From 9d19be0826ab6b22b435160af73042e5de82a758 Mon Sep 17 00:00:00 2001
From: Jinzhu <wosmvp@gmail.com>
Date: Tue, 4 Feb 2020 09:51:19 +0800
Subject: [PATCH] Setup clauses tests

---
 callbacks/query.go    |  4 +---
 clause/clause_test.go | 54 +++++++++++++++++++++++++++++++++++++++++++
 clause/from.go        | 16 +++++++++----
 statement.go          |  5 ++++
 4 files changed, 71 insertions(+), 8 deletions(-)
 create mode 100644 clause/clause_test.go

diff --git a/callbacks/query.go b/callbacks/query.go
index edf8f281..8d13095e 100644
--- a/callbacks/query.go
+++ b/callbacks/query.go
@@ -9,9 +9,7 @@ import (
 
 func Query(db *gorm.DB) {
 	db.Statement.AddClauseIfNotExists(clause.Select{})
-	db.Statement.AddClauseIfNotExists(clause.From{
-		Tables: []clause.Table{{Table: clause.CurrentTable}},
-	})
+	db.Statement.AddClauseIfNotExists(clause.From{})
 
 	db.Statement.Build("SELECT", "FROM", "WHERE", "GROUP BY", "ORDER BY", "LIMIT", "FOR")
 	result, err := db.DB.ExecContext(db.Context, db.Statement.SQL.String(), db.Statement.Vars...)
diff --git a/clause/clause_test.go b/clause/clause_test.go
new file mode 100644
index 00000000..97d30f2d
--- /dev/null
+++ b/clause/clause_test.go
@@ -0,0 +1,54 @@
+package clause_test
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+	"testing"
+
+	"github.com/jinzhu/gorm"
+	"github.com/jinzhu/gorm/clause"
+	"github.com/jinzhu/gorm/schema"
+	"github.com/jinzhu/gorm/tests"
+)
+
+func TestClause(t *testing.T) {
+	var (
+		db, _   = gorm.Open(nil, nil)
+		results = []struct {
+			Clauses []clause.Interface
+			Result  string
+			Vars    []interface{}
+		}{{
+			[]clause.Interface{clause.Select{}, clause.From{}},
+			"SELECT * FROM users", []interface{}{},
+		}}
+	)
+
+	for idx, result := range results {
+		t.Run(fmt.Sprintf("case #%v", idx), func(t *testing.T) {
+			var (
+				user, _ = schema.Parse(&tests.User{}, &sync.Map{}, db.NamingStrategy)
+				stmt    = gorm.Statement{
+					DB: db, Table: user.Table, Schema: user, Clauses: map[string]clause.Clause{},
+				}
+				buildNames []string
+			)
+
+			for _, c := range result.Clauses {
+				buildNames = append(buildNames, c.Name())
+				stmt.AddClause(c)
+			}
+
+			stmt.Build(buildNames...)
+
+			if stmt.SQL.String() != result.Result {
+				t.Errorf("SQL expects %v got %v", result.Result, stmt.SQL.String())
+			}
+
+			if reflect.DeepEqual(stmt.Vars, result.Vars) {
+				t.Errorf("Vars expects %+v got %v", stmt.Vars, result.Vars)
+			}
+		})
+	}
+}
diff --git a/clause/from.go b/clause/from.go
index 1a7bcb5c..b7665bc3 100644
--- a/clause/from.go
+++ b/clause/from.go
@@ -10,14 +10,20 @@ func (From) Name() string {
 	return "FROM"
 }
 
+var currentTable = Table{Table: CurrentTable}
+
 // Build build from clause
 func (from From) Build(builder Builder) {
-	for idx, table := range from.Tables {
-		if idx > 0 {
-			builder.WriteByte(',')
-		}
+	if len(from.Tables) > 0 {
+		for idx, table := range from.Tables {
+			if idx > 0 {
+				builder.WriteByte(',')
+			}
 
-		builder.WriteQuoted(table)
+			builder.WriteQuoted(table)
+		}
+	} else {
+		builder.WriteQuoted(currentTable)
 	}
 }
 
diff --git a/statement.go b/statement.go
index b2407599..26acb319 100644
--- a/statement.go
+++ b/statement.go
@@ -84,6 +84,11 @@ func (stmt Statement) Quote(field interface{}) string {
 
 	switch v := field.(type) {
 	case clause.Table:
+		if v.Table == clause.CurrentTable {
+			str.WriteString(stmt.Table)
+		} else {
+			str.WriteString(v.Table)
+		}
 
 		if v.Alias != "" {
 			str.WriteString(" AS ")