[primer] Add blank line after <details> tag for proper markdown rendering (#10948)

GitHub markdown requires a blank line after <details> for the content
inside to be rendered as markdown rather than plain text.

Author: Pierre-Sassoulas

pylint/testutils/_primer/primer_compare_command.py

@@ -73,15 +73,15 @@ def _create_comment_for_package(
             )
         if new_non_astroid_messages:
             comment += (
-                "The following messages are now emitted:\n\n<details>\n"
+                "The following messages are now emitted:\n\n<details>\n\n"
                 + new_non_astroid_messages
                 + "</details>\n\n"
             )
 
         # Create comment for missing messages
         count = 1
         if missing_messages["messages"]:
-            comment += "The following messages are no longer emitted:\n\n<details>\n"
+            comment += "The following messages are no longer emitted:\n\n<details>\n\n"
             print("No longer emitted:")
         for message in missing_messages["messages"]:
             comment += f"{count}) {message['symbol']}:\n*{message['message']}*\n"
@@ -122,7 +122,12 @@ def _truncate_comment(self, comment: str) -> str:
                 - len(suffix)
                 - len(closing_tag)
             )
-            comment = comment[: max_len - 10] + "...\n"
+            # Cut at the last space before the limit to avoid mid-word truncation.
+            cut_point = comment.rfind(" ", 0, max_len - 10)
+            if cut_point > 0:
+                comment = comment[:cut_point] + "...\n"
+            else:
+                comment = comment[: max_len - 10] + "...\n"
             # Close any <details> tag left open by the truncation.
             if comment.count("<details>") > comment.count("</details>"):
                 comment += closing_tag

tests/testutils/_primer/batched_cases/expected.txt

@@ -6,6 +6,7 @@
 The following messages are no longer emitted:
 
 <details>
+
 1) locally-disabled:
 *Locally disabling redefined-builtin (W0622)*
 https://github.com/pylint-dev/astroid/blob/1234567890abcdef/astroid/__init__.py#L91

tests/testutils/_primer/cases/line_moved/expected.txt

@@ -6,6 +6,7 @@
 The following messages are now emitted:
 
 <details>
+
 1) too-complex:
 *'my_function' is too complex. The McCabe rating is 18*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.py#L103
@@ -14,6 +15,7 @@ https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.
 The following messages are no longer emitted:
 
 <details>
+
 1) too-complex:
 *'my_function' is too complex. The McCabe rating is 18*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.py#L100

tests/testutils/_primer/cases/message_changed/expected.txt

@@ -6,6 +6,7 @@
 The following messages are now emitted:
 
 <details>
+
 1) locally-disabled:
 *Locally disabling redefined-builtin [we added some text in the message] (W0622)*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91
@@ -14,6 +15,7 @@ https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L
 The following messages are no longer emitted:
 
 <details>
+
 1) locally-disabled:
 *Locally disabling redefined-builtin (W0622)*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91

tests/testutils/_primer/cases/message_changed/expected_truncated.txt

@@ -6,11 +6,10 @@
 The following messages are now emitted:
 
 <details>
+
 1) locally-disabled:
-*Locally disabling redefined-builtin [we added some text in the message] (W0622)*
-https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91
+*Locally disabling redefined-builtin [we added some text in the message]...
 </details>
-...
 
 *This comment was truncated because GitHub allows only 525 characters in a comment.*
 

tests/testutils/_primer/cases/message_changed/expected_truncated_in_details.txt

@@ -6,8 +6,9 @@
 The following messages are now emitted:
 
 <details>
+
 1) locally-disabled:
-*Locally disabling redefined-builtin [we added some text in the message...
+*Locally disabling redefined-builtin [we added some text in the...
 </details>
 
 *This comment was truncated because GitHub allows only 420 characters in a comment.*

tests/testutils/_primer/cases/message_changed_line/expected.txt

@@ -6,6 +6,7 @@
 The following messages are now emitted:
 
 <details>
+
 1) too-complex:
 *'my_function' is too complex. The McCabe rating is 17*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.py#L103
@@ -14,6 +15,7 @@ https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.
 The following messages are no longer emitted:
 
 <details>
+
 1) too-complex:
 *'my_function' is too complex. The McCabe rating is 18*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.py#L100

tests/testutils/_primer/cases/mixed_changes/expected.txt

@@ -6,6 +6,7 @@
 The following messages are now emitted:
 
 <details>
+
 1) locally-disabled:
 *Locally disabling redefined-builtin [we added some text in the message] (W0622)*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91
@@ -17,6 +18,7 @@ https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/node_classes.
 The following messages are no longer emitted:
 
 <details>
+
 1) locally-disabled:
 *Locally disabling redefined-builtin (W0622)*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91

tests/testutils/_primer/cases/new_message/expected.txt

@@ -6,6 +6,7 @@
 The following messages are now emitted:
 
 <details>
+
 1) locally-disabled:
 *Locally disabling redefined-builtin [we added some text in the message] (W0622)*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91

tests/testutils/_primer/cases/removed_message/expected.txt

@@ -6,6 +6,7 @@
 The following messages are no longer emitted:
 
 <details>
+
 1) unknown-option-value:
 *Unknown option value for 'disable', expected a valid pylint message and got 'Ellipsis'*
 https://github.com/pylint-dev/astroid/blob/123456789abcdef/astroid/__init__.py#L91