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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/warning/name_redeclaration_by_assignment.ex
defmodule Credo.Check.Warning.NameRedeclarationByAssignment do
@moduledoc """
The names of local variables should not be the same as names of functions
or macros in the same module or in `Kernel`.
Example:
def handle_something do
time = 42
IO.puts time # not clear if we are talking about time/0 or time
end
def time do
TimeHelper.now
end
This might not seem like a big deal, especially for small functions.
But there is no downside to avoiding it, especially in the case of functions
with arity `/0` and Kernel functions.
True story: You might pattern match on a parameter geniusly called `node`.
Then you remove that match for some reason and rename the parameter to `_node`
because it is no longer used.
Later you reintroduce the pattern match on `node` but forget to also rename
`_node` and suddenly the match is actually against `Kernel.node/0` and has the
weirdest side effects.
This happens. I mean, to a friend of mine, it did. Who ... later told me.
"""
@explanation [check: @moduledoc]
@kernel_fun_names [
:make_ref,
:node,
:self
]
@kernel_macro_names [
]
@excluded_names [:_, :sigil_r, :sigil_R]
alias Credo.Code
alias Credo.Code.Module
use Credo.Check, base_priority: :high
def run(source_file, params \\ []) do
issue_meta = IssueMeta.for(source_file, params)
source_file
|> Code.prewalk(&traverse(&1, &2, issue_meta, @excluded_names))
|> List.flatten
|> Enum.reject(&is_nil/1)
end
defp traverse({:defmodule, _, _} = ast, issues, issue_meta, excluded_names) do
names = %{
def_names: Module.def_names_with_op(ast, 0),
excluded_names: excluded_names
}
new_issues = Code.prewalk(ast, &mod_traverse(&1, &2, issue_meta, names))
{ast, issues ++ new_issues}
end
defp traverse(ast, issues, _issue_meta, _excluded_names) do
{ast, issues}
end
defp mod_traverse({:=, _meta, [lhs, _rhs]} = ast, issues, issue_meta, %{} = names) do
case find_issue(lhs, issue_meta, names.def_names, names.excluded_names) do
nil -> {ast, issues}
list when is_list(list) -> {ast, issues ++ list}
new_issue -> {ast, issues ++ [new_issue]}
end
end
defp mod_traverse(ast, issues, _issue_meta, _names) do
{ast, issues}
end
def find_issue({:->, _meta2, [lhs, _rhs]}, issue_meta, def_names, excluded_names) do
find_issue(lhs, issue_meta, def_names, excluded_names)
end
def find_issue({:%{}, _meta2, keywords}, issue_meta, def_names, excluded_names) do
keywords
|> Enum.map(fn
{_lhs, rhs} ->
find_issue(rhs, issue_meta, def_names, excluded_names)
_ ->
nil
end)
end
def find_issue({:{}, _meta2, tuple_list}, issue_meta, def_names, excluded_names) do
find_issue(tuple_list, issue_meta, def_names, excluded_names)
end
def find_issue({:%, _meta, [{:__aliases__, _meta1, _mod}, map]}, issue_meta, def_names, excluded_names) do
find_issue(map, issue_meta, def_names, excluded_names)
end
def find_issue({name, meta, _}, issue_meta, def_names, excluded_names) when is_atom(name) do
line_no = meta[:line]
def_op = def_names |> find_def_op(name)
cond do
excluded_names |> Enum.member?(name) ->
nil
def_op ->
issue_for(issue_meta, line_no, name, message_for_def(def_op))
@kernel_fun_names |> Enum.member?(name) ->
issue_for(issue_meta, line_no, name, "the `Kernel.#{name}` function")
@kernel_macro_names |> Enum.member?(name) ->
issue_for(issue_meta, line_no, name, "the `Kernel.#{name}` macro")
true ->
nil
end
end
def find_issue(list, issue_meta, def_names, excluded_names) when is_list(list) do
list
|> Enum.map(&find_issue(&1, issue_meta, def_names, excluded_names))
end
def find_issue(tuple, issue_meta, def_names, excluded_names) when is_tuple(tuple) do
tuple
|> Tuple.to_list
|> Enum.map(&find_issue(&1, issue_meta, def_names, excluded_names))
end
def find_issue(_, _, _, _) do
nil
end
defp find_def_op(def_names, name) do
def_names
|> Enum.find(fn({def_name, _op}) -> def_name == name end)
|> extract_def_op
end
defp extract_def_op({_, op}), do: op
defp extract_def_op(nil), do: nil
defp message_for_def(op) do
case op do
:def -> "a function in the same module"
:defp -> "a private function in the same module"
:defmacro -> "a macro in the same module"
_ -> "ERROR"
end
end
defp issue_for(issue_meta, line_no, trigger, what) do
format_issue issue_meta,
message: "Assigned variable `#{trigger}` has same name as #{what}.",
trigger: trigger,
line_no: line_no
end
end