Is the code in ES6 modules executed every time we import a module? I'm using webpack and it seems that it does exactly that.
// FormStore.js
import sessionActions from "../../session/actions/session";
// session.spec.js
import sessionActions from "../../../src/session/actions/session";
This causes the code in the session module to be executed twice
I don't know exactly the answer, but I suspect it has to do with karma. I think it's due to having two different bundles.
In karma.config
preprocessors: {
"client/specs/index.ts": ["webpack"],
"client/specs/**/*spec.ts": ["webpack"]
},
webpack: {
entry: {
index: "./client/src/index.tsx",
vendor: []
}
},
Basically, I don't really need to add the index entry point, as this will probably create an additional bundle.
Do you want your code to be executed when imported? If in your /session/actions/session files there is a function call being exported rather than function declaration then it will be called when imported in any bundle you created. You can import different modules in different files.
If you are using karma-webpack
the usage
tells you that
webpack: {
// karma watches the test entry points
// (you don't need to specify the entry option)
// webpack watches dependencies
// webpack configuration
},
A coworker was experiencing the same issue today- the problem seemed to be caused by two imports of one package, but each import referencedthat package using a different path. You appear to be doing the same thing:
// FormStore.js
import sessionActions from "../../session/actions/session"; // note first path
// session.spec.js
import sessionActions from "../../../src/session/actions/session"; // note second path, which is different from first
Is it possible for the import in session.spec.js to import using the same path? If this isn't an option due to relative locations of the files, can you configure your module loader so that sessionActions is aliased (using map or path, for instance). I'm not sure if this is an option in your environment, however.
See:
https://github.com/systemjs/systemjs/blob/master/docs/config-api.md#map
for how to do this using system.js
Related
I'm having trouble using the Backendless plugin for Flutter.
I include
import 'package:backendless_sdk/backendless_sdk.dart';
(as per the instructions) and can then use e.g. Backendless.UserService. But if I try to generate a user to register, e.g.:
var user = new BackendlessUser();
user.setEmail("info#example.org");
user.setPassword("password");
Backendless.UserService.register(user);
I get an error Undefined class 'BackendlessUser' on the first line. This class is defined in src/modules/user_service.dat, which is exported by src/modules/modules.dartlike this:
library modules;
export 'cache.dart';
...
export 'user_service.dart';
which in turn is imported by backendless_sdk.dart like this:
import 'package:backendless_sdk/src/modules/modules.dart';
I would have thought that it would get imported indirectly by the import of backendless_sdk.dart, but apparently not. When I import it explicitly (with the same import statement, but now in my own code and not just indirectly in backendless_sdk.dart), I get a warning Don't import implementation files from another package. But it's not an implementation file; it's exported as part of the public API (at least that's what I understand the export statement to mean).
The Dart tutorial for creating packages suggests to place the export statements directly under lib, not in lib/src, so I'm wondering whether this is an error in the structure of the plugin, or whether I'm doing something wrong.
I'd be grateful both for a solution to this particular problem and also for pointers to how I can better understand packages, libraries, imports and exports in dart; unfortunately I don't find the language specification particularly helpful in this regard.
(The error and the warning are the same whether I use flutter analyze or IntelliJ IDEA.)
The problem has been fixed in the 0.0.3 version of the plugin. Please update the backendless_sdk version in your pubspec.yaml.
You can include the only one import now:
import 'package:backendless_sdk/backendless_sdk.dart';
Please also note, that there are some changes in the syntax. So for your example you should use:
var user = new BackendlessUser()
..email = "info#example.org"
..password = "password";
Backendless.userService.register(user);
Thanks for using Flutter SDK and pointing out this issue.
It's indeed the problem in the structure of the plugin. The Backendless team is aware of it and this problem will be fixed in the next release of the plugin.
For now you can import explicitly and suppress the warning.
I'm using rollup with the Babel and CommonJS plugins, like this:
const inputOptions = {
input: "...",
plugins: [
resolve(),
babel({
exclude: "node_modules/**",
externalHelpers: true,
include: "**/components/**/*.js",
}),
commonjs(),
],
};
But what happens is that modules referenced from components don't seem to be recognized by the CommonJS plugin, they end up as plain require(...) statements in the output (just like the source input) where of course they cannot be resolved. Modules imported (also through require() statements) by modules outside the components directory get picked up properly and included in the bundle.
