FIX: inline [code] not handled properly

The text

a
[code]test[/code]

Would eat up the `test` text cause translation from inline to block
for replace rule was not properly handled

app/assets/javascripts/pretty-text/engines/discourse-markdown/bbcode-block.js.es6

@@ -242,7 +242,14 @@ function applyBBCode(state, startLine, endLine, silent, md) {
   state.lineMax = nextLine;
 
   if (rule.replace) {
-    let content = state.src.slice(state.bMarks[startLine+1], state.eMarks[nextLine-1]);
+    let content;
+
+    if (startLine === nextLine) {
+      content = state.src.slice(start + info.length, closeTag.start);
+    } else {
+      content = state.src.slice(state.bMarks[startLine+1], state.eMarks[nextLine-1]);
+    }
+
     if (!rule.replace.call(this, state, info, content)) {
       return false;
     }

spec/components/pretty_text_spec.rb

@@ -980,6 +980,14 @@ HTML
     expect(PrettyText.cook("a[i]b[/i]c")).to eq('<p>a<span class="bbcode-i">b</span>c</p>')
   end
 
+  it "can handle bbcode after a newline" do
+    # this is not 100% ideal cause we get an extra p here, but this is pretty rare
+    expect(PrettyText.cook("a\n[code]code[/code]")).to eq("<p>a</p>\n<pre><code class=\"lang-auto\">code</code></pre>")
+
+    # this is fine
+    expect(PrettyText.cook("a\na[code]code[/code]")).to eq("<p>a<br>\na<code>code</code></p>")
+  end
+
   it "can onebox local topics" do
     op = Fabricate(:post)
     reply = Fabricate(:post, topic_id: op.topic_id)