Fix SyntaxHighlightFilter spec

app/assets/javascripts/copy_as_gfm.js.es6

@@ -89,7 +89,7 @@
     SyntaxHighlightFilter: {
       'pre.code.highlight'(el, text) {
         let lang = el.getAttribute('lang');
-        if (lang === 'text') {
+        if (lang === 'plaintext') {
           lang = '';
         }
         return '```' + lang + '\n' + text.trim() + '\n```';

lib/banzai/filter/syntax_highlight_filter.rb

@@ -27,6 +27,7 @@ module Banzai
 
           css_classes << " js-syntax-highlight #{lang}"
         rescue
+          lang = nil
           # Gracefully handle syntax highlighter bugs/errors to ensure
           # users can still access an issue/comment/etc.
         end

spec/lib/banzai/filter/syntax_highlight_filter_spec.rb

@@ -6,21 +6,21 @@ describe Banzai::Filter::SyntaxHighlightFilter, lib: true do
   context "when no language is specified" do
     it "highlights as plaintext" do
       result = filter('<pre><code>def fun end</code></pre>')
-      expect(result.to_html).to eq('<pre class="code highlight js-syntax-highlight plaintext" v-pre="true"><code>def fun end</code></pre>')
+      expect(result.to_html).to eq('<pre class="code highlight js-syntax-highlight plaintext" lang="plaintext" v-pre="true"><code>def fun end</code></pre>')
     end
   end
 
   context "when a valid language is specified" do
     it "highlights as that language" do
       result = filter('<pre><code class="ruby">def fun end</code></pre>')
-      expect(result.to_html).to eq('<pre class="code highlight js-syntax-highlight ruby" v-pre="true"><code><span class="k">def</span> <span class="nf">fun</span> <span class="k">end</span></code></pre>')
+      expect(result.to_html).to eq('<pre class="code highlight js-syntax-highlight ruby" lang="ruby" v-pre="true"><code><span class="k">def</span> <span class="nf">fun</span> <span class="k">end</span></code></pre>')
     end
   end
 
   context "when an invalid language is specified" do
     it "highlights as plaintext" do
       result = filter('<pre><code class="gnuplot">This is a test</code></pre>')
-      expect(result.to_html).to eq('<pre class="code highlight js-syntax-highlight plaintext" v-pre="true"><code>This is a test</code></pre>')
+      expect(result.to_html).to eq('<pre class="code highlight js-syntax-highlight plaintext" lang="plaintext" v-pre="true"><code>This is a test</code></pre>')
     end
   end
 
@@ -31,7 +31,7 @@ describe Banzai::Filter::SyntaxHighlightFilter, lib: true do
 
     it "highlights as plaintext" do
       result = filter('<pre><code class="ruby">This is a test</code></pre>')
-      expect(result.to_html).to eq('<pre class="code highlight" v-pre="true"><code>This is a test</code></pre>')
+      expect(result.to_html).to eq('<pre class="code highlight" lang="" v-pre="true"><code>This is a test</code></pre>')
     end
   end
 end