I just put some of my code from a/b.dart to a/b1.dart file and now I started getting lot of errors on importing.
Is there any command or any other fix to import all a/b1.dart file in these files instead of manually opening each file and importing one by one.
I understand that a function or a property can be defined in more than two files and Dart can't make the right choice but if a function or property is defined in just one place, I think there must be some way to import it except searching for a/b.dart and replacing it with a/b.dart + a/b1.dart and then optimizing all imports.
As much as I am aware, Plugins/Extensions for your specific IDE (for dart) can be found that will help you with this problem.
I would recommend using dartdev tools - dartfix
Related
In Flutter, for importing libraries within our own package's lib directory, should we use relative imports
import 'foo.dart'
or package import?
import 'package:my_app/lib/src/foo.dart'
Dart guidelines advocate to use relative imports :
PREFER relative paths when importing libraries within your own package’s lib directory.
whereas Provider package says to always use packages imports :
Always use package imports. Ex: import 'package:my_app/my_code.dart';
Is there a difference other than conciseness? Why would packages imports would reduce errors over relative imports?
From the same Dart guidelines, further down they give this reason for the relative imports:
There is no profound reason to prefer the former—it’s just shorter, and we want to be consistent.
Personally, I prefer the absolute method, despite it being more verbose, as it means when I'm importing from different dart files (in other folders), I don't have to work out where the file to be imported is, relative to the current file. Made-up example:
I have two dart files, at different folder levels, that need to import themes/style.dart:
One is widgets/animation/box_anim.dart, where the relative path import would be:
import '../../themes/style.dart';
The other is screens/home_screen.dart with the relative import:
import '../themes/style.dart';
This can get confusing, so I find it better to just use the absolute in both files, keeping it consistent:
import 'package:myapp/themes/style.dart';
And just stick that rule throughout. So, basically, whatever method you use - Consistency is key!
The Linter for Dart package, also has something to say about this, but is more about the Don'ts of mixing in the '/lib' folder:
DO avoid relative imports for files in lib/.
When mixing relative and absolute imports it's possible to create
confusion where the same member gets imported in two different ways.
An easy way to avoid that is to ensure you have no relative imports
that include lib/ in their paths.
TLDR; Choose the one you prefer, note that prefer_relative_imports is recommended in official Effective Dart guide
First of all, as mentioned in this answer, Provider do not recommands package imports anymore.
Dart linter provides a list of rules, including some predefined rulesets :
pedantic for rules enforced internally at Google
lints or even flutter_lints (previously effective_dart) for rules corresponding to the Effective Dart style guide
flutter for rules used in flutter analyze
Imports rules
There is actually more than two opposites rules concerning imports :
avoid_relative_lib_imports, enabled in pedantic and lints rulesets, basically recommend to avoid imports that have 'lib' in their paths.
The two following are the one you mention :
prefer_relative_imports, enabled in no predefined rulesets, but recommended in Effective Dart guide in opposition to :
always_use_package_imports, enabled in no predefined rulesets. Which means that it is up to you and to your preferences to enable it (be careful, it is incompatible with the previous rule)
Which one should I choose?
Choose the rule you want ! It will not cause any performance issue, and no rule would reduce errors over the other. Just pick one and make your imports consistent across all your project, thanks to Dart linter.
I personnaly prefer using prefer_relative_imports, as it is recommended by Dart team, with this VSCode extension which automatically fix and sort my imports.
Provider do not need packages imports anymore.
This was a workaround to an old Dart bug: Flutter: Retrieving top-level state from child returns null
TL;DR, by mixing relative and absolute imports, sometimes Dart created a duplicate of the class definition.
This led to the absurd line that is:
import 'package:myApp/test.dart' as absolute;
import './test.dart' as relative;
void main() {
print(relative.Test().runtimeType == absolute.Test().runtimeType); // false
}
Since provider relies on runtimeType to resolve objects, then this bug made provider unable to obtain an object in some situations.
My 5 cents on the topic are that absolute (package:my_app/etc/etc2...) imports cause much less trouble than relative ones (../../etc/etc2...) when you decide to reorganize/cleanup your project`s structure because whenever you move a file from one directory to another you change the "starting point" of every relative import that this file uses thus breaking all the relative imports inside the moved file...
I'd personally always prefer absolute to relative paths for this reason
This question already has good answers, but I wanted to mention an insanely annoying and hard-to-find problem I experienced with unit testing that was caused by a relative import.
