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credo
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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/refactor/long_quote_blocks.ex
defmodule Credo.Check.Refactor.LongQuoteBlocks do
@moduledoc """
Long `quote` blocks are generally an indication that too much is done inside
them.
Let's look at why this is problematic:
defmodule MetaCommand do
def __using__(opts \\\\ []) do
modes = opts[:modes]
command_name = opts[:command_name]
quote do
def run(filename) do
contents =
if File.exists?(filename) do
{:ok, file} = File.open(filename, unquote(modes))
{:ok, contents} = IO.read(file, :line)
File.close(file)
contents
else
""
end
case contents do
"" ->
# ...
unquote(command_name) <> rest ->
# ...
end
end
# ...
end
end
end
A cleaner solution would be to call "regular" functions outside the
`quote` block to perform the actual work.
defmodule MyMetaCommand do
def __using__(opts \\\\ []) do
modes = opts[:modes]
command_name = opts[:command_name]
quote do
def run(filename) do
MyMetaCommand.run_on_file(filename, unquote(modes), unquote(command_name))
end
# ...
end
end
def run_on_file(filename, modes, command_name) do
contents =
# actual implementation
end
end
This way it is easier to reason about what is actually happening. And to debug
it.
"""
@explanation [
check: @moduledoc,
params: [
max_line_count: "The maximum number of lines a quote block should be allowed to have.",
ignore_comments: "Ignores comments when counting the lines of a `quote` block."
]
]
@default_params [max_line_count: 150, ignore_comments: false]
use Credo.Check, base_priority: :high
alias Credo.IssueMeta
@doc false
def run(source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
max_line_count = Params.get(params, :max_line_count, @default_params)
ignore_comments = Params.get(params, :ignore_comments, @default_params)
Credo.Code.prewalk(
source_file,
&traverse(&1, &2, issue_meta, max_line_count, ignore_comments)
)
end
defp traverse(
{:quote, meta, arguments} = ast,
issues,
issue_meta,
max_line_count,
ignore_comments
) do
max_line_no = Credo.Code.prewalk(arguments, &find_max_line_no(&1, &2), 0)
line_count = max_line_no - meta[:line]
issue =
if line_count > max_line_count do
source_file = IssueMeta.source_file(issue_meta)
lines =
Credo.Code.to_lines(source_file)
|> Enum.slice(meta[:line] - 1, line_count)
lines =
if ignore_comments do
Enum.reject(lines, fn {_line_no, line} ->
Regex.run(~r/^\s*#/, line)
end)
else
lines
end
if Enum.count(lines) > max_line_count do
issue_for(issue_meta, meta[:line])
end
end
{ast, issues ++ List.wrap(issue)}
end
defp traverse(ast, issues, _issue_meta, _max_line_count, _ignore_comments) do
{ast, issues}
end
defp find_max_line_no({_, meta, _} = ast, max_line_no) do
line_no = meta[:line] || 0
if line_no > max_line_no do
{ast, line_no}
else
{ast, max_line_no}
end
end
defp find_max_line_no(ast, max_line_no) do
{ast, max_line_no}
end
defp issue_for(issue_meta, line_no) do
format_issue(
issue_meta,
message: "Avoid long quote blocks.",
trigger: "quote",
line_no: line_no
)
end
end