jsgen: optional "or blocks" (#6938)

vlib/builtin/js/builtin.js.v

@@ -0,0 +1,6 @@
+module builtin
+
+// used to generate JS throw statements.
+pub fn js_throw(s any) {
+	#throw (s instanceof Error ? s : new Error(s))
+}

vlib/builtin/js/builtin.v

@@ -35,13 +35,13 @@ pub fn eprint(s any) {
 // a 'real' way to exit in the browser.
 pub fn exit(c int) {
 	JS.process.exit(c)
+	js_throw('exit($c)')
 }
 
 pub fn unwrap(opt any) any {
 	o := &Option(opt)
 	if o.not_ok {
-		panic(o.error)
+		js_throw(o.error)
-		return o.error
 	}
 	return opt
 }

vlib/v/gen/js/js.v

@@ -15,7 +15,7 @@ const (
 		'public', 'return', 'static', 'super', 'switch', 'this', 'throw', 'try', 'typeof', 'var', 'void',
 		'while', 'with', 'yield']
 	tabs        = ['', '\t', '\t\t', '\t\t\t', '\t\t\t\t', '\t\t\t\t\t', '\t\t\t\t\t\t', '\t\t\t\t\t\t\t',
-		'\t\t\t\t\t\t\t\t',
+		'\t\t\t\t\t\t\t\t', '\t\t\t\t\t\t\t\t\t', '\t\t\t\t\t\t\t\t\t', '\t\t\t\t\t\t\t\t\t'
 	]
 )
 
@@ -1011,6 +1011,10 @@ fn (mut g JsGen) gen_go_stmt(node ast.GoStmt) {
 				receiver_sym := g.table.get_type_symbol(node.call_expr.receiver_type)
 				name = receiver_sym.name + '.' + name
 			}
+			// todo: please add a name feild without the mod name for ast.CallExpr
+			if name.starts_with('$node.call_expr.mod\.') {
+				name = name[node.call_expr.mod.len+1..]
+			}
 			g.writeln('await new Promise(function(resolve){')
 			g.inc_indent()
 			g.write('${name}(')
@@ -1048,7 +1052,7 @@ fn (mut g JsGen) gen_interface_decl(it ast.InterfaceDecl) {
 fn (mut g JsGen) gen_return_stmt(it ast.Return) {
 	if it.exprs.len == 0 {
 		// Returns nothing
-		g.write('return;')
+		g.writeln('return;')
 		return
 	}
 	g.write('return ')
@@ -1173,7 +1177,11 @@ fn (mut g JsGen) gen_call_expr(it ast.CallExpr) {
 	}
 	call_return_is_optional := it.return_type.has_flag(.optional)
 	if call_return_is_optional {
-		g.write('builtin.unwrap(')
+		g.writeln('(function(){')
+		g.inc_indent()
+		g.writeln('try {')
+		g.inc_indent()
+		g.write('return builtin.unwrap(')
 	}
 	g.expr(it.left)
 	if it.is_method { // foo.bar.baz()
@@ -1224,10 +1232,40 @@ fn (mut g JsGen) gen_call_expr(it ast.CallExpr) {
 			g.write(', ')
 		}
 	}
-	if call_return_is_optional {
+	// end method call
-		g.write('))')
-	} else {
 	g.write(')')
+	if call_return_is_optional {
+		// end unwrap
+		g.writeln(')')
+		g.dec_indent()
+		// begin catch block
+		g.writeln('} catch(err) {')
+		g.inc_indent()
+		// gen or block contents
+		match it.or_block.kind {
+			.block {
+				if it.or_block.stmts.len > 1 {
+					g.stmts(it.or_block.stmts[..it.or_block.stmts.len-1])
+				}
+				g.write('return ')
+				g.stmt(it.or_block.stmts.last())
+			}
+			.propagate {
+				panicstr := '`optional not set (\${err})`'
+				if g.file.mod.name == 'main' && g.fn_decl.name == 'main.main' {
+					g.writeln('return builtin.panic($panicstr)')
+				} else {
+					g.writeln('builtin.js_throw(err)')
+				}
+			}
+			else {}
+		}
+		// end catch
+		g.dec_indent()
+		g.writeln('}')
+		// end anon fn
+		g.dec_indent()
+		g.write('})()')
 	}
 }
 

vlib/v/gen/js/tests/js.v

@@ -59,8 +59,12 @@ fn main() {
 	}
 	for i, x in 'hello' {
 	}
+	mut evens := []int{}
 	for x in 1 .. 10 {
+		y := error_if_even(x) or { x + 1 }
+		evens << y
 	}
+	println(evens)
 	arr := [1, 2, 3, 4, 5]
 	for i in arr {
 	}
@@ -81,6 +85,7 @@ fn main() {
 		println(message)
 	})
 	hl.raw_js_log()
+	propagation() or { println(err) }
 }
 
 fn anon_consumer(greeting string, anon fn (message string)) {
@@ -120,3 +125,13 @@ fn (it Companies) method() int {
 	}
 	return 0
 }
+
+fn error_if_even(num int) ?int {
+	if num % 2 == 0 { return error('number is even') }
+	return num
+}
+
+fn propagation() ? {
+	println('Propagation test:')
+	return error('"Task failed successfully" - Windows XP')
+}

vlib/v/gen/js/tests/optional.v

@@ -0,0 +1,31 @@
+module main
+
+fn main() {
+	try_propagation() or { println("captured: $err") }
+}
+
+fn try_propagation() ? {
+	try_numbers()?
+}
+
+fn try_numbers() ? {
+	for x in 1 .. 10 {
+		y := error_if_even(x) or { x + 1 }
+		println("$x rounded to $y")
+		error_if_prime(y)?
+	}
+}
+
+fn error_if_even(num int) ?int {
+	if num % 2 == 0 { return error('number is even') }
+	return num
+}
+
+fn error_if_prime(num int) ?int {
+	for i in 2..num {
+		if num % i == 0 {
+			return error('$num is prime')
+		}
+	}
+	return num
+}