The expect fail indicator for an exception-catching expect block
expect(
() => myFunction,
throwsA(isA<InvalidUserDataException>())
);
was showing the actual result as exactly the same as the expected result, and zero indication of why it's failing.
After massive trial-and-error, the issue was because the expected InvalidUserDataException (a custom-made class) was being imported to the test file in RELATIVE format vs PACKAGE format.
To find this, I had to compare side-by-side, line-by-line, call-by-call between this test file and another test file that uses the exact same exception expecters (It's lucky, we had this), and just by chance, I happened to scroll to the top of this file's imports and see the blue underline saying prefer relative imports to /lib directory.
No, they're not preferred; they're necessary, because the moment I changed that to a PACKAGE (absolute) import, everything suddenly started working.
What I learned from this is: Use absolute imports for test files (files outside the lib directory)
e.g. inside of src/test/main_test.dart
DON'T: use import '../lib/main.dart'
DO: use package:my_flutter_app/main.dart
Maybe other people knew this already, but I didn't, and I couldn't find anything online with searches about this issue, so I thought I would share my experience that might help others who got stuck around this.
Does anyone know why this happens?
Edit: For context, this happened while using Flutter 2.1.4 (stable) with Sound Null Safety
Do you use Integration Tests?
If the answer is yes, then in most cases you need to use package imports. When you attempt to run your integration tests on a physical device, any relative imports will not be able to find what they're looking for.
Example: https://github.com/fluttercommunity/get_it/issues/76
You can enforce package imports in your project by using these two linting rules:
always_use_package_imports
avoid_relative_lib_imports
I also prefer package imports because they stick even when rearranging your files and folders. Relative imports frequently break and it's a pain to have to remove them and reimport the offending dependency.
One very simple reason to not use package imports: rename your package without editing every dart file
Renaming can happen a few times while the product does not have a definitive name, and you or your product owner decides to change it.
It is much more painful to rename with package imports as your package name is in every import.
Of course you can change it with a find/replace query, but it's a useless edit on every dart file you can avoid with relative imports.
Plus, vscode allows to automatically update relative imports on file move/rename and I have never had any issue with this feature.
Going through some flutter source code and found two different types of imports.
What is the difference between the two and which one is better ?
#1
import 'folder/filename.dart';
#2
import 'package:projectname/folder1/folder2/folder/filename.dart';
There's no performance differences or anything like that.
But.. it is better to use package paths because you won't need to edit all your imports in case you move your file to another location (as they're not relative paths).
Saying that there is no difference at all might be tricky. Because importing files as packages in some place and as simple files in another, dart will consider them two different namespaces. So it can cause type conflicts. The safe way to do it is to choose one method to do it and stick to it.
I have one Fay file which is the heart of my program, however I need some helpers for my logic, for instance a method to replace substrings. From what I understand, if I need such methods which are offered by many Haskell libraries from Hackage directly, I can't use those Haskell libraries, but I must copy-paste the code in my project. So it's what I did, I copy-pasted a "replace" function together with other helpers from the MissingH library in a new file in my project: Utils.hs.
That Utils.hs compiles without problems with Fay. Also I import it in my main Fay file and I get a JS file for the main project file without problems. However at runtime I get the following error:
ReferenceError: Utils$$36$ is not defined
I don't think that Fay will include the code from the helper file in my main JS file, so I'm including both JS files in the loading HTML. And to make even more sure that when I load the main file, that the utils file is loaded, I load it like that:
$.getScript("Utils.js", function(){
$.getScript("FayConfig.js");
});
But despite this I still get the error. I tried compiling the Utils.hs with "--library" but it didn't help.
So my question is, which setup do I need to achieve that the generated JS will find the helper functions that I put in another HS file, knowing that at compile-time, Fay (apparently) finds them without problems? Is there an example of such a setup online? Most of the Fay uses that I found have all the code in a single HS file, though they often use external Fay code from cabal, as with fay-jquery. In my case, setting up a cabal project just for these simple helpers would be overkill.
Which version of Fay are you using (fay --version)? It seems like you are using a version older than
0.16 where forgetting import Prelude wouldn't give any warnings, see this closed ticket. So upgrade fay and/or add import Prelude.
We're also considering renaming operators in the produced output to make error messages like these easier to understand.
