Vim patch v8.2.0578 appears to add more strict HEREDOC syntax

[jsivak]

After building vim to include patch 8.2.0578 (https://github.com/vim/vim/releases/tag/v8.2.0578), black.vim now causes the following error to show at vim startup:

line   43:
E221: Marker cannot start with lower case letter
  File "<string>", line 1
    << endpython3
    ^
SyntaxError: invalid syntax
line   44:
E1042: import/export can only be used in vim9script
line   45:
E1042: import/export can only be used in vim9script
line   46:
E1042: import/export can only be used in vim9script
line   48:
E1077: Missing argument type for exec_prefix
line   49:
E488: Trailing characters:   try:
line   50:
E492: Not an editor command:     default = vim.eval("g:pymode_python").strip()
line   51:
E492: Not an editor command:   except vim.error:
line   52:
E492: Not an editor command:     default = ""
line   53:
E121: Undefined variable: default
line   54:
E133: :return not inside a function
line   56:
E133: :return not inside a function
line   57:
E133: :return not inside a function
line   59:
E1077: Missing argument type for venv_path
line   61:
E133: :return not inside a function
line   62:
E133: :return not inside a function
line   64:
E1077: Missing argument type for venv_path
line   66:
E133: :return not inside a function
line   67:
E133: :return not inside a function
line   69:
E1056: expected a type: [NULL]
line  152:
E1057: Missing :enddef
line  153:
E171: Missing :endif
Press ENTER or type command to continue

I'm not 100% sure of the vim changes, but if the "endpython3" HEREDOC tag in black.vim is changed to Endpython3 (note the uppercase first letter), then black.vim is processed without error in vim.

[jsivak]

This may help explain the original change to the HEREDOC "label/tag" handling: vim/vim#4705

[char101]

I can confirm this. This change is sufficient to fix it.

diff --git a/plugin/black.vim b/plugin/black.vim
index 8106ea1..066f3fd 100644
--- a/plugin/black.vim
+++ b/plugin/black.vim
@@ -45,7 +45,7 @@ if !exists("g:black_skip_string_normalization")
   let g:black_skip_string_normalization = 0
 endif

-python3 << endpython3
+python3 << Endpython3
 import collections
 import os
 import sys
@@ -191,7 +191,7 @@ def BlackUpgrade():
 def BlackVersion():
   print(f'Black, version {black.__version__} on Python {sys.version}.')

-endpython3
+Endpython3

 command! Black :py3 Black()
 command! BlackUpgrade :py3 BlackUpgrade()

[JelleZijlstra]

Thanks for the diagnosis! Please submit a PR with this change.

[char101]

PR created #1348