sqlite3: handle trailing comments and multiple SQL statements in Queries

This commit fixes *SQLiteConn.Query to properly handle trailing comments
after a SQL query statement. Previously, trailing comments could lead to
an infinite loop.

It also changes Query to error if the provided SQL statement contains
multiple queries ("SELECT 1; SELECT 2;") - previously only the last
query was executed ("SELECT 1; SELECT 2;" would yield only 2).

This may be a breaking change as previously: Query consumed all of its
args - despite only using the last query (Query now only uses the args
required to satisfy the first query and errors if there is a mismatch);
Query used only the last query and there may be code using this library
that depends on this behavior.

Personally, I believe the behavior introduced by this commit is correct
and any code relying on the prior undocumented behavior incorrect, but
it could still be a break.

sqlite3.go

@@ -30,7 +30,6 @@ package sqlite3
 #endif
 #include <stdlib.h>
 #include <string.h>
-#include <ctype.h>
 
 #ifdef __CYGWIN__
 # include <errno.h>
@@ -91,16 +90,6 @@ _sqlite3_exec(sqlite3* db, const char* pcmd, long long* rowid, long long* change
   return rv;
 }
 
-static const char *
-_trim_leading_spaces(const char *str) {
-  if (str) {
-    while (isspace(*str)) {
-      str++;
-    }
-  }
-  return str;
-}
-
 #ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
 extern int _sqlite3_step_blocking(sqlite3_stmt *stmt);
 extern int _sqlite3_step_row_blocking(sqlite3_stmt* stmt, long long* rowid, long long* changes);
@@ -121,11 +110,7 @@ _sqlite3_step_row_internal(sqlite3_stmt* stmt, long long* rowid, long long* chan
 static int
 _sqlite3_prepare_v2_internal(sqlite3 *db, const char *zSql, int nBytes, sqlite3_stmt **ppStmt, const char **pzTail)
 {
-  int rv = _sqlite3_prepare_v2_blocking(db, zSql, nBytes, ppStmt, pzTail);
-  if (pzTail) {
-    *pzTail = _trim_leading_spaces(*pzTail);
-  }
-  return rv;
+  return _sqlite3_prepare_v2_blocking(db, zSql, nBytes, ppStmt, pzTail);
 }
 
 #else
@@ -148,12 +133,9 @@ _sqlite3_step_row_internal(sqlite3_stmt* stmt, long long* rowid, long long* chan
 static int
 _sqlite3_prepare_v2_internal(sqlite3 *db, const char *zSql, int nBytes, sqlite3_stmt **ppStmt, const char **pzTail)
 {
-  int rv = sqlite3_prepare_v2(db, zSql, nBytes, ppStmt, pzTail);
-  if (pzTail) {
-    *pzTail = _trim_leading_spaces(*pzTail);
-  }
-  return rv;
+  return sqlite3_prepare_v2(db, zSql, nBytes, ppStmt, pzTail);
 }
+
 #endif
 
 void _sqlite3_result_text(sqlite3_context* ctx, const char* s) {
@@ -950,46 +932,44 @@ func (c *SQLiteConn) query(ctx context.Context, query string, args []driver.Name
 	op := pquery // original pointer
 	defer C.free(unsafe.Pointer(op))
 
-	var stmtArgs []driver.NamedValue
 	var tail *C.char
-	s := new(SQLiteStmt) // escapes to the heap so reuse it
-	start := 0
-	for {
-		*s = SQLiteStmt{c: c, cls: true} // reset
-		rv := C._sqlite3_prepare_v2_internal(c.db, pquery, C.int(-1), &s.s, &tail)
-		if rv != C.SQLITE_OK {
-			return nil, c.lastError()
+	s := &SQLiteStmt{c: c, cls: true}
+	rv := C._sqlite3_prepare_v2_internal(c.db, pquery, C.int(-1), &s.s, &tail)
+	if rv != C.SQLITE_OK {
+		return nil, c.lastError()
+	}
+	if s.s == nil {
+		return &SQLiteRows{s: &SQLiteStmt{closed: true}, closed: true}, nil
+	}
+	na := s.NumInput()
+	if n := len(args); n != na {
+		s.finalize()
+		if n < na {
+			return nil, fmt.Errorf("not enough args to execute query: want %d got %d", na, len(args))
 		}
+		return nil, fmt.Errorf("too many args to execute query: want %d got %d", na, len(args))
+	}
+	rows, err := s.query(ctx, args)
+	if err != nil && err != driver.ErrSkip {
+		s.finalize()
+		return rows, err
+	}
 