You do not need to invoke fay several times, fay outputs all dependencies into the same js file. So there's no difference from using a cabal package in that regard.
Hope this helps, otherwise please give me a way to reproduce this.
Today I cleared my .ivy cache and cleaned my project output targets. Since then I have been getting really strange behaviour when running tests with SBT or editing in the Scala IDE.
Given the following:
package com.abc.rest
import com.abc.utility.IdTLabel
I will get the following error:
object utility is not a member of package com.abc.rest.com.abc
Notice that com.abc is repeated twice, so it appears that the compiler uses the context of the current package when doing the import (maybe it's supposed to do this, but I never noticed it before).
Also, if I try to access classes in package com.abc from anywhere inside com.abc.rest (even using the full path) the compiler will complain that the type can not be found.
It appears that the errors only occur when I try to include files from parent packages. What I do find strange is that my code used to work. It only started happening after I cleaned up my project and my ivy cache, so maybe a later version of the compiler is more strict than the previous one.
I would love some ideas on what I can be doing wrong, or how I can go about troubleshooting this.
Update:
By first importing the parent classes and then defining the current package, the problem goes away:
import com.abc.utility.IdTLabel
import com.abs._
package com.abc.rest {
// Define classes belonging to com.abc.rest here
}
So this works, but I would still love to know why on earth the other way around worked, and then stopped working, and how on earth I can fix it. I had a good look, and could find no packages, objects or traits by the name of com anywhere inside the parent package.
Update relating to Worksheets:
Scala worksheets belonging to the same package share the same scope, which sounds obvious, but wasn't. Worksheets are not sand-boxed - they can see the project, and the project can see them. So all the 'test' object, traits, and classes you create inside the worksheet files, also becomes visible in the rest of the project.
I have so many worksheets that I did not even try to see where the problem came in. I simply moved them all to their own package, and like magic, the problem went away.
So, lesson learned for the day: If you create stuff inside worksheets, it's visible from outside the worksheet.
Anyway, this new found knowledge will come in handy, meaning anything 'interesting' can be build, monitored and tweaked inside the worksheet, while the rest of the project can actually use it. Quite cool actually.
It's still interesting to think how a sbt clean and cleaned up ivy cache managed to highlight the problem that was hidden before, but hey, that's another story....
(At the request of JacobusR, I'm making a proper answer out of my earlier comments).
This can happen if you have defined some class/trait/object inside package com.abc.rest.com. As soon as package com.abc.rest.com exists, and given that you are in package com.abc.rest, com would designate com.abc.rest.com as opposed to _root_.com. Fastest (but non-conclusive) way to check, without even scanning the source files, is to look for any .class files in the "com/abc/rest/com" sub-folder.
In particular you would get this behaviour if any of your files has duplicate package definitions (as in package com.abc.rest; package com.abc.rest; ...). If you have this duplicate package clause somewhere in the same file where you get the error, you wouldn't even see anything fishy with the .class files, as the failure at compiling the file would prevent the generation of .class files for any class definition inside the file.
The final bit of useful information is that as you found out the scala Worksheets are not sandboxed, and what you define in the worksheets affects your project's code (rather than only having the project's code affecting the worksheet). So a duplicate package clause in a worksheet could very well cause the error you got.
If package names conflict, there might be a custom error message for that. See if specifying the full path resolves the issue by starting from __root__. Ex. import __root__.com.foo.bar._
My eclipse is configured so that when I save the java source file, it automatically inserts the missing import declarations. Except when the reference is ambiguous. Fpr instance, the most annoying ambiguity is with List<T> - both java.util and java.awt declare it. Here eclipse demands manual resolution.
I was wondering if it was possible to configure somewhere that whenever List<T> is used then java.util should be imported. Or alternatively, since I am not using java.awt, I could just remove it from the list of possible suggestions.
Any ideas?
Thanks.
This sounds like a possible duplicate of Exclude packages from Eclipse's organize imports.
Basically, you want to change your Type Filters preference to exclude java.awt.* packages. Keep in mind that doing so will make things harder/confusing if you ever try to write AWT/Swing code.
One thing that pops into my mind is altering the class template in the preferences to include the line:
import java.util.List
Unless you are going to use the AWT version of a List, or care about unused import statements, that should solve this annoying issue ..
Manually invoke Organize Imports and it will ask you when an ambiguity is found.