Bylaw.Credo.Check.Elixir.SafeDateTimeComparison (bylaw_credo v0.1.0-alpha.1)

Basics

This check has a base priority of higher and works with any version of Elixir.

Explanation

Avoid direct comparison operators on values that look like dates or times.

Examples

Avoid:

  entry.inserted_at > cutoff_at
  start_date <= end_date

Prefer:

  DateTime.after?(entry.inserted_at, cutoff_at)
  Date.compare(start_date, end_date) in [:lt, :eq]

Notes

Elixir's term ordering can compare structs even when the comparison is not the domain comparison you meant. Date and time types have comparison functions that encode the correct semantics.

Use compare/2, before?/2, or after?/2 from the relevant date/time module. Ecto where clauses are ignored because query comparisons are translated by Ecto instead of using Elixir term ordering.

This check uses static AST analysis, so it favors clear source-level patterns over runtime behavior.

Options

Configure options in .credo.exs with the check tuple:

%{
  configs: [
    %{
      name: "default",
      checks: [
        {Bylaw.Credo.Check.Elixir.SafeDateTimeComparison,
         [
           datetime_suffixes: ~w(_datetime _at _date _time)
         ]}
      ]
    }
  ]
}

• :datetime_suffixes - Variable and field suffixes that make a value look like a date or time. Defaults to _datetime, _at, _date, and _time.

Usage

Add this check to Credo's checks: list in .credo.exs:

%{
  configs: [
    %{
      name: "default",
      checks: [
        {Bylaw.Credo.Check.Elixir.SafeDateTimeComparison, []}
      ]
    }
  ]
}

Check-Specific Parameters

Use the following parameters to configure this check:

:datetime_suffixes

Variable and field suffixes that make a value look like a date or time. Defaults to _datetime, _at, _date, and _time.

This parameter defaults to ["_datetime", "_at", "_date", "_time"].

General Parameters

Like with all checks, general params can be applied.

Parameters can be configured via the .credo.exs config file.