-		na := s.NumInput()
-		if len(args)-start < na {
-			return nil, fmt.Errorf("not enough args to execute query: want %d got %d", na, len(args)-start)
-		}
-		// consume the number of arguments used in the current
-		// statement and append all named arguments not contained
-		// therein
-		stmtArgs = append(stmtArgs[:0], args[start:start+na]...)
-		for i := range args {
-			if (i < start || i >= na) && args[i].Name != "" {
-				stmtArgs = append(stmtArgs, args[i])
-			}
-		}
-		for i := range stmtArgs {
-			stmtArgs[i].Ordinal = i + 1
-		}
-		rows, err := s.query(ctx, stmtArgs)
-		if err != nil && err != driver.ErrSkip {
-			s.finalize()
-			return rows, err
+	// Consume the rest of the query
+	for pquery = tail; pquery != nil && *pquery != 0; pquery = tail {
+		var stmt *C.sqlite3_stmt
+		rv := C._sqlite3_prepare_v2_internal(c.db, pquery, C.int(-1), &stmt, &tail)
+		if rv != C.SQLITE_OK {
+			rows.Close()
+			return nil, c.lastError()
 		}
-		start += na
-		if tail == nil || *tail == '\000' {
-			return rows, nil
+		if stmt != nil {
+			rows.Close()
+			return nil, errors.New("cannot insert multiple commands into a prepared statement") // WARN
 		}
-		rows.Close()
-		s.finalize()
-		pquery = tail
 	}
+
+	return rows, nil
 }
 
 // Begin transaction.
@@ -2043,7 +2023,7 @@ func (s *SQLiteStmt) Query(args []driver.Value) (driver.Rows, error) {
 	return s.query(context.Background(), list)
 }
 
-func (s *SQLiteStmt) query(ctx context.Context, args []driver.NamedValue) (driver.Rows, error) {
+func (s *SQLiteStmt) query(ctx context.Context, args []driver.NamedValue) (*SQLiteRows, error) {
 	if err := s.bind(args); err != nil {
 		return nil, err
 	}

sqlite3_test.go

@@ -18,6 +18,7 @@ import (
 	"math/rand"
 	"net/url"
 	"os"
+	"path/filepath"
 	"reflect"
 	"regexp"
 	"runtime"
@@ -1080,67 +1081,158 @@ func TestExecer(t *testing.T) {
 	defer db.Close()
 
 	_, err = db.Exec(`
-       create table foo (id integer); -- one comment
-       insert into foo(id) values(?);
-       insert into foo(id) values(?);
-       insert into foo(id) values(?); -- another comment
+       CREATE TABLE foo (id INTEGER); -- one comment
+       INSERT INTO foo(id) VALUES(?);
+       INSERT INTO foo(id) VALUES(?);
+       INSERT INTO foo(id) VALUES(?); -- another comment
        `, 1, 2, 3)
 	if err != nil {
 		t.Error("Failed to call db.Exec:", err)
 	}
 }
 
-func TestQueryer(t *testing.T) {
-	tempFilename := TempFilename(t)
-	defer os.Remove(tempFilename)
-	db, err := sql.Open("sqlite3", tempFilename)
+func testQuery(t *testing.T, seed bool, test func(t *testing.T, db *sql.DB)) {
+	db, err := sql.Open("sqlite3", filepath.Join(t.TempDir(), "test.sqlite3"))
 	if err != nil {
 		t.Fatal("Failed to open database:", err)
 	}
 	defer db.Close()
 
-	_, err = db.Exec(`
-		create table foo (id integer);
-	`)
-	if err != nil {
-		t.Error("Failed to call db.Query:", err)
+	if seed {
+		if _, err := db.Exec(`create table foo (id integer);`); err != nil {
+			t.Fatal(err)
+		}
+		_, err := db.Exec(`
+			INSERT INTO foo(id) VALUES(?);
+			INSERT INTO foo(id) VALUES(?);
+			INSERT INTO foo(id) VALUES(?);
+		`, 3, 2, 1)
+		if err != nil {
+			t.Fatal(err)
+		}
 	}
 
