From 2f30e210462caeb1b43802bb7a480a009a067be7 Mon Sep 17 00:00:00 2001
From: Prasanna Kumar <6123002+pgollangi@users.noreply.github.com>
Date: Thu, 16 Nov 2023 17:55:42 +0530
Subject: [PATCH] feat: Allow selecting columns with NULL values (#18)

* feat: Allow selecting columns with NULL values
---
 pkg/select/select.go      |  8 +++++--
 pkg/select/select_test.go | 44 ++++++++++++++++++++++-----------------
 test/data/users.json      |  2 +-
 3 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/pkg/select/select.go b/pkg/select/select.go
index ef195a8..df53d83 100644
--- a/pkg/select/select.go
+++ b/pkg/select/select.go
@@ -166,10 +166,14 @@ func readColumnValue(document *firestore.DocumentSnapshot, data *map[string]inte
 			var colData interface{}
 			colData = *data
 			for _, fPath := range fieldPaths {
-				colData = colData.(map[string]interface{})[fPath]
-				if colData == nil {
+				fieldVal, ok := colData.(map[string]interface{})[fPath]
+				if !ok {
 					return nil, fmt.Errorf(`unknown field "%s" in doc "%s"`, column.field, document.Ref.ID)
 				}
+				colData = fieldVal
+				if colData == nil {
+					break
+				}
 			}
 			val = colData
 		}
diff --git a/pkg/select/select_test.go b/pkg/select/select_test.go
index a225daf..37b5c12 100644
--- a/pkg/select/select_test.go
+++ b/pkg/select/select_test.go
@@ -30,76 +30,82 @@ type TestExpect struct {
 const FirestoreEmulatorHost = "FIRESTORE_EMULATOR_HOST"
 
 var selectTests = []TestExpect{
-	TestExpect{
+	{
 		query:   "select * from users",
 		columns: []string{"id", "email", "username", "address", "name"},
 		length:  "21",
 	},
-	TestExpect{
+	{
 		query:   "select * from `users`",
 		columns: []string{"id", "email", "username", "address", "name"},
 		length:  "21",
 	},
-	TestExpect{
+	{
 		query:   "select id as uid, * from users",
 		columns: []string{"uid", "id", "email", "username", "address", "name"},
 		length:  "21",
 	},
-	TestExpect{
+	{
 		query:   "select *, username as uname from users",
 		columns: []string{"id", "email", "username", "address", "name", "uname"},
 		length:  "21",
 	},
-	TestExpect{
+	{
 		query:   "select  id as uid, *, username as uname from users",
 		columns: []string{"uid", "id", "email", "username", "address", "name", "uname"},
 		length:  "21",
 	},
-	TestExpect{
+	{
 		query:   "select id, email, address from users",
 		columns: []string{"id", "email", "address"},
 		length:  "21",
 	},
-	TestExpect{
+	{
 		query:   "select id, email, address from users limit 5",
 		columns: []string{"id", "email", "address"},
 		length:  "5",
 	},
-	TestExpect{
+	{
 		query:   "select id from users where email='aeatockj@psu.edu'",
 		columns: []string{"id"},
 		length:  "1",
-		records: [][]interface{}{[]interface{}{float64(20)}},
+		records: [][]interface{}{{float64(20)}},
 	},
-	TestExpect{
+	{
 		query:   "select id from users order by id desc limit 1",
 		columns: []string{"id"},
 		length:  "1",
-		records: [][]interface{}{[]interface{}{float64(21)}},
+		records: [][]interface{}{{float64(21)}},
 	},
-	TestExpect{
+	{
 		query:   "select LENGTH(username) as uLen from users where id = 8",
 		columns: []string{"uLen"},
 		length:  "1",
-		records: [][]interface{}{[]interface{}{float64(6)}},
+		records: [][]interface{}{{float64(6)}},
 	},
-	TestExpect{
+	{
 		query:   "select id from users where `address.city` = 'Glendale' and name = 'Eleanora'",
 		columns: []string{"id"},
 		length:  "1",
-		records: [][]interface{}{[]interface{}{float64(10)}},
+		records: [][]interface{}{{float64(10)}},
 	},
-	TestExpect{
+	{
 		query:   "select id > 0 as has_id from users where `address.city` = 'Glendale' and name = 'Eleanora'",
 		columns: []string{"has_id"},
 		length:  "1",
-		records: [][]interface{}{[]interface{}{true}},
+		records: [][]interface{}{{true}},
 	},
-	TestExpect{
+	{
 		query:   "select __name__ from users where id = 1",
 		columns: []string{"__name__"},
 		length:  "1",
-		records: [][]interface{}{[]interface{}{"1"}},
+		records: [][]interface{}{{"1"}},
+	},
+	{
+		query:   "select id, email, username from users where id = 21",
+		columns: []string{"id", "email", "username"},
+		length:  "1",
+		records: [][]interface{}{{float64(21), nil, "ckensleyk"}},
 	},
 }
 
diff --git a/test/data/users.json b/test/data/users.json
index 38e17c5..70ca98a 100644
--- a/test/data/users.json
+++ b/test/data/users.json
@@ -183,7 +183,7 @@
     "id": 21,
     "name": "Doyle",
     "username": "ckensleyk",
-    "email": "ckensleyk@pen.io",
+    "email": null,
     "address": {
       "city": "Fayetteville"
     }