ErrorMessage (error_message v0.1.3) View Source
ErrorMessage
This library exists to simplify error systems in a code base and allow for a simple unified experience when using and reading error messages around the code base
This creates one standard, that all errors should fit into the context
of HTTP error codes, if they don't :internal_server_error should
be used and you can use the message and details to provide a further
level of depth
Installation
The package can be installed by adding error_message to your list of dependencies in mix.exs:
def deps do
[
{:error_message, "~> 0.1.0"}
]
endDocumentation can be found at https://hexdocs.pm/error_message.
Usage Example
iex> id = 1
iex> ErrorMessage.not_found("no user with id #{id}", %{user_id: id})
%ErrorMessage{
code: :not_found,
message: "no user with id 1",
details: %{user_id: 1}
}
iex> ErrorMessage.internal_server_error("critical internal error", %{
...> reason: :massive_issue_with_x
...> })
%ErrorMessage{
code: :internal_server_error,
message: "critical internal error",
details: %{reason: :massive_issue_with_x}
}Why is this important
If we want to have a good way to catch errors around our system as well as be able to display errors that happen throughout our system, it's useful to have a common error api so we can predict what will come out of a system
For example if we used elixir through our server, we would be able to catch a not found pretty easily since we can predict the error code coming in without needing to know the message. This leads to more resilliant code since message changes won't break the functionality of your application
# Because our error system is setup with `find_user` we can easily
# catch no users and have a solid backup plan
with {:error, %ErrorMessage{code: :not_found}} <- find_user(%{name: "bill"}) do
create_user(%{name: "bill"})
endUsage with Phoenix
Another benefit is error rendering to the frontend, because all our errors are part of the HTTP error system, it's quite easy to now return the proper status codes and messages to our frontend clients. For example:
defmodule MyController do
def index(conn, param) do
case find_thing(params) do
{:ok, res} -> json(conn, res)
{:error, e} -> json_error(conn, e)
end
end
defp json_error(conn, %ErrorMessage{code: code} = e) do
conn
|> put_status(code) # Plug.Conn
|> json(ErrorMessage.to_jsonable_map(e))
end
endUsage with Logger
Ontop of being useful for Phoenix we can also find some good use from this
system and Logger, since ErrorMessage implements String.Chars protocol
case do_thing() do
{:ok, value} -> {:ok, do_other_thing(value)}
{:error, e} = res ->
Logger.error("[MyModule] \#{e}")
Logger.warn(to_string(e))
res
end
Link to this section Summary
Functions
Create bad_gateway error message
Create bad_request error message
Create conflict error message
Create expectation_failed error message
Create failed_dependency error message
Create forbidden error message
Create found error message
Create gateway_timeout error message
Create gone error message
Create http_version_not_supported error message
Create im_a_teapot error message
Converts an %ErrorMessage{} struct into an inspectable version
Create insufficient_storage error message
Create internal_server_error error message
Create length_required error message
Create locked error message
Create loop_detected error message
Create method_not_allowed error message
Create misdirected_request error message
Create moved_permanently error message
Create multiple_choices error message
Create network_authentication_required error message
Create not_acceptable error message
Create not_extended error message
Create not_found error message
Create not_implemented error message
Create not_modified error message
Create payment_required error message
Create permanent_redirect error message
Create precondition_failed error message
Create precondition_required error message
Create proxy_authentication_required error message
Create request_entity_too_large error message
Create request_header_fields_too_large error message
Create request_timeout error message
Create request_uri_too_long error message
Create requested_range_not_satisfiable error message
Create see_other error message
Create service_unavailable error message
Create switch_proxy error message
Create temporary_redirect error message
Converts an %ErrorMessage{} struct to a map and makes sure that the
contents of the details map can be converted to json
Converts an %ErrorMessage{} struct to a string formatted error message
Create too_early error message
Create too_many_requests error message
Create unauthorized error message
Create unavailable_for_legal_reasons error message
Create unprocessable_entity error message
Create unsupported_media_type error message
Create upgrade_required error message
Create use_proxy error message
Create variant_also_negotiates error message
Link to this section Types
Specs
code() :: :multiple_choices | :moved_permanently | :found | :see_other | :not_modified | :use_proxy | :switch_proxy | :temporary_redirect | :permanent_redirect | :bad_request | :unauthorized | :payment_required | :forbidden | :not_found | :method_not_allowed | :not_acceptable | :proxy_authentication_required | :request_timeout | :conflict | :gone | :length_required | :precondition_failed | :request_entity_too_large | :request_uri_too_long | :unsupported_media_type | :requested_range_not_satisfiable | :expectation_failed | :im_a_teapot | :misdirected_request | :unprocessable_entity | :locked | :failed_dependency | :too_early | :upgrade_required | :precondition_required | :too_many_requests | :request_header_fields_too_large | :unavailable_for_legal_reasons | :internal_server_error | :not_implemented | :bad_gateway | :service_unavailable | :gateway_timeout | :http_version_not_supported | :variant_also_negotiates | :insufficient_storage | :loop_detected | :not_extended | :network_authentication_required
