Is there a lint for Elixir (like for Javascript) which checks that every function has a type specification?
There is an Erlang compiler switch, +warn_missing_spec, which does this, but I'm having trouble getting it to work with Elixir at the moment, I think there is a bug with it's parsing of the ELIXIR_ERL_OPTS environment variable which is converting +warn_missing_spec into -warn_missing_spec which isn't a valid compiler option. I'm going to open an issue on the tracker, but thought you might like to know that this does indeed exist.
EDIT: As José mentioned below, the correct flag is ERL_COMPILER_OPTIONS. You can enable the missing spec warning during compilation by doing the following:
ERL_COMPILER_OPTIONS="warn_missing_spec" mix compile
Keep in mind you may get superfluous warnings from Elixir itself, for functions like __MODULE__. It should still be useful though. One last thing to note, I discovered this morning that there is a problem using this flag with mix compile, and that it's currently only warning about mix.exs. This is being fixed, and may even be fixed by the time you see this, but it's something to be aware of.
Related
I know it can be done, but I'm having trouble getting it working. I'm still finding my feet with Haskell.
I tried using postgresql-typed, but it wouldn't compile. They don't enable the QuasiQuotes extension, so I don't understand how their code would ever compile. It also fails with an error on the useTPGDatabase statement. I cloned the library's source code from Github, but their tests failed to compile using stack with exactly the same errors.
I considered using hasql-th, but it's not on stackage.org, which immediately puts it in the "too hard basket.". I considered switching to nix but that seems like even more effort.
Does somebody have a reliable recipe for getting an environment working that type-checks SQL at compile time in Haskell?
I considered using hasql-th, but it's not on stackage.org, which immediately puts it in the "too hard basket."
All you need to do is add the latest version of hasql-th to the extra-deps section of your stack.yaml file and all other deps that Stack will suggest to you when you build.
In the end your stack.yaml file should look something like this:
resolver: lts-17.9
extra-deps:
- hasql-th-0.4.0.8
- headed-megaparsec-0.1.0.4
- postgresql-syntax-0.3.0.3
Anticipating a question in the spirit of "Why is it not listed on Stackage?" It's just that nobody has gotten to list these packages yet.
With a snippet like
perl6 -e 'loop { FIRST say "foo"; last }'
I get
WARNINGS for -e:
Useless use of LOOP_BLOCK_1 symbol in sink context (line 1)
foo
I know how to work around the warning. I'm wondering about what the source of the warning is. I found this open ticket, but it doesn't seem to have received any attention.
What is this warning about?
And what about this is useless?
Version
$ perl6 --version
This is Rakudo version 2018.06 built on MoarVM version 2018.06
implementing Perl 6.c.
It's a bug, a bogus warning.
I know how to work around the warning.
That's the main thing.
I'm wondering about what the source of the warning is.
It's a bogus warning from the compiler.
I found this open ticket, but it doesn't seem to have received any attention.
I think it got some attention.
bbkr, who filed the bug, linked to another bug in which they showed their workaround. (It's not adding do but rather removing the FIRST phaser and putting the associated statement outside of the loop just before it.)
If you follow the other links in bbkr's original bug you'll arrive at another bug explaining that the general "unwanted" mechanism needs to be cleaned up. I imagine available round tuits are focused on bigger fish such as this overall mechanism.
Hopefully you can see that it's just a bizarre warning message and a minor nuisance in the bigger scheme of things. It appears to come up if you use the FIRST phaser in a loop construct. It's got the very obvious work around which you presumably know and bbkr showed.
What is this warning about?
Many languages allow you to mix procedural and functional paradigms. Procedural code is run for its side effects. Functional code for its result. Some constructs can do both.
But what if you use a construct that's normally used with the intent of its result being used, and the compiler knows that, but it also knows it's been used in a context in which its value will be ignored?
Perls call this "useless use of ... in sink context" and generally warn the coder about it. ("sink" is an alternative/traditional term for what is often called "void" context in other language cultures.)
This error message is one of these warnings, albeit a bogus one.
And what about this is useless?
Nothing.
The related compiler warning mechanism has gotten confused.
The "Useless use of ... in sink context" part of the message is generic and hopefully self-explanatory.
But there's no way it should be saying things like "LOOP_BLOCK_1 symbol". That's internal mumbo-jumbo.
It's a warning message bug.
While trying to learn Frege I copied some code from Dierk's Real World Frege to the online REPL an tried to execute it (see also How to execute a compiled code snipped in Frege online repl). The scripts I've tried don't compile :-(
What am I doing wrong?
Here are examples of what does not compile:
println ( 2 *-3 ) -- unlike haskell, this will work!
and the whole ValuesAndVariables.fr code
It is unavoidable that over the course of more than a year, an evolving language (and its libraries) change so that older code will not compile anymore.
It would be nice, if we could see an example, instead of a generalization like "most".
The next best thing would be to have an issue in Dierks project that points to the error(s).
But the very best would be en effort to find out what is wrong. This would also intensify your learning process.
Here are two ressources that could help:
https://github.com/Frege/frege/wiki/New-or-Changed-Features -- the release notes for every release, contains a summary of things that have changed between releases, and especially the reasons why code would not compile anymore and how to correct it.
http://www.frege-lang.org/doc/fregedoc.html -- the library docs. May explain possible errors like import not found, or missing identifiers.
