runtime(java): Optionally recognise _module_ import declarations

Define "g:java_syntax_previews" and include number 476 in
its list to enable this recognition:
------------------------------------------------------------
        let g:java_syntax_previews = [476]
------------------------------------------------------------

Reference:
https://openjdk.org/jeps/476

closes: #15709

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/syntax.txt

@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2024 Sep 18
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Sep 19
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2176,11 +2176,12 @@ cycles for such a feature to become either integrated into the platform or
 withdrawn from this effort.  To cater for early adopters, there is optional
 support in Vim for syntax related preview features that are implemented.  You
 can request it by specifying a list of preview feature numbers as follows: >
-	:let g:java_syntax_previews = [455]
+	:let g:java_syntax_previews = [455, 476]
 
 The supported JEP numbers are to be drawn from this table:
 	`430`: String Templates [JDK 21]
 	`455`: Primitive types in Patterns, instanceof, and switch
+	`476`: Module Import Declarations
 
 Note that as soon as the particular preview feature will have been integrated
 into the Java platform, its entry will be removed from the table and related

runtime/syntax/java.vim

@@ -3,7 +3,7 @@
 " 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 18
+" Last Change:		2024 Sep 19
 
 " Please check :help java.vim for comments on some of the options available.
 
@@ -92,6 +92,13 @@ syn keyword javaTypedef		this super
 syn keyword javaOperator	new instanceof
 syn match   javaOperator	"\<var\>\%(\s*(\)\@!"
 
+if s:ff.IsRequestedPreviewFeature(476)
+  " Module imports can be used in any source file.
+  syn match   javaExternal	"\<import\s\+module\>" contains=javaModuleImport
+  syn keyword javaModuleImport	contained module
+  hi def link javaModuleImport	Statement
+endif
+
 " Since the yield statement, which could take a parenthesised operand,
 " and _qualified_ yield methods get along within the switch block
 " (JLS-17, §3.8), it seems futile to make a region definition for this

runtime/syntax/testdir/dumps/java_module_info_00.dump

@@ -1,6 +1,6 @@
 >/+0#0000e05#ffffff0@1| |T|h|i|s| |m|o|d|u|l|e| |d|e|c|l|a|r|a|t|i|o|n| |b|e|l|o|n|g|s| |t|o| |t|h|e| |s|a|m|p|l|e| |p|r|o|j|e|c|t| |p|u|b|l|i|s|h|e|d| |a|t| +0#0000000&@5
 |/+0#0000e05&@1| |h|t@1|p|s|:|/@1|g|i|t|h|u|b|.|c|o|m|/|z@2|y|x|w|v|u|t|/|m|o|d|u|l|e|-|i|n|f|o|.|g|i|t| |.| +0#0000000&@25
-@75
+|i+0#e000e06&|m|p|o|r|t| |m+0#af5f00255&|o|d|u|l|e| +0#0000000&|j|a|v|a|.|b|a|s|e|;| @50
 |i+0#e000e06&|m|p|o|r|t| +0#0000000&|j|a|v|a|.|u|t|i|l|.|S|e|r|v|i|c|e|L|o|a|d|e|r|;| @43
 @75
 |/+0#0000e05&|*@1| +0#0000000&@71
@@ -12,7 +12,7 @@
 | +0#0000e05&|*| |@+0#e000e06&|p|r|o|v|i|d|e|s| |o+0#00e0e07&|r|g|.|d|e|m|o|.|i|n|t|e|r|n|a|l|.|T|e|s|t|a|b|l|e| +0#0000000&@35
 | +0#0000e05&|*| |@+0#e000e06&|s|e@1| +0#0000e05&|S+0#00e0e07&|e|r|v|i|c|e|L|o|a|d|e|r| +0#0000000&@53
 | +0#0000e05&|*|/| +0#0000000&@71
-|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| @47
+|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| |/+0#0000e05&@1| |J|D|K| |2|3|+| |(|-@1|e|n|a|b|l|e|-|p|r|e|v|i|e|w| |-@1|r|e|l|e|a|s|e| |2|3|)|.| +0#0000000&@3
 |{| @73
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|s+0#00e0003&|t|a|t|i|c| +0#0000000&|j|d|k|.|j|f|r|;| @46
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|j|a|v|a|.|b|a|s|e|;| @51

runtime/syntax/testdir/dumps/java_module_info_01.dump

@@ -1,5 +1,5 @@
 | +0#0000e05#ffffff0|*|/| +0#0000000&@71
-|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| @47
+|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| |/+0#0000e05&@1| |J|D|K| |2|3|+| |(|-@1|e|n|a|b|l|e|-|p|r|e|v|i|e|w| |-@1|r|e|l|e|a|s|e| |2|3|)|.| +0#0000000&@3
 |{| @73
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|s+0#00e0003&|t|a|t|i|c| +0#0000000&|j|d|k|.|j|f|r|;| @46
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|j|a|v|a|.|b|a|s|e|;| @51

runtime/syntax/testdir/input/java_module_info.java

@@ -1,6 +1,6 @@
 // This module declaration belongs to the sample project published at
 // https://github.com/zzzyxwvut/module-info.git .
-
+import module java.base;
 import java.util.ServiceLoader;
 
 /**
@@ -12,7 +12,7 @@ import java.util.ServiceLoader;
  * @provides org.demo.internal.Testable
  * @see ServiceLoader
  */
-module org.module.info.demo
+module org.module.info.demo	// JDK 23+ (--enable-preview --release 23).
 {
 	requires static jdk.jfr;
 	requires java.base;

runtime/syntax/testdir/input/setup/java_module_info.vim

@@ -28,3 +28,5 @@ autocmd_add([{
     cmd:	'RestoreFilename()',
     once:	true,
 }])
+
+g:java_syntax_previews = [476]