feat: add unnest method to merge nested SQLStatements (#184)

index.d.ts

@@ -44,6 +44,23 @@ export class SQLStatement {
    */
   append(statement: SQLStatement | string | number): this
 
+  /**
+   * Unnests any nested SQLStatements so that their values are merged into this statement
+   *
+   * ```ts
+   * const book = 'harry potter'
+   * const author = 'J. K. Rowling'
+   * const query = SQL`SELECT author FROM books WHERE genre IN (${SQL`SELECT category FROM books WHERE name = ${book}`}) AND author = ${author}`
+   *
+   * query.unnest()
+   *
+   * query.sql    // => 'SELECT author FROM books WHERE genre IN (SELECT category FROM books WHERE name = ?) AND author = ?'
+   * query.text   // => 'SELECT author FROM books WHERE genre IN (SELECT category FROM books WHERE name = $1) AND author = $2'
+   * query.values // => ['harry potter', 'J. K. Rowling']
+   * ```
+   */
+  unnest(recursive?: boolean): this
+
   /**
    * Sets the name property of this statement for prepared statements in postgres
    *

index.js

@@ -36,6 +36,33 @@ class SQLStatement {
     return this
   }
 
+  /**
+   * Unnest any nested SQLStatements within this SQLStatement
+   * @param {boolean} [recursive=true] Whether to unnest recursively
+   * @returns {this}
+   */
+  unnest(recursive = true) {
+    const strings = []
+    const values = []
+    strings.push(this.strings[0])
+    for (let i = 0; i < this.values.length; i++) {
+      const value = this.values[i]
+      if (value instanceof SQLStatement) {
+        const nest = recursive ? value.unnest(recursive) : value
+        strings[strings.length - 1] += nest.strings[0]
+        strings.push(...nest.strings.slice(1))
+        values.push(...nest.values)
+        strings[strings.length - 1] += this.strings[i + 1]
+      } else {
+        values.push(value)
+        strings.push(this.strings[i + 1])
+      }
+    }
+    this.strings = strings
+    this.values = values
+    return this
+  }
+
   /**
    * Use a prepared statement with Sequelize.
    * Makes `query` return a query with `$n` syntax instead of `?`  and switches the `values` key name to `bind`

test/unit.js

@@ -20,6 +20,76 @@ describe('SQL', () => {
     assert.deepEqual(query.values, [value])
   })
 
+  it('should work with a nested query', () => {
+    const value1 = 1234
+    const value2 = 5678
+    const value3 = 9012
+    const query1 = SQL`SELECT column2 FROM other_table WHERE column = ${value2} ORDER BY column2`
+    const query2 = SQL`SELECT * FROM table WHERE column1 = ${value1} AND column2 IN (${query1}) AND column3 = ${value3}`
+    query2.unnest()
+    assert.equal(
+      query2.sql,
+      'SELECT * FROM table WHERE column1 = ? AND column2 IN (SELECT column2 FROM other_table WHERE column = ? ORDER BY column2) AND column3 = ?'
+    )
+    assert.equal(
+      query2.query,
+      'SELECT * FROM table WHERE column1 = ? AND column2 IN (SELECT column2 FROM other_table WHERE column = ? ORDER BY column2) AND column3 = ?'
+    )
+    assert.equal(
+      query2.text,
+      'SELECT * FROM table WHERE column1 = $1 AND column2 IN (SELECT column2 FROM other_table WHERE column = $2 ORDER BY column2) AND column3 = $3'
+    )
+    assert.deepEqual(query2.values, [value1, value2, value3])
+  })
+
+  it('should work with a deeply nested query', () => {
+    const value1 = 1234
+    const value2 = 5678
+    const value3 = 9012
+    const value4 = 3456
+    const query1 = SQL`SELECT column2 FROM other_table1 WHERE column = ${value2} ORDER BY column2`
+    const query2 = SQL`SELECT column2 FROM other_table2 WHERE column IN (${query1}) AND column3 = ${value3} ORDER BY column3`
+    const query3 = SQL`SELECT * FROM table WHERE column1 = ${value1} AND column2 IN (${query2}) AND column4 = ${value4}`
+    query3.unnest()
+    assert.equal(
+      query3.sql,
+      'SELECT * FROM table WHERE column1 = ? AND column2 IN (SELECT column2 FROM other_table2 WHERE column IN (SELECT column2 FROM other_table1 WHERE column = ? ORDER BY column2) AND column3 = ? ORDER BY column3) AND column4 = ?'
+    )
+    assert.equal(
+      query3.query,
+      'SELECT * FROM table WHERE column1 = ? AND column2 IN (SELECT column2 FROM other_table2 WHERE column IN (SELECT column2 FROM other_table1 WHERE column = ? ORDER BY column2) AND column3 = ? ORDER BY column3) AND column4 = ?'
+    )
+    assert.equal(
+      query3.text,
+      'SELECT * FROM table WHERE column1 = $1 AND column2 IN (SELECT column2 FROM other_table2 WHERE column IN (SELECT column2 FROM other_table1 WHERE column = $2 ORDER BY column2) AND column3 = $3 ORDER BY column3) AND column4 = $4'
+    )
+    assert.deepEqual(query3.values, [value1, value2, value3, value4])
+  })
+
+  it('should work with a deeply nested query and partial unnest', () => {
+    const value1 = 1234
+    const value2 = 5678
+    const value3 = 9012
+    const value4 = 3456
+    const query1 = SQL`SELECT column2 FROM other_table1 WHERE column = ${value2} ORDER BY column2`
+    const query2 = SQL`SELECT column2 FROM other_table2 WHERE column IN (${query1}) AND column3 = ${value3} ORDER BY column3`
+    const query3 = SQL`SELECT * FROM table WHERE column1 = ${value1} AND column2 IN (${query2}) AND column4 = ${value4}`
+    query3.unnest(false)
+    assert.equal(
+      query3.sql,
+      'SELECT * FROM table WHERE column1 = ? AND column2 IN (SELECT column2 FROM other_table2 WHERE column IN (?) AND column3 = ? ORDER BY column3) AND column4 = ?'
+    )
+    assert.equal(
+      query3.query,
+      'SELECT * FROM table WHERE column1 = ? AND column2 IN (SELECT column2 FROM other_table2 WHERE column IN (?) AND column3 = ? ORDER BY column3) AND column4 = ?'
+    )
+    assert.equal(
+      query3.text,
+      'SELECT * FROM table WHERE column1 = $1 AND column2 IN (SELECT column2 FROM other_table2 WHERE column IN ($2) AND column3 = $3 ORDER BY column3) AND column4 = $4'
+    )
+    assert.deepEqual(query3.values, [value1, query1, value3, value4])
+  })
+
   it('should work with falsy values', () => {
     const value1 = false
     const value2 = null