From 7fc92752157af09bb6527a68214061d8332fbf9d Mon Sep 17 00:00:00 2001
From: Erik Dubbelboer <erik@dubbelboer.com>
Date: Fri, 3 May 2024 12:54:11 +0200
Subject: [PATCH] Add WithEmptyCondition

Co-authored-by: Koen Bollen <213502+koenbollen@users.noreply.github.com>
---
 examples/basic_test.go       |  2 +-
 filter/converter.go          |  7 +++++--
 filter/converter_test.go     | 16 +++++++++++++++-
 filter/options.go            | 10 ++++++++++
 integration/postgres_test.go |  4 ++--
 5 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/examples/basic_test.go b/examples/basic_test.go
index 06d0014..d7a3374 100644
--- a/examples/basic_test.go
+++ b/examples/basic_test.go
@@ -30,7 +30,7 @@ func ExampleNewConverter() {
 }
 
 func ExampleNewConverter_emptyfilter() {
-	converter := filter.NewConverter()
+	converter := filter.NewConverter(filter.WithEmptyCondition("TRUE")) // The default is FALSE if you don't change it.
 
 	mongoFilterQuery := `{}`
 	conditions, _, err := converter.Convert([]byte(mongoFilterQuery), 1)
diff --git a/filter/converter.go b/filter/converter.go
index f5a5efb..08ebf4f 100644
--- a/filter/converter.go
+++ b/filter/converter.go
@@ -26,13 +26,16 @@ type Converter struct {
 		driver.Valuer
 		sql.Scanner
 	}
+	emptyCondition string
 }
 
 // NewConverter creates a new Converter with optional nested JSONB field mapping.
 //
 // Note: When using github.com/lib/pq, the filter.WithArrayDriver should be set to pq.Array.
 func NewConverter(options ...Option) *Converter {
-	converter := &Converter{}
+	converter := &Converter{
+		emptyCondition: "FALSE",
+	}
 	for _, option := range options {
 		if option != nil {
 			option(converter)
@@ -57,7 +60,7 @@ func (c *Converter) Convert(query []byte, startAtParameterIndex int) (conditions
 	}
 
 	if len(mongoFilter) == 0 {
-		return "TRUE", []any{}, nil
+		return c.emptyCondition, []any{}, nil
 	}
 
 	conditions, values, err = c.convertFilter(mongoFilter, startAtParameterIndex)
diff --git a/filter/converter_test.go b/filter/converter_test.go
index 94d9a0e..8777060 100644
--- a/filter/converter_test.go
+++ b/filter/converter_test.go
@@ -197,7 +197,7 @@ func TestConverter_Convert(t *testing.T) {
 			"empty filter",
 			nil,
 			`{}`,
-			`TRUE`,
+			`FALSE`,
 			[]any{},
 			nil,
 		}, {
@@ -260,3 +260,17 @@ func TestConverter_Convert_startAtParameterIndex(t *testing.T) {
 		t.Errorf("Converter.Convert(..., 1234551231231231231) error = %v, want nil", err)
 	}
 }
+
+func TestConverter_WithEmptyCondition(t *testing.T) {
+	c := filter.NewConverter(filter.WithEmptyCondition("TRUE"))
+	conditions, values, err := c.Convert([]byte(`{}`), 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := "TRUE"; conditions != want {
+		t.Errorf("Converter.Convert() conditions = %v, want %v", conditions, want)
+	}
+	if len(values) != 0 {
+		t.Errorf("Converter.Convert() values = %v, want nil", values)
+	}
+}
diff --git a/filter/options.go b/filter/options.go
index 399cb9a..769b004 100644
--- a/filter/options.go
+++ b/filter/options.go
@@ -39,3 +39,13 @@ func WithArrayDriver(f func(a any) interface {
 		c.arrayDriver = f
 	}
 }
+
+// WithEmptyCondition is an option to specify the condition to be used when the
+// input query filter is empty. (e.g. you have a query with no conditions)
+//
+// The default value is `FALSE`, because it's the safer choice in most cases.
+func WithEmptyCondition(condition string) Option {
+	return func(c *Converter) {
+		c.emptyCondition = condition
+	}
+}
diff --git a/integration/postgres_test.go b/integration/postgres_test.go
index 6a22143..0a56768 100644
--- a/integration/postgres_test.go
+++ b/integration/postgres_test.go
@@ -293,8 +293,8 @@ func TestIntegration_BasicOperators(t *testing.T) {
 		},
 		{
 			`empty object`,
-			`{}`,
-			[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
+			`{}`, // Should return FALSE as the condition.
+			[]int{},
 			nil,
 		},
 	}