41 lines
1.8 KiB
Markdown
41 lines
1.8 KiB
Markdown
---
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date: "2014-12-24T13:25:00Z"
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description: Simple workaround for supporting deprecated types and warnings_as_errors with erlang.mk.
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tags:
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- erlang
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- programming
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- english
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slug: supporting-deprecated-types-with-erlang-mk
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title: Supporting Deprecated Types with erlang.mk
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---
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In April I wrote about how I use the `platform_define` feature of [rebar](https://github.com/rebar/rebar) to make deprecated types work without removing `warnings_as_errors`. I have switched to [erlang.mk](https://github.com/ninenines/erlang.mk) since then, but needed a similar feature for [one of my libraries](https://github.com/nifoc/noesis).
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Since erlang.mk only uses [make](http://en.wikipedia.org/wiki/Make_(software)), adding support for a `platform_define`-like feature is very straightforward.
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{{< highlight makefile >}}
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otp_release = $(shell erl -noshell -eval 'io:format("~s", [erlang:system_info(otp_release)]), init:stop()')
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otp_17plus = $(shell echo $(otp_release) | grep -q -E "^[[:digit:]]+$$" ; echo $$?)
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{{< / highlight >}}
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The first variable (`otp_release`) will contain the OTP version (e.g. `17`). The second variable (`otp_17plus`) will be either `0` or `1`, depending on wether or not `otp_release` matches a regular expression. The regular expression checks if `otp_release` is just a number (e.g. `17`) or not (e.g. `R16B03-1`).
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That's enough to conditionally add options to `erlc`.
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{{< highlight makefile >}}
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ifeq ($(otp_17plus),0)
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ERLC_OPTS += -Dnamespaced_types=1
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TEST_ERLC_OPTS += -Dnamespaced_types=1
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endif
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{{< / highlight >}}
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This will define `namespaced_types` only on Erlang 17+, allowing us to use the same `ifdef`-switch from April.
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{{< highlight erlang "linenos=table" >}}
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-ifdef(namespaced_types).
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-type xxx_dict() :: dict:dict().
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-else.
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-type xxx_dict() :: dict().
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-endif.
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{{< / highlight >}}
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