fix(client): support non-scalar sub selection

Fixes https://github.com/prisma/prisma/issues/3309

1. Add __typename when a type has no scalar fields.
2. Removes __typename from result when it is the only field (aware of
    $fragment)

cli/packages/prisma-client-lib/src/Client.test.js.md

@@ -83,4 +83,15 @@ Generated by [AVA](https://ava.li).
         content␊
       }␊
     }␊
+
+
+## automatic non-scalar sub selection
+
+> Snapshot 1
+
+    `query ($where: UserWhereInput) {␊
+      users(where: $where) {␊
+        __typename␊
+      }␊
+    }␊
     `

cli/packages/prisma-client-lib/src/Client.test.ts

@@ -3,6 +3,45 @@ import { Client } from './Client'
 import { Model } from './types'
 import { print } from 'graphql'
 
+test('automatic non-scalar sub selection', t => {
+  const typeDefs = `
+    type Query {
+      users(where: UserWhereInput): [User]
+    }
+
+    input UserWhereInput {
+      id: ID!
+    }
+
+    type User {
+      house: House!
+    }
+    
+    type House {
+      id: ID!
+      name: String!
+    }
+  `
+
+  const models: Model[] = []
+
+  const endpoint = 'http://localhost:4466'
+
+  const client: any = new Client({
+    typeDefs,
+    endpoint,
+    models,
+  })
+
+  client.users()
+
+  const document = client.getDocumentForInstructions(
+    Object.keys(client._currentInstructions)[0],
+  )
+
+  t.snapshot(print(document))
+})
+
 test('related type', t => {
   const typeDefs = `
     type Query {
@@ -30,7 +69,7 @@ test('related type', t => {
     },
   ]
 
-  const endpoint = 'http://localhost;4466'
+  const endpoint = 'http://localhost:4466'
 
   const client: any = new Client({
     typeDefs,
@@ -74,7 +113,7 @@ test('deep related type', t => {
     },
   ]
 
-  const endpoint = 'http://localhost;4466'
+  const endpoint = 'http://localhost:4466'
 
   const client: any = new Client({
     typeDefs,
@@ -118,7 +157,7 @@ test('embedded type', t => {
     },
   ]
 
-  const endpoint = 'http://localhost;4466'
+  const endpoint = 'http://localhost:4466'
 
   const client: any = new Client({
     typeDefs,
@@ -171,7 +210,7 @@ test('nested mbedded type', t => {
     },
   ]
 
-  const endpoint = 'http://localhost;4466'
+  const endpoint = 'http://localhost:4466'
 
   const client: any = new Client({
     typeDefs,
@@ -269,7 +308,7 @@ test('nested args', t => {
     },
   ]
 
-  const endpoint = 'http://localhost;4466'
+  const endpoint = 'http://localhost:4466'
 
   const client: any = new Client({
     typeDefs,

cli/packages/prisma-client-lib/src/Client.ts

@@ -182,6 +182,28 @@ export class Client {
     }
     log('unpack it')
 
+    const lastInstruction = instructions[count - 1]
+    const selectionFromFragment = Boolean(lastInstruction.fragment)
+
+    if (
+      !selectionFromFragment &&
+      Array.isArray(pointer) &&
+      pointer.length > 0
+    ) {
+      /*
+        As per the spec: https://github.com/prisma/prisma/issues/3309
+        We need to remove objects of the shape {__typename: <type>} 
+        from the output (except when fragment). Checking one element
+        is enough, as they will have the same shape.
+      */
+      if (
+        Object.keys(pointer[0]).length === 1 &&
+        Object.keys(pointer[0])[0] === '__typename'
+      ) {
+        pointer = []
+      }
+    }
+
     return pointer
   }
 
@@ -335,6 +357,17 @@ export class Client {
       return node
     }, null)
 
+    if (ast.selectionSet.selections.length === 0) {
+      ast.selectionSet.selections = [
+        {
+          kind: 'Field',
+          name: { kind: 'Name', value: '__typename' },
+          arguments: [],
+          directives: [],
+        },
+      ]
+    }
+
     return {
       ast: { ...ast, variableDefinitions },
       variables,