From f0f224c9afb082cdb82da9fb1851f732b748d6a4 Mon Sep 17 00:00:00 2001
From: Rowan Seymour <rowanseymour@gmail.com>
Date: Tue, 19 Sep 2023 13:35:53 -0500
Subject: [PATCH] Add dbutil.ScanAllJSON

---
 dbutil/scan.go      | 17 ++++++++++++++++-
 dbutil/scan_test.go | 25 ++++++++++++++++++++++---
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/dbutil/scan.go b/dbutil/scan.go
index a66fcfb..e83b326 100644
--- a/dbutil/scan.go
+++ b/dbutil/scan.go
@@ -40,7 +40,22 @@ func ScanAndValidateJSON(rows *sql.Rows, destination any) error {
 	return nil
 }
 
-// ScanAllSlice scans a single value from each single column row into the given slice
+// ScanAllJSON scans all rows as a single column containing JSON that be unmarshalled into instances of V.
+func ScanAllJSON[V any](rows *sql.Rows, s []V) ([]V, error) {
+	defer rows.Close()
+
+	var v V
+
+	for rows.Next() {
+		if err := ScanJSON(rows, &v); err != nil {
+			return nil, err
+		}
+		s = append(s, v)
+	}
+	return s, rows.Err()
+}
+
+// ScanAllSlice scans all rows as a single value and returns them in the given slice.
 func ScanAllSlice[V any](rows *sql.Rows, s []V) ([]V, error) {
 	defer rows.Close()
 
diff --git a/dbutil/scan_test.go b/dbutil/scan_test.go
index f35c6c5..7907a31 100644
--- a/dbutil/scan_test.go
+++ b/dbutil/scan_test.go
@@ -32,12 +32,12 @@ func TestScanJSON(t *testing.T) {
 	queryRows := func(sql string, args ...any) *sql.Rows {
 		rows, err := db.QueryContext(ctx, sql, args...)
 		require.NoError(t, err)
-		require.True(t, rows.Next())
 		return rows
 	}
 
 	// if query returns valid JSON which can be unmarshaled into our struct, all good
 	rows := queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid, f.name, f.age FROM foo f WHERE id = 1) r`)
+	require.True(t, rows.Next())
 
 	f := &foo{}
 	err := dbutil.ScanAndValidateJSON(rows, f)
@@ -47,6 +47,7 @@ func TestScanJSON(t *testing.T) {
 	assert.Equal(t, 40, f.Age)
 
 	rows = queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid, f.name, f.age FROM foo f WHERE id = 2) r`)
+	require.True(t, rows.Next())
 
 	err = dbutil.ScanAndValidateJSON(rows, f)
 	assert.NoError(t, err)
@@ -56,34 +57,52 @@ func TestScanJSON(t *testing.T) {
 
 	// error if row value is not JSON
 	rows = queryRows(`SELECT id FROM foo f WHERE id = 1`)
+	require.True(t, rows.Next())
+
 	err = dbutil.ScanAndValidateJSON(rows, f)
 	assert.EqualError(t, err, `error scanning row JSON: sql: Scan error on column index 0, name "id": unsupported Scan, storing driver.Value type int64 into type *json.RawMessage`)
 
 	// error if we can't marshal into the struct
 	rows = queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid as uuid, f.name AS age FROM foo f WHERE id = 1) r`)
+	require.True(t, rows.Next())
+
 	err = dbutil.ScanAndValidateJSON(rows, f)
 	assert.EqualError(t, err, "error unmarshalling row JSON: json: cannot unmarshal string into Go struct field foo.age of type int")
 
 	// error if rows aren't ready to be scanned - e.g. next hasn't been called
-	rows, err = db.QueryContext(ctx, `SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid as uuid, f.name AS name FROM foo f WHERE id = 1) r`)
-	require.NoError(t, err)
+	rows = queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid as uuid, f.name AS name FROM foo f WHERE id = 1) r`)
+
 	err = dbutil.ScanAndValidateJSON(rows, f)
 	assert.EqualError(t, err, "error scanning row JSON: sql: Scan called without calling Next")
 
 	// error if we request validation and returned JSON is invalid
 	rows = queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid, f.name, f.age FROM foo f WHERE id = 3) r`)
+	require.True(t, rows.Next())
 
 	err = dbutil.ScanAndValidateJSON(rows, f)
 	assert.EqualError(t, err, "error validating unmarsalled JSON: Key: 'foo.Age' Error:Field validation for 'Age' failed on the 'min' tag")
 
+	rows.Close()
+
 	// no error if we don't do validation
 	rows = queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid, f.name, f.age FROM foo f WHERE id = 3) r`)
+	require.True(t, rows.Next())
 
 	err = dbutil.ScanJSON(rows, f)
 	assert.NoError(t, err)
 	assert.Equal(t, "a5850c89-dd29-46f6-9de1-d068b3c2db94", f.UUID)
 	assert.Equal(t, "George", f.Name)
 	assert.Equal(t, -1, f.Age)
+
+	rows.Close()
+
+	// can all scan all rows with ScanAllJSON
+	rows = queryRows(`SELECT ROW_TO_JSON(r) FROM (SELECT f.uuid, f.name, f.age FROM foo f) r`)
+
+	var foos []*foo
+	foos, err = dbutil.ScanAllJSON(rows, foos)
+	assert.NoError(t, err)
+	assert.Len(t, foos, 3)
 }
 
 func TestScanAllSlice(t *testing.T) {