sqliteclidriver: use channel events, handle no results via sentinel

go.mod

@@ -5,6 +5,7 @@ go 1.19
 require (
 	github.com/cockroachdb/pebble v1.0.0
 	github.com/dgraph-io/badger/v4 v4.2.0
+	github.com/google/uuid v1.6.0
 	github.com/mattn/go-sqlite3 v1.14.22
 	github.com/pkg/browser v0.0.0-20240102092130-5ac0b6a4141c
 	github.com/redis/go-redis/v9 v9.5.3
@@ -32,7 +33,6 @@ require (
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/golang/snappy v0.0.4 // indirect
 	github.com/google/flatbuffers v1.12.1 // indirect
-	github.com/google/uuid v1.3.0 // indirect
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
 	github.com/klauspost/compress v1.16.0 // indirect
 	github.com/kr/pretty v0.3.1 // indirect

go.sum

@@ -160,8 +160,8 @@ github.com/google/pprof v0.0.0-20200430221834-fc25d7d30c6d/go.mod h1:ZgVRPoUq/hf
 github.com/google/pprof v0.0.0-20200708004538-1a94d8640e99/go.mod h1:ZgVRPoUq/hfqzAqh7sHMqb3I9Rq5C59dIz2SbBwJ4eM=
 github.com/google/pprof v0.0.0-20221118152302-e6195bd50e26 h1:Xim43kblpZXfIBQsbuBVKCudVG457BR2GZFIz3uw3hQ=
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
-github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
-github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/googleapis/gax-go/v2 v2.0.4/go.mod h1:0Wqv26UfaUD9n4G6kQubkQ+KchISgw+vpHVxEJEs9eg=
 github.com/googleapis/gax-go/v2 v2.0.5/go.mod h1:DWXyrwAJ9X0FpwwEdw+IPEYBICEFu5mhpdKc/us6bOk=
 github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=

sqliteclidriver/sqliteclidriver.go

@@ -5,7 +5,6 @@
 // Functionality is limited.
 //
 // Known caveats:
-// - Lexer only understands ? if it's separated by spaces
 // - Bad error handling
 // - Few supported types
 // - Has to escape parameters for CLI instead of preparing them, so not safe for untrusted usage
@@ -23,7 +22,10 @@ import (
 	"fmt"
 	"io"
 	"os/exec"
+
 	"yvbolt/lexer"
+
+	"github.com/google/uuid"
 )
 
 var ErrNotSupported = errors.New("Not supported")
@@ -37,29 +39,13 @@ func (d *SCDriver) Open(connectionString string) (driver.Conn, error) {
 
 	cmd := exec.Command(`/usr/bin/sqlite3`, `-noheader`, `-json`, connectionString) // n.b. doesn't support `--`
 
-	pw, err := cmd.StdinPipe()
+	chEvents, pw, err := ExecEvents(cmd)
-	if err != nil {
-		return nil, err
-	}
-
-	pr, err := cmd.StdoutPipe()
-	if err != nil {
-		return nil, err
-	}
-
-	pe, err := cmd.StderrPipe()
-	if err != nil {
-		return nil, err
-	}
-
-	err = cmd.Start()
 	if err != nil {
 		return nil, err
 	}
 
 	return &SCConn{
-		stdout: pr,
+		listen: chEvents,
-		stderr: pe,
 		w:      pw,
 	}, nil
 }
@@ -90,8 +76,7 @@ var _ driver.Connector = &SCConnector{} // interface assertion
 //
 
 type SCConn struct {
-	stdout io.Reader
+	listen <-chan processEvent
-	stderr io.Reader
 	w      io.WriteCloser
 }
 
@@ -105,6 +90,10 @@ func (c *SCConn) Prepare(query string) (driver.Stmt, error) {
 		return nil, errors.New("Empty query")
 	}
 
