From 3617e51c019175a7b17d7de3539a7fdbb4642a74 Mon Sep 17 00:00:00 2001
From: John <john@johng.cn>
Date: Mon, 28 Sep 2020 23:52:02 +0800
Subject: [PATCH] improve gdb.Model.ScanList

---
 database/gdb/gdb_type_result_scanlist.go | 36 ++++++++++++++++++------
 go.mod                                   |  1 +
 util/gconv/gconv_struct.go               |  6 ++--
 util/gconv/gconv_structs.go              |  3 +-
 4 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/database/gdb/gdb_type_result_scanlist.go b/database/gdb/gdb_type_result_scanlist.go
index 3b4a41648..9db4565db 100644
--- a/database/gdb/gdb_type_result_scanlist.go
+++ b/database/gdb/gdb_type_result_scanlist.go
@@ -181,7 +181,7 @@ func (r Result) ScanList(listPointer interface{}, attributeName string, relation
 			}
 		}
 		if len(relationDataMap) > 0 && !relationValue.IsValid() {
-			return fmt.Errorf(`invalid relation: %s, %s`, relation[0], relation[1])
+			return fmt.Errorf(`invalid relation: "%s:%s"`, relation[0], relation[1])
 		}
 		switch attrKind {
 		case reflect.Array, reflect.Slice:
@@ -196,7 +196,7 @@ func (r Result) ScanList(listPointer interface{}, attributeName string, relation
 					}
 				} else {
 					// May be the attribute does not exist yet.
-					return fmt.Errorf(`invalid relation: %s, %s`, relation[0], relation[1])
+					return fmt.Errorf(`invalid relation: "%s:%s"`, relation[0], relation[1])
 				}
 			} else {
 				return fmt.Errorf(`relationKey should not be empty as field "%s" is slice`, attributeName)
@@ -207,15 +207,25 @@ func (r Result) ScanList(listPointer interface{}, attributeName string, relation
 			if len(relationDataMap) > 0 {
 				relationField = relationValue.FieldByName(relationAttrName)
 				if relationField.IsValid() {
-					if err = gconv.Struct(relationDataMap[gconv.String(relationField.Interface())], e); err != nil {
+					v := relationDataMap[gconv.String(relationField.Interface())]
+					if v == nil {
+						// There's no relational data.
+						continue
+					}
+					if err = gconv.Struct(v, e); err != nil {
 						return err
 					}
 				} else {
 					// May be the attribute does not exist yet.
-					return fmt.Errorf(`invalid relation: %s, %s`, relation[0], relation[1])
+					return fmt.Errorf(`invalid relation: "%s:%s"`, relation[0], relation[1])
 				}
 			} else {
-				if err = gconv.Struct(r[i], e); err != nil {
+				v := r[i]
+				if v == nil {
+					// There's no relational data.
+					continue
+				}
+				if err = gconv.Struct(v, e); err != nil {
 					return err
 				}
 			}
@@ -226,15 +236,25 @@ func (r Result) ScanList(listPointer interface{}, attributeName string, relation
 			if len(relationDataMap) > 0 {
 				relationField = relationValue.FieldByName(relationAttrName)
 				if relationField.IsValid() {
-					if err = gconv.Struct(relationDataMap[gconv.String(relationField.Interface())], e); err != nil {
+					v := relationDataMap[gconv.String(relationField.Interface())]
+					if v == nil {
+						// There's no relational data.
+						continue
+					}
+					if err = gconv.Struct(v, e); err != nil {
 						return err
 					}
 				} else {
 					// May be the attribute does not exist yet.
-					return fmt.Errorf(`invalid relation: %s, %s`, relation[0], relation[1])
+					return fmt.Errorf(`invalid relation: "%s:%s"`, relation[0], relation[1])
 				}
 			} else {
-				if err = gconv.Struct(r[i], e); err != nil {
+				v := r[i]
+				if v == nil {
+					// There's no relational data.
+					continue
+				}
+				if err = gconv.Struct(v, e); err != nil {
 					return err
 				}
 			}
diff --git a/go.mod b/go.mod
index 385d6c370..56d7cae7a 100644
--- a/go.mod
+++ b/go.mod
@@ -12,6 +12,7 @@ require (
 	github.com/gqcn/structs v1.1.1
 	github.com/grokify/html-strip-tags-go v0.0.0-20190921062105-daaa06bf1aaf
 	github.com/json-iterator/go v1.1.10
+	github.com/mattn/go-runewidth v0.0.9 // indirect
 	github.com/olekukonko/tablewriter v0.0.1
 	golang.org/x/net v0.0.0-20200602114024-627f9648deb9
 	golang.org/x/text v0.3.2
diff --git a/util/gconv/gconv_struct.go b/util/gconv/gconv_struct.go
index 44e9cf5c6..26cd0de03 100644
--- a/util/gconv/gconv_struct.go
+++ b/util/gconv/gconv_struct.go
@@ -50,7 +50,8 @@ func StructDeep(params interface{}, pointer interface{}, mapping ...map[string]s
 // doStruct is the core internal converting function for any data to struct recursively or not.
 func doStruct(params interface{}, pointer interface{}, recursive bool, mapping ...map[string]string) (err error) {
 	if params == nil {
-		return gerror.New("params cannot be nil")
+		// If <params> is nil, no conversion.
+		return nil
 	}
 	if pointer == nil {
 		return gerror.New("object pointer cannot be nil")
@@ -73,7 +74,8 @@ func doStruct(params interface{}, pointer interface{}, recursive bool, mapping .
 	// DO NOT use MapDeep here.
 	paramsMap := Map(params)
 	if paramsMap == nil {
-		return gerror.Newf("invalid params: %v", params)
+		//return gerror.Newf("invalid params: %v", params)
+		return nil
 	}
 
 	// Using reflect to do the converting,
diff --git a/util/gconv/gconv_structs.go b/util/gconv/gconv_structs.go
index f447fcf6f..1885acc49 100644
--- a/util/gconv/gconv_structs.go
+++ b/util/gconv/gconv_structs.go
@@ -30,7 +30,8 @@ func StructsDeep(params interface{}, pointer interface{}, mapping ...map[string]
 // it will create the struct/pointer internally.
 func doStructs(params interface{}, pointer interface{}, deep bool, mapping ...map[string]string) (err error) {
 	if params == nil {
-		return gerror.New("params cannot be nil")
+		// If <params> is nil, no conversion.
+		return nil
 	}
 	if pointer == nil {
 		return gerror.New("object pointer cannot be nil")