Change default validation level to strict and honor validation_level

Before this commit MJML-Rails *always* raised an exception if there is any
template validation error.

In MJML there are two validation levels though (besides disabling
validation at all):

- `strict`: Raise an error if there are any problems, abort
- `soft`: Do your best and compile what you can, but do not raise any
  error. Output errors on stderr.

Right now it does not matter what validation level is used in
MJML-Rails: It always raises an error if something is wrong with the
template, which actually makes the setting `MJML.validation_level`
superfluous.

With this commit, MJML-Rails follows the MJML convention to only abort
if the validation level is `strict`. If it is `soft`, it lets MJML do
what it can and only logs the errors, like MJML does.

To prevent apps using the default configuration from breaking, the
default validation level is changed to `strict`, too. This means it
raises an error on an invalid template like it did before.

README.md

@@ -95,18 +95,20 @@ If there are configurations you'd like change:
 - render errors: defaults to `true` (errors raised)
 - minify: defaults to `false` (not minified)
 - beautify: defaults to `true` (beautified)
-- validation_level: defaults to `soft` (MJML syntax validation)
+- validation_level: defaults to `strict` (abort on any template error, see [MJML validation documentation](https://github.com/mjmlio/mjml/tree/master/packages/mjml-validator#validating-mjml) for possible values)
 
 ```ruby
 # config/initializers/mjml.rb
 Mjml.setup do |config|
-  # set to `false` to ignore errors silently
-  config.raise_render_exception = true
+  # ignore errors silently
+  config.raise_render_exception = false
 
   # optimize the size of your email
   config.beautify = false
   config.minify = true
-  config.validation_level = "strict"
+
+  # render illformed MJML templates, not recommended
+  config.validation_level = "soft"
 end
 ```
 

lib/mjml.rb

@@ -15,7 +15,7 @@ module Mjml
   @@mjml_binary_error_string = "Couldn't find the MJML #{Mjml.mjml_binary_version_supported} binary.. have you run $ npm install mjml?"
   @@beautify = true
   @@minify = false
-  @@validation_level = "soft"
+  @@validation_level = "strict"
 
   def self.check_version(bin)
     stdout, _, status = run_mjml('--version', mjml_bin: bin)

lib/mjml/parser.rb

@@ -33,11 +33,12 @@ def render
     # Exec mjml command
     #
     # @return [String] The result as string
-    def run(in_tmp_file, beautify=true, minify=false, validation_level="soft")
+    def run(in_tmp_file, beautify=true, minify=false, validation_level="strict")
       Tempfile.create(["out", ".html"]) do |out_tmp_file|
         command = "-r #{in_tmp_file} -o #{out_tmp_file.path} --config.beautify #{beautify} --config.minify #{minify} --config.validationLevel #{validation_level}"
-        _, stderr, _ = Mjml.run_mjml(command)
-        raise ParseError.new(stderr.chomp) unless stderr.blank?
+        _, stderr, status = Mjml.run_mjml(command)
+        raise ParseError.new(stderr.chomp) unless status.success?
+        Mjml.logger.warn(stderr.chomp) unless stderr.blank?
         out_tmp_file.read
       end
     end

test/mjml_test.rb

@@ -67,9 +67,18 @@ class NotifierMailerTest < ActiveSupport::TestCase
     assert email.text_part.body.match(%r{Please visit https://www.example.com})
   end
 
-  test "Invalid template raises error correctly" do
-    email = NotifierMailer.invalid_template("user@example.com")
-    assert_raise(ActionView::Template::Error) { email.html_part.to_s }
+  test "Invalid template raises error with validation level strict" do
+    with_settings(validation_level: 'strict') do
+      email = NotifierMailer.invalid_template("user@example.com")
+      assert_raise(ActionView::Template::Error) { email.html_part.to_s }
+    end
+  end
+
+  test "Invalid template gets compiled with validation level soft" do
+    with_settings(validation_level: 'soft') do
+      email = NotifierMailer.invalid_template("user@example.com")
+      assert email.html_part.to_s.blank?
+    end
   end
 end
 

test/parser_test.rb

@@ -31,24 +31,24 @@
       it 'uses defaults if no config is set' do
         expect(Mjml.beautify).must_equal(true)
         expect(Mjml.minify).must_equal(false)
-        expect(Mjml.validation_level).must_equal('soft')
+        expect(Mjml.validation_level).must_equal('strict')
       end
 
       it 'uses setup config' do
         Mjml.setup do |config|
           config.beautify = false
           config.minify = true
-          config.validation_level = 'strict'
+          config.validation_level = 'soft'
         end
 
         expect(Mjml.beautify).must_equal(false)
         expect(Mjml.minify).must_equal(true)
-        expect(Mjml.validation_level).must_equal('strict')
+        expect(Mjml.validation_level).must_equal('soft')
 
         Mjml.setup do |config|
           config.beautify = true
           config.minify = false
-          config.validation_level = 'soft'
+          config.validation_level = 'strict'
         end
       end
     end