+	if f[len(f)-1] != ";" {
+		f = append(f, ";") // Query must end in semicolon
+	}
+
 	return &SCStmt{
 		conn:  c,
 		query: f,
@@ -216,24 +205,97 @@ func (s *SCStmt) Exec(args []driver.Value) (driver.Result, error) {
 }
 
 func (s *SCStmt) Query(args []driver.Value) (driver.Rows, error) {
+	ctx := context.Background()
 
 	submit, err := s.buildQuery(args)
 	if err != nil {
 		return nil, err
 	}
 
+	// If there are no results to the query, the sqlite3 -json mode does not
+	// print anything on stdout at all and we would hang forever
+	// Add a followup sentinel query that we can detect
+	const sentinelKey = `__sqliteclidriver_sentinel`
+	sentinelVal := uuid.Must(uuid.NewRandom()).String()
+	submit = append(submit, []byte(fmt.Sprintf("SELECT \"%s\" AS %s;\n", sentinelVal, sentinelKey))...)
+
+	//
+
 	_, err = io.CopyN(s.conn.w, bytes.NewReader(submit), int64(len(submit)))
 	if err != nil {
 		return nil, fmt.Errorf("Write: %w", err)
 	}
 
+	// Consume process events until either error or the json decoder is satisfied
+	pr, pw := io.Pipe()
+
+	listenContext, listenContextCancel := context.WithCancel(ctx) // Use to stop signalling once json decoder is satisfied
+
+	go func() {
+		defer pw.Close()
+		for {
+			select {
+			case msg, ok := <-s.conn.listen:
+				if !ok {
+					pw.CloseWithError(fmt.Errorf("process already closed"))
+					return
+				}
+				if msg.err != nil {
+					pw.CloseWithError(msg.err)
+					return
+				}
+
+				if msg.evtype == evtypeStdout {
+					_, err := io.CopyN(pw, bytes.NewReader(msg.data), int64(len(msg.data)))
+					if err != nil {
+						pw.CloseWithError(msg.err)
+						return
+					}
+				} else {
+					// Anything else (process event / stderr)
+					// Throw
+					pw.CloseWithError(fmt.Errorf("other thing %#v", msg))
+					return
+				}
+
+			case <-listenContext.Done():
+				return
+			}
+		}
+	}()
+
 	// We expect some kind of thing on stdout
+	// If something happens on stderr, or to the process, pr will read an error
 	ret := []map[string]any{}
-	err = json.NewDecoder(s.conn.stdout).Decode(&ret)
+	decoder := json.NewDecoder(pr)
+	err = decoder.Decode(&ret)
 	if err != nil {
 		return nil, err
 	}
 
+	// Check if this was the data or the sentinel
+	wasSentinel := false
+	if len(ret) > 0 {
+		if val, ok := ret[0][sentinelKey]; ok {
+			if check, ok := val.(string); ok && check == sentinelVal {
+				// It was the sentinel
+				wasSentinel = true
+				// Nothing more to parse
+			}
+		}
+	}
+
+	if !wasSentinel {
+		// Need to decode again (from the same decoder reader) until we find the sentinel
+		surplus := []map[string]any{}
+		err = decoder.Decode(&surplus)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	listenContextCancel()
+
 	// Drain stderr
 	// TODO
 

sqliteclidriver/sqliteclidriver_test.go

@@ -55,3 +55,24 @@ func TestSqliteCliDriver(t *testing.T) {
 
 	}
 }
+
+func TestSqliteCliDriverNoResults(t *testing.T) {
+	db, err := sql.Open("sqliteclidriver", ":memory:")
+	require.NoError(t, err)
+
+	// Repeat this part to ensure we can make followup queries on the same connection
+	for i := 0; i < 3; i++ {
+		_, err = db.Query(`SELECT 1 AS expect_no_result WHERE 1=2`)
+		require.NoError(t, err)
+
+		// Mix of results and no-results
+		rr := db.QueryRow(`SELECT 1 AS expect_result WHERE 1=1`)
+		require.NoError(t, rr.Err())
+
+		var result int64
+		err = rr.Scan(&result)
+		require.NoError(t, err)
+		require.EqualValues(t, result, 1)
+	}
+
+}