Specs
Specs
Link to this section Functions
Specs
Create bad_gateway error message
Example
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Create bad_request error message
Example
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Create conflict error message
Example
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Create expectation_failed error message
Example
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Create failed_dependency error message
Example
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Create forbidden error message
Example
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Create found error message
Example
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Create gateway_timeout error message
Example
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Create gone error message
Example
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Create http_version_not_supported error message
Example
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Create im_a_teapot error message
Example
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Converts an %ErrorMessage{} struct into an inspectable version
## Example
iex> ErrorMessage.inspect(ErrorMessage.not_found("couldn't find user", %{user_id: "as21fasdfJ"}))
"#ErrorMessage<code: :not_found, message: \"couldn't find user\">\nDetails: %{user_id: \"as21fasdfJ\"}"Specs
Create insufficient_storage error message
Example
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Create internal_server_error error message
Example
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Create length_required error message
Example
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Create locked error message
Example
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Create loop_detected error message
Example
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Create method_not_allowed error message
Example
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Create misdirected_request error message
Example
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Create moved_permanently error message
Example
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Create multiple_choices error message
Example
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Create network_authentication_required error message
Example
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Create not_acceptable error message
Example
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Create not_extended error message
Example
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Create not_found error message
Example
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Create not_implemented error message
Example
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Create not_modified error message
Example
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Create payment_required error message
Example
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Create permanent_redirect error message
Example
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Create precondition_failed error message
Example
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Create precondition_required error message
Example
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Create proxy_authentication_required error message
Example
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Create request_entity_too_large error message
Example
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Create request_header_fields_too_large error message
Example
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Create request_timeout error message
Example
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Create request_uri_too_long error message
Example
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Create requested_range_not_satisfiable error message
Example
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Create see_other error message
Example
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Create switch_proxy error message
Example
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Create temporary_redirect error message
Example
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Converts an %ErrorMessage{} struct to a map and makes sure that the
contents of the details map can be converted to json
## Example
iex> ErrorMessage.to_jsonable_map(ErrorMessage.not_found("couldn't find user", %{user_id: "as21fasdfJ"}))
%{code: :not_found, message: "couldn't find user", details: %{user_id: "as21fasdfJ"}}
iex> error = ErrorMessage.im_a_teapot("teapot", %{
...> user: %{health: {:alive, 500}},
...> test: %TestStruct{a: [Date.new!(2020, 1, 10)]}
...> })
iex> ErrorMessage.to_jsonable_map(error)
%{
code: :im_a_teapot,
message: "teapot",
details: %{
user: %{health: [:alive, 500]},
test: %{struct: "ErrorMessageTest.TestStruct", data: %{a: ["2020-01-10"]}}
}
}Specs
Converts an %ErrorMessage{} struct to a string formatted error message
## Example
iex> ErrorMessage.to_string(ErrorMessage.internal_server_error("Something bad happened", %{result: :unknown}))
"internal_server_error - Something bad happened\nDetails: %{result: :unknown}"Specs
Create too_early error message
Example
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Create too_many_requests error message
Example
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Create unauthorized error message
Example
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Create unprocessable_entity error message
Example
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Create unsupported_media_type error message
Example
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Create upgrade_required error message
Example
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Create use_proxy error message
Example
iex>
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Create variant_also_negotiates error message
Example
iex>