aprs.me/test/mix_unused/analyzer_test.exs

defmodule MixUnused.AnalyzerTest do
  use ExUnit.Case, async: false

  alias MixUnused.Analyzer

  setup_all do
    # Cache one analyze() result and reuse across tests. analyze() walks
    # every BEAM file and is the slow part — running it once per module
    # avoids paying that cost per test.
    {:ok, baseline: Analyzer.analyze()}
  end

  describe "format/1" do
    test "renders a friendly message when there are no entries" do
      assert Analyzer.format([]) =~ "No unused public functions"
    end

    test "groups by module, lists each entry, and includes file:line" do
      entries = [
        %{module: Foo, name: :a, arity: 1, file: "lib/foo.ex", line: 5},
        %{module: Foo, name: :b, arity: 0, file: "lib/foo.ex", line: 10},
        %{module: Bar, name: :c, arity: 2, file: "lib/bar.ex", line: 7}
      ]

      out = Analyzer.format(entries)
      assert out =~ "Unused public functions"
      assert out =~ "Foo"
      assert out =~ "def a/1"
      assert out =~ "def b/0"
      assert out =~ "lib/foo.ex:5"
      assert out =~ "lib/foo.ex:10"
      assert out =~ "Bar"
      assert out =~ "def c/2"
      assert out =~ "lib/bar.ex:7"
    end

    test "shows just the file when line is nil" do
      entries = [
        %{module: Foo, name: :x, arity: 0, file: "lib/foo.ex", line: nil}
      ]

      out = Analyzer.format(entries)
      assert out =~ "(lib/foo.ex)"
    end

    test "shows '?' when both file and line are missing" do
      entries = [
        %{module: Foo, name: :x, arity: 0, file: nil, line: nil}
      ]

      out = Analyzer.format(entries)
      assert out =~ "(?)"
    end
  end

  describe "analyze/1 against the running project" do
    test "returns a list of unused-entry maps", %{baseline: result} do
      assert is_list(result)

      # Every entry has the expected shape.
      Enum.each(result, fn entry ->
        assert is_atom(entry.module)
        assert is_atom(entry.name)
        assert is_integer(entry.arity)
        assert is_nil(entry.file) or is_binary(entry.file)
        assert is_nil(entry.line) or is_integer(entry.line)
      end)
    end

    test "result is sorted by module then name then arity", %{baseline: result} do
      sorted =
        Enum.sort_by(result, fn e -> {Atom.to_string(e.module), e.name, e.arity} end)

      # The analyzer's own sort key uses the atom directly, but inspect-string
      # ordering differs only for funky atoms — so we just confirm the result
      # is non-decreasing under our string-based sort.
      assert Enum.map(result, & &1.module) ==
               Enum.map(sorted, & &1.module)
    end

    test "exclude option removes whole modules from the output", %{baseline: result} do
      [first | _] = result

      assert first

      excluded = Analyzer.analyze(exclude: [first.module])
      refute Enum.any?(excluded, &(&1.module == first.module))
    end

    test "exclude option removes specific MFA triples", %{baseline: result} do
      [first | _] = result

      assert first

      excluded =
        Analyzer.analyze(exclude: [{first.module, first.name, first.arity}])

      refute Enum.any?(
               excluded,
               &(&1.module == first.module and &1.name == first.name and &1.arity == first.arity)
             )
    end

    test "honors :app option — empty list when filtered to a non-existent app" do
      result = Analyzer.analyze(app: :no_such_app_for_real)
      assert result == []
    end

    test ":app=nil hits in_app?(_, nil) → true (no filtering)" do
      # When app is nil, in_app? returns true for every module — so the
      # analyzer scans everything in the compile path, not just the project.
      # This exercises line 86 (defp in_app?(_module, nil), do: true).
      tmp = Path.join(System.tmp_dir!(), "mu_app_nil_#{System.unique_integer([:positive])}")
      File.mkdir_p!(tmp)

      try do
        result = Analyzer.analyze(app: nil, compile_path: tmp)
        assert result == []
      after
        File.rm_rf(tmp)
      end
    end

    test "honors :compile_path option pointing to an empty directory" do
      tmp = Path.join(System.tmp_dir!(), "mu_empty_#{System.unique_integer([:positive])}")
      File.mkdir_p!(tmp)

      try do
        result = Analyzer.analyze(compile_path: tmp)
        assert result == []
      after
        File.rm_rf(tmp)
      end
    end

    test "honors :compile_path option pointing to a non-existent directory" do
      result = Analyzer.analyze(compile_path: "/nonexistent/path/for/test/#{System.unique_integer([:positive])}")
      assert result == []
    end

    test "exclude with both module atoms and MFA tuples filters both kinds", %{baseline: result} do
      [first, second | _] = result

      excluded =
        Analyzer.analyze(exclude: [first.module, {second.module, second.name, second.arity}])

      refute Enum.any?(excluded, &(&1.module == first.module))

      refute Enum.any?(
               excluded,
               &(&1.module == second.module and &1.name == second.name and &1.arity == second.arity)
             )
    end
  end

  describe "format/1 with grouped multiple-modules and missing line metadata" do
    test "formats a mix of present and missing line numbers" do
      entries = [
        %{module: A, name: :one, arity: 1, file: "lib/a.ex", line: 5},
        %{module: A, name: :two, arity: 0, file: "lib/a.ex", line: nil},
        %{module: B, name: :three, arity: 2, file: nil, line: nil}
      ]

      out = Analyzer.format(entries)
      assert out =~ "A"
      assert out =~ "B"
      assert out =~ "lib/a.ex:5"
      assert out =~ "(lib/a.ex)"
      assert out =~ "(?)"
    end
  end
end