Fix multi-line conditional parsing in HTML email template previews (#393)

* Fix multi-line conditional parsing bug

- Multi-line conditionals ending with a trailing line break will no
  longer insert a `</mark>` tag into the rendered template preview

* Micro-optimization

* Fix typo

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: whabanks

notifications_utils/field.py

@@ -70,6 +70,7 @@ class Field:
 
     placeholder_tag = "<mark class='placeholder'>(({}))</mark>"
     conditional_placeholder_tag = "<mark class='placeholder-conditional'><span class='condition'>(({}??</span>{}))</mark>"
+    conditional_placeholder_tag_block = "<div class='placeholder-conditional'><span class='condition'>(({}??</span>{}))</div>"
     placeholder_tag_translated = "<span class='placeholder-no-brackets'>[{}]</span>"
     placeholder_tag_redacted = "<mark class='placeholder-redacted'>[hidden]</mark>"
 
@@ -81,10 +82,12 @@ def __init__(
         markdown_lists: bool = False,
         redact_missing_personalisation: bool = False,
         translated: bool = False,
+        markdown_renderer: Optional[Callable] = None,
     ):
         self.content = content
         self.values = values
         self.markdown_lists = markdown_lists
+        self.markdown_renderer = markdown_renderer
         if translated:
             self.placeholder_tag = self.placeholder_tag_translated
 
@@ -128,9 +131,21 @@ def format_match(self, match):
             return self.placeholder_tag_redacted
 
         if placeholder.is_conditional():
-            return self.conditional_placeholder_tag.format(
-                self.sanitizer(placeholder.name), self.sanitizer(placeholder.conditional_text)
-            )
+            conditional_text = self.sanitizer(placeholder.conditional_text)
+            sanitized_name = self.sanitizer(placeholder.name)
+
+            if "\n" in conditional_text and self.markdown_renderer:
+                # Multi-line conditional: pre-render markdown so lists, links, etc.
+                # display correctly. Use a block-level <div> wrapper so the outer
+                # mistune pass treats it as an HTML block and won't break it apart.
+                stripped = conditional_text.strip()
+                rendered = self.markdown_renderer(stripped).strip() if stripped else ""
+                return self.conditional_placeholder_tag_block.format(sanitized_name, rendered) + "\n"
+            elif "\n" in conditional_text:
+                # Multi-line but no renderer available: convert newlines to <br>
+                conditional_text = conditional_text.strip("\n").replace("\n", "<br>")
+
+            return self.conditional_placeholder_tag.format(sanitized_name, conditional_text)
 
         return self.placeholder_tag.format(self.sanitizer(placeholder.name))
 

notifications_utils/template.py

@@ -819,6 +819,7 @@ def get_html_email_body(template_content, template_values, redact_missing_person
                 html=html,
                 markdown_lists=True,
                 redact_missing_personalisation=redact_missing_personalisation,
+                markdown_renderer=_render_conditional_email_markdown,
             )
         )
         .then(unlink_govuk_escaped)
@@ -834,6 +835,22 @@ def get_html_email_body(template_content, template_values, redact_missing_person
     )
 
 
+def _render_conditional_email_markdown(content):
+    """Render markdown for multiline conditional preview content.
+
+    Conditionals are pre-rendered, so we need to mirror the parsing pipeline in get_html_email_body
+    to ensure that language tags, RTL, lists, etc. that are inside conditionals are also pre-rendered
+    else the main markdown rendering pass in get_html_email_body breaks them apart and mangles formatting.
+    """
+    result = escape_lang_tags(content)
+    result = escape_rtl_tags(result)
+    result = notify_email_markdown(result)
+    result = remove_nested_list_padding(result)
+    result = add_language_divs(result)
+    result = add_rtl_divs(result)
+    return result
+
+
 def do_nice_typography(value):
     return (
         Take(value)

tests/test_template_types.py

@@ -20,6 +20,7 @@
     SMSPreviewTemplate,
     Template,
     WithSubjectTemplate,
+    _render_conditional_email_markdown,
 )
 
 
@@ -943,15 +944,29 @@ def test_subject_line_gets_replaced():
             {},
             [
                 mock.call("subject", {}, html="escape", redact_missing_personalisation=False),
-                mock.call("content", {}, html="escape", markdown_lists=True, redact_missing_personalisation=False),
+                mock.call(
+                    "content",
+                    {},
+                    html="escape",
+                    markdown_lists=True,
+                    redact_missing_personalisation=False,
+                    markdown_renderer=_render_conditional_email_markdown,
+                ),
                 mock.call("content", {}, html="escape", markdown_lists=True),
             ],
         ),
         (
             EmailPreviewTemplate,
             {},
             [
-                mock.call("content", {}, html="escape", markdown_lists=True, redact_missing_personalisation=False),
+                mock.call(
+                    "content",
+                    {},
+                    html="escape",
+                    markdown_lists=True,
+                    redact_missing_personalisation=False,
+                    markdown_renderer=_render_conditional_email_markdown,
+                ),
                 mock.call("subject", {}, html="escape", redact_missing_personalisation=False),
                 mock.call("((email address))", {}),
             ],
@@ -1035,7 +1050,14 @@ def test_subject_line_gets_replaced():
             EmailPreviewTemplate,
             {"redact_missing_personalisation": True},
             [
-                mock.call("content", {}, html="escape", markdown_lists=True, redact_missing_personalisation=True),
+                mock.call(
+                    "content",
+                    {},
+                    html="escape",
+                    markdown_lists=True,
+                    redact_missing_personalisation=True,
+                    markdown_renderer=_render_conditional_email_markdown,
+                ),
                 mock.call("subject", {}, html="escape", redact_missing_personalisation=True),
                 mock.call("((email address))", {}),
             ],