Merge pull request #113 from DefactoSoftware/pien/check-file-empty

Fix error with empty style definitions json file

Author: EasterPeanut

README.md

@@ -7,7 +7,11 @@
 
 ExCSSModules defines two ways to read the stylesheet: embedded and read.
 
-If you set the `embed_stylesheet` option to the `use` macro the stylesheet definitions JSON have to be compiled before the application is compiled. This flag is used for production to optimize read times. Additionally, you can add a task to generate missing stylesheet definitions JSON files when compiling ExCSSModules, to prevent compilation errors when one of the stylesheet definitions JSON might be missing:
+If you set the `embed_stylesheet` option to the `use` macro the stylesheet definitions JSON have to be compiled before the application is compiled. This flag is used for production to optimize read times. 
+
+If you don't set the flag or set it to false, the stylesheet definition JSON files are read live from the server which creates a lot of IO for each request.
+
+Additionally, you can pass a task to generate missing stylesheet definitions JSON files when compiling ExCSSModules, to prevent compilation errors when one of the stylesheet definitions JSON might be missing:
 
 ```ex
 defmodule Mix.Tasks.GenerateMissingJson do
@@ -28,7 +32,18 @@ defmodule Mix.Tasks.GenerateMissingJson do
 end
 ```
 
-If you don't set the flag or set it to false, the stylesheet definition JSON files are read live from the server which creates a lot of IO for each request.
+This task can be passed through the option `build_stylesheet_definitions_json_task`: 
+
+```ex
+use ExCSSModules.View,
+  namespace: MyApplicationWeb,
+  embed_stylesheet: ApplicationSettings.built_for?(:prod),
+  build_stylesheet_definitions_json_task: unquote(Mix.Tasks.GenerateMissingJson),
+  stylesheet:
+    __ENV__.file
+    |> Path.dirname()
+    |> Path.join("./style.css")
+```
 
 ## Installation
 Install from [Hex.pm](https://hex.pm/packages/ex_css_modules):

lib/ex_css_modules/ex_css_modules.ex

@@ -37,24 +37,45 @@ defmodule ExCSSModules do
   def stylesheet(definition, build_json_task), do: read_stylesheet(definition, build_json_task)
 
   defp read_stylesheet(filename, build_json_task) do
-    cond do
-      File.exists?(filename <> ".json") ->
-        (filename <> ".json")
-        |> File.read!()
-        |> json_library().decode!()
-
-      build_json_task && File.exists?(filename) ->
-        with {:ok, json_filename} <- build_json_task.run(filename: filename) do
-          json_filename
+    if File.exists?(filename) do
+      cond do
+        File.exists?("#{filename}.json") && not empty_file?("#{filename}.json") ->
+          "#{filename}.json"
           |> File.read!()
           |> json_library().decode!()
-        end
 
-      true ->
-        %{}
+        build_json_task ->
+          with {:ok, json_filename} <- build_json_task.run(filename: filename) do
+            json_filename
+            |> File.read!()
+            |> json_library().decode!()
+          end
+
+        not File.exists?("#{filename}.json") ->
+          message =
+            """
+            File does not exist.
+            Error compiling ExCSSModules: Be sure to build your style definitions JSON files before compiling your application.
+            """
+
+          raise(CompileError, description: message, file: "#{filename}.json")
+
+        empty_file?("#{filename}.json") ->
+          message =
+            """
+            File is empty.
+            Error compiling ExCSSModules: Remove the file and/or (re)build your style definitions JSON files before compiling your application.
+            """
+
+          raise(CompileError, description: message, file: "#{filename}.json")
+      end
+    else
+      %{}
     end
   end
 
+  defp empty_file?(filename), do: File.read!(filename) == ""
+
   @doc """
   Reads the class definitions from the definition map and maps them to a class
   attribute. The `keys` argument is used to retrieve the class name or multiple

lib/ex_css_modules/view.ex

@@ -11,7 +11,7 @@ defmodule ExCSSModules.View do
   also be enabled through the `:embed_by_default` config option.
 
   If adds the following functions to the View:
-  - stylesheet/0 - same as ExCSSModules.stylesheet/1 with the stylesheet predefined
+  - stylesheet/0 - same as ExCSSModules.stylesheet/2 with the stylesheet predefined
   - class/1 - same as ExCSSModules.class/2 with the stylesheet predefined
   - class_name/1 - same as ExCSSModules.class_name/2 with the stylesheet predefined
   - class_name/2 - same as ExCSSModules.class_name/3 with the stylesheet predefined

test/ex_css_modules/view_test.exs

@@ -1,78 +1,136 @@
 defmodule ExCSSModules.ViewTest do
   @example_stylesheet __ENV__.file
-                      |> Path.dirname
+                      |> Path.dirname()
                       |> Path.join("../support/stylesheet.css")
 
   use ExUnit.Case
 
-  defmodule ViewModuleTest do
-    use ExCSSModules.View, stylesheet: __ENV__.file
-                                       |> Path.dirname
-                                       |> Path.join("../support/stylesheet.css")
+  defmodule ViewModule.Test do
+    use ExCSSModules.View,
+      stylesheet:
+        __ENV__.file
+        |> Path.dirname()
+        |> Path.join("../support/stylesheet.css")
   end
 
