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credo lib credo check readability single_pipe.ex
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lib/credo/check/readability/single_pipe.ex

defmodule Credo.Check.Readability.SinglePipe do
@moduledoc """
Pipes (`|>`) should only be used when piping data through multiple calls.
So while this is fine:
list
|> Enum.take(5)
|> Enum.shuffle
|> evaluate
The code in this example ...
list
|> evaluate
... should be refactored to look like this:
evaluate(list)
Using a single |> to invoke functions makes the code harder to read. Instead,
write a function call when a pipeline is only one function long.
"""
@explanation [check: @moduledoc]
use Credo.Check, base_priority: :high
@doc false
def run(%SourceFile{ast: ast} = source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
{_continue, issues} =
Credo.Code.prewalk(ast, &traverse(&1, &2, issue_meta), {true, []})
issues
end
defp traverse({:|>, _, [{:|>, _, _} | _]} = ast, {_, issues}, _) do
{ast, {false, issues}}
end
defp traverse({:|>, meta, _} = ast, {true, issues}, issue_meta) do
{ast, {false, issues ++ [issue_for(issue_meta, meta[:line], "single pipe")]}}
end
defp traverse(ast, {_, issues}, _issue_meta) do
{ast, {true, issues}}
end
def issue_for(issue_meta, line_no, trigger) do
format_issue issue_meta,
message: "Use a function call when a pipeline is only one function long",
trigger: trigger,
line_no: line_no
end
end