Elixir 1.7 Improves Error Handling, Logging, and Testing
source link: https://www.tuicool.com/articles/hit/mMRVR3y
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Elixir 1.7
is focused on quality of life improvements, writes Elixir creator José Valim. Those include a new __STACKTRACE__
construct to retrieve the stacktrace, integration with Erlang’s new :logger
module, improvements to Elixir’s unit testing library ExUnit, and support for metadata in documentation.
Elixir 1.7 exception system has been improved by making the ArgumentError
, ArithmeticError
, and KeyError
exceptions provide more diagnostic information and adding a new __STACKTRACE__
construct that can be used instead of System.stacktrace/0
to retrieve the stacktrace:
try do ... something that may fail ... rescue exception -> log(exception, __STACKTRACE__) reraise(exception, __STACKTRACE__) end
__STACKTRACE__
is lexically scoped and does not rely on side-effects, unlike System.stacktrace/0
. According to Valim, this could bring performance improvements in a future Elixir release since it can make it not necessary anymore to keep track of stacktraces after the try
block ends.
The Elixir Logger
module now plugs into Erlang’s :logger
, which is available with Erlang/OTP 21, and fully leverages the latter’s richer metadata, including:
-
:crash_reason
, a two-element tuple with the throw/error/exit reason as first argument and the stacktrace as second. A throw will always have the structure{:nocatch, term}
, while errors will always be Exceptions, and exits cover the rest of cases. -
:initial_call
, the initial call that started the process. -
:registered_name
, the process registered name as an atom.
Additionally, Logger
macros like debug
, info
, etc., will not evaluate their arguments unless the message is effectively logged, and a new :compile_time_purge_matching
option enables filtering log entries based on compile-time metadata. For example, this is how you configure Logger
ignore log calls from application :foo
with level lower than :info
, as well all logger calls from Bar.foo/3
:
config :logger, compile_time_purge_matching: [ [application: :foo, level_lower_than: :info], [module: Bar, function: "foo/3"] ]
As mentioned, Elixir’s unit testing library ExUnit
has also been improved by making the assert
macro returns more detailed information. For example, if the assert some_function(expr1, var2)
statement fails, it will print out the values of the arguments to some_function
, thus sparing the developer the effort to re-run the test to inspect their values.
As a final note, Elixir 1.7 also introduces the possibility of annotating documentation with metadata, such as in the following example:
@moduledoc "A brand new module" @moduledoc authors: ["Jane", "Mary"], since: "1.4.0"
The ExDoc
tool in Elixir 1.7 is able to leverage those metadata to flag the use of deprecated modules, functions, callbacks, and types, and to show when a given feature was introduced.
Do not miss the official release notes for full detail about the changes in Elixir 1.7.
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