-	_, err = db.Exec(`
-		insert into foo(id) values(?);
-		insert into foo(id) values(?);
-		insert into foo(id) values(?);
-	`, 3, 2, 1)
-	if err != nil {
-		t.Error("Failed to call db.Exec:", err)
-	}
-	rows, err := db.Query(`
-		select id from foo order by id;
-	`)
-	if err != nil {
-		t.Error("Failed to call db.Query:", err)
-	}
-	defer rows.Close()
-	n := 0
-	for rows.Next() {
-		var id int
-		err = rows.Scan(&id)
+	// Capture panic so tests can continue
+	defer func() {
+		if e := recover(); e != nil {
+			buf := make([]byte, 32*1024)
+			n := runtime.Stack(buf, false)
+			t.Fatalf("\npanic: %v\n\n%s\n", e, buf[:n])
+		}
+	}()
+	test(t, db)
+}
+
+func testQueryValues(t *testing.T, query string, args ...interface{}) []interface{} {
+	var values []interface{}
+	testQuery(t, true, func(t *testing.T, db *sql.DB) {
+		rows, err := db.Query(query, args...)
 		if err != nil {
-			t.Error("Failed to db.Query:", err)
+			t.Fatal(err)
 		}
-		if id != n+1 {
-			t.Error("Failed to db.Query: not matched results")
+		if rows == nil {
+			t.Fatal("nil rows")
 		}
-		n = n + 1
+		for i := 0; rows.Next(); i++ {
+			if i > 1_000 {
+				t.Fatal("To many iterations of rows.Next():", i)
+			}
+			var v interface{}
+			if err := rows.Scan(&v); err != nil {
+				t.Fatal(err)
+			}
+			values = append(values, v)
+		}
+		if err := rows.Err(); err != nil {
+			t.Fatal(err)
+		}
+		if err := rows.Close(); err != nil {
+			t.Fatal(err)
+		}
+	})
+	return values
+}
+
+func TestQuery(t *testing.T) {
+	queries := []struct {
+		query string
+		args  []interface{}
+	}{
+		{"SELECT id FROM foo ORDER BY id;", nil},
+		{"SELECT id FROM foo WHERE id != ? ORDER BY id;", []interface{}{4}},
+		{"SELECT id FROM foo WHERE id IN (?, ?, ?) ORDER BY id;", []interface{}{1, 2, 3}},
+
+		// Comments
+		{"SELECT id FROM foo ORDER BY id; -- comment", nil},
+		{"SELECT id FROM foo ORDER BY id;\n -- comment\n", nil},
+		{
+			`-- FOO
+			 SELECT id FROM foo ORDER BY id; -- BAR
+			 /* BAZ */`,
+			nil,
+		},
 	}
-	if err := rows.Err(); err != nil {
-		t.Errorf("Post-scan failed: %v\n", err)
+	want := []interface{}{
+		int64(1),
+		int64(2),
+		int64(3),
+	}
+	for _, q := range queries {
+		t.Run("", func(t *testing.T) {
+			got := testQueryValues(t, q.query, q.args...)
+			if !reflect.DeepEqual(got, want) {
+				t.Fatalf("Query(%q, %v) = %v; want: %v", q.query, q.args, got, want)
+			}
+		})
 	}
-	if n != 3 {
-		t.Errorf("Expected 3 rows but retrieved %v", n)
+}
+
+func TestQueryNoSQL(t *testing.T) {
+	got := testQueryValues(t, "")
+	if got != nil {
+		t.Fatalf("Query(%q, %v) = %v; want: %v", "", nil, got, nil)
 	}
 }
 
+func testQueryError(t *testing.T, query string, args ...interface{}) {
+	testQuery(t, true, func(t *testing.T, db *sql.DB) {
+		rows, err := db.Query(query, args...)
+		if err == nil {
+			t.Error("Expected an error got:", err)
+		}
+		if rows != nil {
+			t.Error("Returned rows should be nil on error!")
+			// Attempt to iterate over rows to make sure they don't panic.
+			for i := 0; rows.Next(); i++ {
+				if i > 1_000 {
+					t.Fatal("To many iterations of rows.Next():", i)
+				}
+			}
+			if err := rows.Err(); err != nil {
+				t.Error(err)
+			}
+			rows.Close()
+		}
+	})
+}
+
+func TestQueryNotEnoughArgs(t *testing.T) {
+	testQueryError(t, "SELECT FROM foo WHERE id = ? OR id = ?);", 1)
+}
+
+func TestQueryTooManyArgs(t *testing.T) {
+	// TODO: test error message / kind
+	testQueryError(t, "SELECT FROM foo WHERE id = ?);", 1, 2)
+}
+
+func TestQueryMultipleStatements(t *testing.T) {
+	testQueryError(t, "SELECT 1; SELECT 2;")
+}
+
+func TestQueryInvalidTable(t *testing.T) {
+	testQueryError(t, "SELECT COUNT(*) FROM does_not_exist;")
+}
+
 func TestStress(t *testing.T) {
 	tempFilename := TempFilename(t)
 	defer os.Remove(tempFilename)
@@ -2112,7 +2204,6 @@ var benchmarks = []testing.InternalBenchmark{
 	{Name: "BenchmarkRows", F: benchmarkRows},
 	{Name: "BenchmarkStmtRows", F: benchmarkStmtRows},
 	{Name: "BenchmarkExecStep", F: benchmarkExecStep},
-	{Name: "BenchmarkQueryStep", F: benchmarkQueryStep},
 }
 
 func (db *TestDB) mustExec(sql string, args ...any) sql.Result {
@@ -2580,12 +2671,3 @@ func benchmarkExecStep(b *testing.B) {
 		}
 	}
 }
-
-func benchmarkQueryStep(b *testing.B) {
-	var i int
-	for n := 0; n < b.N; n++ {
-		if err := db.QueryRow(largeSelectStmt).Scan(&i); err != nil {
-			b.Fatal(err)
-		}
-	}
-}