-  defmodule EmbeddedViewModuleTest do
-    use ExCSSModules.View, stylesheet: __ENV__.file
-                                       |> Path.dirname
-                                       |> Path.join("../support/stylesheet.css"),
-                           embed_stylesheet: true
+  defmodule ViewModule.Embedded.Test do
+    use ExCSSModules.View,
+      stylesheet:
+        __ENV__.file
+        |> Path.dirname()
+        |> Path.join("../support/stylesheet.css"),
+      embed_stylesheet: true
+  end
+
+  defmodule ViewModule.StylesheetDefinitions.EmptyObject.Test do
+    use ExCSSModules.View,
+      stylesheet:
+        __ENV__.file
+        |> Path.dirname()
+        |> Path.join("../support/stylesheet_definitions_with_empty_object.css")
+  end
+
+  defmodule ViewModule.StylesheetDefinitions.EmptyFile.Test do
+    use ExCSSModules.View,
+      stylesheet:
+        __ENV__.file
+        |> Path.dirname()
+        |> Path.join("../support/empty_file.css")
+  end
+
+  defmodule ViewModule.StylesheetDefinitions.NoFile.Test do
+    use ExCSSModules.View,
+      stylesheet:
+        __ENV__.file
+        |> Path.dirname()
+        |> Path.join("../support/no_stylesheet_definitions.css")
   end
 
   describe "stylesheet_definition/0" do
     test "gets the stylesheet string" do
-      assert ViewModuleTest.stylesheet_definition
-        == Path.expand(@example_stylesheet)
+      assert ViewModule.Test.stylesheet_definition() ==
+               Path.expand(@example_stylesheet)
     end
 
     test "gets the embedded stylesheet" do
-      assert EmbeddedViewModuleTest.stylesheet_definition
-        == ExCSSModules.stylesheet(@example_stylesheet)
+      assert ViewModule.Embedded.Test.stylesheet_definition() ==
+               ExCSSModules.stylesheet(@example_stylesheet)
     end
   end
 
   describe "stylesheet/0" do
     test "calls the stylesheet" do
-      assert ViewModuleTest.stylesheet
-        == ExCSSModules.stylesheet(@example_stylesheet)
+      assert ViewModule.Test.stylesheet() ==
+               ExCSSModules.stylesheet(@example_stylesheet)
+    end
+
+    test "returns an empty map if the stylesheet definitions json file contains just an empty object" do
+      assert ViewModule.StylesheetDefinitions.EmptyObject.Test.stylesheet() == %{}
+    end
+
+    test "raises if the stylesheet definitions json file is empty" do
+      message =
+        """
+        test/support/empty_file.css.json: File is empty.
+        Error compiling ExCSSModules: Remove the file and/or (re)build your style definitions JSON files before compiling your application.
+        """
+
+      assert_raise(CompileError, message, fn ->
+        ViewModule.StylesheetDefinitions.EmptyFile.Test.stylesheet()
+      end)
+    end
+
+    test "raises if the stylesheet definitions json file does not exist" do
+      message =
+        """
+        test/support/no_stylesheet_definitions.css.json: File does not exist.
+        Error compiling ExCSSModules: Be sure to build your style definitions JSON files before compiling your application.
+        """
+
+      assert_raise(CompileError, message, fn ->
+        ViewModule.StylesheetDefinitions.NoFile.Test.stylesheet()
+      end)
     end
   end
 
   describe "class_selector/1" do
     test "prepends the class_name with a dot" do
-      assert ViewModuleTest.class_selector("title") ==
-        ExCSSModules.class_selector(@example_stylesheet, "title")
+      assert ViewModule.Test.class_selector("title") ==
+               ExCSSModules.class_selector(@example_stylesheet, "title")
     end
   end
 
   describe "class_name/1" do
     test "calls the css/2 method on ExCSSModules" do
-      assert ViewModuleTest.class_name("title") ==
-        ExCSSModules.class_name(@example_stylesheet, "title")
+      assert ViewModule.Test.class_name("title") ==
+               ExCSSModules.class_name(@example_stylesheet, "title")
     end
   end
 
   describe "class_name/2" do
     test "calls the css/3 method on ExCSSModules" do
-      assert ViewModuleTest.class_name("title", true) ==
-        ExCSSModules.class_name(@example_stylesheet, "title", true)
-      assert ViewModuleTest.class_name("title", false) ==
-        ExCSSModules.class_name(@example_stylesheet, "title", false)
+      assert ViewModule.Test.class_name("title", true) ==
+               ExCSSModules.class_name(@example_stylesheet, "title", true)
+
+      assert ViewModule.Test.class_name("title", false) ==
+               ExCSSModules.class_name(@example_stylesheet, "title", false)
     end
   end
 
   describe "class/1" do
     test "calls the class/2 method on ExCSSModules" do
-      assert ViewModuleTest.class("title") ==
-        ExCSSModules.class(@example_stylesheet, "title")
+      assert ViewModule.Test.class("title") ==
+               ExCSSModules.class(@example_stylesheet, "title")
     end
   end
 
   describe "class/2" do
     test "calls the class/3 method on ExCSSModules" do
-      assert ViewModuleTest.class("title", true) ==
-        ExCSSModules.class(@example_stylesheet, "title", true)
-      assert ViewModuleTest.class("title", false) ==
-        ExCSSModules.class(@example_stylesheet, "title", false)
+      assert ViewModule.Test.class("title", true) ==
+               ExCSSModules.class(@example_stylesheet, "title", true)
+
+      assert ViewModule.Test.class("title", false) ==
+               ExCSSModules.class(@example_stylesheet, "title", false)
     end
   end
 end

test/support/empty_file.css

@@ -0,0 +1 @@
+{}