Fix issue with expecting default ignore file when checking file size

lib/mix/tasks/dialyzer.ex

@@ -182,17 +182,23 @@ defmodule Mix.Tasks.Dialyzer do
       ignore_warnings = Dialyxir.Project.dialyzer_ignore_warnings()
 
       cond do
-        !ignore_warnings && File.exists?(default) ->
+        !ignore_warnings && File.exists?(default) &&
+            match?(%{size: size} when size == 0, File.stat!(default)) ->
           info("""
-          No :ignore_warnings opt specified in mix.exs. Using default: #{default}.
+          No :ignore_warnings opt specified in mix.exs. Using default, but file is empty.
           """)
 
         ignore_warnings && File.exists?(ignore_warnings) &&
-            match?(%{size: size} when size == 0, File.stat!(default)) ->
+            match?(%{size: size} when size == 0, File.stat!(ignore_warnings)) ->
           info("""
           :ignore_warnings opt specified in mix.exs: #{ignore_warnings}, but file is empty.
           """)
 
+        !ignore_warnings && File.exists?(default) ->
+          info("""
+          No :ignore_warnings opt specified in mix.exs. Using default: #{default}.
+          """)
+
         ignore_warnings && File.exists?(ignore_warnings) ->
           info("""
           ignore_warnings: #{ignore_warnings}

test/dialyxir/formatter_test.exs

@@ -56,7 +56,7 @@
   end
 
   describe "exs ignore" do
     test "evaluates an ignore file and ignores warnings matching the pattern" do
       warnings = [
         {:warn_return_no_exit, {~c"lib/short_description.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}},
@@ -92,7 +92,28 @@
       end)
     end
 
+    test "ignores an empty default ignore file" do
+      in_project(:ignore_default_empty, fn ->
+        {:ok, remaining,  :no_unused_filters} =
+          Formatter.format_and_filter([], Project, [], [IgnoreFileStrictFormatter])
+
+        assert Project.dialyzer_ignore_warnings() == nil
+        assert remaining == []
+      end)
+    end
+
+    test "ignores an empty ignore file specified in mix" do
+      in_project(:ignore_empty, fn ->
+        {:ok, remaining,  :no_unused_filters} =
+          Formatter.format_and_filter([], Project, [], [IgnoreFileStrictFormatter])
+
+        assert Project.dialyzer_ignore_warnings() == "ignore_empty_test.exs"
+        assert remaining == []
+      end)
+    end
+
+
     test "does not filter lines not matching the pattern" do
       warning =
         {:warn_return_no_exit, {~c"a/different_file.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}}
@@ -105,7 +126,7 @@
       end)
     end
 
     test "can filter by regex" do
       warning =
         {:warn_return_no_exit, {~c"a/regex_file.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}}
@@ -118,7 +139,7 @@
       end)
     end
 
     test "lists unnecessary skips as warnings if ignoring exit status" do
       warning =
         {:warn_return_no_exit, {~c"a/regex_file.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}}
@@ -133,7 +154,7 @@
       end)
     end
 
     test "error on unnecessary skips without ignore_exit_status" do
       warning =
         {:warn_return_no_exit, {~c"a/regex_file.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}}
@@ -148,7 +169,7 @@
       end)
     end
 
     test "overwrite ':list_unused_filters_present'" do
       warning =
         {:warn_return_no_exit, {~c"a/regex_file.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}}
@@ -177,7 +198,7 @@
   end
 
   describe "multiple formatters" do
     test "short and github" do
       warning =
         {:warn_return_no_exit, {~c"a/different_file.ex", 17},
          {:no_return, [:only_normal, :format_long, 1]}}
@@ -192,7 +213,7 @@
     end
   end
 
   test "listing unused filter behaves the same for different formats" do
     warnings = [
       {:warn_return_no_exit, {~c"a/regex_file.ex", 17},
        {:no_return, [:only_normal, :format_long, 1]}},

test/fixtures/ignore_default_empty/mix.exs

@@ -0,0 +1,14 @@
+defmodule Ignore.Mixfile do
+  use Mix.Project
+
+  def project do
+    [
+      app: :ignore,
+      version: "0.1.0",
+      prune_code_paths: false,
+      dialyzer: [
+        list_unused_filters: true
+      ]
+    ]
+  end
+end

test/fixtures/ignore_empty/mix.exs

@@ -0,0 +1,15 @@
+defmodule Ignore.Mixfile do
+  use Mix.Project
+
+  def project do
+    [
+      app: :ignore,
+      version: "0.1.0",
+      prune_code_paths: false,
+      dialyzer: [
+        ignore_warnings: "ignore_empty_test.exs",
+        list_unused_filters: true
+      ]
+    ]
+  end
+end