Initial commit.

4 files changed, 221 insertions, 0 deletions

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..a696c94
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,8 @@
+module gitlab.com/rhogenson/sqlr
+
+go 1.21.6
+
+require (
+	github.com/google/go-cmp v0.6.0
+	github.com/mattn/go-sqlite3 v1.14.22
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..4917b35
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,4 @@
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/mattn/go-sqlite3 v1.14.22 h1:2gZY6PC6kBnID23Tichd1K+Z0oS6nE/XwU+Vz/5o4kU=
+github.com/mattn/go-sqlite3 v1.14.22/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
diff --git a/sqlr.go b/sqlr.go
new file mode 100644
index 0000000..0224c7c
--- /dev/null
+++ b/sqlr.go
@@ -0,0 +1,51 @@
+// Package sqlr ("squealer") provides some convenience wrappers around
+// database/sql in the spirit of encoding/json.
+package sqlr
+
+import (
+	"database/sql"
+	"fmt"
+	"reflect"
+)
+
+// Scan calls rows.Scan to unpack a single row into the fields of v.
+func Scan(rows *sql.Rows, v any) error {
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Pointer || rv.Elem().Kind() != reflect.Struct {
+		return fmt.Errorf("Scan needs a pointer to a struct")
+	}
+	inner := rv.Elem()
+	innerType := inner.Type()
+
+	fields := make(map[string]reflect.StructField)
+	inner.FieldByNameFunc(func(fieldName string) bool {
+		field, ok := innerType.FieldByName(fieldName)
+		if !ok {
+			return false
+		}
+		tag, ok := field.Tag.Lookup("sql")
+		if !ok {
+			fields[fieldName] = field
+			return false
+		}
+		if tag != "-" {
+			fields[tag] = field
+		}
+		return false
+	})
+
+	cols, err := rows.Columns()
+	if err != nil {
+		return err
+	}
+	dest := make([]any, len(cols))
+	for i, c := range cols {
+		field, ok := fields[c]
+		if !ok {
+			return fmt.Errorf("no field with tag %q", c)
+		}
+		dest[i] = inner.FieldByIndex(field.Index).Addr().Interface()
+	}
+
+	return rows.Scan(dest...)
+}
diff --git a/sqlr_test.go b/sqlr_test.go
new file mode 100644
index 0000000..4323f11
--- /dev/null
+++ b/sqlr_test.go
@@ -0,0 +1,158 @@
+package sqlr
+
+import (
+	"context"
+	"database/sql"
+	"github.com/google/go-cmp/cmp"
+	_ "github.com/mattn/go-sqlite3"
+	"reflect"
+	"testing"
+)
+
+func TestScan(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range []struct {
+		desc  string
+		db    string
+		query string
+		want  any
+	}{{
+		desc: "match field names",
+		db: `
+			CREATE TABLE Tbl (ColA, ColB);
+			INSERT INTO Tbl VALUES (100, "test")`,
+		query: "SELECT ColA, ColB FROM Tbl",
+		want: &struct {
+			ColA int
+			ColB string
+		}{100, "test"},
+	}, {
+		desc: "select star",
+		db: `
+			CREATE TABLE Tbl (ColA, ColB);
+			INSERT INTO Tbl VALUES (100, "test")`,
+		query: "SELECT * FROM Tbl",
+		want: &struct {
+			ColA int
+			ColB string
+		}{100, "test"},
+	}, {
+		desc: "ignored field",
+		db: `
+			CREATE TABLE Tbl (Col);
+			INSERT INTO Tbl VALUES (100)`,
+		query: "SELECT Col FROM Tbl",
+		want:  &struct{ Col, OtherField int }{Col: 100},
+	}, {
+		desc: "tag",
+		db: `
+			CREATE TABLE Tbl (col_a, col_b);
+			INSERT INTO Tbl VALUES (100, "test")`,
+		query: "SELECT col_a, col_b FROM Tbl",
+		want: &struct {
+			ColA int    `sql:"col_a"`
+			ColB string `sql:"col_b"`
+		}{100, "test"},
+	}} {
+		t.Run(tc.desc, func(t *testing.T) {
+			db, err := sql.Open("sqlite3", ":memory:")
+			if err != nil {
+				t.Fatalf("Failed to create in-memory database: %s", err)
+			}
+			defer db.Close()
+			if _, err := db.ExecContext(ctx, tc.db); err != nil {
+				t.Fatalf("Failed to initialize test database: %s", err)
+			}
+
+			rows, err := db.QueryContext(ctx, tc.query)
+			if err != nil {
+				t.Fatalf("Failed to query test database: %s", err)
+			}
+			if !rows.Next() {
+				t.Fatalf("No data")
+			}
+
+			got := reflect.New(reflect.TypeOf(tc.want).Elem()).Interface()
+			if err := Scan(rows, got); err != nil {
+				t.Fatalf("Scan failed: %s", err)
+			}
+			if err := rows.Close(); err != nil {
+				t.Fatalf("Close rows: %s", err)
+			}
+			if err := rows.Err(); err != nil {
+				t.Fatalf("Database read error: %s", err)
+			}
+
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Errorf("Scan returned unexpected diff (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestScan_Errors(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range []struct {
+		desc  string
+		db    string
+		query string
+		out   any
+	}{{
+		desc: "wrong type",
+		db: `
+			CREATE TABLE Tbl (Col);
+			INSERT INTO Tbl VALUES (100)`,
+		query: "SELECT Col FROM Tbl",
+		out:   5,
+	}, {
+		desc: "nil pointer",
+		db: `
+			CREATE TABLE Tbl (Col);
+			INSERT INTO Tbl VALUES (100)`,
+		query: "SELECT Col FROM Tbl",
+		out:   nil,
+	}, {
+		desc: "no field",
+		db: `
+			CREATE TABLE Tbl (ColA, ColB);
+			INSERT INTO Tbl VALUES (100, "test")`,
+		query: "SELECT ColA, ColB FROM Tbl",
+		out:   new(struct{ ColA int }),
+	}, {
+		desc: "ignored field",
+		db: `
+			CREATE TABLE Tbl (Col);
+			INSERT INTO Tbl VALUES (100)`,
+		query: "SELECT Col FROM Tbl",
+		out: new(struct {
+			Col int `sql:"-"`
+		}),
+	}} {
+		t.Run(tc.desc, func(t *testing.T) {
+			db, err := sql.Open("sqlite3", ":memory:")
+			if err != nil {
+				t.Fatalf("Failed to create in-memory database: %s", err)
+			}
+			defer db.Close()
+			if _, err := db.ExecContext(ctx, tc.db); err != nil {
+				t.Fatalf("Failed to initialize test database: %s", err)
+			}
+
+			rows, err := db.QueryContext(ctx, tc.query)
+			if err != nil {
+				t.Fatalf("Failed to query test database: %s", err)
+			}
+			defer rows.Close()
+			if !rows.Next() {
+				t.Fatalf("No data")
+			}
+
+			err = Scan(rows, tc.out)
+			if err == nil {
+				t.Errorf("Scan returned nil, want error")
+			}
+		})
+	}
+}