ForgeCredoChecks (forge_credo_checks v0.8.0)

Custom Credo checks targeting anti-patterns that LLMs commonly produce.

Stock Credo ships checks for filter |> filter, reject |> reject, map |> join, map |> into, etc. but not the cases where one operation composes with the complementary one, nor the common map-building, sort-then-pick, and map-shape normalization anti-patterns. These checks fill those gaps.

Two-pass Enum chains (suggests Enum.reduce/3)

• ForgeCredoChecks.FilterMap: Enum.filter |> Enum.map
• ForgeCredoChecks.RejectMap: Enum.reject |> Enum.map
• ForgeCredoChecks.MapReject: Enum.map |> Enum.reject
• ForgeCredoChecks.MapRejectNil: Enum.map |> Enum.reject(&is_nil/1)

Hand-rolled map building (suggests Map.new/2)

• ForgeCredoChecks.MapNewFromInto: Enum.into(%{}, fn ...)
• ForgeCredoChecks.MapNewFromReduce: Enum.reduce(_, %{}, &Map.put(acc, k, v))

Wasteful list-extremum patterns

• ForgeCredoChecks.ReverseListFirst: xs |> Enum.reverse() |> List.first() becomes List.last(xs)
• ForgeCredoChecks.SortListFirst: Enum.sort \| List.first becomes Enum.min/Enum.max/*_by

Map shape normalization

• ForgeCredoChecks.MapGetWithOr: Map.get(_, _) || fallback
• ForgeCredoChecks.ChainedMapGet: Map.get(_, _) || Map.get(_, _)

LLM tells

• ForgeCredoChecks.NoInlineRegex: inline ~r/~R regex sigils inside function bodies
• ForgeCredoChecks.NoAnyOrTermTypes: any() / term() in specs, callbacks, and type definitions
• ForgeCredoChecks.MultilineStringConcat: multi-line string-literal <> concatenation (use a heredoc)

Architecture and test discipline

• ForgeCredoChecks.OneModulePerFile: every defmodule after the first in a source file (test files excluded by default)
• ForgeCredoChecks.TaintedSourceInspection: source-grep constructs applied to text read from non-test .ex / .exs files
• ForgeCredoChecks.TimingAndPrivateStateGuard: Process.sleep/1 and :sys.replace_state/2 call nodes
• ForgeCredoChecks.NoApplicationGetEnvInLib: Application.get_env/2,3 inside lib/ (use compile_env or fetch_env! instead)
• ForgeCredoChecks.TelemetryControlFlow: :telemetry.attach/attach_many with an inline handler that performs control flow (send, GenServer.call/cast) instead of observation-only recording