patch 8.2.2529: Vim9: Not possible to use legacy and Vim9 script in one file

Problem:    Vim9: Not possible to use legacy and Vim9 script in one file.
Solution:   Vim9: allow for "if false" before :vim9script. (closes #7851)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 77a7a71..371f3d6 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2595,8 +2595,12 @@
 
 #ifdef FEAT_EVAL
     // Set flag that any command was executed, used by ex_vim9script().
+    // Not if this was a command that wasn't executed or :endif.
     if (getline_equal(ea.getline, ea.cookie, getsourceline)
-						    && current_sctx.sc_sid > 0)
+	    && current_sctx.sc_sid > 0
+	    && ea.cmdidx != CMD_endif
+	    && (cstack->cs_idx < 0
+		    || (cstack->cs_flags[cstack->cs_idx] & CSF_ACTIVE)))
 	SCRIPT_ITEM(current_sctx.sc_sid)->sn_state = SN_STATE_HAD_COMMAND;
 
     /*
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 922080d..f444bb5 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -1262,6 +1262,27 @@
   nunmap <F3>
 enddef
 
+def Test_vim9script_mix()
+  var lines =<< trim END
+    if has(g:feature)
+      " legacy script
+      let g:legacy = 1
+      finish
+    endif
+    vim9script
+    g:legacy = 0
+  END
+  g:feature = 'eval'
+  g:legacy = -1
+  CheckScriptSuccess(lines)
+  assert_equal(1, g:legacy)
+
+  g:feature = 'noteval'
+  g:legacy = -1
+  CheckScriptSuccess(lines)
+  assert_equal(0, g:legacy)
+enddef
+
 def Test_vim9script_fails()
   CheckScriptFailure(['scriptversion 2', 'vim9script'], 'E1039:')
   CheckScriptFailure(['vim9script', 'scriptversion 2'], 'E1040:')
diff --git a/src/version.c b/src/version.c
index 4c0fb5c..68b5ab4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2529,
+/**/
     2528,
 /**/
     2527,