fix: set prev token in render_list_item and add block_text to ignore_blocks (#456)

* fix: set prev token in render_list_item and add block_text to ignore_blocks

The RSTRenderer.block_quote method accesses token.prev to decide
whether to emit a .. separator before the blockquote.  When a
blockquote appears inside a list item, render_list_item called
renderer.render_token directly without tracking prev, so
blockquote tokens never received a prev reference.  This caused a
KeyError in older versions and silently degraded output in the
current version (missing or incorrect .. separators).

- Track prev in render_list_item, mirroring how RSTRenderer.iter_tokens
  already does for top-level tokens.
- Add block_text (the list-internal paragraph token type) to the
  ignore_blocks tuple so a blockquote following list-internal text
  does not get a spurious .. separator.

* Test RST list item blockquote separation

Author: gaoflow

src/mistune/renderers/_list.py

@@ -34,11 +34,14 @@ def render_list_item(
 
     leading = cast(str, parent["leading"]) + marker
     text = ""
+    prev = None
     for tok in item["children"]:
         if tok["type"] == "list":
             tok["parent"] = parent
         elif tok["type"] == "blank_line":
             continue
+        tok["prev"] = prev
+        prev = tok
         text += renderer.render_token(tok, state)
 
     lines = text.splitlines()

src/mistune/renderers/rst.py

@@ -130,6 +130,7 @@ def block_quote(self, token: Dict[str, Any], state: BlockState) -> str:
         prev = token.get("prev")
         ignore_blocks = (
             "paragraph",
+            "block_text",
             "thematic_break",
             "linebreak",
             "heading",

tests/fixtures/renderer_rst.txt

@@ -256,3 +256,19 @@ hello
 - item
      quote
 ````````````````````````````````
+
+```````````````````````````````` example
+- item
+
+  > first
+
+  > second
+.
+- item
+
+     first
+
+  ..
+
+     second
+````````````````````````````````