

require('./lib/babel.js');

If we uglified the files with “whitespace only” mode, it could totally* work!

*Probobly

Aren’t we setting some kind of limit of forks? We should probably not create more forks than there are CPUs.