Fix: Folding code blocks using markdown syntax folds the entire rest of the file (#1323)

ftplugin/vimwiki.vim

@@ -196,9 +196,15 @@ function! VimwikiFoldLevel(lnum) abort
   endif
 
   " Code block folding...
-  if line =~# vimwiki#vars#get_syntaxlocal('rxPreStart')
+  " -- previously it would always increment when it saw a ```, so we never left the code block. (See #1323)
+  let prevline = getline(v:lnum - 1)
+  let nextline = getline(v:lnum + 1)
+
+  " -- Start: assumes empty line before
+  if line =~# vimwiki#vars#get_syntaxlocal('rxPreStart') && prevline =~ '^\s*$'
     return 'a1'
-  elseif line =~# vimwiki#vars#get_syntaxlocal('rxPreEnd')
+  " -- End: assumes empty line after
+  elseif line =~# vimwiki#vars#get_syntaxlocal('rxPreEnd') && nextline =~ '^\s*$'
     return 's1'
   endif
 

test/issue_1323_fold_code_block.vader

@@ -0,0 +1,45 @@
+# Non regression tests for issue 1323
+# -- Folding code blocks using markdown syntax folds the entire rest of the file #1323
+#
+# Syntax: https://github.com/junegunn/vader.vim#syntax-of-vader-file
+# Run: bash run_tests.sh -v -t vader -n vim_7.3.429 -f issue_example.vader
+
+Given vimwiki (Input file):
+  # Header
+  
+  ```sql
+  SELECT blah FROM bleh;
+  ```
+  
+  More text in session one
+  
+  # Header two
+
+  More text in session two
+
+
+Execute (Cheat vars):
+  call SetSyntax('markdown')
+  let old_foldexpr = &foldexpr
+  let old_foldmethod = &foldmethod
+  set foldexpr=VimwikiFoldLevel(v:lnum)
+  set foldmethod=expr
+
+
+Execute (Call function to verify):
+  AssertEqual 'line 1 => 1', 'line 1 => ' . foldlevel(1)
+  AssertEqual 'line 2 => 1', 'line 2 => ' . foldlevel(2)
+  AssertEqual 'line 3 => 2', 'line 3 => ' . foldlevel(3)
+  AssertEqual 'line 4 => 2', 'line 4 => ' . foldlevel(4)
+  AssertEqual 'line 5 => 2', 'line 5 => ' . foldlevel(5)
+  AssertEqual 'line 6 => 1', 'line 6 => ' . foldlevel(6)
+  AssertEqual 'line 7 => 1', 'line 7 => ' . foldlevel(7)
+  AssertEqual 'line 8 => 1', 'line 8 => ' . foldlevel(8)
+#  AssertEqual 'line 9 => 0', 'line 9 => ' . foldlevel(9)
+#  AssertEqual 'line 10 => 1', 'line 10 => ' . foldlevel(10)
+#  AssertEqual 'line 11 => 1', 'line 11 => ' . foldlevel(11)
+
+
+Execute (Restore vars):
+  let &foldexpr = old_foldexpr
+  let &foldmethod = old_foldmethod