vim-patch:60310a4: runtime(java): Manage circularity for every :syn-included syntax file

With "g:markdown_fenced_languages" defined and "java" added
to its list, a circular dependency between the Markdown and
Java syntax files will be made.  To break it, no Markdown
documentation comments will be recognised in fenced blocks
in Markdown files; in order to view Java source files,
"java" must be removed from "g:markdown_fenced_languages",
and this task can be automated as follows.

1) Add to "~/.after/ftplugin/java.vim":
------------------------------------------------------------
if exists("g:markdown_fenced_languages") &&
	\ !(exists("g:java_ignore_javadoc") ||
	\ exists("g:java_ignore_markdown"))
    let s:idx = index(g:markdown_fenced_languages, 'java')
    if s:idx > -1
	call remove(g:markdown_fenced_languages, s:idx)
    endif
    unlet s:idx
endif
------------------------------------------------------------

2) Optionally add to "~/.after/ftplugin/markdown.vim":
------------------------------------------------------------
if exists("g:markdown_fenced_languages") &&
	\ index(g:markdown_fenced_languages, 'java') < 0
    call add(g:markdown_fenced_languages, 'java')
endif
------------------------------------------------------------

(Make sure that the above snippets appear in the files under
the "ftplugin" NOT "syntax" directory.)

Finally, unless the new version of the syntax file is made
available from "$VIMRUNTIME" (and from "~/.vim/syntax" if
necessary), OTHER discoverable file versions will be used
whose behaviour may interfere with this fix.

related: vim/vim#15740
closes: vim/vim#15796

https://github.com/vim/vim/commit/60310a4b2630a4d3bb0b6da9bc03061ecfbac9ee

Co-authored-by: Aliaksei Budavei <0x000c70@gmail.com>

1 files changed, 38 insertions, 10 deletions

diff --git a/runtime/syntax/java.vim b/runtime/syntax/java.vim
index 737219afce..307fc26349 100644
--- a/runtime/syntax/java.vim
+++ b/runtime/syntax/java.vim
@@ -3,16 +3,32 @@
 " Maintainer:		Aliaksei Budavei <0x000c70 AT gmail DOT com>
 " Former Maintainer:	Claudio Fleiner <claudio@fleiner.com>
 " Repository:		https://github.com/zzzyxwvut/java-vim.git
-" Last Change:		2024 Sep 28
+" Last Change:		2024 Oct 03
 
-" Please check :help java.vim for comments on some of the options available.
+" Please check ":help java.vim" for comments on some of the options
+" available.
 
-" quit when a syntax file was already loaded
-if !exists("g:main_syntax")
-  if exists("b:current_syntax")
-    finish
+" Do not aggregate syntax items from circular inclusion.
+if exists("b:current_syntax")
+  finish
+endif
+
+if exists("g:main_syntax")
+  " Reject attendant circularity for every :syn-included syntax file,
+  " but ACCEPT FAILURE when "g:main_syntax" is set to "java".
+  if g:main_syntax == 'html'
+    if !exists("g:java_ignore_html")
+      let g:java_ignore_html = 1
+      let s:clear_java_ignore_html = 1
+    endif
+  elseif g:main_syntax == 'markdown'
+    if !exists("g:java_ignore_markdown")
+      let g:java_ignore_markdown = 1
+      let s:clear_java_ignore_markdown = 1
+    endif
   endif
-  " we define it here so that included files can test for it
+else
+  " Allow syntax files that include this file test for its inclusion.
   let g:main_syntax = 'java'
 endif
 
@@ -364,15 +380,17 @@ if !exists("g:java_ignore_javadoc") && (s:with_html || s:with_markdown) && g:mai
 
   " Include HTML syntax coloring for Javadoc comments.
   if s:with_html
-    syntax include @javaHtml syntax/html.vim
-    unlet b:current_syntax
+    try
+      syntax include @javaHtml syntax/html.vim
+    finally
+      unlet! b:current_syntax
+    endtry
   endif
 
   " Include Markdown syntax coloring (v7.2.437) for Javadoc comments.
   if s:with_markdown
     try
       syntax include @javaMarkdown syntax/markdown.vim
-      unlet b:current_syntax
       let s:ff.WithMarkdown = s:ff.LeftConstant
     catch /\<E48[45]:/
       call s:ReportOnce(v:exception)
@@ -383,6 +401,8 @@ if !exists("g:java_ignore_javadoc") && (s:with_html || s:with_markdown) && g:mai
       hi clear markdownCodeBlock
       hi clear markdownCodeDelimiter
       hi clear markdownLinkDelimiter
+    finally
+      unlet! b:current_syntax
     endtry
   endif
 
@@ -839,6 +859,14 @@ if g:main_syntax == 'java'
   unlet g:main_syntax
 endif
 
+if exists("s:clear_java_ignore_html")
+  unlet! s:clear_java_ignore_html g:java_ignore_html
+endif
+
+if exists("s:clear_java_ignore_markdown")
+  unlet! s:clear_java_ignore_markdown g:java_ignore_markdown
+endif
+
 let b:spell_options = "contained"
 let &cpo = s:cpo_save
 unlet s:cpo_save s:ff s:with_html s:with_markdown