From 2b465b064691a22cf82b979bf435240d496849c9 Mon Sep 17 00:00:00 2001
From: Gani Georgiev <gani.georgiev@gmail.com>
Date: Fri, 14 Jul 2023 08:36:01 +0300
Subject: [PATCH] load a default fetchFunc for dao.ExpandRecord(s)

---
 CHANGELOG.md               |  2 ++
 daos/record_expand.go      | 14 +++++++++---
 daos/record_expand_test.go | 44 ++++++++++++++++++++++----------------
 3 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 35a18737..d64c7601 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -80,6 +80,8 @@
 - (@todo docs) For consistency and convenience it is now possible to call `Dao.RecordQuery(collectionModelOrIdentifier)` with just the collection id or name.
   In case an invalid collection id/name string is passed the query will be resolved with cancelled context error.
 
+- (@todo docs) Use a default fetch function that will return all relations in case the fetchFunc argument of `Dao.ExpandRecord()` and `Dao.ExpandRecords()` is `nil`.
+
 
 ## v0.16.8
 
diff --git a/daos/record_expand.go b/daos/record_expand.go
index f20d8328..9eec8a4d 100644
--- a/daos/record_expand.go
+++ b/daos/record_expand.go
@@ -1,7 +1,6 @@
 package daos
 
 import (
-	"errors"
 	"fmt"
 	"regexp"
 	"strings"
@@ -24,6 +23,9 @@ type ExpandFetchFunc func(relCollection *models.Collection, relIds []string) ([]
 
 // ExpandRecord expands the relations of a single Record model.
 //
+// If fetchFunc is not set, then a default function will be used that
+// returns all relation records.
+//
 // Returns a map with the failed expand parameters and their errors.
 func (dao *Dao) ExpandRecord(record *models.Record, expands []string, fetchFunc ExpandFetchFunc) map[string]error {
 	return dao.ExpandRecords([]*models.Record{record}, expands, fetchFunc)
@@ -31,6 +33,9 @@ func (dao *Dao) ExpandRecord(record *models.Record, expands []string, fetchFunc
 
 // ExpandRecords expands the relations of the provided Record models list.
 //
+// If fetchFunc is not set, then a default function will be used that
+// returns all relation records.
+//
 // Returns a map with the failed expand parameters and their errors.
 func (dao *Dao) ExpandRecords(records []*models.Record, expands []string, fetchFunc ExpandFetchFunc) map[string]error {
 	normalized := normalizeExpands(expands)
@@ -49,13 +54,16 @@ func (dao *Dao) ExpandRecords(records []*models.Record, expands []string, fetchF
 var indirectExpandRegex = regexp.MustCompile(`^(\w+)\((\w+)\)$`)
 
 // notes:
-// - fetchFunc must be non-nil func
+// - if fetchFunc is nil, dao.FindRecordsByIds will be used
 // - all records are expected to be from the same collection
 // - if MaxExpandDepth is reached, the function returns nil ignoring the remaining expand path
 // - indirect expands are supported only with single relation fields
 func (dao *Dao) expandRecords(records []*models.Record, expandPath string, fetchFunc ExpandFetchFunc, recursionLevel int) error {
 	if fetchFunc == nil {
-		return errors.New("Relation records fetchFunc is not set.")
+		// load a default fetchFunc
+		fetchFunc = func(relCollection *models.Collection, relIds []string) ([]*models.Record, error) {
+			return dao.FindRecordsByIds(relCollection.Id, relIds)
+		}
 	}
 
 	if expandPath == "" || recursionLevel > MaxExpandDepth || len(records) == 0 {
diff --git a/daos/record_expand_test.go b/daos/record_expand_test.go
index d37294d5..5439754f 100644
--- a/daos/record_expand_test.go
+++ b/daos/record_expand_test.go
@@ -48,15 +48,6 @@ func TestExpandRecords(t *testing.T) {
 			0,
 			0,
 		},
-		{
-			"empty fetchFunc",
-			"demo4",
-			[]string{"i9naidtvr6qsgb4", "qzaqccwrmva4o1n"},
-			[]string{"self_rel_one", "self_rel_many.self_rel_one"},
-			nil,
-			0,
-			2,
-		},
 		{
 			"fetchFunc with error",
 			"demo4",
@@ -101,6 +92,19 @@ func TestExpandRecords(t *testing.T) {
 			0,
 			1,
 		},
+		{
+			"with nil fetchfunc",
+			"users",
+			[]string{
+				"bgs820n361vj1qd",
+				"4q1xlclmfloku33",
+				"oap640cot4yru2s", // no rels
+			},
+			[]string{"rel"},
+			nil,
+			2,
+			0,
+		},
 		{
 			"expand normalizations",
 			"demo4",
@@ -132,6 +136,19 @@ func TestExpandRecords(t *testing.T) {
 			2,
 			0,
 		},
+		{
+			"with nil fetchfunc",
+			"users",
+			[]string{
+				"bgs820n361vj1qd",
+				"4q1xlclmfloku33",
+				"oap640cot4yru2s", // no rels
+			},
+			[]string{"rel"},
+			nil,
+			2,
+			0,
+		},
 		{
 			"maxExpandDepth reached",
 			"demo4",
@@ -228,15 +245,6 @@ func TestExpandRecord(t *testing.T) {
 			0,
 			0,
 		},
-		{
-			"empty fetchFunc",
-			"demo4",
-			"i9naidtvr6qsgb4",
-			[]string{"self_rel_one", "self_rel_many.self_rel_one"},
-			nil,
-			0,
-			2,
-		},
 		{
 			"fetchFunc with error",
 			"demo4",