1
0
Fork 0

Post about Erlang 17.0 and namespaced_types

This commit is contained in:
Daniel Kempkens 2014-04-18 20:24:34 +02:00
parent 08a201c48d
commit ce8a2093e9

View file

@ -0,0 +1,51 @@
---
layout: post
title: 'Erlang 17.0: Supporting Deprecated Types Without Removing warnings_as_errors'
description: "Simple workaround for supporting deprecated types and warnings_as_errors."
date: 2014-04-18 21:25:00 CEST
category: posts
tags: [erlang, programming, english]
image:
feature: header/abstract-10.jpg
credit: dargadgetz
creditlink: http://www.dargadgetz.com/ios-7-abstract-wallpaper-pack-for-iphone-5-and-ipod-touch-retina/
comments: true
share: true
---
Erlang 17.0 [deprecated some pre-defined types](http://www.erlang.org/download/otp_src_17.0.readme) like `dict()` and `gb_tree()` in favor of `dict:dict()` and `gb_tree:tree()`. The workaround they suggest (`nowarn_deprecated_type`) works in 17.0, but would break once the deprecated types are removed.
Not using `nowarn_deprecated_type` means that you can't use `warnings_as_errors`, because it would make deprecation warnings an error.
A rather nice solution to this issue an option that [rebar](https://github.com/rebar/rebar) takes: `platform_define`.
>It is also possible to specify platform specific options by specifying a pair or a triplet where the first string is a regex that is checked against the string
>
> OtpRelease ++ "-" ++ SysArch ++ "-" ++ Words.
>
>where
>
> OtpRelease = erlang:system_info(otp_release).
> SysArch = erlang:system_info(system_architecture).
> Words = integer_to_list(8 * erlang:system_info({wordsize, external})).
This allows us to set a `namespaced_types` option on 17.0+ only.
{% highlight erlang %}
{erl_opts, [
{platform_define, "^[0-9]+", namespaced_types},
debug_info,
warnings_as_errors
]}.
{% endhighlight %}
In your source files you can then check if the option is set and define an (internal) type accordingly.
{% highlight erlang linenos %}
-ifdef(namespaced_types).
-type xxx_dict() :: dict:dict().
-else.
-type xxx_dict() :: dict().
-endif.
{% endhighlight %}
I learned about this trick by looking at how [meck](https://github.com/eproxus/meck) handles Erlang 17.0 support.