Fix diagnostic module (#12906)

Author: RblSb

src/context/display/displayFields.ml

@@ -447,7 +447,7 @@ let handle_missing_field_raise ctx tthis i mode with_type pfield =
 		mf_cause = FieldAccess;
 	} in
 	let cm = DiagnosticsPrinter.make_missing_fields_message diag in
-	CompilerMessage.add_module_diagnostic ctx.com (t_infos mt).mt_module cm
+	CompilerMessage.add_module_diagnostic ctx.com ctx.m.curmod cm
 
 let handle_missing_ident ctx i mode with_type p =
 	match ctx.e.curfun with

tests/server/src/cases/issues/Issue12861.hx

@@ -0,0 +1,49 @@
+package cases.issues;
+
+import haxe.display.Diagnostic;
+
+// Regression test for https://github.com/HaxeFoundation/haxe/issues/12861
+// Stale diagnostics must be cleared after the underlying problem is fixed.
+class Issue12861 extends TestCase {
+	function test(_) {
+		// File with a type error: Int has no field charAt
+		final errContent = getTemplate("diagnostics/Issue12861.hx");
+		// Fixed version: use String instead of Int
+		final okContent = "class Issue12861 { static function main() { var v:String = ''; var _ = v.charAt(0); } }";
+
+		final args = ["--main", "Issue12861", "--interp", "--no-output"];
+
+		// --- First diagnostics run: file has the type error ---
+		vfs.putContent("Issue12861.hx", errContent);
+		final res1 = runHaxeJson(args, DisplayMethods.Diagnostics, {file: new FsPath("Issue12861.hx")});
+		Assert.equals(1, res1.length);
+		final diags1:Array<Diagnostic<Dynamic>> = cast res1[0].diagnostics;
+		// Exactly one MissingFields diagnostic expected (Int has no field charAt)
+		Assert.equals(1, diags1.length);
+		Assert.isTrue(diags1.exists(d -> d.kind == MissingFields));
+
+		// --- Second diagnostics run on the SAME erroneous file (after invalidation) ---
+		// Without the fix, add_module_diagnostic polluted Int's cached
+		// m_cache_bound_objects on the first run.  The second run would then
+		// replay that stale message AND add another one, producing 2 entries.
+		runHaxeJson([], ServerMethods.Invalidate, {file: new FsPath("Issue12861.hx")});
+		final res2 = runHaxeJson(args, DisplayMethods.Diagnostics, {file: new FsPath("Issue12861.hx")});
+		Assert.equals(1, res2.length);
+		final diags2:Array<Diagnostic<Dynamic>> = cast res2[0].diagnostics;
+		// Must still be exactly 1, not 2 or more (no stacking)
+		Assert.equals(1, diags2.length);
+		Assert.isTrue(diags2.exists(d -> d.kind == MissingFields));
+
+		// --- Third diagnostics run: fix the file ---
+		// The old error must not persist; the result must be clean.
+		vfs.putContent("Issue12861.hx", okContent);
+		runHaxeJson([], ServerMethods.Invalidate, {file: new FsPath("Issue12861.hx")});
+		final res3 = runHaxeJson(args, DisplayMethods.Diagnostics, {file: new FsPath("Issue12861.hx")});
+		// Without the fix, the stale DKMissingFields from Int's cache was
+		// replayed here, making res3 still show an error.
+		if (res3.length > 0) {
+			final diags3:Array<Diagnostic<Dynamic>> = cast res3[0].diagnostics;
+			Assert.isFalse(diags3.exists(d -> d.kind == MissingFields));
+		}
+	}
+}

tests/server/test/templates/diagnostics/Issue12861.hx

@@ -0,0 +1,6 @@
+class Issue12861 {
+	static function main() {
+		var v:Int = 0;
+		var _ = v.charAt(0); // Int has no field charAt
+	}
+}