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A static code analysis tool with a focus on code consistency and teaching.
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Files
lib/credo/check/warning/unsafe_to_atom.ex
defmodule Credo.Check.Warning.UnsafeToAtom do
use Credo.Check,
id: "EX5016",
base_priority: :high,
category: :warning,
tags: [:controversial],
explanations: [
check: """
Creating atoms from unknown or external sources dynamically is a potentially
unsafe operation because atoms are not garbage-collected by the runtime.
Creating an atom from a string or charlist should be done by using
String.to_existing_atom(string)
or
List.to_existing_atom(charlist)
Module aliases should be constructed using
Module.safe_concat(prefix, suffix)
or
Module.safe_concat([prefix, infix, suffix])
Jason.decode/Jason.decode! should be called using `keys: :atoms!` (*not* `keys: :atoms`):
Jason.decode(str, keys: :atoms!)
or `:keys` should be omitted (which defaults to `:strings`):
Jason.decode(str)
"""
]
@doc false
@impl true
def run(%SourceFile{} = source_file, params) do
ctx = Context.build(source_file, params, __MODULE__)
result = Credo.Code.prewalk(source_file, &walk/2, ctx)
result.issues
end
defp walk({:@, _, _}, ctx) do
{nil, ctx}
end
defp walk({:unquote, _, [_ | _] = _args}, ctx) do
{nil, ctx}
end
# module.unquote(:"some_atom")
defp walk({{:., _, [_, :unquote]}, _, [_ | _] = _args}, ctx) do
{nil, ctx}
end
defp walk({:|>, _meta1, [_lhs, {{:., _meta2, call}, meta, args}]} = ast, ctx) do
case get_forbidden_pipe(call, args) do
{bad, suggestion, trigger} ->
{ast, put_issue(ctx, issue_for(ctx, meta, bad, suggestion, trigger))}
nil ->
{ast, ctx}
end
end
defp walk({{:., _loc, call}, meta, args} = ast, ctx) do
case get_forbidden_call(call, args) do
{bad, suggestion, trigger} ->
{ast, put_issue(ctx, issue_for(ctx, meta, bad, suggestion, trigger))}
nil ->
{ast, ctx}
end
end
defp walk(ast, ctx) do
{ast, ctx}
end
defp get_forbidden_call([:erlang, :list_to_atom], [_]) do
{":erlang.list_to_atom/1", ":erlang.list_to_existing_atom/1", ":erlang.list_to_atom"}
end
defp get_forbidden_call([:erlang, :binary_to_atom], [_, _]) do
{":erlang.binary_to_atom/2", ":erlang.binary_to_existing_atom/2", ":erlang.binary_to_atom"}
end
defp get_forbidden_call([{:__aliases__, _, [:String]}, :to_atom], [_]) do
{"String.to_atom/1", "String.to_existing_atom/1", "String.to_atom"}
end
defp get_forbidden_call([{:__aliases__, _, [:List]}, :to_atom], [_]) do
{"List.to_atom/1", "List.to_existing_atom/1", "List.to_atom"}
end
defp get_forbidden_call([{:__aliases__, _, [:Module]}, :concat], [_]) do
{"Module.concat/1", "Module.safe_concat/1", "Module.concat"}
end
defp get_forbidden_call([{:__aliases__, _, [:Module]}, :concat], [_, _]) do
{"Module.concat/2", "Module.safe_concat/2", "Module.concat"}
end
defp get_forbidden_call([{:__aliases__, _, [:Jason]}, decode], args)
when decode in [:decode, :decode!] do
args
|> Enum.any?(fn arg -> Keyword.keyword?(arg) and Keyword.get(arg, :keys) == :atoms end)
|> if do
{"Jason.#{decode}(..., keys: :atoms)", "Jason.#{decode}(..., keys: :atoms!)",
"Jason.#{decode}"}
else
nil
end
end
defp get_forbidden_call(_, _) do
nil
end
defp get_forbidden_pipe([:erlang, :list_to_atom], []) do
{":erlang.list_to_atom/1", ":erlang.list_to_existing_atom/1", ":erlang.list_to_atom"}
end
defp get_forbidden_pipe([:erlang, :binary_to_atom], [_]) do
{":erlang.binary_to_atom/2", ":erlang.binary_to_existing_atom/2", ":erlang.binary_to_atom"}
end
defp get_forbidden_pipe([{:__aliases__, _, [:String]}, :to_atom], []) do
{"String.to_atom/1", "String.to_existing_atom/1", "String.to_atom"}
end
defp get_forbidden_pipe([{:__aliases__, _, [:List]}, :to_atom], []) do
{"List.to_atom/1", "List.to_existing_atom/1", "List.to_atom"}
end
defp get_forbidden_pipe([{:__aliases__, _, [:Module]}, :concat], []) do
{"Module.concat/1", "Module.safe_concat/1", "Module.concat"}
end
defp get_forbidden_pipe(_, _) do
nil
end
defp issue_for(ctx, meta, call, suggestion, trigger) do
format_issue(ctx,
message: "Prefer #{suggestion} over #{call} to avoid creating atoms at runtime.",
trigger: trigger,
line_no: meta[:line]
)
end
end