fix: select everything when forming subspell (#382)

otherwise the columns might be quolified unnecessarily, or worse, insufficient for further joining

docs/querying.md

@@ -477,6 +477,36 @@ Post.include('comments', 'author')
 Post.find().with('comments').with('author')
 ```
 
+Please be noted that the chaining order of `.with()` matters, queries like below are not equivalent:
+
+```js
+Post.findOne().with('comments')
+// NOT EQUALS TO
+Post.find().with('comments').first
+```
+
+By type definitions, both queries will return a Post instance or null depending on the record can be found or not. But the generated SQLs are quite different:
+
+```sql
+SELECT * FROM (SELECT * FROM posts LIMIT 1) AS posts LEFT JOIN comments ON comments.post_id = posts.id
+-- NOT EQUALS TO
+SELECT * FROM posts AS posts LEFT JOIN comments ON comments.post_id = posts.id LIMIT 1
+```
+
+The major difference is the place of `LIMIT`, the former query will fetch the first post and all of its associated comments, the latter query however, will only return the first post and its first comment.
+
+We can keep on chaining the query methods if comments need to be limited as well:
+
+```js
+Post.findOne().with('comments').limit(10)
+```
+
+which is equivalent of SQL below:
+
+```sql
+SELECT * FROM (SELECT * FROM posts LIMIT 1) AS posts LEFT JOIN comments ON comments.post_id = posts.id LIMIT 10
+```
+
 ### Arbitrary Joins
 
 If a join is needed but not predefined in `Model.describe()`, it can still be accomplished with `.join()`:

docs/zh/querying.md

@@ -471,6 +471,36 @@ Post.include('comments', 'author')
 Post.find().with('comments').with('author')
 ```
 
+注意，链式调用 `.with()` 产生的作用会跟调用顺序有关系，下面两个写法是不等价的：
+
+```js
+Post.findOne().with('comments')
+// 不等同于
+Post.find().with('comments').first
+```
+
+虽然从接口定义来看，两者都会返回 Post 实例或者 null，但是两者所执行的 SQL 会有差别：
+
+```sql
+SELECT * FROM (SELECT * FROM posts LIMIT 1) AS posts LEFT JOIN comments ON comments.post_id = posts.id
+-- 不等同于
+SELECT * FROM posts AS posts LEFT JOIN comments ON comments.post_id = posts.id LIMIT 1
+```
+
+可以看到区别在于 LIMIT 所在的位置，前者会返回第一条 Post 及其所有的 Comment，后者则只会返回第一条 Post 及其第一条 Comment。
+
+使用第一种查询时，如果需要限制返回的评论数量，可以直接写：
+
+```js
+Post.findOne().with('comments').limit(10)
+```
+
+等价于下面的 SQL：
+
+```sql
+SELECT * FROM (SELECT * FROM posts LIMIT 1) AS posts LEFT JOIN comments ON comments.post_id = posts.id LIMIT 10
+```
+
 ### 任意 JOIN
 
 如果需要 JOIN 未在 `Model.describe()` 预先定义的关联关系，可以使用 `.join()` 方法：

src/spell.js

@@ -387,9 +387,7 @@ class Spell {
 
   #emptySpell() {
     Object.assign(this, {
-      columns: [],
-      whereConditions: this.Model.shardingKey ? this.whereConditions : [],
-      // whereConditions: [],
+      whereConditions: [],
       groups: [],
       orders: [],
       havingConditions: [],
@@ -808,6 +806,7 @@ class Spell {
   $with(...qualifiers) {
     if (this.rowCount > 0 || this.skip > 0) {
       const spell = this.dup;
+      spell.columns = [];
       this.#emptySpell();
       this.table = { type: 'subquery', value: spell };
     }

test/integration/suite/associations.test.js

@@ -324,5 +324,13 @@ describe('=> Associations order / offset / limit', function() {
       assert.equal(posts[0].title, 'New Post');
       assert.equal(posts[0].comments.length, 2);
     });
+
+    it('on subquery with select', async function() {
+      await assert.doesNotReject(async function() {
+        const post = await Post.first.select('title').with('comments');
+        assert.ok(post);
+        assert.ok(Array.isArray(post.comments));
+      });
+    });
   });
 });