bugfix: boxes/helper: Fix generation of correct quote fences.

This commit corrects generation of fences for quoted messages. The new
logic for generation of quote fence is borrowed from the webapp. Fences
are generated after searching for maximum length occurence of ` through
regex, and wrapping the quote block with the generated fence. This
allows for proper quoting of messages containing a code-block or another
quote inside them.

Tests added.

Math & spoiler cases, and test ids, added by neiljp.

Author: zee-bit

tests/helper/test_helper.py

@@ -3,7 +3,7 @@
 import zulipterminal.helper
 from zulipterminal.helper import (
     canonicalize_color, classify_unread_counts, display_error_if_present,
-    hash_util_decode, index_messages, notify, powerset,
+    get_unused_fence, hash_util_decode, index_messages, notify, powerset,
 )
 
 
@@ -314,3 +314,26 @@ def test_hash_util_decode(quoted_string, expected_unquoted_string):
     return_value = hash_util_decode(quoted_string)
 
     assert return_value == expected_unquoted_string
+
+
+@pytest.mark.parametrize('message_content, expected_fence', [
+    ('Hi `test_here`', '```'),
+    ('```quote\nZ(dot)T(dot)\n```\nempty body', '````'),
+    ('```python\ndef zulip():\n  pass\n```\ncode-block', '````'),
+    ('````\ndont_know_what_this_does\n````', '`````'),
+    ('````quote\n```\ndef zulip():\n  pass\n```\n````', '`````'),
+    ('```math\n\\int_a^b f(t)\\, dt = F(b) - F(a)\n```', '````'),
+    ('```spoiler Header Text\nSpoiler content\n```', '````'),
+], ids=[
+    "inline_code",
+    "block_quote",
+    "block_code_python",
+    "block_code",
+    "block_code_quoted",
+    "block_math",
+    "block_spoiler",
+])
+def test_get_unused_fence(message_content, expected_fence):
+    generated_fence = get_unused_fence(message_content)
+
+    assert generated_fence == expected_fence

zulipterminal/helper.py

@@ -5,7 +5,7 @@
 from collections import OrderedDict, defaultdict
 from functools import wraps
 from itertools import chain, combinations
-from re import ASCII, match
+from re import ASCII, MULTILINE, findall, match
 from threading import Thread
 from typing import (
     Any, Callable, DefaultDict, Dict, FrozenSet, Iterable, List, Set, Tuple,
@@ -655,3 +655,21 @@ def hash_util_decode(string: str) -> str:
     # Acknowledge custom string replacements in zulip/zulip's
     # zerver/lib/url_encoding.py before unquote.
     return unquote(string.replace('.', '%'))
+
+
+def get_unused_fence(content: str) -> str:
+    """
+    Generates fence for quoted-message based on regex pattern
+    of continuous back-ticks. Referred and translated from
+    zulip/static/shared/js/fenced_code.js.
+    """
+    fence_length_regex = '^ {0,3}(`{3,})'
+    max_length_fence = 3
+
+    matches = findall(fence_length_regex, content,
+                      flags=MULTILINE)
+    if len(matches) != 0:
+        max_length_fence = max(max_length_fence,
+                               len(max(matches, key=len)) + 1)
+
+    return '`' * max_length_fence

zulipterminal/ui_tools/boxes.py

@@ -23,8 +23,8 @@
     STREAM_TOPIC_SEPARATOR, TIME_MENTION_MARKER,
 )
 from zulipterminal.helper import (
-    Message, format_string, match_emoji, match_group, match_stream,
-    match_topics, match_user,
+    Message, format_string, get_unused_fence, match_emoji, match_group,
+    match_stream, match_topics, match_user,
 )
 from zulipterminal.ui_tools.buttons import EditModeButton
 from zulipterminal.ui_tools.tables import render_table
@@ -1225,8 +1225,16 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
             self.model.controller.view.middle_column.set_focus('footer')
         elif is_command_key('QUOTE_REPLY', key):
             self.keypress(size, 'enter')
-            quote = '```quote\n' + self.model.client.get_raw_message(
-                self.message['id'])['raw_content'] + '\n```\n'
+
+            # To correctly quote a message that contains quote/code-blocks,
+            # we need to fence quoted message containing ``` with ````,
+            # ```` with ````` and so on.
+            message_raw_content = self.model.client.get_raw_message(
+                self.message['id'])['raw_content']
+            fence = get_unused_fence(message_raw_content)
+
+            quote = '{0}quote\n{1}\n{0}\n'.format(fence, message_raw_content)
+
             self.model.controller.view.write_box.msg_write_box.set_edit_text(
                 quote)
             self.model.controller.view.write_box.msg_write_box.set_edit_pos(