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alias_order.ex
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alias_order.ex
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defmodule Credo.Check.Readability.AliasOrder do
use Credo.Check,
base_priority: :low,
explanations: [
check: """
Alphabetically ordered lists are more easily scannable by the read.
# preferred
alias ModuleA
alias ModuleB
alias ModuleC
# NOT preferred
alias ModuleA
alias ModuleC
alias ModuleB
Alias should be alphabetically ordered among their group:
# preferred
alias ModuleC
alias ModuleD
alias ModuleA
alias ModuleB
# NOT preferred
alias ModuleC
alias ModuleD
alias ModuleB
alias ModuleA
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.
"""
]
alias Credo.Code
alias Credo.Code.Name
@doc false
@impl true
def run(%SourceFile{} = source_file, params) do
issue_meta = IssueMeta.for(source_file, params)
Code.prewalk(source_file, &traverse(&1, &2, issue_meta))
end
defp traverse({:defmodule, _, _} = ast, issues, issue_meta) do
new_issues =
ast
|> extract_alias_groups()
|> Enum.reduce([], &traverse_groups(&1, &2, issue_meta))
{ast, issues ++ new_issues}
end
defp traverse(ast, issues, _), do: {ast, issues}
defp traverse_groups(group, acc, issue_meta) do
group
|> Enum.chunk_every(2, 1)
|> Enum.reduce_while(nil, &process_group/2)
|> case do
nil ->
acc
line ->
acc ++ [issue_for(issue_meta, line)]
end
end
defp process_group([{line_no, mod_list_second, a}, {_line_no, _mod_list_second, b}], _)
when a > b do
module =
case mod_list_second do
{base, _} -> base
value -> value
end
issue_opts = issue_opts(line_no, module, module)
{:halt, issue_opts}
end
defp process_group([{line_no1, mod_list_first, _}, {line_no2, mod_list_second, _}], _) do
issue_opts =
cond do
issue = inner_group_order_issue(line_no1, mod_list_first) ->
issue
issue = inner_group_order_issue(line_no2, mod_list_second) ->
issue
true ->
nil
end
if issue_opts do
{:halt, issue_opts}
else
{:cont, nil}
end
end
defp process_group([{line_no1, mod_list_first, _}], _) do
if issue_opts = inner_group_order_issue(line_no1, mod_list_first) do
{:halt, issue_opts}
else
{:cont, nil}
end
end
defp process_group(_, _), do: {:cont, nil}
defp inner_group_order_issue(_line_no, {_base, []}), do: nil
defp inner_group_order_issue(line_no, {base, mod_list}) do
downcased_mod_list = Enum.map(mod_list, &String.downcase(to_string(&1)))
sorted_downcased_mod_list = Enum.sort(downcased_mod_list)
if downcased_mod_list != sorted_downcased_mod_list do
trigger =
downcased_mod_list
|> Enum.with_index()
|> Enum.find_value(fn {downcased_mod_entry, index} ->
if downcased_mod_entry != Enum.at(sorted_downcased_mod_list, index) do
Enum.at(mod_list, index)
end
end)
issue_opts(line_no, [base, trigger], trigger)
end
end
defp issue_opts(line_no, module, trigger) do
%{
line_no: line_no,
trigger: trigger,
module: module
}
end
defp extract_alias_groups({:defmodule, _, _} = ast) do
ast
|> Code.postwalk(&find_alias_groups/2)
|> Enum.reverse()
|> Enum.reduce([[]], fn definition, acc ->
case definition do
nil ->
[[]] ++ acc
definition ->
[group | groups] = acc
[group ++ [definition]] ++ groups
end
end)
|> Enum.reverse()
end
defp find_alias_groups(
{:alias, _, [{:__aliases__, meta, mod_list} | _]} = ast,
aliases
) do
compare_name = compare_name(ast)
modules = [{meta[:line], {Name.full(mod_list), []}, compare_name}]
accumulate_alias_into_group(ast, modules, meta[:line], aliases)
end
defp find_alias_groups(
{:alias, _,
[
{{:., _, [{:__aliases__, meta, mod_list}, :{}]}, _, multi_mod_list}
]} = ast,
aliases
) do
multi_mod_list =
multi_mod_list
|> Enum.map(fn {:__aliases__, _, mod_list} -> mod_name(mod_list) end)
compare_name = compare_name(ast)
modules = [{meta[:line], {Name.full(mod_list), multi_mod_list}, compare_name}]
nested_mod_line = meta[:line] + 1
accumulate_alias_into_group(ast, modules, nested_mod_line, aliases)
end
defp find_alias_groups(ast, aliases), do: {ast, aliases}
defp mod_name(mod_list) do
Enum.map_join(mod_list, ".", &to_string/1)
end
defp compare_name(value) do
value
|> Macro.to_string()
|> String.downcase()
|> String.replace(~r/[\{\}]/, "")
|> String.replace(~r/,.+/, "")
end
defp accumulate_alias_into_group(ast, modules, line, [{line_no, _, _} | _] = aliases)
when line_no != 0 and line_no != line - 1 do
{ast, modules ++ [nil] ++ aliases}
end
defp accumulate_alias_into_group(ast, modules, _, aliases) do
{ast, modules ++ aliases}
end
defp issue_for(issue_meta, %{line_no: line_no, trigger: trigger, module: module}) do
format_issue(
issue_meta,
message: "The alias `#{Name.full(module)}` is not alphabetically ordered among its group.",
trigger: trigger,
line_no: line_no
)
end
end