fix: defer single-element maps checking

encoder/compiler.go

@@ -529,7 +529,7 @@ func (self *_Compiler) compileMapBody(p *_Program, sp int, vt reflect.Type) {
     p.pin(v)
     p.int(_OP_byte, ':')
     p.add(_OP_map_value_next)
-    self.compileOne(p, sp + 1, vt.Elem(), false)
+    self.compileOne(p, sp + 2, vt.Elem(), false)
     p.int(_OP_goto, j)
     p.pin(i)
     p.pin(j)

encoder/mapiter.go

@@ -158,9 +158,8 @@ func iteratorStart(t *rt.GoMapType, m *rt.GoMap, fv uint64) (*_MapIterator, erro
     it := newIterator()
     mapiterinit(t, m, &it.it)
 
-    /* check for key-sorting
-     * empty map or map with only 1 item don't need sorting */
-    if m.Count <= 1 || (fv & uint64(SortMapKeys)) == 0 {
+    /* check for key-sorting, empty map don't need sorting */
+    if m.Count == 0 || (fv & uint64(SortMapKeys)) == 0 {
         it.ki = -1
         return it, nil
     }
@@ -178,9 +177,10 @@ func iteratorStart(t *rt.GoMapType, m *rt.GoMap, fv uint64) (*_MapIterator, erro
         }
     }
 
-    /* sort the keys */
-    it.ki = 1
-    radixQsort(it.data(), 0, maxDepth(it.kv.Len))
+    /* sort the keys, map with only 1 item don't need sorting */
+    if it.ki = 1; m.Count > 1 {
+        radixQsort(it.data(), 0, maxDepth(it.kv.Len))
+    }
 
     /* load the first pair into iterator */
     it.it.V = it.at(0).v

issue98_test.go

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2021 ByteDance Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sonic
+
+import (
+    `testing`
+
+    `github.com/bytedance/sonic/encoder`
+    `github.com/stretchr/testify/require`
+)
+
+func TestIssue98_SingleElementMapWithKeySorting(t *testing.T) {
+    v, err := encoder.Encode(map[int64]bool{1234: true}, encoder.SortMapKeys)
+    require.NoError(t, err)
+    require.Equal(t, `{"1234":true}`, string(v))
+}