fix: edit table value using value mut object instead of insert

src/ops/set.rs

@@ -52,17 +52,23 @@ pub fn set_value(
     }
 }
 
+// insert will overwrite the decoration of the original key
+// When the table is empty, only write the default decoration
+// When the table has values, we need to read the existing decoration and apply it to the newly written value
+// When the key to be written exists, only the value should be modified without changing the key's decoration
 fn insert_tablelike<'a>(table: &mut (dyn TableLike + 'a), key: &str, value: Item) {
     if table.is_empty() {
         table.insert(key, value);
-    } else if table.contains_key(key) {
-        let pre_value = table.get(key).unwrap();
+    } else if let Some((mut pre_key, pre_value)) = table.get_key_value_mut(key) {
         let (prefix, suffix) = get_item_decor(pre_value);
         if let Item::Value(value) = value {
-            // insert function will auto foramt the key in table and inlinetable
-            table.insert(key, Item::Value(value.decorated(prefix, suffix)));
+            *pre_value = Item::Value(value.decorated(prefix, suffix));
+        } else if value.is_table() && !pre_value.is_table() {
+            // remove space before equal sign
+            pre_key.leaf_decor_mut().set_suffix("");
+            *pre_value = value;
         } else {
-            table.insert(key, value);
+            *pre_value = value;
         };
     } else {
         if let Item::Value(value) = value {

tests/array_edit.test.ts

@@ -72,7 +72,7 @@ describe("array edit", () => {
             expect(edit(aot, "foo.bar.[0].age", 20, opt)).toBe(dedent`
                 [foo]
                 bar = [
-                    { name = "tom", age = 20 }
+                    { name = "tom",age = 20 }
                 ]
             `)
         })

tests/edit.test.ts

@@ -151,6 +151,29 @@ describe("edit", () => {
             a = 1
             b = 2
         `)
+
+        const input1 = dedent`
+            [foo]
+            # comment
+            bar = 1
+        `
+        expect(edit(input1, "foo.bar", 2, opt)).toBe(dedent`
+            [foo]
+            # comment
+            bar = 2
+        `)
+        expect(edit(input1, "foo.bar", { baz: 3 }, opt)).toBe(dedent`
+            [foo]
+            # comment
+            bar = { baz = 3 }
+        `)
+        // TODO: This is a known bug: https://github.com/toml-rs/toml/issues/691
+        // expect(edit(input1, "foo.bar", { baz: 3 }, {...opt, inline: false})).toMatchInlineSnapshot(`
+        //   "[foo]
+        //   # comment
+        //   [foo.bar]
+        //   baz = 3"
+        // `)
     })
 
     it("set datetime", () => {
@@ -310,4 +333,17 @@ describe("issue", () => {
             "
         `)
     })
+
+    it("issue#8", () => {
+        const toml = dedent`
+            [package]
+            # comment
+            rand = "1"
+        `
+        expect(edit(toml, "package.rand", "2", opt)).toBe(dedent`
+            [package]
+            # comment
+            rand = "2"
+        `)
+    })
 })