Avoid scanning the filesystem to filter files per check

lib/credo/check/runner.ex

@@ -43,43 +43,17 @@ defmodule Credo.Check.Runner do
     files_excluded = Params.files_excluded(params, check)
 
     found_relevant_files =
-      cond do
-        files_included == known_files and files_excluded == [] ->
-          []
-
-        exec.read_from_stdin ->
-          # TODO: I am unhappy with how convoluted this gets
-          #       but it is necessary to avoid hitting the filesystem when reading from STDIN
-          [%Credo.SourceFile{filename: filename}] = Execution.get_source_files(exec)
-
-          file_included? =
-            if files_included != known_files do
-              Credo.Sources.filename_matches?(filename, files_included)
-            else
-              true
-            end
-
-          file_excluded? =
-            if files_excluded != [] do
-              Credo.Sources.filename_matches?(filename, files_excluded)
-            else
-              false
-            end
-
-          if !file_included? || file_excluded? do
-            :skip_run
-          else
-            []
-          end
-
-        true ->
-          exec
-          |> Execution.working_dir()
-          |> Credo.Sources.find_in_dir(files_included, files_excluded)
-          |> case do
-            [] -> :skip_run
-            files -> files
-          end
+      if files_included == known_files and files_excluded == [] do
+        []
+      else
+        known_files
+        |> Enum.map(&Path.expand/1)
+        |> Enum.filter(&Credo.Sources.filename_matches?(&1, files_included))
+        |> Enum.reject(&Credo.Sources.filename_matches?(&1, files_excluded))
+        |> case do
+          [] -> :skip_run
+          files -> files
+        end
       end
 
     source_files =

test/credo/check/runner_test.exs

@@ -1,2 +1,159 @@
 defmodule Credo.Check.RunnerTest do
+  use ExUnit.Case, async: true
+
+  alias Credo.Check.Runner
+  alias Credo.Execution
+  alias Credo.Execution.ExecutionSourceFiles
+  alias Credo.SourceFile
+
+  defmodule CollectFilenamesCheck do
+    def param_defaults do
+      [
+        files: %{
+          included: nil,
+          excluded: []
+        }
+      ]
+    end
+
+    def run_on_all_source_files(_exec, source_files, params) do
+      filenames = Enum.map(source_files, & &1.filename)
+      send(params[:test_pid], {:checked_files, filenames})
+      :ok
+    end
+  end
+
+  describe "read_from_stdin behaviour" do
+    test "runs the check on the stdin file when it matches files.included", %{test_pid: test_pid} do
+      filename = Path.expand("lib/foo.ex")
+      source_file = %SourceFile{filename: filename}
+
+      exec =
+        ExecutionSourceFiles.start_server(%Execution{
+          read_from_stdin: true,
+          checks: %{
+            enabled: [
+              {CollectFilenamesCheck,
+               [files: %{included: ["lib/**/*.ex"], excluded: []}, test_pid: test_pid]}
+            ],
+            disabled: []
+          }
+        })
+
+      ExecutionSourceFiles.put(exec, [source_file])
+
+      :ok = Runner.run([source_file], exec)
+
+      assert_receive {:checked_files, [^filename]}
+    end
+
+    test "runs the check with no files when the stdin file does not match files.included",
+         %{test_pid: test_pid} do
+      filename = Path.expand("test/foo_test.exs")
+      source_file = %SourceFile{filename: filename}
+
+      exec =
+        ExecutionSourceFiles.start_server(%Execution{
+          read_from_stdin: true,
+          checks: %{
+            enabled: [
+              {CollectFilenamesCheck,
+               [files: %{included: ["lib/**/*.ex"], excluded: []}, test_pid: test_pid]}
+            ],
+            disabled: []
+          }
+        })
+
+      ExecutionSourceFiles.put(exec, [source_file])
+
+      :ok = Runner.run([source_file], exec)
+
+      assert_receive {:checked_files, []}
+    end
+  end
+
+  describe "watch / rerun behaviour" do
+    test "runs the check only on the changed file", %{test_pid: test_pid} do
+      foo = Path.expand("lib/foo.ex")
+      bar = Path.expand("lib/bar.ex")
+
+      source_files = [
+        %SourceFile{filename: foo},
+        %SourceFile{filename: bar}
+      ]
+
+      exec =
+        ExecutionSourceFiles.start_server(%Execution{
+          read_from_stdin: false,
+          checks: %{
+            enabled: [
+              {CollectFilenamesCheck, [__rerun_files_that_changed__: [foo], test_pid: test_pid]}
+            ],
+            disabled: []
+          }
+        })
+
+      ExecutionSourceFiles.put(exec, source_files)
+
+      :ok = Runner.run(source_files, exec)
+
+      assert_receive {:checked_files, [^foo]}
+    end
+
+    test "runs the check with no files when the changed file is not a known source file",
+         %{test_pid: test_pid} do
+      foo = Path.expand("lib/foo.ex")
+      bar = Path.expand("lib/bar.ex")
+      baz = Path.expand("lib/baz.ex")
+
+      source_files = [
+        %SourceFile{filename: foo},
+        %SourceFile{filename: bar}
+      ]
+
+      exec =
+        ExecutionSourceFiles.start_server(%Execution{
+          read_from_stdin: false,
+          checks: %{
+            enabled: [
+              {CollectFilenamesCheck, [__rerun_files_that_changed__: [baz], test_pid: test_pid]}
+            ],
+            disabled: []
+          }
+        })
+
+      ExecutionSourceFiles.put(exec, source_files)
+
+      :ok = Runner.run(source_files, exec)
+
+      assert_receive {:checked_files, []}
+    end
+  end
+
+  describe "files pattern filtering" do
+    test "filters known files using files patterns from params", %{test_pid: test_pid} do
+      dir = "test/fixtures/integration_test_config"
+      filename = Path.expand(Path.join(dir, "lib/clean.ex"))
+      source_file = %SourceFile{filename: filename}
+
+      exec =
+        ExecutionSourceFiles.start_server(%Execution{
+          cli_options: %{path: dir},
+          read_from_stdin: false,
+          checks: %{
+            enabled: [
+              {CollectFilenamesCheck,
+               [__files__: %{included: ["lib/*.ex"], excluded: []}, test_pid: test_pid]}
+            ],
+            disabled: []
+          }
+        })
+
+      ExecutionSourceFiles.put(exec, [source_file])
+
+      :ok = Runner.run([source_file], exec)
+
+      assert_receive {:checked_files, [^filename]}
+    end
+  end
 end