Go, give it a try. And I'm convinced Dierk will be happy to accept pull requests.
Edit: Fixes for announced errors.
The error in:
println ( 2 *-3 )
stems indeed from a syntactical change.
It is, as of recently, demanded that adjacent operators be separated by at least one space.
Hence
println (2 * -3)
However, the error message you got here was:
can't resolve `*-`, did you mean `-` perhaps?
which could have triggered the idea that it tries to interpret *- as a single operator.
The other error in ValuesAndVariables1.fr is indeed a show stopper for a beginner. The background is that we have one pi that has type Double and one that has type Float and potentially many more through type class Floating, so one needs to tell which one to print.
The following will work:
import Prelude.Math -- unless already imported
println Float.pi
println (pi :: Double)
the online REPL at http://try.frege-lang.org is currently based on Frege V3.23.370-g898bc8c . Dierk's code examples are based on V3.21.500-g88270a0 (which can be seen in the gradle build file).
It seems that the Frege developers decided to change the Frege syntax slightly between those versions. THe result is that you will not be able to run these code snippets in the online REPL anymore.
We are trying to use grunt-lesslint in our project, as our UI developer is comfortable fix errors in less file. grunt-recess seems more powerful but not sure if it can point errors in less file itself. I am unable to comprehend enough from lesslint page, and there do not seem to be many examples. Does anyone know the following:
How to prevent lesslint from displaying on the console. I use formatters and the report file is generated, but it also prints on console, which I do not want to.
How to make lesslint fail only in the case of errors (not warnings). Also csslint seems to report errors also, while lesslint mostly gives warnings only, why is that so? Does lesslint throw errors as well? How to make it fail only in case of errors?
I tried using 'checkstyle-xml' formatter, but it does not seem to use it (I have used in jshint and it gives a properly formatted xml, which it does not give for lesslint).
Is it possible to compile less (many files or directories) in conjunction with lesslint? Any example?
Thanks,
Paddy
I'd say it's more of a common practice to display stdout for this kind of thing; the JSHint plugin does it, as does any other linting plugin that I've used. If you get in another developer that uses Grunt they'll probably expect stdout too. If you really want to override this, use grunt-verbosity: https://npmjs.org/package/grunt-verbosity
Again, this is a convention in Grunt; if a task has any warnings then it fails. The reason being if you lint a file and the linter flags something up it should be dealt with straight away, rather than delay it; six months time you have 500 errors that you haven't fixed and you're less likely to fix them then. Most linting plugins allow you to specify custom options (I've used CSS Lint and that is very customisable), so if you don't like a rule you can always disable it.
This should work. If there's a bug with this feature you should report it on the issue tracker, where it will be noticed by the developers of the plugin. https://github.com/kevinsawicki/grunt-lesslint/issues
Yes. You can set up a custom task that runs both your linter and compile in one step: something like grunt.registerTask('buildless', 'Lint and compile LESS files.', ['lesslint', 'less']); note that you'll have to install https://github.com/gruntjs/grunt-contrib-less to get that to work. Also note that, failing linting will not compile your LESS files; mandate that your code always passes the lint check; you'll help everyone involved in the project.
I'm very keen to update a number of our servers to PHP 5.3. This would be in readiness for Zend Framework 2 and also for the apparent performance updates. Unfortunately, i have large amounts of legacy code on these servers which in time will be fixed, but cannot all be fixed before the migration. I'm considering updating but disabling the deprecated function error on all but a few development sites where i can begin to work through updating old code.
error_reporting(E_ALL ^ E_DEPRECATED);
Is there any fundamental reason why this would be a bad idea?
Well, you could forget that you set the flag and wonder why your application breaks in a next PHP update. It can be very frustrating to debug an application without proper error reporting. That's one reason I can think of.
However, if you do it, document it somewhere. It can save you a couple of hours before you remember setting the flag at all.
If you haven't already you should read the migration guide with particular focus on Backward Incompatible Changes and Removed Extensions.
You have bigger issues than deprecation. Ignoring E_DEPRECATED will not suffice. Because of the incompatible changes there will also be other type of errors or, maybe, even worse, unexpected behaviors.
Here's a simple example:
<?php
function goto($line){
echo $line;
}
goto(7);
?>
This code will work fine and output 7 in PHP 5.2.x but will give you a parse error in PHP 5.3.x.
What you need to do is take each item in that guide and check your code and update where needed. To make this faster you could ignore the deprecated functionality in a first phase and just disable error reporting for E_DEPRECATED, but you can't assume that you will only get some harmless warnings when porting to another major PHP branch.
Also don't forget about your hack and fix the deprecated issues as soon as possible.
Regards,
Alin
Note: I tried to answer the question from a practical point of view, so please don't tell me that ignoring warnings is bad. I know that, but I also know that time is not an infinite resource.
I presume you have some kind of test server? If not, you really should set one up and test your code in PHP 5.3. If your code is thoroughly Unit Tested, testing it will take seconds, and fixing it will be fairly quick too, as the unit tests will tell you exactly where to look. If not, then consider making Unit Testing it all a priority before the next release, and in the meantime go through it all, first with E_DEPRECATED warnings disabled and fix anything which comes up, then with it re-enabled once you have time. You could also run a global find-and-replace for easier to fix errors.