cgen: add `gen_map_equality_fn` to compare maps (#5770)

vlib/v/gen/cgen.v

@@ -79,6 +79,7 @@ mut:
 	str_types            []string // types that need automatic str() generation
 	threaded_fns         []string // for generating unique wrapper types and fns for `go xxx()`
 	array_fn_definitions []string // array equality functions that have been defined
+	map_fn_definitions   []string // map equality functions that have been defined
 	is_json_fn           bool // inside json.encode()
 	json_types           []string // to avoid json gen duplicates
 	pcs                  []ProfileCounterMeta // -prof profile counter fn_names => fn counter name
@@ -1955,7 +1956,24 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 		} else if node.op == .ne {
 			g.write('!${ptr_typ}_arr_eq(')
 		}
-	    if node.left_type.is_ptr() {
+		if node.left_type.is_ptr() {
+			g.write('*')
+		}
+		g.expr(node.left)
+		g.write(', ')
+		if node.right_type.is_ptr() {
+			g.write('*')
+		}
+		g.expr(node.right)
+		g.write(')')
+	} else if node.op in [.eq, .ne] && left_sym.kind == .map && right_sym.kind == .map {
+		ptr_typ := g.gen_map_equality_fn(left_type)
+		if node.op == .eq {
+			g.write('${ptr_typ}_map_eq(')
+		} else if node.op == .ne {
+			g.write('!${ptr_typ}_map_eq(')
+		}
+		if node.left_type.is_ptr() {
 			g.write('*')
 		}
 		g.expr(node.left)
@@ -3029,6 +3047,41 @@ fn (mut g Gen) gen_array_equality_fn(left table.Type) string {
 	return ptr_typ
 }
 
+fn (mut g Gen) gen_map_equality_fn(left table.Type) string {
+	left_sym := g.table.get_type_symbol(left)
+	typ_name := g.typ(left)
+	ptr_typ := typ_name[typ_name.index_after('_', 0) + 1..].trim('*')
+	value_sym := g.table.get_type_symbol(left_sym.map_info().value_type)
+	value_typ := g.typ(left_sym.map_info().value_type)
+	if value_sym.kind == .map {
+		// Recursively generate map element comparison function code if array element is map type
+		g.gen_map_equality_fn(left_sym.map_info().value_type)
+	}
+	if ptr_typ in g.map_fn_definitions {
+		return ptr_typ
+	}
+	g.map_fn_definitions << ptr_typ
+	g.definitions.writeln('bool ${ptr_typ}_map_eq(map_$ptr_typ a, map_$ptr_typ b) {')
+	g.definitions.writeln('\tif (a.len != b.len) {')
+	g.definitions.writeln('\t\treturn false;')
+	g.definitions.writeln('\t}')
+	g.definitions.writeln('\tarray_string _keys = map_keys(&a);')
+	g.definitions.writeln('\tfor (int i = 0; i < _keys.len; ++i) {')
+	g.definitions.writeln('\t\tstring k = string_clone( ((string*)_keys.data)[i]);')
+	g.definitions.writeln('\t\t$value_typ v = (*($value_typ*)map_get(a, k, &($value_typ[]){ 0 }));')
+	if value_sym.kind == .string {
+		g.definitions.writeln('\t\tif (!map_exists(b, k) || string_ne((*($value_typ*)map_get(b, k, &($value_typ[]){tos_lit("")})), v)) {')
+	} else {
+		g.definitions.writeln('\t\tif (!map_exists(b, k) || (*($value_typ*)map_get(b, k, &($value_typ[]){ 0 })) != v) {')
+	}
+	g.definitions.writeln('\t\t\treturn false;')
+	g.definitions.writeln('\t\t}')
+	g.definitions.writeln('\t}')
+	g.definitions.writeln('\treturn true;')
+	g.definitions.writeln('}')
+	return ptr_typ
+}
+
 fn verror(s string) {
 	util.verror('cgen error', s)
 }

vlib/v/tests/map_equality_test.v

@@ -0,0 +1,18 @@
+fn test_map_equality() {
+	a1 := {'a':1, 'b':2}
+	b1 := {'b':2, 'a':1}
+	c1 := {'a':2, 'b':1}
+
+	assert a1 == b1
+	assert a1 != c1
+
+	a2 := {'a':1}
+	b2 := {'a':1, 'b':2}
+
+	assert a2 != b2
+
+	a3 := {'a':'1', 'b':'2'}
+	b3 := {'b':'2', 'a':'1'}
+
+	assert a3 == b3
+}