feat: implement on_conflict (#113)

Author: izqalan

src/builder.ts

@@ -125,12 +125,17 @@ export class PostgrestQueryBuilder<T> extends PostgrestBuilder<T> {
    *
    * @param values  The values to insert.
    * @param upsert  If `true`, performs an UPSERT.
+   * @param onConflict By specifying the `on_conflict` query parameter, you can make UPSERT work on a column(s) that has a UNIQUE constraint.
    */
-  insert(values: Partial<T> | Partial<T>[], { upsert = false } = {}): PostgrestBuilder<T> {
+  insert(
+    values: Partial<T> | Partial<T>[],
+    { upsert = false, onConflict }: { upsert?: boolean; onConflict?: string } = {}
+  ): PostgrestBuilder<T> {
     this.method = 'POST'
     this.headers['Prefer'] = upsert
       ? 'return=representation,resolution=merge-duplicates'
       : 'return=representation'
+    if (upsert && onConflict !== undefined) this.url.searchParams.set('on_conflict', onConflict)
     this.body = values
     return this
   }

test/__snapshots__/basic.test.ts.snap

@@ -595,6 +595,32 @@ Object {
 }
 `;
 
+exports[`on_conflict insert 1`] = `
+Object {
+  "body": Array [
+    Object {
+      "age_range": "[20,30)",
+      "catchphrase": "'fat' 'rat'",
+      "data": null,
+      "status": "ONLINE",
+      "username": "dragarcia",
+    },
+  ],
+  "data": Array [
+    Object {
+      "age_range": "[20,30)",
+      "catchphrase": "'fat' 'rat'",
+      "data": null,
+      "status": "ONLINE",
+      "username": "dragarcia",
+    },
+  ],
+  "error": null,
+  "status": 201,
+  "statusText": "Created",
+}
+`;
+
 exports[`stored procedure 1`] = `
 Object {
   "body": "ONLINE",

test/basic.test.ts

@@ -29,6 +29,13 @@ test('switch schema', async () => {
   expect(res).toMatchSnapshot()
 })
 
+test('on_conflict insert', async () => {
+  const res = await postgrest
+    .from('users')
+    .insert({ username: 'dragarcia' }, { upsert: true, onConflict: 'username' })
+  expect(res).toMatchSnapshot()
+})
+
 describe('basic insert, update, delete', () => {
   test('basic insert', async () => {
     let res = await postgrest