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credo lib credo check readability strict_module_layout.ex
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lib/credo/check/readability/strict_module_layout.ex

defmodule Credo.Check.Readability.StrictModuleLayout do
use Credo.Check,
base_priority: :low,
tags: [:controversial],
explanations: [
check: """
Provide module parts in a required order.
# preferred
defmodule MyMod do
@moduledoc "moduledoc"
use Foo
import Bar
alias Baz
require Qux
end
Like all `Readability` issues, this one is not a technical concern.
But you can improve the odds of others reading and liking your code by making
it easier to follow.
""",
params: [
order: """
List of atoms identifying the desired order of module parts.
Supported values are:
- `:moduledoc` - `@moduledoc` module attribute
- `:shortdoc` - `@shortdoc` module attribute
- `:behaviour` - `@behaviour` module attribute
- `:use` - `use` expression
- `:import` - `import` expression
- `:alias` - `alias` expression
- `:require` - `require` expression
- `:defstruct` - `defstruct` expression
- `:opaque` - `@opaque` module attribute
- `:type` - `@type` module attribute
- `:typep` - `@typep` module attribute
- `:callback` - `@callback` module attribute
- `:macrocallback` - `@macrocallback` module attribute
- `:optional_callbacks` - `@optional_callbacks` module attribute
- `:module_attribute` - other module attribute
- `:public_fun` - public function
- `:private_fun` - private function or a public function marked with `@doc false`
- `:public_macro` - public macro
- `:private_macro` - private macro or a public macro marked with `@doc false`
- `:callback_impl` - public function or macro marked with `@impl`
- `:public_guard` - public guard
- `:private_guard` - private guard or a public guard marked with `@doc false`
- `:module` - inner module definition (`defmodule` expression inside a module)
Notice that the desired order always starts from the top.
For example, if you provide the order `~w/public_fun private_fun/a`,
it means that everything else (e.g. `@moduledoc`) must appear after
function definitions.
""",
ignore: """
List of atoms identifying the module parts which are not checked, and may
therefore appear anywhere in the module. Supported values are the same as
in the `:order` param.
"""
]
],
param_defaults: [
order: ~w/shortdoc moduledoc behaviour use import alias require/a,
ignore: []
]
alias Credo.Code
alias Credo.CLI.Output.UI
@doc false
@impl true
def run(%SourceFile{} = source_file, params \\ []) do
params = normalize_params(params)
source_file
|> Code.ast()
|> Credo.Code.Module.analyze()
|> all_errors(params, IssueMeta.for(source_file, params))
|> Enum.sort_by(&{&1.line_no, &1.column})
end
defp normalize_params(params) do
order =
params
|> Params.get(:order, __MODULE__)
|> Enum.map(fn element ->
# TODO: This is done for backward compatibility and should be removed in some future version.
with :callback_fun <- element do
UI.warn([
:red,
"** (StrictModuleLayout) Check param `:callback_fun` has been deprecated. Use `:callback_impl` instead.\n\n",
" Use `mix credo explain #{Credo.Code.Module.name(__MODULE__)}` to learn more. \n"
])
:callback_impl
end
end)
Keyword.put(params, :order, order)
end
defp all_errors(modules_and_parts, params, issue_meta) do
expected_order = expected_order(params)
ignored_parts = Keyword.get(params, :ignore, [])
Enum.reduce(
modules_and_parts,
[],
fn {module, parts}, errors ->
parts =
parts
|> Stream.map(fn
# Converting `callback_macro` and `callback_fun` into a common `callback_impl`,
# because enforcing an internal order between these two kinds is counterproductive if
# a module implements multiple behaviours. In such cases, we typically want to group
# callbacks by the implementation, not by the kind (fun vs macro).
{callback_impl, location} when callback_impl in ~w/callback_macro callback_fun/a ->
{:callback_impl, location}
other ->
other
end)
|> Stream.reject(fn {part, _location} -> part in ignored_parts end)
module_errors(module, parts, expected_order, issue_meta) ++ errors
end
)
end
defp expected_order(params) do
params
|> Keyword.fetch!(:order)
|> Enum.with_index()
|> Map.new()
end
defp module_errors(module, parts, expected_order, issue_meta) do
Enum.reduce(
parts,
%{module: module, current_part: nil, errors: []},
&check_part_location(&2, &1, expected_order, issue_meta)
).errors
end
defp check_part_location(state, {part, file_pos}, expected_order, issue_meta) do
state
|> validate_order(part, file_pos, expected_order, issue_meta)
|> Map.put(:current_part, part)
end
defp validate_order(state, part, file_pos, expected_order, issue_meta) do
if is_nil(state.current_part) or
order(state.current_part, expected_order) <= order(part, expected_order),
do: state,
else: add_error(state, part, file_pos, issue_meta)
end
defp order(part, expected_order), do: Map.get(expected_order, part, map_size(expected_order))
defp add_error(state, part, file_pos, issue_meta) do
update_in(
state.errors,
&[error(issue_meta, part, state.current_part, state.module, file_pos) | &1]
)
end
defp error(issue_meta, part, current_part, module, file_pos) do
format_issue(
issue_meta,
message: "#{part_to_string(part)} must appear before #{part_to_string(current_part)}",
trigger: inspect(module),
line_no: Keyword.get(file_pos, :line),
column: Keyword.get(file_pos, :column)
)
end
defp part_to_string(:module_attribute), do: "module attribute"
defp part_to_string(:public_guard), do: "public guard"
defp part_to_string(:public_macro), do: "public macro"
defp part_to_string(:public_fun), do: "public function"
defp part_to_string(:private_fun), do: "private function"
defp part_to_string(:callback_impl), do: "callback implementation"
defp part_to_string(part), do: "#{part}"
end