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credo
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0.0.1-dev
A static code analysis tool with a focus on code consistency and teaching.
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Files
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Files
lib/credo/check/readability/predicate_function_names.ex
defmodule Credo.Check.Readability.PredicateFunctionNames do
@moduledoc """
Predicate functions/macros should be named accordingly:
* For functions, they should end in a question mark.
# okay
defp user?(cookie) do
end
defp has_attachment?(mail) do
end
# not okay
defp is_user?(cookie) do
end
defp is_user(cookie) do
end
* For guard-safe macros they should have the prefix `is_` and not end in a question mark.
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.
"""
@explanation [check: @moduledoc]
@def_ops [:def, :defp, :defmacro]
use Credo.Check, base_priority: :high
def run(%SourceFile{} = source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
Credo.Code.traverse(source_file, &traverse(&1, &2, issue_meta))
end
for op <- @def_ops do
# catch variables named e.g. `defp`
defp traverse({unquote(op), _meta, nil} = ast, issues, _issue_meta) do
{ast, issues}
end
defp traverse({unquote(op) = op, _meta, arguments} = ast, issues, issue_meta) do
{ast, issues_for_definition(op, arguments, issues, issue_meta)}
end
end
defp traverse(ast, issues, _issue_meta) do
{ast, issues}
end
defp issues_for_definition(op, body, issues, issue_meta) do
case Enum.at(body, 0) do
{name, meta, nil} ->
issues_for_name(op, name, meta, issues, issue_meta)
_ ->
issues
end
end
def issues_for_name(_op, name, meta, issues, issue_meta) do
name = name |> to_string
cond do
String.starts_with?(name, "is_") && String.ends_with?(name, "?") ->
[issue_for(issue_meta, meta[:line], name, :predicate_and_question_mark) | issues]
String.starts_with?(name, "is_") ->
[issue_for(issue_meta, meta[:line], name, :only_predicate) | issues]
true ->
issues
end
end
defp issue_for(issue_meta, line_no, trigger, _) do
format_issue issue_meta,
message: "Predicate function names should not start with 'is', and should end in a question mark.",
trigger: trigger,
line_no: line_no
end
end