lab42_message

Synopsis

Simple Library to manage Errors and Results.

Its Simplicity is inspired by Dave Thomas' keynote, condensed here https://pragdave.me/blog/2018/06/02/project-structure.html

API

A container for error messages.

Defining some severities.

Create results depending on error messages.

Convenience functions for adding, filtering and sorting messages.

Lab42.Message.add_critical/3

Create a message with severity :critical and add in front of other messages

iex(10)> add_critical([], "Just a critical message", {1, 3})
[%Lab42.Message{message: "Just a critical message", severity: :critical, location: {1, 3}}]

Lab42.Message.add_debug/3

Create a message with severity :debug and add in front of other messages

iex(2)> add_debug([], "Just a debug message", {1, 3})
[%Lab42.Message{message: "Just a debug message", severity: :debug, location: {1, 3}}]

Lab42.Message.add_error/3

Create a message with severity :error and add in front of other messages

iex(8)> add_error([], "Just a error message", {1, 3})
[%Lab42.Message{message: "Just a error message", severity: :error, location: {1, 3}}]

Lab42.Message.add_fatal/3

Create a message with severity :fatal and add in front of other messages

iex(12)> add_fatal([], "Just a fatal message", {1, 3})
[%Lab42.Message{message: "Just a fatal message", severity: :fatal, location: {1, 3}}]

Lab42.Message.add_info/3

Create a message with severity :info and add in front of other messages

iex(4)> add_info([], "Just a info message", {1, 3})
[%Lab42.Message{message: "Just a info message", severity: :info, location: {1, 3}}]

Lab42.Message.add_warning/3

Create a message with severity :warning and add in front of other messages

iex(6)> add_warning([], "Just a warning message", {1, 3})
[%Lab42.Message{message: "Just a warning message", severity: :warning, location: {1, 3}}]

Lab42.Message.make_critical/2

Create a message with severity :critical

iex(11)> make_critical("Just a critical message", {1, 3})
%Lab42.Message{message: "Just a critical message", severity: :critical, location: {1, 3}}

Lab42.Message.make_debug/2

Create a message with severity :debug

iex(3)> make_debug("Just a debug message", {1, 3})
%Lab42.Message{message: "Just a debug message", severity: :debug, location: {1, 3}}

Lab42.Message.make_error/2

Create a message with severity :error

iex(9)> make_error("Just a error message", {1, 3})
%Lab42.Message{message: "Just a error message", severity: :error, location: {1, 3}}

Lab42.Message.make_fatal/2

Create a message with severity :fatal

iex(13)> make_fatal("Just a fatal message", {1, 3})
%Lab42.Message{message: "Just a fatal message", severity: :fatal, location: {1, 3}}

Lab42.Message.make_info/2

Create a message with severity :info

iex(5)> make_info("Just a info message", {1, 3})
%Lab42.Message{message: "Just a info message", severity: :info, location: {1, 3}}

Lab42.Message.make_warning/2

Create a message with severity :warning

iex(7)> make_warning("Just a warning message", {1, 3})
%Lab42.Message{message: "Just a warning message", severity: :warning, location: {1, 3}}

Lab42.Message.max_severity/2

Returns the maximum priority of messages A list of messages can be passed in

iex(15)> messages =
...(15)>   []
...(15)>   |> add_error("error1", 1)
...(15)>   |> add_info("info2", 2)
...(15)>   |> add_warning("warning3", 3)
...(15)> max_severity(messages)
:error

However a list of message tuples is also allowed

iex(16)> messages =
...(16)>   []
...(16)>   |> add_error("error1", 1)
...(16)>   |> add_fatal("fatal2", 2)
...(16)>   |> add_warning("warning3", 3)
...(16)>   |> messages()
...(16)> max_severity(messages)
:fatal

In accordance of the robustness principle the last can even be mixed

iex(17)> messages =
...(17)>   []
...(17)>   |> add_error("what an error", 42)
...(17)>   |> add_info("what an info", 42)
...(17)> max_severity([{:critical, "", nil}|messages])
:critical

And last, but not least it might be convenient to get the severity_value instead of the symbolic severity

iex(18)> messages =
...(18)>   []
...(18)>   |> add_error("what an error", 42)
...(18)>   |> add_info("what an info", 42)
...(18)> max_severity([{:critical, "", nil}|messages], value: true)
4

Lab42.Message.messages/2

Extract messages from a list of messages into a library agnositic form as triples. As all the add_* functions create a list in reverse order, this function also rereverses the message tuples.

iex(19)> messages =
...(19)>   []
...(19)>   |> add_error("error1", 1)
...(19)>   |> add_info("info2", 2)
...(19)>   |> add_warning("warning3", 3)
...(19)> messages(messages)
[ {:error, "error1", 1}, {:warning, "warning3", 3} ]

As you can see only messages with severity of warning and up are returned.

One can of course get messages with less severity too:

iex(20)> messages =
...(20)>   []
...(20)>   |> add_error("error1", 1)
...(20)>   |> add_info("info2", 2)
...(20)>   |> add_debug("debug3", 3)
...(20)> messages(messages, severity: :info)
[ {:error, "error1", 1}, {:info, "info2", 2} ]

And, eventually, for your convenience, instead of severity: :debug a shorter and more expressive :all can be passed in

iex(21)> messages =
...(21)>   []
...(21)>   |> add_error("error1", 1)
...(21)>   |> add_info("info2", 2)
...(21)>   |> add_debug("debug3", 3)
...(21)> messages(messages, :all)
[ {:error, "error1", 1}, {:info, "info2", 2}, {:debug, "debug3", 3} ]

Lab42.Message.result/3

Wrap a value and error messages into a result tuple, messages themselves are converted to message tuples as with messages. Also warnings still deliver an :ok reesult.œ

iex(22)> messages = []
...(22)>   |> add_debug("hello", 1)
...(22)>   |> add_info("hello again", 2)
...(22)>   |> add_warning("world", 3)
...(22)> result(messages, "result")
{:ok, "result", [{:warning, "world", 3}]}

However the presence of errors or worse returns an :error result. N.B. that the input can be a mixture of Lab42.Message structs and agnostic tuples.

iex(23)> messages = [{:fatal, "that was not good", 0}]
...(23)>   |> add_debug("hello", 1)
...(23)> result(messages, "result")
{:error, "result", [{:fatal, "that was not good", 0}]}

As with messages one can control what level of errors shall be included, here is an example where warnings are surpressed

iex(24)> messages = []
...(24)>   |> add_error("hello", 1)
...(24)>   |> add_info("hello again", 2)
...(24)>   |> add_warning("world", 3)
...(24)> result(messages, 42, severity: :error)
{:error, 42, [{:error, "hello", 1}]}

Author

License

Apache-2.0