I have tried moving the babel plugin up (before the resolve plugin), but this had no effect. I also tried moving it down, but then Rollup chokes on the JSX in the components.
I also tried removing the include option, so that all files go through Babel and then the result is that no modules get picked up besides the entry point, so it really seems like the Babel and CommonJS plugins aren't playing along nicely, though I can hardly imagine I'm the only one with a setup like this. Am I missing something?
Update: One other thing that I notice is that the files for which the requires() aren't recognized, aren't properly exported either. Instead, for each component that fails, I see this in the output bundle:
module.exports = ComponentName;
var componentName = /*#__PURE__*/Object.freeze({
});
The module.exports line comes from the source, but that Object.freeze() statement is something rollup adds, maybe because it doesn't see any default export?
To add a bit of extra confusion: There's actually one component that gets transpiled by Babel and for which the module resolution works and the requires() get replaced like you'd expect, but all the components included from that component in turn have the defective behavior described above.
Update 2: I have been able to reproduce the problem in a minimal example as well, and it allowed me to pinpoint why things worked for the one component, but not by the components it includes in turn. Apparently, functional React components work properly, but class components trigger the issue. So now my hypothesis is that the Babel transform for ES6 classes somehow confuses the CommonJS plugin.
Update 3: As I believe this is a bug, I have also created issues with the relevant projects: https://github.com/rollup/rollup-plugin-babel/issues/297 and https://github.com/rollup/rollup-plugin-commonjs/issues/369
Where do I put common server-side JavaScript files used by most of my jobs? I do not want to get fancy and create a new Node module, I just need a place to put a couple of utility functions.
A Node module is the only way that works I could find. I created a .js file (for instance utils.js) in the package folder where jobs/ and widgets/ are, and put all my common code for export:
module.export = {
commonFunction: function () { ... },
:
};
In my jobs, I import the common code I need with:
var utils = require('../../utils.js');
and use the exported properties offered by utils.
I want to clean my code structure and put class/object files in another directories in my gatling project.
If i put all simulation class and utils class in the same directory and same package i do not need an import statement and everything works fine.
Let's say my structure is as follow :
/user-files
----/simulations
--------MySimulation.scala
----/utils
--------Router.scala
I have tried several import or naming configuration to be able to use Router in my Simulation.
Follow package naming as directories structure
Put simulations and utils class in the same package
I have also tried different style of import
//using package
import packagename.Router
//another try
import packagename.Router._
//without package name
import Router._
My attempt to search a solution on scala docs or stack overflow didn't helped me.
This is the error given after executing gatling.bat
not found: value Router
You can't do that this way: there's one single source folder, which is by default /user-files/simulations.
If you want to use folders/packages (which is a good thing), you can have a structure such as:
/user-files
----/simulations
--------MySimulation.scala
--------/utils
------------Router.scala
Then, in Scala, packages and folder hierarchy are not related, BUT it's a good practice to use the same convention as in Java.
So, you would have:
package utils
object Router
then in MySimulation:
import utils.Router
I'm writing a small simulation program in Scala. It is actor-based so I've created a file messages.scala that contains all of the messages that are valid in the system.
Outside of this, I have a management component, management.scala and a file that defines the nodes and links classes nodes.scala. Management and node files both import sim.messages._ and then management does import sim.nodes._ as it needs to be able to instantiate things from that file.
The problem comes with one message type Tick that is used by both management.scala and nodes.scala. Upon compiling the management component, I get:
error: reference to Tick is ambiguous;
it is imported twice in the same scope by
import sim.nodes._
and import sim.messages._
I tried removing the import of messages in the management component since they were apparently already imported in to this scope but then they couldn't find them anymore. Ideas?
Try
import sim.nodes._
import sim.nodes.{ Tick => NodesTick }
and/or
import sim.messages._
import sim.messages.{ Tick => MessagesTick }
Of course, you will have to rename the references to Tick with the right one.