parser, fmt: parse methods on JS interfaces, write JS method bodies (#…

…21088)

vlib/v/fmt/fmt.v

@@ -1104,7 +1104,7 @@ fn (mut f Fmt) fn_body(node ast.FnDecl) {
 	defer {
 		f.fn_scope = prev_fn_scope
 	}
-	if node.language == .v {
+	if node.language == .v || (node.is_method && node.language == .js) {
 		if !node.no_body {
 			f.write(' {')
 			pre_comments := node.comments.filter(it.pos.pos < node.name_pos.pos)

vlib/v/fmt/tests/interface_js_interop_method_keep.vv

@@ -0,0 +1,11 @@
+pub interface JS.CanvasRenderingContext2D {
+	setLineDash(JS.Array)
+}
+
+pub fn (ctx JS.CanvasRenderingContext2D) set_line_dash(arr []f64) {
+	tmp := JS.Array.prototype.constructor()
+	for x in arr {
+		tmp.push(JS.Number(x))
+	}
+	ctx.setLineDash(tmp)
+}

vlib/v/parser/fn.v

@@ -577,7 +577,7 @@ run them via `v file.v` instead',
 	mut stmts := []ast.Stmt{}
 	body_start_pos := p.tok.pos()
 	if p.tok.kind == .lcbr {
-		if language != .v {
+		if language != .v && !(language == .js && type_sym.info is ast.Interface) {
 			p.error_with_pos('interop functions cannot have a body', body_start_pos)
 		}
 		p.inside_fn = true

vlib/v/parser/tests/interop_js_func_body_err.out

@@ -0,0 +1,3 @@
+vlib/v/parser/tests/interop_js_func_body_err.vv:1:43: error: interop functions cannot have a body
+    1 | fn JS.state_is_ready_on_leave(retval int) {}
+      |                                           ^

vlib/v/parser/tests/interop_js_func_body_err.vv

@@ -0,0 +1 @@
+fn JS.state_is_ready_on_leave(retval int) {}